// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/fs/namespace.c
*
* (C) Copyright Al Viro 2000, 2001
*
* Based on code from fs/super.c, copyright Linus Torvalds and others.
* Heavily rewritten.
*/
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/capability.h>
#include <linux/mnt_namespace.h>
#include <linux/user_namespace.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/cred.h>
#include <linux/idr.h>
#include <linux/init.h> /* init_rootfs */
#include <linux/fs_struct.h> /* get_fs_root et.al. */
#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
#include <linux/file.h>
#include <linux/uaccess.h>
#include <linux/proc_ns.h>
#include <linux/magic.h>
#include <linux/memblock.h>
#include <linux/proc_fs.h>
#include <linux/task_work.h>
#include <linux/sched/task.h>
#include <uapi/linux/mount.h>
#include <linux/fs_context.h>
#include <linux/shmem_fs.h>
#include <linux/mnt_idmapping.h>
#include <linux/nospec.h>
#include "pnode.h"
#include "internal.h"
/* Maximum number of mounts in a mount namespace */
static unsigned int sysctl_mount_max __read_mostly = 100000;
static unsigned int m_hash_mask __ro_after_init;
static unsigned int m_hash_shift __ro_after_init;
static unsigned int mp_hash_mask __ro_after_init;
static unsigned int mp_hash_shift __ro_after_init;
static __initdata unsigned long mhash_entries;
static int __init set_mhash_entries(char *str)
{
if (!str)
return 0;
mhash_entries = simple_strtoul(str, &str, 0);
return 1;
}
__setup("mhash_entries=", set_mhash_entries);
static __initdata unsigned long mphash_entries;
static int __init set_mphash_entries(char *str)
{
if (!str)
return 0;
mphash_entries = simple_strtoul(str, &str, 0);
return 1;
}
__setup("mphash_entries=", set_mphash_entries);
static u64 event;
static DEFINE_IDA(mnt_id_ida);
static DEFINE_IDA(mnt_group_ida);
/* Don't allow confusion with old 32bit mount ID */
#define MNT_UNIQUE_ID_OFFSET (1ULL << 31)
static atomic64_t mnt_id_ctr = ATOMIC64_INIT(MNT_UNIQUE_ID_OFFSET);
static struct hlist_head *mount_hashtable __ro_after_init;
static struct hlist_head *mountpoint_hashtable __ro_after_init;
static struct kmem_cache *mnt_cache __ro_after_init;
static DECLARE_RWSEM(namespace_sem);
static HLIST_HEAD(unmounted); /* protected by namespace_sem */
static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
static DEFINE_RWLOCK(mnt_ns_tree_lock);
static struct rb_root mnt_ns_tree = RB_ROOT; /* protected by mnt_ns_tree_lock */
struct mount_kattr {
unsigned int attr_set;
unsigned int attr_clr;
unsigned int propagation;
unsigned int lookup_flags;
bool recurse;
struct user_namespace *mnt_userns;
struct mnt_idmap *mnt_idmap;
};
/* /sys/fs */
struct kobject *fs_kobj __ro_after_init;
EXPORT_SYMBOL_GPL(fs_kobj);
/*
* vfsmount lock may be taken for read to prevent changes to the
* vfsmount hash, ie. during mountpoint lookups or walking back
* up the tree.
*
* It should be taken for write in all cases where the vfsmount
* tree or hash is modified or when a vfsmount structure is modified.
*/
__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
static int mnt_ns_cmp(u64 seq, const struct mnt_namespace *ns)
{
u64 seq_b = ns->seq;
if (seq < seq_b)
return -1;
if (seq > seq_b)
return 1;
return 0;
}
static inline struct mnt_namespace *node_to_mnt_ns(const struct rb_node *node)
{
if (!node)
return NULL;
return rb_entry(node, struct mnt_namespace, mnt_ns_tree_node);
}
static bool mnt_ns_less(struct rb_node *a, const struct rb_node *b)
{
struct mnt_namespace *ns_a = node_to_mnt_ns(a);
struct mnt_namespace *ns_b = node_to_mnt_ns(b);
u64 seq_a = ns_a->seq;
return mnt_ns_cmp(seq_a, ns_b) < 0;
}
static void mnt_ns_tree_add(struct mnt_namespace *ns)
{
guard(write_lock)(&mnt_ns_tree_lock);
rb_add(&ns->mnt_ns_tree_node, &mnt_ns_tree, mnt_ns_less);
}
static void mnt_ns_release(struct mnt_namespace *ns)
{
lockdep_assert_not_held(&mnt_ns_tree_lock);
/* keep alive for {list,stat}mount() */
if (refcount_dec_and_test(&ns->passive)) {
put_user_ns(ns->user_ns);
kfree(ns);
}
}
DEFINE_FREE(mnt_ns_release, struct mnt_namespace *, if (_T) mnt_ns_release(_T))
static void mnt_ns_tree_remove(struct mnt_namespace *ns)
{
/* remove from global mount namespace list */
if (!is_anon_ns(ns)) {
guard(write_lock)(&mnt_ns_tree_lock);
rb_erase(&ns->mnt_ns_tree_node, &mnt_ns_tree);
}
mnt_ns_release(ns);
}
/*
* Returns the mount namespace which either has the specified id, or has the
* next smallest id afer the specified one.
*/
static struct mnt_namespace *mnt_ns_find_id_at(u64 mnt_ns_id)
{
struct rb_node *node = mnt_ns_tree.rb_node;
struct mnt_namespace *ret = NULL;
lockdep_assert_held(&mnt_ns_tree_lock);
while (node) {
struct mnt_namespace *n = node_to_mnt_ns(node);
if (mnt_ns_id <= n->seq) {
ret = node_to_mnt_ns(node);
if (mnt_ns_id == n->seq)
break;
node = node->rb_left;
} else {
node = node->rb_right;
}
}
return ret;
}
/*
* Lookup a mount namespace by id and take a passive reference count. Taking a
* passive reference means the mount namespace can be emptied if e.g., the last
* task holding an active reference exits. To access the mounts of the
* namespace the @namespace_sem must first be acquired. If the namespace has
* already shut down before acquiring @namespace_sem, {list,stat}mount() will
* see that the mount rbtree of the namespace is empty.
*/
static struct mnt_namespace *lookup_mnt_ns(u64 mnt_ns_id)
{
struct mnt_namespace *ns;
guard(read_lock)(&mnt_ns_tree_lock);
ns = mnt_ns_find_id_at(mnt_ns_id);
if (!ns || ns->seq != mnt_ns_id)
return NULL;
refcount_inc(&ns->passive);
return ns;
}
static inline void lock_mount_hash(void)
{
write_seqlock(&mount_lock);
}
static inline void unlock_mount_hash(void)
{
write_sequnlock(&mount_lock);
}
static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
{
unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
tmp = tmp + (tmp >> m_hash_shift);
return &mount_hashtable[tmp & m_hash_mask];
}
static inline struct hlist_head *mp_hash(struct dentry *dentry)
{
unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
tmp = tmp + (tmp >> mp_hash_shift);
return &mountpoint_hashtable[tmp & mp_hash_mask];
}
static int mnt_alloc_id(struct mount *mnt)
{
int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
if (res < 0)
return res;
mnt->mnt_id = res;
mnt->mnt_id_unique = atomic64_inc_return(&mnt_id_ctr);
return 0;
}
static void mnt_free_id(struct mount *mnt)
{
ida_free(&mnt_id_ida, mnt->mnt_id);
}
/*
* Allocate a new peer group ID
*/
static int mnt_alloc_group_id(struct mount *mnt)
{
int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
if (res < 0)
return res;
mnt->mnt_group_id = res;
return 0;
}
/*
* Release a peer group ID
*/
void mnt_release_group_id(struct mount *mnt)
{
ida_free(&mnt_group_ida, mnt->mnt_group_id);
mnt->mnt_group_id = 0;
}
/*
* vfsmount lock must be held for read
*/
static inline void mnt_add_count(struct mount *mnt, int n)
{
#ifdef CONFIG_SMP
this_cpu_add(mnt->mnt_pcp->mnt_count, n);
#else
preempt_disable();
mnt->mnt_count += n;
preempt_enable();
#endif
}
/*
* vfsmount lock must be held for write
*/
int mnt_get_count(struct mount *mnt)
{
#ifdef CONFIG_SMP
int count = 0;
int cpu;
for_each_possible_cpu(cpu) {
count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
}
return count;
#else
return mnt->mnt_count;
#endif
}
static struct mount *alloc_vfsmnt(const char *name)
{
struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
if (mnt) {
int err;
err = mnt_alloc_id(mnt);
if (err)
goto out_free_cache;
if (name) {
mnt->mnt_devname = kstrdup_const(name,
GFP_KERNEL_ACCOUNT);
if (!mnt->mnt_devname)
goto out_free_id;
}
#ifdef CONFIG_SMP
mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
if (!mnt->mnt_pcp)
goto out_free_devname;
this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
#else
mnt->mnt_count = 1;
mnt->mnt_writers = 0;
#endif
INIT_HLIST_NODE(&mnt->mnt_hash);
INIT_LIST_HEAD(&mnt->mnt_child);
INIT_LIST_HEAD(&mnt->mnt_mounts);
INIT_LIST_HEAD(&mnt->mnt_list);
INIT_LIST_HEAD(&mnt->mnt_expire);
INIT_LIST_HEAD(&mnt->mnt_share);
INIT_LIST_HEAD(&mnt->mnt_slave_list);
INIT_LIST_HEAD(&mnt->mnt_slave);
INIT_HLIST_NODE(&mnt->mnt_mp_list);
INIT_LIST_HEAD(&mnt->mnt_umounting);
INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
mnt->mnt.mnt_idmap = &nop_mnt_idmap;
}
return mnt;
#ifdef CONFIG_SMP
out_free_devname:
kfree_const(mnt->mnt_devname);
#endif
out_free_id:
mnt_free_id(mnt);
out_free_cache:
kmem_cache_free(mnt_cache, mnt);
return NULL;
}
/*
* Most r/o checks on a fs are for operations that take
* discrete amounts of time, like a write() or unlink().
* We must keep track of when those operations start
* (for permission checks) and when they end, so that
* we can determine when writes are able to occur to
* a filesystem.
*/
/*
* __mnt_is_readonly: check whether a mount is read-only
* @mnt: the mount to check for its write status
*
* This shouldn't be used directly ouside of the VFS.
* It does not guarantee that the filesystem will stay
* r/w, just that it is right *now*. This can not and
* should not be used in place of IS_RDONLY(inode).
* mnt_want/drop_write() will _keep_ the filesystem
* r/w.
*/
bool __mnt_is_readonly(struct vfsmount *mnt)
{
return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb);
}
EXPORT_SYMBOL_GPL(__mnt_is_readonly);
static inline void mnt_inc_writers(struct mount *mnt)
{
#ifdef CONFIG_SMP
this_cpu_inc(mnt->mnt_pcp->mnt_writers);
#else
mnt->mnt_writers++;
#endif
}
static inline void mnt_dec_writers(struct mount *mnt)
{
#ifdef CONFIG_SMP
this_cpu_dec(mnt->mnt_pcp->mnt_writers);
#else
mnt->mnt_writers--;
#endif
}
static unsigned int mnt_get_writers(struct mount *mnt)
{
#ifdef CONFIG_SMP
unsigned int count = 0;
int cpu;
for_each_possible_cpu(cpu) {
count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
}
return count;
#else
return mnt->mnt_writers;
#endif
}
static int mnt_is_readonly(struct vfsmount *mnt)
{
if (READ_ONCE(mnt->mnt_sb->s_readonly_remount))
return 1;
/*
* The barrier pairs with the barrier in sb_start_ro_state_change()
* making sure if we don't see s_readonly_remount set yet, we also will
* not see any superblock / mount flag changes done by remount.
* It also pairs with the barrier in sb_end_ro_state_change()
* assuring that if we see s_readonly_remount already cleared, we will
* see the values of superblock / mount flags updated by remount.
*/
smp_rmb();
return __mnt_is_readonly(mnt);
}
/*
* Most r/o & frozen checks on a fs are for operations that take discrete
* amounts of time, like a write() or unlink(). We must keep track of when
* those operations start (for permission checks) and when they end, so that we
* can determine when writes are able to occur to a filesystem.
*/
/**
* mnt_get_write_access - get write access to a mount without freeze protection
* @m: the mount on which to take a write
*
* This tells the low-level filesystem that a write is about to be performed to
* it, and makes sure that writes are allowed (mnt it read-write) before
* returning success. This operation does not protect against filesystem being
* frozen. When the write operation is finished, mnt_put_write_access() must be
* called. This is effectively a refcount.
*/
int mnt_get_write_access(struct vfsmount *m)
{
struct mount *mnt = real_mount(m);
int ret = 0;
preempt_disable();
mnt_inc_writers(mnt);
/*
* The store to mnt_inc_writers must be visible before we pass
* MNT_WRITE_HOLD loop below, so that the slowpath can see our
* incremented count after it has set MNT_WRITE_HOLD.
*/
smp_mb();
might_lock(&mount_lock.lock);
while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
cpu_relax();
} else {
/*
* This prevents priority inversion, if the task
* setting MNT_WRITE_HOLD got preempted on a remote
* CPU, and it prevents life lock if the task setting
* MNT_WRITE_HOLD has a lower priority and is bound to
* the same CPU as the task that is spinning here.
*/
preempt_enable();
lock_mount_hash();
unlock_mount_hash();
preempt_disable();
}
}
/*
* The barrier pairs with the barrier sb_start_ro_state_change() making
* sure that if we see MNT_WRITE_HOLD cleared, we will also see
* s_readonly_remount set (or even SB_RDONLY / MNT_READONLY flags) in
* mnt_is_readonly() and bail in case we are racing with remount
* read-only.
*/
smp_rmb();
if (mnt_is_readonly(m)) {
mnt_dec_writers(mnt);
ret = -EROFS;
}
preempt_enable();
return ret;
}
EXPORT_SYMBOL_GPL(mnt_get_write_access);
/**
* mnt_want_write - get write access to a mount
* @m: the mount on which to take a write
*
* This tells the low-level filesystem that a write is about to be performed to
* it, and makes sure that writes are allowed (mount is read-write, filesystem
* is not frozen) before returning success. When the write operation is
* finished, mnt_drop_write() must be called. This is effectively a refcount.
*/
int mnt_want_write(struct vfsmount *m)
{
int ret;
sb_start_write(m->mnt_sb);
ret = mnt_get_write_access(m);
if (ret)
sb_end_write(m->mnt_sb);
return ret;
}
EXPORT_SYMBOL_GPL(mnt_want_write);
/**
* mnt_get_write_access_file - get write access to a file's mount
* @file: the file who's mount on which to take a write
*
* This is like mnt_get_write_access, but if @file is already open for write it
* skips incrementing mnt_writers (since the open file already has a reference)
* and instead only does the check for emergency r/o remounts. This must be
* paired with mnt_put_write_access_file.
*/
int mnt_get_write_access_file(struct file *file)
{
if (file->f_mode & FMODE_WRITER) {
/*
* Superblock may have become readonly while there are still
* writable fd's, e.g. due to a fs error with errors=remount-ro
*/
if (__mnt_is_readonly(file->f_path.mnt))
return -EROFS;
return 0;
}
return mnt_get_write_access(file->f_path.mnt);
}
/**
* mnt_want_write_file - get write access to a file's mount
* @file: the file who's mount on which to take a write
*
* This is like mnt_want_write, but if the file is already open for writing it
* skips incrementing mnt_writers (since the open file already has a reference)
* and instead only does the freeze protection and the check for emergency r/o
* remounts. This must be paired with mnt_drop_write_file.
*/
int mnt_want_write_file(struct file *file)
{
int ret;
sb_start_write(file_inode(file)->i_sb);
ret = mnt_get_write_access_file(file);
if (ret)
sb_end_write(file_inode(file)->i_sb);
return ret;
}
EXPORT_SYMBOL_GPL(mnt_want_write_file);
/**
* mnt_put_write_access - give up write access to a mount
* @mnt: the mount on which to give up write access
*
* Tells the low-level filesystem that we are done
* performing writes to it. Must be matched with
* mnt_get_write_access() call above.
*/
void mnt_put_write_access(struct vfsmount *mnt)
{
preempt_disable();
mnt_dec_writers(real_mount(mnt));
preempt_enable();
}
EXPORT_SYMBOL_GPL(mnt_put_write_access);
/**
* mnt_drop_write - give up write access to a mount
* @mnt: the mount on which to give up write access
*
* Tells the low-level filesystem that we are done performing writes to it and
* also allows filesystem to be frozen again. Must be matched with
* mnt_want_write() call above.
*/
void mnt_drop_write(struct vfsmount *mnt)
{
mnt_put_write_access(mnt);
sb_end_write(mnt->mnt_sb);
}
EXPORT_SYMBOL_GPL(mnt_drop_write);
void mnt_put_write_access_file(struct file *file)
{
if (!(file->f_mode & FMODE_WRITER))
mnt_put_write_access(file->f_path.mnt);
}
void mnt_drop_write_file(struct file *file)
{
mnt_put_write_access_file(file);
sb_end_write(file_inode(file)->i_sb);
}
EXPORT_SYMBOL(mnt_drop_write_file);
/**
* mnt_hold_writers - prevent write access to the given mount
* @mnt: mnt to prevent write access to
*
* Prevents write access to @mnt if there are no active writers for @mnt.
* This function needs to be called and return successfully before changing
* properties of @mnt that need to remain stable for callers with write access
* to @mnt.
*
* After this functions has been called successfully callers must pair it with
* a call to mnt_unhold_writers() in order to stop preventing write access to
* @mnt.
*
* Context: This function expects lock_mount_hash() to be held serializing
* setting MNT_WRITE_HOLD.
* Return: On success 0 is returned.
* On error, -EBUSY is returned.
*/
static inline int mnt_hold_writers(struct mount *mnt)
{
mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
/*
* After storing MNT_WRITE_HOLD, we'll read the counters. This store
* should be visible before we do.
*/
smp_mb();
/*
* With writers on hold, if this value is zero, then there are
* definitely no active writers (although held writers may subsequently
* increment the count, they'll have to wait, and decrement it after
* seeing MNT_READONLY).
*
* It is OK to have counter incremented on one CPU and decremented on
* another: the sum will add up correctly. The danger would be when we
* sum up each counter, if we read a counter before it is incremented,
* but then read another CPU's count which it has been subsequently
* decremented from -- we would see more decrements than we should.
* MNT_WRITE_HOLD protects against this scenario, because
* mnt_want_write first increments count, then smp_mb, then spins on
* MNT_WRITE_HOLD, so it can't be decremented by another CPU while
* we're counting up here.
*/
if (mnt_get_writers(mnt) > 0)
return -EBUSY;
return 0;
}
/**
* mnt_unhold_writers - stop preventing write access to the given mount
* @mnt: mnt to stop preventing write access to
*
* Stop preventing write access to @mnt allowing callers to gain write access
* to @mnt again.
*
* This function can only be called after a successful call to
* mnt_hold_writers().
*
* Context: This function expects lock_mount_hash() to be held.
*/
static inline void mnt_unhold_writers(struct mount *mnt)
{
/*
* MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
* that become unheld will see MNT_READONLY.
*/
smp_wmb();
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
}
static int mnt_make_readonly(struct mount *mnt)
{
int ret;
ret = mnt_hold_writers(mnt);
if (!ret)
mnt->mnt.mnt_flags |= MNT_READONLY;
mnt_unhold_writers(mnt);
return ret;
}
int sb_prepare_remount_readonly(struct super_block *sb)
{
struct mount *mnt;
int err = 0;
/* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
if (atomic_long_read(&sb->s_remove_count))
return -EBUSY;
lock_mount_hash();
list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
err = mnt_hold_writers(mnt);
if (err)
break;
}
}
if (!err && atomic_long_read(&sb->s_remove_count))
err = -EBUSY;
if (!err)
sb_start_ro_state_change(sb);
list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
}
unlock_mount_hash();
return err;
}
static void free_vfsmnt(struct mount *mnt)
{
mnt_idmap_put(mnt_idmap(&mnt->mnt));
kfree_const(mnt->mnt_devname);
#ifdef CONFIG_SMP
free_percpu(mnt->mnt_pcp);
#endif
kmem_cache_free(mnt_cache, mnt);
}
static void delayed_free_vfsmnt(struct rcu_head *head)
{
free_vfsmnt(container_of(head, struct mount, mnt_rcu));
}
/* call under rcu_read_lock */
int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
{
struct mount *mnt;
if (read_seqretry(&mount_lock, seq))
return 1;
if (bastard == NULL)
return 0;
mnt = real_mount(bastard);
mnt_add_count(mnt, 1);
smp_mb(); // see mntput_no_expire()
if (likely(!read_seqretry(&mount_lock, seq)))
return 0;
if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
mnt_add_count(mnt, -1);
return 1;
}
lock_mount_hash();
if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
mnt_add_count(mnt, -1);
unlock_mount_hash();
return 1;
}
unlock_mount_hash();
/* caller will mntput() */
return -1;
}
/* call under rcu_read_lock */
static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
{
int res = __legitimize_mnt(bastard, seq);
if (likely(!res))
return true;
if (unlikely(res < 0)) {
rcu_read_unlock();
mntput(bastard);
rcu_read_lock();
}
return false;
}
/**
* __lookup_mnt - find first child mount
* @mnt: parent mount
* @dentry: mountpoint
*
* If @mnt has a child mount @c mounted @dentry find and return it.
*
* Note that the child mount @c need not be unique. There are cases
* where shadow mounts are created. For example, during mount
* propagation when a source mount @mnt whose root got overmounted by a
* mount @o after path lookup but before @namespace_sem could be
* acquired gets copied and propagated. So @mnt gets copied including
* @o. When @mnt is propagated to a destination mount @d that already
* has another mount @n mounted at the same mountpoint then the source
* mount @mnt will be tucked beneath @n, i.e., @n will be mounted on
* @mnt and @mnt mounted on @d. Now both @n and @o are mounted at @mnt
* on @dentry.
*
* Return: The first child of @mnt mounted @dentry or NULL.
*/
struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
{
struct hlist_head *head = m_hash(mnt, dentry);
struct mount *p;
hlist_for_each_entry_rcu(p, head, mnt_hash)
if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
return p;
return NULL;
}
/*
* lookup_mnt - Return the first child mount mounted at path
*
* "First" means first mounted chronologically. If you create the
* following mounts:
*
* mount /dev/sda1 /mnt
* mount /dev/sda2 /mnt
* mount /dev/sda3 /mnt
*
* Then lookup_mnt() on the base /mnt dentry in the root mount will
* return successively the root dentry and vfsmount of /dev/sda1, then
* /dev/sda2, then /dev/sda3, then NULL.
*
* lookup_mnt takes a reference to the found vfsmount.
*/
struct vfsmount *lookup_mnt(const struct path *path)
{
struct mount *child_mnt;
struct vfsmount *m;
unsigned seq;
rcu_read_lock();
do {
seq = read_seqbegin(&mount_lock);
child_mnt = __lookup_mnt(path->mnt, path->dentry);
m = child_mnt ? &child_mnt->mnt : NULL;
} while (!legitimize_mnt(m, seq));
rcu_read_unlock();
return m;
}
/*
* __is_local_mountpoint - Test to see if dentry is a mountpoint in the
* current mount namespace.
*
* The common case is dentries are not mountpoints at all and that
* test is handled inline. For the slow case when we are actually
* dealing with a mountpoint of some kind, walk through all of the
* mounts in the current mount namespace and test to see if the dentry
* is a mountpoint.
*
* The mount_hashtable is not usable in the context because we
* need to identify all mounts that may be in the current mount
* namespace not just a mount that happens to have some specified
* parent mount.
*/
bool __is_local_mountpoint(struct dentry *dentry)
{
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
struct mount *mnt, *n;
bool is_covered = false;
down_read(&namespace_sem);
rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) {
is_covered = (mnt->mnt_mountpoint == dentry);
if (is_covered)
break;
}
up_read(&namespace_sem);
return is_covered;
}
static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
{
struct hlist_head *chain = mp_hash(dentry);
struct mountpoint *mp;
hlist_for_each_entry(mp, chain, m_hash) {
if (mp->m_dentry == dentry) {
mp->m_count++;
return mp;
}
}
return NULL;
}
static struct mountpoint *get_mountpoint(struct dentry *dentry)
{
struct mountpoint *mp, *new = NULL;
int ret;
if (d_mountpoint(dentry)) {
/* might be worth a WARN_ON() */
if (d_unlinked(dentry))
return ERR_PTR(-ENOENT);
mountpoint:
read_seqlock_excl(&mount_lock);
mp = lookup_mountpoint(dentry);
read_sequnlock_excl(&mount_lock);
if (mp)
goto done;
}
if (!new)
new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
if (!new)
return ERR_PTR(-ENOMEM);
/* Exactly one processes may set d_mounted */
ret = d_set_mounted(dentry);
/* Someone else set d_mounted? */
if (ret == -EBUSY)
goto mountpoint;
/* The dentry is not available as a mountpoint? */
mp = ERR_PTR(ret);
if (ret)
goto done;
/* Add the new mountpoint to the hash table */
read_seqlock_excl(&mount_lock);
new->m_dentry = dget(dentry);
new->m_count = 1;
hlist_add_head(&new->m_hash, mp_hash(dentry));
INIT_HLIST_HEAD(&new->m_list);
read_sequnlock_excl(&mount_lock);
mp = new;
new = NULL;
done:
kfree(new);
return mp;
}
/*
* vfsmount lock must be held. Additionally, the caller is responsible
* for serializing calls for given disposal list.
*/
static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
{
if (!--mp->m_count) {
struct dentry *dentry = mp->m_dentry;
BUG_ON(!hlist_empty(&mp->m_list));
spin_lock(&dentry->d_lock);
dentry->d_flags &= ~DCACHE_MOUNTED;
spin_unlock(&dentry->d_lock);
dput_to_list(dentry, list);
hlist_del(&mp->m_hash);
kfree(mp);
}
}
/* called with namespace_lock and vfsmount lock */
static void put_mountpoint(struct mountpoint *mp)
{
__put_mountpoint(mp, &ex_mountpoints);
}
static inline int check_mnt(struct mount *mnt)
{
return mnt->mnt_ns == current->nsproxy->mnt_ns;
}
/*
* vfsmount lock must be held for write
*/
static void touch_mnt_namespace(struct mnt_namespace *ns)
{
if (ns) {
ns->event = ++event;
wake_up_interruptible(&ns->poll);
}
}
/*
* vfsmount lock must be held for write
*/
static void __touch_mnt_namespace(struct mnt_namespace *ns)
{
if (ns && ns->event != event) {
ns->event = event;
wake_up_interruptible(&ns->poll);
}
}
/*
* vfsmount lock must be held for write
*/
static struct mountpoint *unhash_mnt(struct mount *mnt)
{
struct mountpoint *mp;
mnt->mnt_parent = mnt;
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
list_del_init(&mnt->mnt_child);
hlist_del_init_rcu(&mnt->mnt_hash);
hlist_del_init(&mnt->mnt_mp_list);
mp = mnt->mnt_mp;
mnt->mnt_mp = NULL;
return mp;
}
/*
* vfsmount lock must be held for write
*/
static void umount_mnt(struct mount *mnt)
{
put_mountpoint(unhash_mnt(mnt));
}
/*
* vfsmount lock must be held for write
*/
void mnt_set_mountpoint(struct mount *mnt,
struct mountpoint *mp,
struct mount *child_mnt)
{
mp->m_count++;
mnt_add_count(mnt, 1); /* essentially, that's mntget */
child_mnt->mnt_mountpoint = mp->m_dentry;
child_mnt->mnt_parent = mnt;
child_mnt->mnt_mp = mp;
hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
}
/**
* mnt_set_mountpoint_beneath - mount a mount beneath another one
*
* @new_parent: the source mount
* @top_mnt: the mount beneath which @new_parent is mounted
* @new_mp: the new mountpoint of @top_mnt on @new_parent
*
* Remove @top_mnt from its current mountpoint @top_mnt->mnt_mp and
* parent @top_mnt->mnt_parent and mount it on top of @new_parent at
* @new_mp. And mount @new_parent on the old parent and old
* mountpoint of @top_mnt.
*
* Context: This function expects namespace_lock() and lock_mount_hash()
* to have been acquired in that order.
*/
static void mnt_set_mountpoint_beneath(struct mount *new_parent,
struct mount *top_mnt,
struct mountpoint *new_mp)
{
struct mount *old_top_parent = top_mnt->mnt_parent;
struct mountpoint *old_top_mp = top_mnt->mnt_mp;
mnt_set_mountpoint(old_top_parent, old_top_mp, new_parent);
mnt_change_mountpoint(new_parent, new_mp, top_mnt);
}
static void __attach_mnt(struct mount *mnt, struct mount *parent)
{
hlist_add_head_rcu(&mnt->mnt_hash,
m_hash(&parent->mnt, mnt->mnt_mountpoint));
list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
}
/**
* attach_mnt - mount a mount, attach to @mount_hashtable and parent's
* list of child mounts
* @parent: the parent
* @mnt: the new mount
* @mp: the new mountpoint
* @beneath: whether to mount @mnt beneath or on top of @parent
*
* If @beneath is false, mount @mnt at @mp on @parent. Then attach @mnt
* to @parent's child mount list and to @mount_hashtable.
*
* If @beneath is true, remove @mnt from its current parent and
* mountpoint and mount it on @mp on @parent, and mount @parent on the
* old parent and old mountpoint of @mnt. Finally, attach @parent to
* @mnt_hashtable and @parent->mnt_parent->mnt_mounts.
*
* Note, when __attach_mnt() is called @mnt->mnt_parent already points
* to the correct parent.
*
* Context: This function expects namespace_lock() and lock_mount_hash()
* to have been acquired in that order.
*/
static void attach_mnt(struct mount *mnt, struct mount *parent,
struct mountpoint *mp, bool beneath)
{
if (beneath)
mnt_set_mountpoint_beneath(mnt, parent, mp);
else
mnt_set_mountpoint(parent, mp, mnt);
/*
* Note, @mnt->mnt_parent has to be used. If @mnt was mounted
* beneath @parent then @mnt will need to be attached to
* @parent's old parent, not @parent. IOW, @mnt->mnt_parent
* isn't the same mount as @parent.
*/
__attach_mnt(mnt, mnt->mnt_parent);
}
void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
{
struct mountpoint *old_mp = mnt->mnt_mp;
struct mount *old_parent = mnt->mnt_parent;
list_del_init(&mnt->mnt_child);
hlist_del_init(&mnt->mnt_mp_list);
hlist_del_init_rcu(&mnt->mnt_hash);
attach_mnt(mnt, parent, mp, false);
put_mountpoint(old_mp);
mnt_add_count(old_parent, -1);
}
static inline struct mount *node_to_mount(struct rb_node *node)
{
return node ? rb_entry(node, struct mount, mnt_node) : NULL;
}
static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt)
{
struct rb_node **link = &ns->mounts.rb_node;
struct rb_node *parent = NULL;
WARN_ON(mnt->mnt.mnt_flags & MNT_ONRB);
mnt->mnt_ns = ns;
while (*link) {
parent = *link;
if (mnt->mnt_id_unique < node_to_mount(parent)->mnt_id_unique)
link = &parent->rb_left;
else
link = &parent->rb_right;
}
rb_link_node(&mnt->mnt_node, parent, link);
rb_insert_color(&mnt->mnt_node, &ns->mounts);
mnt->mnt.mnt_flags |= MNT_ONRB;
}
/*
* vfsmount lock must be held for write
*/
static void commit_tree(struct mount *mnt)
{
struct mount *parent = mnt->mnt_parent;
struct mount *m;
LIST_HEAD(head);
struct mnt_namespace *n = parent->mnt_ns;
BUG_ON(parent == mnt);
list_add_tail(&head, &mnt->mnt_list);
while (!list_empty(&head)) {
m = list_first_entry(&head, typeof(*m), mnt_list);
list_del(&m->mnt_list);
mnt_add_to_ns(n, m);
}
n->nr_mounts += n->pending_mounts;
n->pending_mounts = 0;
__attach_mnt(mnt, parent);
touch_mnt_namespace(n);
}
static struct mount *next_mnt(struct mount *p, struct mount *root)
{
struct list_head *next = p->mnt_mounts.next;
if (next == &p->mnt_mounts) {
while (1) {
if (p == root)
return NULL;
next = p->mnt_child.next;
if (next != &p->mnt_parent->mnt_mounts)
break;
p = p->mnt_parent;
}
}
return list_entry(next, struct mount, mnt_child);
}
static struct mount *skip_mnt_tree(struct mount *p)
{
struct list_head *prev = p->mnt_mounts.prev;
while (prev != &p->mnt_mounts) {
p = list_entry(prev, struct mount, mnt_child);
prev = p->mnt_mounts.prev;
}
return p;
}
/**
* vfs_create_mount - Create a mount for a configured superblock
* @fc: The configuration context with the superblock attached
*
* Create a mount to an already configured superblock. If necessary, the
* caller should invoke vfs_get_tree() before calling this.
*
* Note that this does not attach the mount to anything.
*/
struct vfsmount *vfs_create_mount(struct fs_context *fc)
{
struct mount *mnt;
if (!fc->root)
return ERR_PTR(-EINVAL);
mnt = alloc_vfsmnt(fc->source ?: "none");
if (!mnt)
return ERR_PTR(-ENOMEM);
if (fc->sb_flags & SB_KERNMOUNT)
mnt->mnt.mnt_flags = MNT_INTERNAL;
atomic_inc(&fc->root->d_sb->s_active);
mnt->mnt.mnt_sb = fc->root->d_sb;
mnt->mnt.mnt_root = dget(fc->root);
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
mnt->mnt_parent = mnt;
lock_mount_hash();
list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
unlock_mount_hash();
return &mnt->mnt;
}
EXPORT_SYMBOL(vfs_create_mount);
struct vfsmount *fc_mount(struct fs_context *fc)
{
int err = vfs_get_tree(fc);
if (!err) {
up_write(&fc->root->d_sb->s_umount);
return vfs_create_mount(fc);
}
return ERR_PTR(err);
}
EXPORT_SYMBOL(fc_mount);
struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name,
void *data)
{
struct fs_context *fc;
struct vfsmount *mnt;
int ret = 0;
if (!type)
return ERR_PTR(-EINVAL);
fc = fs_context_for_mount(type, flags);
if (IS_ERR(fc))
return ERR_CAST(fc);
if (name)
ret = vfs_parse_fs_string(fc, "source",
name, strlen(name));
if (!ret)
ret = parse_monolithic_mount_data(fc, data);
if (!ret)
mnt = fc_mount(fc);
else
mnt = ERR_PTR(ret);
put_fs_context(fc);
return mnt;
}
EXPORT_SYMBOL_GPL(vfs_kern_mount);
struct vfsmount *
vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
const char *name, void *data)
{
/* Until it is worked out how to pass the user namespace
* through from the parent mount to the submount don't support
* unprivileged mounts with submounts.
*/
if (mountpoint->d_sb->s_user_ns != &init_user_ns)
return ERR_PTR(-EPERM);
return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
}
EXPORT_SYMBOL_GPL(vfs_submount);
static struct mount *clone_mnt(struct mount *old, struct dentry *root,
int flag)
{
struct super_block *sb = old->mnt.mnt_sb;
struct mount *mnt;
int err;
mnt = alloc_vfsmnt(old->mnt_devname);
if (!mnt)
return ERR_PTR(-ENOMEM);
if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
mnt->mnt_group_id = 0; /* not a peer of original */
else
mnt->mnt_group_id = old->mnt_group_id;
if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
err = mnt_alloc_group_id(mnt);
if (err)
goto out_free;
}
mnt->mnt.mnt_flags = old->mnt.mnt_flags;
mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL|MNT_ONRB);
atomic_inc(&sb->s_active);
mnt->mnt.mnt_idmap = mnt_idmap_get(mnt_idmap(&old->mnt));
mnt->mnt.mnt_sb = sb;
mnt->mnt.mnt_root = dget(root);
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
mnt->mnt_parent = mnt;
lock_mount_hash();
list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
unlock_mount_hash();
if ((flag & CL_SLAVE) ||
((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
list_add(&mnt->mnt_slave, &old->mnt_slave_list);
mnt->mnt_master = old;
CLEAR_MNT_SHARED(mnt);
} else if (!(flag & CL_PRIVATE)) {
if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
list_add(&mnt->mnt_share, &old->mnt_share);
if (IS_MNT_SLAVE(old))
list_add(&mnt->mnt_slave, &old->mnt_slave);
mnt->mnt_master = old->mnt_master;
} else {
CLEAR_MNT_SHARED(mnt);
}
if (flag & CL_MAKE_SHARED)
set_mnt_shared(mnt);
/* stick the duplicate mount on the same expiry list
* as the original if that was on one */
if (flag & CL_EXPIRE) {
if (!list_empty(&old->mnt_expire))
list_add(&mnt->mnt_expire, &old->mnt_expire);
}
return mnt;
out_free:
mnt_free_id(mnt);
free_vfsmnt(mnt);
return ERR_PTR(err);
}
static void cleanup_mnt(struct mount *mnt)
{
struct hlist_node *p;
struct mount *m;
/*
* The warning here probably indicates that somebody messed
* up a mnt_want/drop_write() pair. If this happens, the
* filesystem was probably unable to make r/w->r/o transitions.
* The locking used to deal with mnt_count decrement provides barriers,
* so mnt_get_writers() below is safe.
*/
WARN_ON(mnt_get_writers(mnt));
if (unlikely(mnt->mnt_pins.first))
mnt_pin_kill(mnt);
hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
hlist_del(&m->mnt_umount);
mntput(&m->mnt);
}
fsnotify_vfsmount_delete(&mnt->mnt);
dput(mnt->mnt.mnt_root);
deactivate_super(mnt->mnt.mnt_sb);
mnt_free_id(mnt);
call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
}
static void __cleanup_mnt(struct rcu_head *head)
{
cleanup_mnt(container_of(head, struct mount, mnt_rcu));
}
static LLIST_HEAD(delayed_mntput_list);
static void delayed_mntput(struct work_struct *unused)
{
struct llist_node *node = llist_del_all(&delayed_mntput_list);
struct mount *m, *t;
llist_for_each_entry_safe(m, t, node, mnt_llist)
cleanup_mnt(m);
}
static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
static void mntput_no_expire(struct mount *mnt)
{
LIST_HEAD(list);
int count;
rcu_read_lock();
if (likely(READ_ONCE(mnt->mnt_ns))) {
/*
* Since we don't do lock_mount_hash() here,
* ->mnt_ns can change under us. However, if it's
* non-NULL, then there's a reference that won't
* be dropped until after an RCU delay done after
* turning ->mnt_ns NULL. So if we observe it
* non-NULL under rcu_read_lock(), the reference
* we are dropping is not the final one.
*/
mnt_add_count(mnt, -1);
rcu_read_unlock();
return;
}
lock_mount_hash();
/*
* make sure that if __legitimize_mnt() has not seen us grab
* mount_lock, we'll see their refcount increment here.
*/
smp_mb();
mnt_add_count(mnt, -1);
count = mnt_get_count(mnt);
if (count != 0) {
WARN_ON(count < 0);
rcu_read_unlock();
unlock_mount_hash();
return;
}
if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
rcu_read_unlock();
unlock_mount_hash();
return;
}
mnt->mnt.mnt_flags |= MNT_DOOMED;
rcu_read_unlock();
list_del(&mnt->mnt_instance);
if (unlikely(!list_empty(&mnt->mnt_mounts))) {
struct mount *p, *tmp;
list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
__put_mountpoint(unhash_mnt(p), &list);
hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
}
}
unlock_mount_hash();
shrink_dentry_list(&list);
if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
struct task_struct *task = current;
if (likely(!(task->flags & PF_KTHREAD))) {
init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME))
return;
}
if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
schedule_delayed_work(&delayed_mntput_work, 1);
return;
}
cleanup_mnt(mnt);
}
void mntput(struct vfsmount *mnt)
{
if (mnt) {
struct mount *m = real_mount(mnt);
/* avoid cacheline pingpong */
if (unlikely(m->mnt_expiry_mark))
WRITE_ONCE(m->mnt_expiry_mark, 0);
mntput_no_expire(m);
}
}
EXPORT_SYMBOL(mntput);
struct vfsmount *mntget(struct vfsmount *mnt)
{
if (mnt)
mnt_add_count(real_mount(mnt), 1);
return mnt;
}
EXPORT_SYMBOL(mntget);
/*
* Make a mount point inaccessible to new lookups.
* Because there may still be current users, the caller MUST WAIT
* for an RCU grace period before destroying the mount point.
*/
void mnt_make_shortterm(struct vfsmount *mnt)
{
if (mnt)
real_mount(mnt)->mnt_ns = NULL;
}
/**
* path_is_mountpoint() - Check if path is a mount in the current namespace.
* @path: path to check
*
* d_mountpoint() can only be used reliably to establish if a dentry is
* not mounted in any namespace and that common case is handled inline.
* d_mountpoint() isn't aware of the possibility there may be multiple
* mounts using a given dentry in a different namespace. This function
* checks if the passed in path is a mountpoint rather than the dentry
* alone.
*/
bool path_is_mountpoint(const struct path *path)
{
unsigned seq;
bool res;
if (!d_mountpoint(path->dentry))
return false;
rcu_read_lock();
do {
seq = read_seqbegin(&mount_lock);
res = __path_is_mountpoint(path);
} while (read_seqretry(&mount_lock, seq));
rcu_read_unlock();
return res;
}
EXPORT_SYMBOL(path_is_mountpoint);
struct vfsmount *mnt_clone_internal(const struct path *path)
{
struct mount *p;
p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
if (IS_ERR(p))
return ERR_CAST(p);
p->mnt.mnt_flags |= MNT_INTERNAL;
return &p->mnt;
}
/*
* Returns the mount which either has the specified mnt_id, or has the next
* smallest id afer the specified one.
*/
static struct mount *mnt_find_id_at(struct mnt_namespace *ns, u64 mnt_id)
{
struct rb_node *node = ns->mounts.rb_node;
struct mount *ret = NULL;
while (node) {
struct mount *m = node_to_mount(node);
if (mnt_id <= m->mnt_id_unique) {
ret = node_to_mount(node);
if (mnt_id == m->mnt_id_unique)
break;
node = node->rb_left;
} else {
node = node->rb_right;
}
}
return ret;
}
/*
* Returns the mount which either has the specified mnt_id, or has the next
* greater id before the specified one.
*/
static struct mount *mnt_find_id_at_reverse(struct mnt_namespace *ns, u64 mnt_id)
{
struct rb_node *node = ns->mounts.rb_node;
struct mount *ret = NULL;
while (node) {
struct mount *m = node_to_mount(node);
if (mnt_id >= m->mnt_id_unique) {
ret = node_to_mount(node);
if (mnt_id == m->mnt_id_unique)
break;
node = node->rb_right;
} else {
node = node->rb_left;
}
}
return ret;
}
#ifdef CONFIG_PROC_FS
/* iterator; we want it to have access to namespace_sem, thus here... */
static void *m_start(struct seq_file *m, loff_t *pos)
{
struct proc_mounts *p = m->private;
down_read(&namespace_sem);
return mnt_find_id_at(p->ns, *pos);
}
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
struct mount *next = NULL, *mnt = v;
struct rb_node *node = rb_next(&mnt->mnt_node);
++*pos;
if (node) {
next = node_to_mount(node);
*pos = next->mnt_id_unique;
}
return next;
}
static void m_stop(struct seq_file *m, void *v)
{
up_read(&namespace_sem);
}
static int m_show(struct seq_file *m, void *v)
{
struct proc_mounts *p = m->private;
struct mount *r = v;
return p->show(m, &r->mnt);
}
const struct seq_operations mounts_op = {
.start = m_start,
.next = m_next,
.stop = m_stop,
.show = m_show,
};
#endif /* CONFIG_PROC_FS */
/**
* may_umount_tree - check if a mount tree is busy
* @m: root of mount tree
*
* This is called to check if a tree of mounts has any
* open files, pwds, chroots or sub mounts that are
* busy.
*/
int may_umount_tree(struct vfsmount *m)
{
struct mount *mnt = real_mount(m);
int actual_refs = 0;
int minimum_refs = 0;
struct mount *p;
BUG_ON(!m);
/* write lock needed for mnt_get_count */
lock_mount_hash();
for (p = mnt; p; p = next_mnt(p, mnt)) {
actual_refs += mnt_get_count(p);
minimum_refs += 2;
}
unlock_mount_hash();
if (actual_refs > minimum_refs)
return 0;
return 1;
}
EXPORT_SYMBOL(may_umount_tree);
/**
* may_umount - check if a mount point is busy
* @mnt: root of mount
*
* This is called to check if a mount point has any
* open files, pwds, chroots or sub mounts. If the
* mount has sub mounts this will return busy
* regardless of whether the sub mounts are busy.
*
* Doesn't take quota and stuff into account. IOW, in some cases it will
* give false negatives. The main reason why it's here is that we need
* a non-destructive way to look for easily umountable filesystems.
*/
int may_umount(struct vfsmount *mnt)
{
int ret = 1;
down_read(&namespace_sem);
lock_mount_hash();
if (propagate_mount_busy(real_mount(mnt), 2))
ret = 0;
unlock_mount_hash();
up_read(&namespace_sem);
return ret;
}
EXPORT_SYMBOL(may_umount);
static void namespace_unlock(void)
{
struct hlist_head head;
struct hlist_node *p;
struct mount *m;
LIST_HEAD(list);
hlist_move_list(&unmounted, &head);
list_splice_init(&ex_mountpoints, &list);
up_write(&namespace_sem);
shrink_dentry_list(&list);
if (likely(hlist_empty(&head)))
return;
synchronize_rcu_expedited();
hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
hlist_del(&m->mnt_umount);
mntput(&m->mnt);
}
}
static inline void namespace_lock(void)
{
down_write(&namespace_sem);
}
enum umount_tree_flags {
UMOUNT_SYNC = 1,
UMOUNT_PROPAGATE = 2,
UMOUNT_CONNECTED = 4,
};
static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
{
/* Leaving mounts connected is only valid for lazy umounts */
if (how & UMOUNT_SYNC)
return true;
/* A mount without a parent has nothing to be connected to */
if (!mnt_has_parent(mnt))
return true;
/* Because the reference counting rules change when mounts are
* unmounted and connected, umounted mounts may not be
* connected to mounted mounts.
*/
if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
return true;
/* Has it been requested that the mount remain connected? */
if (how & UMOUNT_CONNECTED)
return false;
/* Is the mount locked such that it needs to remain connected? */
if (IS_MNT_LOCKED(mnt))
return false;
/* By default disconnect the mount */
return true;
}
/*
* mount_lock must be held
* namespace_sem must be held for write
*/
static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
{
LIST_HEAD(tmp_list);
struct mount *p;
if (how & UMOUNT_PROPAGATE)
propagate_mount_unlock(mnt);
/* Gather the mounts to umount */
for (p = mnt; p; p = next_mnt(p, mnt)) {
p->mnt.mnt_flags |= MNT_UMOUNT;
if (p->mnt.mnt_flags & MNT_ONRB)
move_from_ns(p, &tmp_list);
else
list_move(&p->mnt_list, &tmp_list);
}
/* Hide the mounts from mnt_mounts */
list_for_each_entry(p, &tmp_list, mnt_list) {
list_del_init(&p->mnt_child);
}
/* Add propagated mounts to the tmp_list */
if (how & UMOUNT_PROPAGATE)
propagate_umount(&tmp_list);
while (!list_empty(&tmp_list)) {
struct mnt_namespace *ns;
bool disconnect;
p = list_first_entry(&tmp_list, struct mount, mnt_list);
list_del_init(&p->mnt_expire);
list_del_init(&p->mnt_list);
ns = p->mnt_ns;
if (ns) {
ns->nr_mounts--;
__touch_mnt_namespace(ns);
}
p->mnt_ns = NULL;
if (how & UMOUNT_SYNC)
p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
disconnect = disconnect_mount(p, how);
if (mnt_has_parent(p)) {
mnt_add_count(p->mnt_parent, -1);
if (!disconnect) {
/* Don't forget about p */
list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
} else {
umount_mnt(p);
}
}
change_mnt_propagation(p, MS_PRIVATE);
if (disconnect)
hlist_add_head(&p->mnt_umount, &unmounted);
}
}
static void shrink_submounts(struct mount *mnt);
static int do_umount_root(struct super_block *sb)
{
int ret = 0;
down_write(&sb->s_umount);
if (!sb_rdonly(sb)) {
struct fs_context *fc;
fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY,
SB_RDONLY);
if (IS_ERR(fc)) {
ret = PTR_ERR(fc);
} else {
ret = parse_monolithic_mount_data(fc, NULL);
if (!ret)
ret = reconfigure_super(fc);
put_fs_context(fc);
}
}
up_write(&sb->s_umount);
return ret;
}
static int do_umount(struct mount *mnt, int flags)
{
struct super_block *sb = mnt->mnt.mnt_sb;
int retval;
retval = security_sb_umount(&mnt->mnt, flags);
if (retval)
return retval;
/*
* Allow userspace to request a mountpoint be expired rather than
* unmounting unconditionally. Unmount only happens if:
* (1) the mark is already set (the mark is cleared by mntput())
* (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
*/
if (flags & MNT_EXPIRE) {
if (&mnt->mnt == current->fs->root.mnt ||
flags & (MNT_FORCE | MNT_DETACH))
return -EINVAL;
/*
* probably don't strictly need the lock here if we examined
* all race cases, but it's a slowpath.
*/
lock_mount_hash();
if (mnt_get_count(mnt) != 2) {
unlock_mount_hash();
return -EBUSY;
}
unlock_mount_hash();
if (!xchg(&mnt->mnt_expiry_mark, 1))
return -EAGAIN;
}
/*
* If we may have to abort operations to get out of this
* mount, and they will themselves hold resources we must
* allow the fs to do things. In the Unix tradition of
* 'Gee thats tricky lets do it in userspace' the umount_begin
* might fail to complete on the first run through as other tasks
* must return, and the like. Thats for the mount program to worry
* about for the moment.
*/
if (flags & MNT_FORCE && sb->s_op->umount_begin) {
sb->s_op->umount_begin(sb);
}
/*
* No sense to grab the lock for this test, but test itself looks
* somewhat bogus. Suggestions for better replacement?
* Ho-hum... In principle, we might treat that as umount + switch
* to rootfs. GC would eventually take care of the old vfsmount.
* Actually it makes sense, especially if rootfs would contain a
* /reboot - static binary that would close all descriptors and
* call reboot(9). Then init(8) could umount root and exec /reboot.
*/
if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
/*
* Special case for "unmounting" root ...
* we just try to remount it readonly.
*/
if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
return -EPERM;
return do_umount_root(sb);
}
namespace_lock();
lock_mount_hash();
/* Recheck MNT_LOCKED with the locks held */
retval = -EINVAL;
if (mnt->mnt.mnt_flags & MNT_LOCKED)
goto out;
event++;
if (flags & MNT_DETACH) {
if (mnt->mnt.mnt_flags & MNT_ONRB ||
!list_empty(&mnt->mnt_list))
umount_tree(mnt, UMOUNT_PROPAGATE);
retval = 0;
} else {
shrink_submounts(mnt);
retval = -EBUSY;
if (!propagate_mount_busy(mnt, 2)) {
if (mnt->mnt.mnt_flags & MNT_ONRB ||
!list_empty(&mnt->mnt_list))
umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
retval = 0;
}
}
out:
unlock_mount_hash();
namespace_unlock();
return retval;
}
/*
* __detach_mounts - lazily unmount all mounts on the specified dentry
*
* During unlink, rmdir, and d_drop it is possible to loose the path
* to an existing mountpoint, and wind up leaking the mount.
* detach_mounts allows lazily unmounting those mounts instead of
* leaking them.
*
* The caller may hold dentry->d_inode->i_mutex.
*/
void __detach_mounts(struct dentry *dentry)
{
struct mountpoint *mp;
struct mount *mnt;
namespace_lock();
lock_mount_hash();
mp = lookup_mountpoint(dentry);
if (!mp)
goto out_unlock;
event++;
while (!hlist_empty(&mp->m_list)) {
mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
umount_mnt(mnt);
hlist_add_head(&mnt->mnt_umount, &unmounted);
}
else umount_tree(mnt, UMOUNT_CONNECTED);
}
put_mountpoint(mp);
out_unlock:
unlock_mount_hash();
namespace_unlock();
}
/*
* Is the caller allowed to modify his namespace?
*/
bool may_mount(void)
{
return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
}
static void warn_mandlock(void)
{
pr_warn_once("=======================================================\n"
"WARNING: The mand mount option has been deprecated and\n"
" and is ignored by this kernel. Remove the mand\n"
" option from the mount to silence this warning.\n"
"=======================================================\n");
}
static int can_umount(const struct path *path, int flags)
{
struct mount *mnt = real_mount(path->mnt);
if (!may_mount())
return -EPERM;
if (!path_mounted(path))
return -EINVAL;
if (!check_mnt(mnt))
return -EINVAL;
if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
return -EINVAL;
if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
// caller is responsible for flags being sane
int path_umount(struct path *path, int flags)
{
struct mount *mnt = real_mount(path->mnt);
int ret;
ret = can_umount(path, flags);
if (!ret)
ret = do_umount(mnt, flags);
/* we mustn't call path_put() as that would clear mnt_expiry_mark */
dput(path->dentry);
mntput_no_expire(mnt);
return ret;
}
static int ksys_umount(char __user *name, int flags)
{
int lookup_flags = LOOKUP_MOUNTPOINT;
struct path path;
int ret;
// basic validity checks done first
if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
return -EINVAL;
if (!(flags & UMOUNT_NOFOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
if (ret)
return ret;
return path_umount(&path, flags);
}
SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
{
return ksys_umount(name, flags);
}
#ifdef __ARCH_WANT_SYS_OLDUMOUNT
/*
* The 2.0 compatible umount. No flags.
*/
SYSCALL_DEFINE1(oldumount, char __user *, name)
{
return ksys_umount(name, 0);
}
#endif
static bool is_mnt_ns_file(struct dentry *dentry)
{
/* Is this a proxy for a mount namespace? */
return dentry->d_op == &ns_dentry_operations &&
dentry->d_fsdata == &mntns_operations;
}
struct ns_common *from_mnt_ns(struct mnt_namespace *mnt)
{
return &mnt->ns;
}
struct mnt_namespace *__lookup_next_mnt_ns(struct mnt_namespace *mntns, bool previous)
{
guard(read_lock)(&mnt_ns_tree_lock);
for (;;) {
struct rb_node *node;
if (previous)
node = rb_prev(&mntns->mnt_ns_tree_node);
else
node = rb_next(&mntns->mnt_ns_tree_node);
if (!node)
return ERR_PTR(-ENOENT);
mntns = node_to_mnt_ns(node);
node = &mntns->mnt_ns_tree_node;
if (!ns_capable_noaudit(mntns->user_ns, CAP_SYS_ADMIN))
continue;
/*
* Holding mnt_ns_tree_lock prevents the mount namespace from
* being freed but it may well be on it's deathbed. We want an
* active reference, not just a passive one here as we're
* persisting the mount namespace.
*/
if (!refcount_inc_not_zero(&mntns->ns.count))
continue;
return mntns;
}
}
static bool mnt_ns_loop(struct dentry *dentry)
{
/* Could bind mounting the mount namespace inode cause a
* mount namespace loop?
*/
struct mnt_namespace *mnt_ns;
if (!is_mnt_ns_file(dentry))
return false;
mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
}
struct mount *copy_tree(struct mount *src_root, struct dentry *dentry,
int flag)
{
struct mount *res, *src_parent, *src_root_child, *src_mnt,
*dst_parent, *dst_mnt;
if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(src_root))
return ERR_PTR(-EINVAL);
if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
return ERR_PTR(-EINVAL);
res = dst_mnt = clone_mnt(src_root, dentry, flag);
if (IS_ERR(dst_mnt))
return dst_mnt;
src_parent = src_root;
dst_mnt->mnt_mountpoint = src_root->mnt_mountpoint;
list_for_each_entry(src_root_child, &src_root->mnt_mounts, mnt_child) {
if (!is_subdir(src_root_child->mnt_mountpoint, dentry))
continue;
for (src_mnt = src_root_child; src_mnt;
src_mnt = next_mnt(src_mnt, src_root_child)) {
if (!(flag & CL_COPY_UNBINDABLE) &&
IS_MNT_UNBINDABLE(src_mnt)) {
if (src_mnt->mnt.mnt_flags & MNT_LOCKED) {
/* Both unbindable and locked. */
dst_mnt = ERR_PTR(-EPERM);
goto out;
} else {
src_mnt = skip_mnt_tree(src_mnt);
continue;
}
}
if (!(flag & CL_COPY_MNT_NS_FILE) &&
is_mnt_ns_file(src_mnt->mnt.mnt_root)) {
src_mnt = skip_mnt_tree(src_mnt);
continue;
}
while (src_parent != src_mnt->mnt_parent) {
src_parent = src_parent->mnt_parent;
dst_mnt = dst_mnt->mnt_parent;
}
src_parent = src_mnt;
dst_parent = dst_mnt;
dst_mnt = clone_mnt(src_mnt, src_mnt->mnt.mnt_root, flag);
if (IS_ERR(dst_mnt))
goto out;
lock_mount_hash();
list_add_tail(&dst_mnt->mnt_list, &res->mnt_list);
attach_mnt(dst_mnt, dst_parent, src_parent->mnt_mp, false);
unlock_mount_hash();
}
}
return res;
out:
if (res) {
lock_mount_hash();
umount_tree(res, UMOUNT_SYNC);
unlock_mount_hash();
}
return dst_mnt;
}
/* Caller should check returned pointer for errors */
struct vfsmount *collect_mounts(const struct path *path)
{
struct mount *tree;
namespace_lock();
if (!check_mnt(real_mount(path->mnt)))
tree = ERR_PTR(-EINVAL);
else
tree = copy_tree(real_mount(path->mnt), path->dentry,
CL_COPY_ALL | CL_PRIVATE);
namespace_unlock();
if (IS_ERR(tree))
return ERR_CAST(tree);
return &tree->mnt;
}
static void free_mnt_ns(struct mnt_namespace *);
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
void dissolve_on_fput(struct vfsmount *mnt)
{
struct mnt_namespace *ns;
namespace_lock();
lock_mount_hash();
ns = real_mount(mnt)->mnt_ns;
if (ns) {
if (is_anon_ns(ns))
umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
else
ns = NULL;
}
unlock_mount_hash();
namespace_unlock();
if (ns)
free_mnt_ns(ns);
}
void drop_collected_mounts(struct vfsmount *mnt)
{
namespace_lock();
lock_mount_hash();
umount_tree(real_mount(mnt), 0);
unlock_mount_hash();
namespace_unlock();
}
bool has_locked_children(struct mount *mnt, struct dentry *dentry)
{
struct mount *child;
list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
if (!is_subdir(child->mnt_mountpoint, dentry))
continue;
if (child->mnt.mnt_flags & MNT_LOCKED)
return true;
}
return false;
}
/**
* clone_private_mount - create a private clone of a path
* @path: path to clone
*
* This creates a new vfsmount, which will be the clone of @path. The new mount
* will not be attached anywhere in the namespace and will be private (i.e.
* changes to the originating mount won't be propagated into this).
*
* Release with mntput().
*/
struct vfsmount *clone_private_mount(const struct path *path)
{
struct mount *old_mnt = real_mount(path->mnt);
struct mount *new_mnt;
down_read(&namespace_sem);
if (IS_MNT_UNBINDABLE(old_mnt))
goto invalid;
if (!check_mnt(old_mnt))
goto invalid;
if (has_locked_children(old_mnt, path->dentry))
goto invalid;
new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
up_read(&namespace_sem);
if (IS_ERR(new_mnt))
return ERR_CAST(new_mnt);
/* Longterm mount to be removed by kern_unmount*() */
new_mnt->mnt_ns = MNT_NS_INTERNAL;
return &new_mnt->mnt;
invalid:
up_read(&namespace_sem);
return ERR_PTR(-EINVAL);
}
EXPORT_SYMBOL_GPL(clone_private_mount);
int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
struct vfsmount *root)
{
struct mount *mnt;
int res = f(root, arg);
if (res)
return res;
list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
res = f(&mnt->mnt, arg);
if (res)
return res;
}
return 0;
}
static void lock_mnt_tree(struct mount *mnt)
{
struct mount *p;
for (p = mnt; p; p = next_mnt(p, mnt)) {
int flags = p->mnt.mnt_flags;
/* Don't allow unprivileged users to change mount flags */
flags |= MNT_LOCK_ATIME;
if (flags & MNT_READONLY)
flags |= MNT_LOCK_READONLY;
if (flags & MNT_NODEV)
flags |= MNT_LOCK_NODEV;
if (flags & MNT_NOSUID)
flags |= MNT_LOCK_NOSUID;
if (flags & MNT_NOEXEC)
flags |= MNT_LOCK_NOEXEC;
/* Don't allow unprivileged users to reveal what is under a mount */
if (list_empty(&p->mnt_expire))
flags |= MNT_LOCKED;
p->mnt.mnt_flags = flags;
}
}
static void cleanup_group_ids(struct mount *mnt, struct mount *end)
{
struct mount *p;
for (p = mnt; p != end; p = next_mnt(p, mnt)) {
if (p->mnt_group_id && !IS_MNT_SHARED(p))
mnt_release_group_id(p);
}
}
static int invent_group_ids(struct mount *mnt, bool recurse)
{
struct mount *p;
for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
int err = mnt_alloc_group_id(p);
if (err) {
cleanup_group_ids(mnt, p);
return err;
}
}
}
return 0;
}
int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
{
unsigned int max = READ_ONCE(sysctl_mount_max);
unsigned int mounts = 0;
struct mount *p;
if (ns->nr_mounts >= max)
return -ENOSPC;
max -= ns->nr_mounts;
if (ns->pending_mounts >= max)
return -ENOSPC;
max -= ns->pending_mounts;
for (p = mnt; p; p = next_mnt(p, mnt))
mounts++;
if (mounts > max)
return -ENOSPC;
ns->pending_mounts += mounts;
return 0;
}
enum mnt_tree_flags_t {
MNT_TREE_MOVE = BIT(0),
MNT_TREE_BENEATH = BIT(1),
};
/**
* attach_recursive_mnt - attach a source mount tree
* @source_mnt: mount tree to be attached
* @top_mnt: mount that @source_mnt will be mounted on or mounted beneath
* @dest_mp: the mountpoint @source_mnt will be mounted at
* @flags: modify how @source_mnt is supposed to be attached
*
* NOTE: in the table below explains the semantics when a source mount
* of a given type is attached to a destination mount of a given type.
* ---------------------------------------------------------------------------
* | BIND MOUNT OPERATION |
* |**************************************************************************
* | source-->| shared | private | slave | unbindable |
* | dest | | | | |
* | | | | | | |
* | v | | | | |
* |**************************************************************************
* | shared | shared (++) | shared (+) | shared(+++)| invalid |
* | | | | | |
* |non-shared| shared (+) | private | slave (*) | invalid |
* ***************************************************************************
* A bind operation clones the source mount and mounts the clone on the
* destination mount.
*
* (++) the cloned mount is propagated to all the mounts in the propagation
* tree of the destination mount and the cloned mount is added to
* the peer group of the source mount.
* (+) the cloned mount is created under the destination mount and is marked
* as shared. The cloned mount is added to the peer group of the source
* mount.
* (+++) the mount is propagated to all the mounts in the propagation tree
* of the destination mount and the cloned mount is made slave
* of the same master as that of the source mount. The cloned mount
* is marked as 'shared and slave'.
* (*) the cloned mount is made a slave of the same master as that of the
* source mount.
*
* ---------------------------------------------------------------------------
* | MOVE MOUNT OPERATION |
* |**************************************************************************
* | source-->| shared | private | slave | unbindable |
* | dest | | | | |
* | | | | | | |
* | v | | | | |
* |**************************************************************************
* | shared | shared (+) | shared (+) | shared(+++) | invalid |
* | | | | | |
* |non-shared| shared (+*) | private | slave (*) | unbindable |
* ***************************************************************************
*
* (+) the mount is moved to the destination. And is then propagated to
* all the mounts in the propagation tree of the destination mount.
* (+*) the mount is moved to the destination.
* (+++) the mount is moved to the destination and is then propagated to
* all the mounts belonging to the destination mount's propagation tree.
* the mount is marked as 'shared and slave'.
* (*) the mount continues to be a slave at the new location.
*
* if the source mount is a tree, the operations explained above is
* applied to each mount in the tree.
* Must be called without spinlocks held, since this function can sleep
* in allocations.
*
* Context: The function expects namespace_lock() to be held.
* Return: If @source_mnt was successfully attached 0 is returned.
* Otherwise a negative error code is returned.
*/
static int attach_recursive_mnt(struct mount *source_mnt,
struct mount *top_mnt,
struct mountpoint *dest_mp,
enum mnt_tree_flags_t flags)
{
struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
HLIST_HEAD(tree_list);
struct mnt_namespace *ns = top_mnt->mnt_ns;
struct mountpoint *smp;
struct mount *child, *dest_mnt, *p;
struct hlist_node *n;
int err = 0;
bool moving = flags & MNT_TREE_MOVE, beneath = flags & MNT_TREE_BENEATH;
/*
* Preallocate a mountpoint in case the new mounts need to be
* mounted beneath mounts on the same mountpoint.
*/
smp = get_mountpoint(source_mnt->mnt.mnt_root);
if (IS_ERR(smp))
return PTR_ERR(smp);
/* Is there space to add these mounts to the mount namespace? */
if (!moving) {
err = count_mounts(ns, source_mnt);
if (err)
goto out;
}
if (beneath)
dest_mnt = top_mnt->mnt_parent;
else
dest_mnt = top_mnt;
if (IS_MNT_SHARED(dest_mnt)) {
err = invent_group_ids(source_mnt, true);
if (err)
goto out;
err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
}
lock_mount_hash();
if (err)
goto out_cleanup_ids;
if (IS_MNT_SHARED(dest_mnt)) {
for (p = source_mnt; p; p = next_mnt(p, source_mnt))
set_mnt_shared(p);
}
if (moving) {
if (beneath)
dest_mp = smp;
unhash_mnt(source_mnt);
attach_mnt(source_mnt, top_mnt, dest_mp, beneath);
touch_mnt_namespace(source_mnt->mnt_ns);
} else {
if (source_mnt->mnt_ns) {
LIST_HEAD(head);
/* move from anon - the caller will destroy */
for (p = source_mnt; p; p = next_mnt(p, source_mnt))
move_from_ns(p, &head);
list_del_init(&head);
}
if (beneath)
mnt_set_mountpoint_beneath(source_mnt, top_mnt, smp);
else
mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
commit_tree(source_mnt);
}
hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
struct mount *q;
hlist_del_init(&child->mnt_hash);
q = __lookup_mnt(&child->mnt_parent->mnt,
child->mnt_mountpoint);
if (q)
mnt_change_mountpoint(child, smp, q);
/* Notice when we are propagating across user namespaces */
if (child->mnt_parent->mnt_ns->user_ns != user_ns)
lock_mnt_tree(child);
child->mnt.mnt_flags &= ~MNT_LOCKED;
commit_tree(child);
}
put_mountpoint(smp);
unlock_mount_hash();
return 0;
out_cleanup_ids:
while (!hlist_empty(&tree_list)) {
child = hlist_entry(tree_list.first, struct mount, mnt_hash);
child->mnt_parent->mnt_ns->pending_mounts = 0;
umount_tree(child, UMOUNT_SYNC);
}
unlock_mount_hash();
cleanup_group_ids(source_mnt, NULL);
out:
ns->pending_mounts = 0;
read_seqlock_excl(&mount_lock);
put_mountpoint(smp);
read_sequnlock_excl(&mount_lock);
return err;
}
/**
* do_lock_mount - lock mount and mountpoint
* @path: target path
* @beneath: whether the intention is to mount beneath @path
*
* Follow the mount stack on @path until the top mount @mnt is found. If
* the initial @path->{mnt,dentry} is a mountpoint lookup the first
* mount stacked on top of it. Then simply follow @{mnt,mnt->mnt_root}
* until nothing is stacked on top of it anymore.
*
* Acquire the inode_lock() on the top mount's ->mnt_root to protect
* against concurrent removal of the new mountpoint from another mount
* namespace.
*
* If @beneath is requested, acquire inode_lock() on @mnt's mountpoint
* @mp on @mnt->mnt_parent must be acquired. This protects against a
* concurrent unlink of @mp->mnt_dentry from another mount namespace
* where @mnt doesn't have a child mount mounted @mp. A concurrent
* removal of @mnt->mnt_root doesn't matter as nothing will be mounted
* on top of it for @beneath.
*
* In addition, @beneath needs to make sure that @mnt hasn't been
* unmounted or moved from its current mountpoint in between dropping
* @mount_lock and acquiring @namespace_sem. For the !@beneath case @mnt
* being unmounted would be detected later by e.g., calling
* check_mnt(mnt) in the function it's called from. For the @beneath
* case however, it's useful to detect it directly in do_lock_mount().
* If @mnt hasn't been unmounted then @mnt->mnt_mountpoint still points
* to @mnt->mnt_mp->m_dentry. But if @mnt has been unmounted it will
* point to @mnt->mnt_root and @mnt->mnt_mp will be NULL.
*
* Return: Either the target mountpoint on the top mount or the top
* mount's mountpoint.
*/
static struct mountpoint *do_lock_mount(struct path *path, bool beneath)
{
struct vfsmount *mnt = path->mnt;
struct dentry *dentry;
struct mountpoint *mp = ERR_PTR(-ENOENT);
for (;;) {
struct mount *m;
if (beneath) {
m = real_mount(mnt);
read_seqlock_excl(&mount_lock);
dentry = dget(m->mnt_mountpoint);
read_sequnlock_excl(&mount_lock);
} else {
dentry = path->dentry;
}
inode_lock(dentry->d_inode);
if (unlikely(cant_mount(dentry))) {
inode_unlock(dentry->d_inode);
goto out;
}
namespace_lock();
if (beneath && (!is_mounted(mnt) || m->mnt_mountpoint != dentry)) {
namespace_unlock();
inode_unlock(dentry->d_inode);
goto out;
}
mnt = lookup_mnt(path);
if (likely(!mnt))
break;
namespace_unlock();
inode_unlock(dentry->d_inode);
if (beneath)
dput(dentry);
path_put(path);
path->mnt = mnt;
path->dentry = dget(mnt->mnt_root);
}
mp = get_mountpoint(dentry);
if (IS_ERR(mp)) {
namespace_unlock();
inode_unlock(dentry->d_inode);
}
out:
if (beneath)
dput(dentry);
return mp;
}
static inline struct mountpoint *lock_mount(struct path *path)
{
return do_lock_mount(path, false);
}
static void unlock_mount(struct mountpoint *where)
{
struct dentry *dentry = where->m_dentry;
read_seqlock_excl(&mount_lock);
put_mountpoint(where);
read_sequnlock_excl(&mount_lock);
namespace_unlock();
inode_unlock(dentry->d_inode);
}
static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
{
if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
return -EINVAL;
if (d_is_dir(mp->m_dentry) !=
d_is_dir(mnt->mnt.mnt_root))
return -ENOTDIR;
return attach_recursive_mnt(mnt, p, mp, 0);
}
/*
* Sanity check the flags to change_mnt_propagation.
*/
static int flags_to_propagation_type(int ms_flags)
{
int type = ms_flags & ~(MS_REC | MS_SILENT);
/* Fail if any non-propagation flags are set */
if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
return 0;
/* Only one propagation flag should be set */
if (!is_power_of_2(type))
return 0;
return type;
}
/*
* recursively change the type of the mountpoint.
*/
static int do_change_type(struct path *path, int ms_flags)
{
struct mount *m;
struct mount *mnt = real_mount(path->mnt);
int recurse = ms_flags & MS_REC;
int type;
int err = 0;
if (!path_mounted(path))
return -EINVAL;
type = flags_to_propagation_type(ms_flags);
if (!type)
return -EINVAL;
namespace_lock();
if (type == MS_SHARED) {
err = invent_group_ids(mnt, recurse);
if (err)
goto out_unlock;
}
lock_mount_hash();
for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
change_mnt_propagation(m, type);
unlock_mount_hash();
out_unlock:
namespace_unlock();
return err;
}
static struct mount *__do_loopback(struct path *old_path, int recurse)
{
struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
if (IS_MNT_UNBINDABLE(old))
return mnt;
if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
return mnt;
if (!recurse && has_locked_children(old, old_path->dentry))
return mnt;
if (recurse)
mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
else
mnt = clone_mnt(old, old_path->dentry, 0);
if (!IS_ERR(mnt))
mnt->mnt.mnt_flags &= ~MNT_LOCKED;
return mnt;
}
/*
* do loopback mount.
*/
static int do_loopback(struct path *path, const char *old_name,
int recurse)
{
struct path old_path;
struct mount *mnt = NULL, *parent;
struct mountpoint *mp;
int err;
if (!old_name || !*old_name)
return -EINVAL;
err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
if (err)
return err;
err = -EINVAL;
if (mnt_ns_loop(old_path.dentry))
goto out;
mp = lock_mount(path);
if (IS_ERR(mp)) {
err = PTR_ERR(mp);
goto out;
}
parent = real_mount(path->mnt);
if (!check_mnt(parent))
goto out2;
mnt = __do_loopback(&old_path, recurse);
if (IS_ERR(mnt)) {
err = PTR_ERR(mnt);
goto out2;
}
err = graft_tree(mnt, parent, mp);
if (err) {
lock_mount_hash();
umount_tree(mnt, UMOUNT_SYNC);
unlock_mount_hash();
}
out2:
unlock_mount(mp);
out:
path_put(&old_path);
return err;
}
static struct file *open_detached_copy(struct path *path, bool recursive)
{
struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
struct mount *mnt, *p;
struct file *file;
if (IS_ERR(ns))
return ERR_CAST(ns);
namespace_lock();
mnt = __do_loopback(path, recursive);
if (IS_ERR(mnt)) {
namespace_unlock();
free_mnt_ns(ns);
return ERR_CAST(mnt);
}
lock_mount_hash();
for (p = mnt; p; p = next_mnt(p, mnt)) {
mnt_add_to_ns(ns, p);
ns->nr_mounts++;
}
ns->root = mnt;
mntget(&mnt->mnt);
unlock_mount_hash();
namespace_unlock();
mntput(path->mnt);
path->mnt = &mnt->mnt;
file = dentry_open(path, O_PATH, current_cred());
if (IS_ERR(file))
dissolve_on_fput(path->mnt);
else
file->f_mode |= FMODE_NEED_UNMOUNT;
return file;
}
SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
{
struct file *file;
struct path path;
int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
bool detached = flags & OPEN_TREE_CLONE;
int error;
int fd;
BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
OPEN_TREE_CLOEXEC))
return -EINVAL;
if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
return -EINVAL;
if (flags & AT_NO_AUTOMOUNT)
lookup_flags &= ~LOOKUP_AUTOMOUNT;
if (flags & AT_SYMLINK_NOFOLLOW)
lookup_flags &= ~LOOKUP_FOLLOW;
if (flags & AT_EMPTY_PATH)
lookup_flags |= LOOKUP_EMPTY;
if (detached && !may_mount())
return -EPERM;
fd = get_unused_fd_flags(flags & O_CLOEXEC);
if (fd < 0)
return fd;
error = user_path_at(dfd, filename, lookup_flags, &path);
if (unlikely(error)) {
file = ERR_PTR(error);
} else {
if (detached)
file = open_detached_copy(&path, flags & AT_RECURSIVE);
else
file = dentry_open(&path, O_PATH, current_cred());
path_put(&path);
}
if (IS_ERR(file)) {
put_unused_fd(fd);
return PTR_ERR(file);
}
fd_install(fd, file);
return fd;
}
/*
* Don't allow locked mount flags to be cleared.
*
* No locks need to be held here while testing the various MNT_LOCK
* flags because those flags can never be cleared once they are set.
*/
static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
{
unsigned int fl = mnt->mnt.mnt_flags;
if ((fl & MNT_LOCK_READONLY) &&
!(mnt_flags & MNT_READONLY))
return false;
if ((fl & MNT_LOCK_NODEV) &&
!(mnt_flags & MNT_NODEV))
return false;
if ((fl & MNT_LOCK_NOSUID) &&
!(mnt_flags & MNT_NOSUID))
return false;
if ((fl & MNT_LOCK_NOEXEC) &&
!(mnt_flags & MNT_NOEXEC))
return false;
if ((fl & MNT_LOCK_ATIME) &&
((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
return false;
return true;
}
static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
{
bool readonly_request = (mnt_flags & MNT_READONLY);
if (readonly_request == __mnt_is_readonly(&mnt->mnt))
return 0;
if (readonly_request)
return mnt_make_readonly(mnt);
mnt->mnt.mnt_flags &= ~MNT_READONLY;
return 0;
}
static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
{
mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
mnt->mnt.mnt_flags = mnt_flags;
touch_mnt_namespace(mnt->mnt_ns);
}
static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
{
struct super_block *sb = mnt->mnt_sb;
if (!__mnt_is_readonly(mnt) &&
(!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) &&
(ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
char *buf, *mntpath;
buf = (char *)__get_free_page(GFP_KERNEL);
if (buf)
mntpath = d_path(mountpoint, buf, PAGE_SIZE);
else
mntpath = ERR_PTR(-ENOMEM);
if (IS_ERR(mntpath))
mntpath = "(unknown)";
pr_warn("%s filesystem being %s at %s supports timestamps until %ptTd (0x%llx)\n",
sb->s_type->name,
is_mounted(mnt) ? "remounted" : "mounted",
mntpath, &sb->s_time_max,
(unsigned long long)sb->s_time_max);
sb->s_iflags |= SB_I_TS_EXPIRY_WARNED;
if (buf)
free_page((unsigned long)buf);
}
}
/*
* Handle reconfiguration of the mountpoint only without alteration of the
* superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
* to mount(2).
*/
static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
{
struct super_block *sb = path->mnt->mnt_sb;
struct mount *mnt = real_mount(path->mnt);
int ret;
if (!check_mnt(mnt))
return -EINVAL;
if (!path_mounted(path))
return -EINVAL;
if (!can_change_locked_flags(mnt, mnt_flags))
return -EPERM;
/*
* We're only checking whether the superblock is read-only not
* changing it, so only take down_read(&sb->s_umount).
*/
down_read(&sb->s_umount);
lock_mount_hash();
ret = change_mount_ro_state(mnt, mnt_flags);
if (ret == 0)
set_mount_attributes(mnt, mnt_flags);
unlock_mount_hash();
up_read(&sb->s_umount);
mnt_warn_timestamp_expiry(path, &mnt->mnt);
return ret;
}
/*
* change filesystem flags. dir should be a physical root of filesystem.
* If you've mounted a non-root directory somewhere and want to do remount
* on it - tough luck.
*/
static int do_remount(struct path *path, int ms_flags, int sb_flags,
int mnt_flags, void *data)
{
int err;
struct super_block *sb = path->mnt->mnt_sb;
struct mount *mnt = real_mount(path->mnt);
struct fs_context *fc;
if (!check_mnt(mnt))
return -EINVAL;
if (!path_mounted(path))
return -EINVAL;
if (!can_change_locked_flags(mnt, mnt_flags))
return -EPERM;
fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK);
if (IS_ERR(fc))
return PTR_ERR(fc);
/*
* Indicate to the filesystem that the remount request is coming
* from the legacy mount system call.
*/
fc->oldapi = true;
err = parse_monolithic_mount_data(fc, data);
if (!err) {
down_write(&sb->s_umount);
err = -EPERM;
if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
err = reconfigure_super(fc);
if (!err) {
lock_mount_hash();
set_mount_attributes(mnt, mnt_flags);
unlock_mount_hash();
}
}
up_write(&sb->s_umount);
}
mnt_warn_timestamp_expiry(path, &mnt->mnt);
put_fs_context(fc);
return err;
}
static inline int tree_contains_unbindable(struct mount *mnt)
{
struct mount *p;
for (p = mnt; p; p = next_mnt(p, mnt)) {
if (IS_MNT_UNBINDABLE(p))
return 1;
}
return 0;
}
/*
* Check that there aren't references to earlier/same mount namespaces in the
* specified subtree. Such references can act as pins for mount namespaces
* that aren't checked by the mount-cycle checking code, thereby allowing
* cycles to be made.
*/
static bool check_for_nsfs_mounts(struct mount *subtree)
{
struct mount *p;
bool ret = false;
lock_mount_hash();
for (p = subtree; p; p = next_mnt(p, subtree))
if (mnt_ns_loop(p->mnt.mnt_root))
goto out;
ret = true;
out:
unlock_mount_hash();
return ret;
}
static int do_set_group(struct path *from_path, struct path *to_path)
{
struct mount *from, *to;
int err;
from = real_mount(from_path->mnt);
to = real_mount(to_path->mnt);
namespace_lock();
err = -EINVAL;
/* To and From must be mounted */
if (!is_mounted(&from->mnt))
goto out;
if (!is_mounted(&to->mnt))
goto out;
err = -EPERM;
/* We should be allowed to modify mount namespaces of both mounts */
if (!ns_capable(from->mnt_ns->user_ns, CAP_SYS_ADMIN))
goto out;
if (!ns_capable(to->mnt_ns->user_ns, CAP_SYS_ADMIN))
goto out;
err = -EINVAL;
/* To and From paths should be mount roots */
if (!path_mounted(from_path))
goto out;
if (!path_mounted(to_path))
goto out;
/* Setting sharing groups is only allowed across same superblock */
if (from->mnt.mnt_sb != to->mnt.mnt_sb)
goto out;
/* From mount root should be wider than To mount root */
if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root))
goto out;
/* From mount should not have locked children in place of To's root */
if (has_locked_children(from, to->mnt.mnt_root))
goto out;
/* Setting sharing groups is only allowed on private mounts */
if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to))
goto out;
/* From should not be private */
if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from))
goto out;
if (IS_MNT_SLAVE(from)) {
struct mount *m = from->mnt_master;
list_add(&to->mnt_slave, &m->mnt_slave_list);
to->mnt_master = m;
}
if (IS_MNT_SHARED(from)) {
to->mnt_group_id = from->mnt_group_id;
list_add(&to->mnt_share, &from->mnt_share);
lock_mount_hash();
set_mnt_shared(to);
unlock_mount_hash();
}
err = 0;
out:
namespace_unlock();
return err;
}
/**
* path_overmounted - check if path is overmounted
* @path: path to check
*
* Check if path is overmounted, i.e., if there's a mount on top of
* @path->mnt with @path->dentry as mountpoint.
*
* Context: This function expects namespace_lock() to be held.
* Return: If path is overmounted true is returned, false if not.
*/
static inline bool path_overmounted(const struct path *path)
{
rcu_read_lock();
if (unlikely(__lookup_mnt(path->mnt, path->dentry))) {
rcu_read_unlock();
return true;
}
rcu_read_unlock();
return false;
}
/**
* can_move_mount_beneath - check that we can mount beneath the top mount
* @from: mount to mount beneath
* @to: mount under which to mount
* @mp: mountpoint of @to
*
* - Make sure that @to->dentry is actually the root of a mount under
* which we can mount another mount.
* - Make sure that nothing can be mounted beneath the caller's current
* root or the rootfs of the namespace.
* - Make sure that the caller can unmount the topmost mount ensuring
* that the caller could reveal the underlying mountpoint.
* - Ensure that nothing has been mounted on top of @from before we
* grabbed @namespace_sem to avoid creating pointless shadow mounts.
* - Prevent mounting beneath a mount if the propagation relationship
* between the source mount, parent mount, and top mount would lead to
* nonsensical mount trees.
*
* Context: This function expects namespace_lock() to be held.
* Return: On success 0, and on error a negative error code is returned.
*/
static int can_move_mount_beneath(const struct path *from,
const struct path *to,
const struct mountpoint *mp)
{
struct mount *mnt_from = real_mount(from->mnt),
*mnt_to = real_mount(to->mnt),
*parent_mnt_to = mnt_to->mnt_parent;
if (!mnt_has_parent(mnt_to))
return -EINVAL;
if (!path_mounted(to))
return -EINVAL;
if (IS_MNT_LOCKED(mnt_to))
return -EINVAL;
/* Avoid creating shadow mounts during mount propagation. */
if (path_overmounted(from))
return -EINVAL;
/*
* Mounting beneath the rootfs only makes sense when the
* semantics of pivot_root(".", ".") are used.
*/
if (&mnt_to->mnt == current->fs->root.mnt)
return -EINVAL;
if (parent_mnt_to == current->nsproxy->mnt_ns->root)
return -EINVAL;
for (struct mount *p = mnt_from; mnt_has_parent(p); p = p->mnt_parent)
if (p == mnt_to)
return -EINVAL;
/*
* If the parent mount propagates to the child mount this would
* mean mounting @mnt_from on @mnt_to->mnt_parent and then
* propagating a copy @c of @mnt_from on top of @mnt_to. This
* defeats the whole purpose of mounting beneath another mount.
*/
if (propagation_would_overmount(parent_mnt_to, mnt_to, mp))
return -EINVAL;
/*
* If @mnt_to->mnt_parent propagates to @mnt_from this would
* mean propagating a copy @c of @mnt_from on top of @mnt_from.
* Afterwards @mnt_from would be mounted on top of
* @mnt_to->mnt_parent and @mnt_to would be unmounted from
* @mnt->mnt_parent and remounted on @mnt_from. But since @c is
* already mounted on @mnt_from, @mnt_to would ultimately be
* remounted on top of @c. Afterwards, @mnt_from would be
* covered by a copy @c of @mnt_from and @c would be covered by
* @mnt_from itself. This defeats the whole purpose of mounting
* @mnt_from beneath @mnt_to.
*/
if (propagation_would_overmount(parent_mnt_to, mnt_from, mp))
return -EINVAL;
return 0;
}
static int do_move_mount(struct path *old_path, struct path *new_path,
bool beneath)
{
struct mnt_namespace *ns;
struct mount *p;
struct mount *old;
struct mount *parent;
struct mountpoint *mp, *old_mp;
int err;
bool attached;
enum mnt_tree_flags_t flags = 0;
mp = do_lock_mount(new_path, beneath);
if (IS_ERR(mp))
return PTR_ERR(mp);
old = real_mount(old_path->mnt);
p = real_mount(new_path->mnt);
parent = old->mnt_parent;
attached = mnt_has_parent(old);
if (attached)
flags |= MNT_TREE_MOVE;
old_mp = old->mnt_mp;
ns = old->mnt_ns;
err = -EINVAL;
/* The mountpoint must be in our namespace. */
if (!check_mnt(p))
goto out;
/* The thing moved must be mounted... */
if (!is_mounted(&old->mnt))
goto out;
/* ... and either ours or the root of anon namespace */
if (!(attached ? check_mnt(old) : is_anon_ns(ns)))
goto out;
if (old->mnt.mnt_flags & MNT_LOCKED)
goto out;
if (!path_mounted(old_path))
goto out;
if (d_is_dir(new_path->dentry) !=
d_is_dir(old_path->dentry))
goto out;
/*
* Don't move a mount residing in a shared parent.
*/
if (attached && IS_MNT_SHARED(parent))
goto out;
if (beneath) {
err = can_move_mount_beneath(old_path, new_path, mp);
if (err)
goto out;
err = -EINVAL;
p = p->mnt_parent;
flags |= MNT_TREE_BENEATH;
}
/*
* Don't move a mount tree containing unbindable mounts to a destination
* mount which is shared.
*/
if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
goto out;
err = -ELOOP;
if (!check_for_nsfs_mounts(old))
goto out;
for (; mnt_has_parent(p); p = p->mnt_parent)
if (p == old)
goto out;
err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, flags);
if (err)
goto out;
/* if the mount is moved, it should no longer be expire
* automatically */
list_del_init(&old->mnt_expire);
if (attached)
put_mountpoint(old_mp);
out:
unlock_mount(mp);
if (!err) {
if (attached)
mntput_no_expire(parent);
else
free_mnt_ns(ns);
}
return err;
}
static int do_move_mount_old(struct path *path, const char *old_name)
{
struct path old_path;
int err;
if (!old_name || !*old_name)
return -EINVAL;
err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
if (err)
return err;
err = do_move_mount(&old_path, path, false);
path_put(&old_path);
return err;
}
/*
* add a mount into a namespace's mount tree
*/
static int do_add_mount(struct mount *newmnt, struct mountpoint *mp,
const struct path *path, int mnt_flags)
{
struct mount *parent = real_mount(path->mnt);
mnt_flags &= ~MNT_INTERNAL_FLAGS;
if (unlikely(!check_mnt(parent))) {
/* that's acceptable only for automounts done in private ns */
if (!(mnt_flags & MNT_SHRINKABLE))
return -EINVAL;
/* ... and for those we'd better have mountpoint still alive */
if (!parent->mnt_ns)
return -EINVAL;
}
/* Refuse the same filesystem on the same mount point */
if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path_mounted(path))
return -EBUSY;
if (d_is_symlink(newmnt->mnt.mnt_root))
return -EINVAL;
newmnt->mnt.mnt_flags = mnt_flags;
return graft_tree(newmnt, parent, mp);
}
static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
/*
* Create a new mount using a superblock configuration and request it
* be added to the namespace tree.
*/
static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
unsigned int mnt_flags)
{
struct vfsmount *mnt;
struct mountpoint *mp;
struct super_block *sb = fc->root->d_sb;
int error;
error = security_sb_kern_mount(sb);
if (!error && mount_too_revealing(sb, &mnt_flags))
error = -EPERM;
if (unlikely(error)) {
fc_drop_locked(fc);
return error;
}
up_write(&sb->s_umount);
mnt = vfs_create_mount(fc);
if (IS_ERR(mnt))
return PTR_ERR(mnt);
mnt_warn_timestamp_expiry(mountpoint, mnt);
mp = lock_mount(mountpoint);
if (IS_ERR(mp)) {
mntput(mnt);
return PTR_ERR(mp);
}
error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags);
unlock_mount(mp);
if (error < 0)
mntput(mnt);
return error;
}
/*
* create a new mount for userspace and request it to be added into the
* namespace's tree
*/
static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
int mnt_flags, const char *name, void *data)
{
struct file_system_type *type;
struct fs_context *fc;
const char *subtype = NULL;
int err = 0;
if (!fstype)
return -EINVAL;
type = get_fs_type(fstype);
if (!type)
return -ENODEV;
if (type->fs_flags & FS_HAS_SUBTYPE) {
subtype = strchr(fstype, '.');
if (subtype) {
subtype++;
if (!*subtype) {
put_filesystem(type);
return -EINVAL;
}
}
}
fc = fs_context_for_mount(type, sb_flags);
put_filesystem(type);
if (IS_ERR(fc))
return PTR_ERR(fc);
/*
* Indicate to the filesystem that the mount request is coming
* from the legacy mount system call.
*/
fc->oldapi = true;
if (subtype)
err = vfs_parse_fs_string(fc, "subtype",
subtype, strlen(subtype));
if (!err && name)
err = vfs_parse_fs_string(fc, "source", name, strlen(name));
if (!err)
err = parse_monolithic_mount_data(fc, data);
if (!err && !mount_capable(fc))
err = -EPERM;
if (!err)
err = vfs_get_tree(fc);
if (!err)
err = do_new_mount_fc(fc, path, mnt_flags);
put_fs_context(fc);
return err;
}
int finish_automount(struct vfsmount *m, const struct path *path)
{
struct dentry *dentry = path->dentry;
struct mountpoint *mp;
struct mount *mnt;
int err;
if (!m)
return 0;
if (IS_ERR(m))
return PTR_ERR(m);
mnt = real_mount(m);
/* The new mount record should have at least 2 refs to prevent it being
* expired before we get a chance to add it
*/
BUG_ON(mnt_get_count(mnt) < 2);
if (m->mnt_sb == path->mnt->mnt_sb &&
m->mnt_root == dentry) {
err = -ELOOP;
goto discard;
}
/*
* we don't want to use lock_mount() - in this case finding something
* that overmounts our mountpoint to be means "quitely drop what we've
* got", not "try to mount it on top".
*/
inode_lock(dentry->d_inode);
namespace_lock();
if (unlikely(cant_mount(dentry))) {
err = -ENOENT;
goto discard_locked;
}
if (path_overmounted(path)) {
err = 0;
goto discard_locked;
}
mp = get_mountpoint(dentry);
if (IS_ERR(mp)) {
err = PTR_ERR(mp);
goto discard_locked;
}
err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
unlock_mount(mp);
if (unlikely(err))
goto discard;
mntput(m);
return 0;
discard_locked:
namespace_unlock();
inode_unlock(dentry->d_inode);
discard:
/* remove m from any expiration list it may be on */
if (!list_empty(&mnt->mnt_expire)) {
namespace_lock();
list_del_init(&mnt->mnt_expire);
namespace_unlock();
}
mntput(m);
mntput(m);
return err;
}
/**
* mnt_set_expiry - Put a mount on an expiration list
* @mnt: The mount to list.
* @expiry_list: The list to add the mount to.
*/
void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
{
namespace_lock();
list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
namespace_unlock();
}
EXPORT_SYMBOL(mnt_set_expiry);
/*
* process a list of expirable mountpoints with the intent of discarding any
* mountpoints that aren't in use and haven't been touched since last we came
* here
*/
void mark_mounts_for_expiry(struct list_head *mounts)
{
struct mount *mnt, *next;
LIST_HEAD(graveyard);
if (list_empty(mounts))
return;
namespace_lock();
lock_mount_hash();
/* extract from the expiration list every vfsmount that matches the
* following criteria:
* - only referenced by its parent vfsmount
* - still marked for expiry (marked on the last call here; marks are
* cleared by mntput())
*/
list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
if (!xchg(&mnt->mnt_expiry_mark, 1) ||
propagate_mount_busy(mnt, 1))
continue;
list_move(&mnt->mnt_expire, &graveyard);
}
while (!list_empty(&graveyard)) {
mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
touch_mnt_namespace(mnt->mnt_ns);
umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
}
unlock_mount_hash();
namespace_unlock();
}
EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
/*
* Ripoff of 'select_parent()'
*
* search the list of submounts for a given mountpoint, and move any
* shrinkable submounts to the 'graveyard' list.
*/
static int select_submounts(struct mount *parent, struct list_head *graveyard)
{
struct mount *this_parent = parent;
struct list_head *next;
int found = 0;
repeat:
next = this_parent->mnt_mounts.next;
resume:
while (next != &this_parent->mnt_mounts) {
struct list_head *tmp = next;
struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
next = tmp->next;
if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
continue;
/*
* Descend a level if the d_mounts list is non-empty.
*/
if (!list_empty(&mnt->mnt_mounts)) {
this_parent = mnt;
goto repeat;
}
if (!propagate_mount_busy(mnt, 1)) {
list_move_tail(&mnt->mnt_expire, graveyard);
found++;
}
}
/*
* All done at this level ... ascend and resume the search
*/
if (this_parent != parent) {
next = this_parent->mnt_child.next;
this_parent = this_parent->mnt_parent;
goto resume;
}
return found;
}
/*
* process a list of expirable mountpoints with the intent of discarding any
* submounts of a specific parent mountpoint
*
* mount_lock must be held for write
*/
static void shrink_submounts(struct mount *mnt)
{
LIST_HEAD(graveyard);
struct mount *m;
/* extract submounts of 'mountpoint' from the expiration list */
while (select_submounts(mnt, &graveyard)) {
while (!list_empty(&graveyard)) {
m = list_first_entry(&graveyard, struct mount,
mnt_expire);
touch_mnt_namespace(m->mnt_ns);
umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
}
}
}
static void *copy_mount_options(const void __user * data)
{
char *copy;
unsigned left, offset;
if (!data)
return NULL;
copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!copy)
return ERR_PTR(-ENOMEM);
left = copy_from_user(copy, data, PAGE_SIZE);
/*
* Not all architectures have an exact copy_from_user(). Resort to
* byte at a time.
*/
offset = PAGE_SIZE - left;
while (left) {
char c;
if (get_user(c, (const char __user *)data + offset))
break;
copy[offset] = c;
left--;
offset++;
}
if (left == PAGE_SIZE) {
kfree(copy);
return ERR_PTR(-EFAULT);
}
return copy;
}
static char *copy_mount_string(const void __user *data)
{
return data ? strndup_user(data, PATH_MAX) : NULL;
}
/*
* Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
* be given to the mount() call (ie: read-only, no-dev, no-suid etc).
*
* data is a (void *) that can point to any structure up to
* PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
* information (or be NULL).
*
* Pre-0.97 versions of mount() didn't have a flags word.
* When the flags word was introduced its top half was required
* to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
* Therefore, if this magic number is present, it carries no information
* and must be discarded.
*/
int path_mount(const char *dev_name, struct path *path,
const char *type_page, unsigned long flags, void *data_page)
{
unsigned int mnt_flags = 0, sb_flags;
int ret;
/* Discard magic */
if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
flags &= ~MS_MGC_MSK;
/* Basic sanity checks */
if (data_page)
((char *)data_page)[PAGE_SIZE - 1] = 0;
if (flags & MS_NOUSER)
return -EINVAL;
ret = security_sb_mount(dev_name, path, type_page, flags, data_page);
if (ret)
return ret;
if (!may_mount())
return -EPERM;
if (flags & SB_MANDLOCK)
warn_mandlock();
/* Default to relatime unless overriden */
if (!(flags & MS_NOATIME))
mnt_flags |= MNT_RELATIME;
/* Separate the per-mountpoint flags */
if (flags & MS_NOSUID)
mnt_flags |= MNT_NOSUID;
if (flags & MS_NODEV)
mnt_flags |= MNT_NODEV;
if (flags & MS_NOEXEC)
mnt_flags |= MNT_NOEXEC;
if (flags & MS_NOATIME)
mnt_flags |= MNT_NOATIME;
if (flags & MS_NODIRATIME)
mnt_flags |= MNT_NODIRATIME;
if (flags & MS_STRICTATIME)
mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
if (flags & MS_RDONLY)
mnt_flags |= MNT_READONLY;
if (flags & MS_NOSYMFOLLOW)
mnt_flags |= MNT_NOSYMFOLLOW;
/* The default atime for remount is preservation */
if ((flags & MS_REMOUNT) &&
((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
MS_STRICTATIME)) == 0)) {
mnt_flags &= ~MNT_ATIME_MASK;
mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK;
}
sb_flags = flags & (SB_RDONLY |
SB_SYNCHRONOUS |
SB_MANDLOCK |
SB_DIRSYNC |
SB_SILENT |
SB_POSIXACL |
SB_LAZYTIME |
SB_I_VERSION);
if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
return do_reconfigure_mnt(path, mnt_flags);
if (flags & MS_REMOUNT)
return do_remount(path, flags, sb_flags, mnt_flags, data_page);
if (flags & MS_BIND)
return do_loopback(path, dev_name, flags & MS_REC);
if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
return do_change_type(path, flags);
if (flags & MS_MOVE)
return do_move_mount_old(path, dev_name);
return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name,
data_page);
}
long do_mount(const char *dev_name, const char __user *dir_name,
const char *type_page, unsigned long flags, void *data_page)
{
struct path path;
int ret;
ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path);
if (ret)
return ret;
ret = path_mount(dev_name, &path, type_page, flags, data_page);
path_put(&path);
return ret;
}
static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
{
return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
}
static void dec_mnt_namespaces(struct ucounts *ucounts)
{
dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
}
static void free_mnt_ns(struct mnt_namespace *ns)
{
if (!is_anon_ns(ns))
ns_free_inum(&ns->ns);
dec_mnt_namespaces(ns->ucounts);
mnt_ns_tree_remove(ns);
}
/*
* Assign a sequence number so we can detect when we attempt to bind
* mount a reference to an older mount namespace into the current
* mount namespace, preventing reference counting loops. A 64bit
* number incrementing at 10Ghz will take 12,427 years to wrap which
* is effectively never, so we can ignore the possibility.
*/
static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
{
struct mnt_namespace *new_ns;
struct ucounts *ucounts;
int ret;
ucounts = inc_mnt_namespaces(user_ns);
if (!ucounts)
return ERR_PTR(-ENOSPC);
new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL_ACCOUNT);
if (!new_ns) {
dec_mnt_namespaces(ucounts);
return ERR_PTR(-ENOMEM);
}
if (!anon) {
ret = ns_alloc_inum(&new_ns->ns);
if (ret) {
kfree(new_ns);
dec_mnt_namespaces(ucounts);
return ERR_PTR(ret);
}
}
new_ns->ns.ops = &mntns_operations;
if (!anon)
new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
refcount_set(&new_ns->ns.count, 1);
refcount_set(&new_ns->passive, 1);
new_ns->mounts = RB_ROOT;
RB_CLEAR_NODE(&new_ns->mnt_ns_tree_node);
init_waitqueue_head(&new_ns->poll);
new_ns->user_ns = get_user_ns(user_ns);
new_ns->ucounts = ucounts;
return new_ns;
}
__latent_entropy
struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
struct user_namespace *user_ns, struct fs_struct *new_fs)
{
struct mnt_namespace *new_ns;
struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
struct mount *p, *q;
struct mount *old;
struct mount *new;
int copy_flags;
BUG_ON(!ns);
if (likely(!(flags & CLONE_NEWNS))) {
get_mnt_ns(ns);
return ns;
}
old = ns->root;
new_ns = alloc_mnt_ns(user_ns, false);
if (IS_ERR(new_ns))
return new_ns;
namespace_lock();
/* First pass: copy the tree topology */
copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
if (user_ns != ns->user_ns)
copy_flags |= CL_SHARED_TO_SLAVE;
new = copy_tree(old, old->mnt.mnt_root, copy_flags);
if (IS_ERR(new)) {
namespace_unlock();
free_mnt_ns(new_ns);
return ERR_CAST(new);
}
if (user_ns != ns->user_ns) {
lock_mount_hash();
lock_mnt_tree(new);
unlock_mount_hash();
}
new_ns->root = new;
/*
* Second pass: switch the tsk->fs->* elements and mark new vfsmounts
* as belonging to new namespace. We have already acquired a private
* fs_struct, so tsk->fs->lock is not needed.
*/
p = old;
q = new;
while (p) {
mnt_add_to_ns(new_ns, q);
new_ns->nr_mounts++;
if (new_fs) {
if (&p->mnt == new_fs->root.mnt) {
new_fs->root.mnt = mntget(&q->mnt);
rootmnt = &p->mnt;
}
if (&p->mnt == new_fs->pwd.mnt) {
new_fs->pwd.mnt = mntget(&q->mnt);
pwdmnt = &p->mnt;
}
}
p = next_mnt(p, old);
q = next_mnt(q, new);
if (!q)
break;
// an mntns binding we'd skipped?
while (p->mnt.mnt_root != q->mnt.mnt_root)
p = next_mnt(skip_mnt_tree(p), old);
}
mnt_ns_tree_add(new_ns);
namespace_unlock();
if (rootmnt)
mntput(rootmnt);
if (pwdmnt)
mntput(pwdmnt);
return new_ns;
}
struct dentry *mount_subtree(struct vfsmount *m, const char *name)
{
struct mount *mnt = real_mount(m);
struct mnt_namespace *ns;
struct super_block *s;
struct path path;
int err;
ns = alloc_mnt_ns(&init_user_ns, true);
if (IS_ERR(ns)) {
mntput(m);
return ERR_CAST(ns);
}
ns->root = mnt;
ns->nr_mounts++;
mnt_add_to_ns(ns, mnt);
err = vfs_path_lookup(m->mnt_root, m,
name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
put_mnt_ns(ns);
if (err)
return ERR_PTR(err);
/* trade a vfsmount reference for active sb one */
s = path.mnt->mnt_sb;
atomic_inc(&s->s_active);
mntput(path.mnt);
/* lock the sucker */
down_write(&s->s_umount);
/* ... and return the root of (sub)tree on it */
return path.dentry;
}
EXPORT_SYMBOL(mount_subtree);
SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
char __user *, type, unsigned long, flags, void __user *, data)
{
int ret;
char *kernel_type;
char *kernel_dev;
void *options;
kernel_type = copy_mount_string(type);
ret = PTR_ERR(kernel_type);
if (IS_ERR(kernel_type))
goto out_type;
kernel_dev = copy_mount_string(dev_name);
ret = PTR_ERR(kernel_dev);
if (IS_ERR(kernel_dev))
goto out_dev;
options = copy_mount_options(data);
ret = PTR_ERR(options);
if (IS_ERR(options))
goto out_data;
ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options);
kfree(options);
out_data:
kfree(kernel_dev);
out_dev:
kfree(kernel_type);
out_type:
return ret;
}
#define FSMOUNT_VALID_FLAGS \
(MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
MOUNT_ATTR_NOSYMFOLLOW)
#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
#define MOUNT_SETATTR_PROPAGATION_FLAGS \
(MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
{
unsigned int mnt_flags = 0;
if (attr_flags & MOUNT_ATTR_RDONLY)
mnt_flags |= MNT_READONLY;
if (attr_flags & MOUNT_ATTR_NOSUID)
mnt_flags |= MNT_NOSUID;
if (attr_flags & MOUNT_ATTR_NODEV)
mnt_flags |= MNT_NODEV;
if (attr_flags & MOUNT_ATTR_NOEXEC)
mnt_flags |= MNT_NOEXEC;
if (attr_flags & MOUNT_ATTR_NODIRATIME)
mnt_flags |= MNT_NODIRATIME;
if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW)
mnt_flags |= MNT_NOSYMFOLLOW;
return mnt_flags;
}
/*
* Create a kernel mount representation for a new, prepared superblock
* (specified by fs_fd) and attach to an open_tree-like file descriptor.
*/
SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
unsigned int, attr_flags)
{
struct mnt_namespace *ns;
struct fs_context *fc;
struct file *file;
struct path newmount;
struct mount *mnt;
struct fd f;
unsigned int mnt_flags = 0;
long ret;
if (!may_mount())
return -EPERM;
if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
return -EINVAL;
if (attr_flags & ~FSMOUNT_VALID_FLAGS)
return -EINVAL;
mnt_flags = attr_flags_to_mnt_flags(attr_flags);
switch (attr_flags & MOUNT_ATTR__ATIME) {
case MOUNT_ATTR_STRICTATIME:
break;
case MOUNT_ATTR_NOATIME:
mnt_flags |= MNT_NOATIME;
break;
case MOUNT_ATTR_RELATIME:
mnt_flags |= MNT_RELATIME;
break;
default:
return -EINVAL;
}
f = fdget(fs_fd);
if (!fd_file(f))
return -EBADF;
ret = -EINVAL;
if (fd_file(f)->f_op != &fscontext_fops)
goto err_fsfd;
fc = fd_file(f)->private_data;
ret = mutex_lock_interruptible(&fc->uapi_mutex);
if (ret < 0)
goto err_fsfd;
/* There must be a valid superblock or we can't mount it */
ret = -EINVAL;
if (!fc->root)
goto err_unlock;
ret = -EPERM;
if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
pr_warn("VFS: Mount too revealing\n");
goto err_unlock;
}
ret = -EBUSY;
if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
goto err_unlock;
if (fc->sb_flags & SB_MANDLOCK)
warn_mandlock();
newmount.mnt = vfs_create_mount(fc);
if (IS_ERR(newmount.mnt)) {
ret = PTR_ERR(newmount.mnt);
goto err_unlock;
}
newmount.dentry = dget(fc->root);
newmount.mnt->mnt_flags = mnt_flags;
/* We've done the mount bit - now move the file context into more or
* less the same state as if we'd done an fspick(). We don't want to
* do any memory allocation or anything like that at this point as we
* don't want to have to handle any errors incurred.
*/
vfs_clean_context(fc);
ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
if (IS_ERR(ns)) {
ret = PTR_ERR(ns);
goto err_path;
}
mnt = real_mount(newmount.mnt);
ns->root = mnt;
ns->nr_mounts = 1;
mnt_add_to_ns(ns, mnt);
mntget(newmount.mnt);
/* Attach to an apparent O_PATH fd with a note that we need to unmount
* it, not just simply put it.
*/
file = dentry_open(&newmount, O_PATH, fc->cred);
if (IS_ERR(file)) {
dissolve_on_fput(newmount.mnt);
ret = PTR_ERR(file);
goto err_path;
}
file->f_mode |= FMODE_NEED_UNMOUNT;
ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
if (ret >= 0)
fd_install(ret, file);
else
fput(file);
err_path:
path_put(&newmount);
err_unlock:
mutex_unlock(&fc->uapi_mutex);
err_fsfd:
fdput(f);
return ret;
}
/*
* Move a mount from one place to another. In combination with
* fsopen()/fsmount() this is used to install a new mount and in combination
* with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
* a mount subtree.
*
* Note the flags value is a combination of MOVE_MOUNT_* flags.
*/
SYSCALL_DEFINE5(move_mount,
int, from_dfd, const char __user *, from_pathname,
int, to_dfd, const char __user *, to_pathname,
unsigned int, flags)
{
struct path from_path, to_path;
unsigned int lflags;
int ret = 0;
if (!may_mount())
return -EPERM;
if (flags & ~MOVE_MOUNT__MASK)
return -EINVAL;
if ((flags & (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP)) ==
(MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP))
return -EINVAL;
/* If someone gives a pathname, they aren't permitted to move
* from an fd that requires unmount as we can't get at the flag
* to clear it afterwards.
*/
lflags = 0;
if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
if (ret < 0)
return ret;
lflags = 0;
if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
if (ret < 0)
goto out_from;
ret = security_move_mount(&from_path, &to_path);
if (ret < 0)
goto out_to;
if (flags & MOVE_MOUNT_SET_GROUP)
ret = do_set_group(&from_path, &to_path);
else
ret = do_move_mount(&from_path, &to_path,
(flags & MOVE_MOUNT_BENEATH));
out_to:
path_put(&to_path);
out_from:
path_put(&from_path);
return ret;
}
/*
* Return true if path is reachable from root
*
* namespace_sem or mount_lock is held
*/
bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
const struct path *root)
{
while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
dentry = mnt->mnt_mountpoint;
mnt = mnt->mnt_parent;
}
return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
}
bool path_is_under(const struct path *path1, const struct path *path2)
{
bool res;
read_seqlock_excl(&mount_lock);
res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
read_sequnlock_excl(&mount_lock);
return res;
}
EXPORT_SYMBOL(path_is_under);
/*
* pivot_root Semantics:
* Moves the root file system of the current process to the directory put_old,
* makes new_root as the new root file system of the current process, and sets
* root/cwd of all processes which had them on the current root to new_root.
*
* Restrictions:
* The new_root and put_old must be directories, and must not be on the
* same file system as the current process root. The put_old must be
* underneath new_root, i.e. adding a non-zero number of /.. to the string
* pointed to by put_old must yield the same directory as new_root. No other
* file system may be mounted on put_old. After all, new_root is a mountpoint.
*
* Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
* See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
* in this situation.
*
* Notes:
* - we don't move root/cwd if they are not at the root (reason: if something
* cared enough to change them, it's probably wrong to force them elsewhere)
* - it's okay to pick a root that isn't the root of a file system, e.g.
* /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
* though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
* first.
*/
SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
const char __user *, put_old)
{
struct path new, old, root;
struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
struct mountpoint *old_mp, *root_mp;
int error;
if (!may_mount())
return -EPERM;
error = user_path_at(AT_FDCWD, new_root,
LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new);
if (error)
goto out0;
error = user_path_at(AT_FDCWD, put_old,
LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old);
if (error)
goto out1;
error = security_sb_pivotroot(&old, &new);
if (error)
goto out2;
get_fs_root(current->fs, &root);
old_mp = lock_mount(&old);
error = PTR_ERR(old_mp);
if (IS_ERR(old_mp))
goto out3;
error = -EINVAL;
new_mnt = real_mount(new.mnt);
root_mnt = real_mount(root.mnt);
old_mnt = real_mount(old.mnt);
ex_parent = new_mnt->mnt_parent;
root_parent = root_mnt->mnt_parent;
if (IS_MNT_SHARED(old_mnt) ||
IS_MNT_SHARED(ex_parent) ||
IS_MNT_SHARED(root_parent))
goto out4;
if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
goto out4;
if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
goto out4;
error = -ENOENT;
if (d_unlinked(new.dentry))
goto out4;
error = -EBUSY;
if (new_mnt == root_mnt || old_mnt == root_mnt)
goto out4; /* loop, on the same file system */
error = -EINVAL;
if (!path_mounted(&root))
goto out4; /* not a mountpoint */
if (!mnt_has_parent(root_mnt))
goto out4; /* not attached */
if (!path_mounted(&new))
goto out4; /* not a mountpoint */
if (!mnt_has_parent(new_mnt))
goto out4; /* not attached */
/* make sure we can reach put_old from new_root */
if (!is_path_reachable(old_mnt, old.dentry, &new))
goto out4;
/* make certain new is below the root */
if (!is_path_reachable(new_mnt, new.dentry, &root))
goto out4;
lock_mount_hash();
umount_mnt(new_mnt);
root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */
if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
new_mnt->mnt.mnt_flags |= MNT_LOCKED;
root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
}
/* mount old root on put_old */
attach_mnt(root_mnt, old_mnt, old_mp, false);
/* mount new_root on / */
attach_mnt(new_mnt, root_parent, root_mp, false);
mnt_add_count(root_parent, -1);
touch_mnt_namespace(current->nsproxy->mnt_ns);
/* A moved mount should not expire automatically */
list_del_init(&new_mnt->mnt_expire);
put_mountpoint(root_mp);
unlock_mount_hash();
chroot_fs_refs(&root, &new);
error = 0;
out4:
unlock_mount(old_mp);
if (!error)
mntput_no_expire(ex_parent);
out3:
path_put(&root);
out2:
path_put(&old);
out1:
path_put(&new);
out0:
return error;
}
static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
{
unsigned int flags = mnt->mnt.mnt_flags;
/* flags to clear */
flags &= ~kattr->attr_clr;
/* flags to raise */
flags |= kattr->attr_set;
return flags;
}
static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
{
struct vfsmount *m = &mnt->mnt;
struct user_namespace *fs_userns = m->mnt_sb->s_user_ns;
if (!kattr->mnt_idmap)
return 0;
/*
* Creating an idmapped mount with the filesystem wide idmapping
* doesn't make sense so block that. We don't allow mushy semantics.
*/
if (kattr->mnt_userns == m->mnt_sb->s_user_ns)
return -EINVAL;
/*
* Once a mount has been idmapped we don't allow it to change its
* mapping. It makes things simpler and callers can just create
* another bind-mount they can idmap if they want to.
*/
if (is_idmapped_mnt(m))
return -EPERM;
/* The underlying filesystem doesn't support idmapped mounts yet. */
if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP))
return -EINVAL;
/* The filesystem has turned off idmapped mounts. */
if (m->mnt_sb->s_iflags & SB_I_NOIDMAP)
return -EINVAL;
/* We're not controlling the superblock. */
if (!ns_capable(fs_userns, CAP_SYS_ADMIN))
return -EPERM;
/* Mount has already been visible in the filesystem hierarchy. */
if (!is_anon_ns(mnt->mnt_ns))
return -EINVAL;
return 0;
}
/**
* mnt_allow_writers() - check whether the attribute change allows writers
* @kattr: the new mount attributes
* @mnt: the mount to which @kattr will be applied
*
* Check whether thew new mount attributes in @kattr allow concurrent writers.
*
* Return: true if writers need to be held, false if not
*/
static inline bool mnt_allow_writers(const struct mount_kattr *kattr,
const struct mount *mnt)
{
return (!(kattr->attr_set & MNT_READONLY) ||
(mnt->mnt.mnt_flags & MNT_READONLY)) &&
!kattr->mnt_idmap;
}
static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt)
{
struct mount *m;
int err;
for (m = mnt; m; m = next_mnt(m, mnt)) {
if (!can_change_locked_flags(m, recalc_flags(kattr, m))) {
err = -EPERM;
break;
}
err = can_idmap_mount(kattr, m);
if (err)
break;
if (!mnt_allow_writers(kattr, m)) {
err = mnt_hold_writers(m);
if (err)
break;
}
if (!kattr->recurse)
return 0;
}
if (err) {
struct mount *p;
/*
* If we had to call mnt_hold_writers() MNT_WRITE_HOLD will
* be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all
* mounts and needs to take care to include the first mount.
*/
for (p = mnt; p; p = next_mnt(p, mnt)) {
/* If we had to hold writers unblock them. */
if (p->mnt.mnt_flags & MNT_WRITE_HOLD)
mnt_unhold_writers(p);
/*
* We're done once the first mount we changed got
* MNT_WRITE_HOLD unset.
*/
if (p == m)
break;
}
}
return err;
}
static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
{
if (!kattr->mnt_idmap)
return;
/*
* Pairs with smp_load_acquire() in mnt_idmap().
*
* Since we only allow a mount to change the idmapping once and
* verified this in can_idmap_mount() we know that the mount has
* @nop_mnt_idmap attached to it. So there's no need to drop any
* references.
*/
smp_store_release(&mnt->mnt.mnt_idmap, mnt_idmap_get(kattr->mnt_idmap));
}
static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt)
{
struct mount *m;
for (m = mnt; m; m = next_mnt(m, mnt)) {
unsigned int flags;
do_idmap_mount(kattr, m);
flags = recalc_flags(kattr, m);
WRITE_ONCE(m->mnt.mnt_flags, flags);
/* If we had to hold writers unblock them. */
if (m->mnt.mnt_flags & MNT_WRITE_HOLD)
mnt_unhold_writers(m);
if (kattr->propagation)
change_mnt_propagation(m, kattr->propagation);
if (!kattr->recurse)
break;
}
touch_mnt_namespace(mnt->mnt_ns);
}
static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
{
struct mount *mnt = real_mount(path->mnt);
int err = 0;
if (!path_mounted(path))
return -EINVAL;
if (kattr->mnt_userns) {
struct mnt_idmap *mnt_idmap;
mnt_idmap = alloc_mnt_idmap(kattr->mnt_userns);
if (IS_ERR(mnt_idmap))
return PTR_ERR(mnt_idmap);
kattr->mnt_idmap = mnt_idmap;
}
if (kattr->propagation) {
/*
* Only take namespace_lock() if we're actually changing
* propagation.
*/
namespace_lock();
if (kattr->propagation == MS_SHARED) {
err = invent_group_ids(mnt, kattr->recurse);
if (err) {
namespace_unlock();
return err;
}
}
}
err = -EINVAL;
lock_mount_hash();
/* Ensure that this isn't anything purely vfs internal. */
if (!is_mounted(&mnt->mnt))
goto out;
/*
* If this is an attached mount make sure it's located in the callers
* mount namespace. If it's not don't let the caller interact with it.
*
* If this mount doesn't have a parent it's most often simply a
* detached mount with an anonymous mount namespace. IOW, something
* that's simply not attached yet. But there are apparently also users
* that do change mount properties on the rootfs itself. That obviously
* neither has a parent nor is it a detached mount so we cannot
* unconditionally check for detached mounts.
*/
if ((mnt_has_parent(mnt) || !is_anon_ns(mnt->mnt_ns)) && !check_mnt(mnt))
goto out;
/*
* First, we get the mount tree in a shape where we can change mount
* properties without failure. If we succeeded to do so we commit all
* changes and if we failed we clean up.
*/
err = mount_setattr_prepare(kattr, mnt);
if (!err)
mount_setattr_commit(kattr, mnt);
out:
unlock_mount_hash();
if (kattr->propagation) {
if (err)
cleanup_group_ids(mnt, NULL);
namespace_unlock();
}
return err;
}
static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
struct mount_kattr *kattr, unsigned int flags)
{
int err = 0;
struct ns_common *ns;
struct user_namespace *mnt_userns;
struct fd f;
if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP))
return 0;
/*
* We currently do not support clearing an idmapped mount. If this ever
* is a use-case we can revisit this but for now let's keep it simple
* and not allow it.
*/
if (attr->attr_clr & MOUNT_ATTR_IDMAP)
return -EINVAL;
if (attr->userns_fd > INT_MAX)
return -EINVAL;
f = fdget(attr->userns_fd);
if (!fd_file(f))
return -EBADF;
if (!proc_ns_file(fd_file(f))) {
err = -EINVAL;
goto out_fput;
}
ns = get_proc_ns(file_inode(fd_file(f)));
if (ns->ops->type != CLONE_NEWUSER) {
err = -EINVAL;
goto out_fput;
}
/*
* The initial idmapping cannot be used to create an idmapped
* mount. We use the initial idmapping as an indicator of a mount
* that is not idmapped. It can simply be passed into helpers that
* are aware of idmapped mounts as a convenient shortcut. A user
* can just create a dedicated identity mapping to achieve the same
* result.
*/
mnt_userns = container_of(ns, struct user_namespace, ns);
if (mnt_userns == &init_user_ns) {
err = -EPERM;
goto out_fput;
}
/* We're not controlling the target namespace. */
if (!ns_capable(mnt_userns, CAP_SYS_ADMIN)) {
err = -EPERM;
goto out_fput;
}
kattr->mnt_userns = get_user_ns(mnt_userns);
out_fput:
fdput(f);
return err;
}
static int build_mount_kattr(const struct mount_attr *attr, size_t usize,
struct mount_kattr *kattr, unsigned int flags)
{
unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
if (flags & AT_NO_AUTOMOUNT)
lookup_flags &= ~LOOKUP_AUTOMOUNT;
if (flags & AT_SYMLINK_NOFOLLOW)
lookup_flags &= ~LOOKUP_FOLLOW;
if (flags & AT_EMPTY_PATH)
lookup_flags |= LOOKUP_EMPTY;
*kattr = (struct mount_kattr) {
.lookup_flags = lookup_flags,
.recurse = !!(flags & AT_RECURSIVE),
};
if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS)
return -EINVAL;
if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1)
return -EINVAL;
kattr->propagation = attr->propagation;
if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS)
return -EINVAL;
kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set);
kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr);
/*
* Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
* users wanting to transition to a different atime setting cannot
* simply specify the atime setting in @attr_set, but must also
* specify MOUNT_ATTR__ATIME in the @attr_clr field.
* So ensure that MOUNT_ATTR__ATIME can't be partially set in
* @attr_clr and that @attr_set can't have any atime bits set if
* MOUNT_ATTR__ATIME isn't set in @attr_clr.
*/
if (attr->attr_clr & MOUNT_ATTR__ATIME) {
if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME)
return -EINVAL;
/*
* Clear all previous time settings as they are mutually
* exclusive.
*/
kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME;
switch (attr->attr_set & MOUNT_ATTR__ATIME) {
case MOUNT_ATTR_RELATIME:
kattr->attr_set |= MNT_RELATIME;
break;
case MOUNT_ATTR_NOATIME:
kattr->attr_set |= MNT_NOATIME;
break;
case MOUNT_ATTR_STRICTATIME:
break;
default:
return -EINVAL;
}
} else {
if (attr->attr_set & MOUNT_ATTR__ATIME)
return -EINVAL;
}
return build_mount_idmapped(attr, usize, kattr, flags);
}
static void finish_mount_kattr(struct mount_kattr *kattr)
{
put_user_ns(kattr->mnt_userns);
kattr->mnt_userns = NULL;
if (kattr->mnt_idmap)
mnt_idmap_put(kattr->mnt_idmap);
}
SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
unsigned int, flags, struct mount_attr __user *, uattr,
size_t, usize)
{
int err;
struct path target;
struct mount_attr attr;
struct mount_kattr kattr;
BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0);
if (flags & ~(AT_EMPTY_PATH |
AT_RECURSIVE |
AT_SYMLINK_NOFOLLOW |
AT_NO_AUTOMOUNT))
return -EINVAL;
if (unlikely(usize > PAGE_SIZE))
return -E2BIG;
if (unlikely(usize < MOUNT_ATTR_SIZE_VER0))
return -EINVAL;
if (!may_mount())
return -EPERM;
err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize);
if (err)
return err;
/* Don't bother walking through the mounts if this is a nop. */
if (attr.attr_set == 0 &&
attr.attr_clr == 0 &&
attr.propagation == 0)
return 0;
err = build_mount_kattr(&attr, usize, &kattr, flags);
if (err)
return err;
err = user_path_at(dfd, path, kattr.lookup_flags, &target);
if (!err) {
err = do_mount_setattr(&target, &kattr);
path_put(&target);
}
finish_mount_kattr(&kattr);
return err;
}
int show_path(struct seq_file *m, struct dentry *root)
{
if (root->d_sb->s_op->show_path)
return root->d_sb->s_op->show_path(m, root);
seq_dentry(m, root, " \t\n\\");
return 0;
}
static struct vfsmount *lookup_mnt_in_ns(u64 id, struct mnt_namespace *ns)
{
struct mount *mnt = mnt_find_id_at(ns, id);
if (!mnt || mnt->mnt_id_unique != id)
return NULL;
return &mnt->mnt;
}
struct kstatmount {
struct statmount __user *buf;
size_t bufsize;
struct vfsmount *mnt;
u64 mask;
struct path root;
struct statmount sm;
struct seq_file seq;
};
static u64 mnt_to_attr_flags(struct vfsmount *mnt)
{
unsigned int mnt_flags = READ_ONCE(mnt->mnt_flags);
u64 attr_flags = 0;
if (mnt_flags & MNT_READONLY)
attr_flags |= MOUNT_ATTR_RDONLY;
if (mnt_flags & MNT_NOSUID)
attr_flags |= MOUNT_ATTR_NOSUID;
if (mnt_flags & MNT_NODEV)
attr_flags |= MOUNT_ATTR_NODEV;
if (mnt_flags & MNT_NOEXEC)
attr_flags |= MOUNT_ATTR_NOEXEC;
if (mnt_flags & MNT_NODIRATIME)
attr_flags |= MOUNT_ATTR_NODIRATIME;
if (mnt_flags & MNT_NOSYMFOLLOW)
attr_flags |= MOUNT_ATTR_NOSYMFOLLOW;
if (mnt_flags & MNT_NOATIME)
attr_flags |= MOUNT_ATTR_NOATIME;
else if (mnt_flags & MNT_RELATIME)
attr_flags |= MOUNT_ATTR_RELATIME;
else
attr_flags |= MOUNT_ATTR_STRICTATIME;
if (is_idmapped_mnt(mnt))
attr_flags |= MOUNT_ATTR_IDMAP;
return attr_flags;
}
static u64 mnt_to_propagation_flags(struct mount *m)
{
u64 propagation = 0;
if (IS_MNT_SHARED(m))
propagation |= MS_SHARED;
if (IS_MNT_SLAVE(m))
propagation |= MS_SLAVE;
if (IS_MNT_UNBINDABLE(m))
propagation |= MS_UNBINDABLE;
if (!propagation)
propagation |= MS_PRIVATE;
return propagation;
}
static void statmount_sb_basic(struct kstatmount *s)
{
struct super_block *sb = s->mnt->mnt_sb;
s->sm.mask |= STATMOUNT_SB_BASIC;
s->sm.sb_dev_major = MAJOR(sb->s_dev);
s->sm.sb_dev_minor = MINOR(sb->s_dev);
s->sm.sb_magic = sb->s_magic;
s->sm.sb_flags = sb->s_flags & (SB_RDONLY|SB_SYNCHRONOUS|SB_DIRSYNC|SB_LAZYTIME);
}
static void statmount_mnt_basic(struct kstatmount *s)
{
struct mount *m = real_mount(s->mnt);
s->sm.mask |= STATMOUNT_MNT_BASIC;
s->sm.mnt_id = m->mnt_id_unique;
s->sm.mnt_parent_id = m->mnt_parent->mnt_id_unique;
s->sm.mnt_id_old = m->mnt_id;
s->sm.mnt_parent_id_old = m->mnt_parent->mnt_id;
s->sm.mnt_attr = mnt_to_attr_flags(&m->mnt);
s->sm.mnt_propagation = mnt_to_propagation_flags(m);
s->sm.mnt_peer_group = IS_MNT_SHARED(m) ? m->mnt_group_id : 0;
s->sm.mnt_master = IS_MNT_SLAVE(m) ? m->mnt_master->mnt_group_id : 0;
}
static void statmount_propagate_from(struct kstatmount *s)
{
struct mount *m = real_mount(s->mnt);
s->sm.mask |= STATMOUNT_PROPAGATE_FROM;
if (IS_MNT_SLAVE(m))
s->sm.propagate_from = get_dominating_id(m, ¤t->fs->root);
}
static int statmount_mnt_root(struct kstatmount *s, struct seq_file *seq)
{
int ret;
size_t start = seq->count;
ret = show_path(seq, s->mnt->mnt_root);
if (ret)
return ret;
if (unlikely(seq_has_overflowed(seq)))
return -EAGAIN;
/*
* Unescape the result. It would be better if supplied string was not
* escaped in the first place, but that's a pretty invasive change.
*/
seq->buf[seq->count] = '\0';
seq->count = start;
seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL));
return 0;
}
static int statmount_mnt_point(struct kstatmount *s, struct seq_file *seq)
{
struct vfsmount *mnt = s->mnt;
struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
int err;
err = seq_path_root(seq, &mnt_path, &s->root, "");
return err == SEQ_SKIP ? 0 : err;
}
static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq)
{
struct super_block *sb = s->mnt->mnt_sb;
seq_puts(seq, sb->s_type->name);
return 0;
}
static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns)
{
s->sm.mask |= STATMOUNT_MNT_NS_ID;
s->sm.mnt_ns_id = ns->seq;
}
static int statmount_mnt_opts(struct kstatmount *s, struct seq_file *seq)
{
struct vfsmount *mnt = s->mnt;
struct super_block *sb = mnt->mnt_sb;
int err;
if (sb->s_op->show_options) {
size_t start = seq->count;
err = sb->s_op->show_options(seq, mnt->mnt_root);
if (err)
return err;
if (unlikely(seq_has_overflowed(seq)))
return -EAGAIN;
if (seq->count == start)
return 0;
/* skip leading comma */
memmove(seq->buf + start, seq->buf + start + 1,
seq->count - start - 1);
seq->count--;
}
return 0;
}
static int statmount_string(struct kstatmount *s, u64 flag)
{
int ret;
size_t kbufsize;
struct seq_file *seq = &s->seq;
struct statmount *sm = &s->sm;
switch (flag) {
case STATMOUNT_FS_TYPE:
sm->fs_type = seq->count;
ret = statmount_fs_type(s, seq);
break;
case STATMOUNT_MNT_ROOT:
sm->mnt_root = seq->count;
ret = statmount_mnt_root(s, seq);
break;
case STATMOUNT_MNT_POINT:
sm->mnt_point = seq->count;
ret = statmount_mnt_point(s, seq);
break;
case STATMOUNT_MNT_OPTS:
sm->mnt_opts = seq->count;
ret = statmount_mnt_opts(s, seq);
break;
default:
WARN_ON_ONCE(true);
return -EINVAL;
}
if (unlikely(check_add_overflow(sizeof(*sm), seq->count, &kbufsize)))
return -EOVERFLOW;
if (kbufsize >= s->bufsize)
return -EOVERFLOW;
/* signal a retry */
if (unlikely(seq_has_overflowed(seq)))
return -EAGAIN;
if (ret)
return ret;
seq->buf[seq->count++] = '\0';
sm->mask |= flag;
return 0;
}
static int copy_statmount_to_user(struct kstatmount *s)
{
struct statmount *sm = &s->sm;
struct seq_file *seq = &s->seq;
char __user *str = ((char __user *)s->buf) + sizeof(*sm);
size_t copysize = min_t(size_t, s->bufsize, sizeof(*sm));
if (seq->count && copy_to_user(str, seq->buf, seq->count))
return -EFAULT;
/* Return the number of bytes copied to the buffer */
sm->size = copysize + seq->count;
if (copy_to_user(s->buf, sm, copysize))
return -EFAULT;
return 0;
}
static struct mount *listmnt_next(struct mount *curr, bool reverse)
{
struct rb_node *node;
if (reverse)
node = rb_prev(&curr->mnt_node);
else
node = rb_next(&curr->mnt_node);
return node_to_mount(node);
}
static int grab_requested_root(struct mnt_namespace *ns, struct path *root)
{
struct mount *first, *child;
rwsem_assert_held(&namespace_sem);
/* We're looking at our own ns, just use get_fs_root. */
if (ns == current->nsproxy->mnt_ns) {
get_fs_root(current->fs, root);
return 0;
}
/*
* We have to find the first mount in our ns and use that, however it
* may not exist, so handle that properly.
*/
if (RB_EMPTY_ROOT(&ns->mounts))
return -ENOENT;
first = child = ns->root;
for (;;) {
child = listmnt_next(child, false);
if (!child)
return -ENOENT;
if (child->mnt_parent == first)
break;
}
root->mnt = mntget(&child->mnt);
root->dentry = dget(root->mnt->mnt_root);
return 0;
}
static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
struct mnt_namespace *ns)
{
struct path root __free(path_put) = {};
struct mount *m;
int err;
/* Has the namespace already been emptied? */
if (mnt_ns_id && RB_EMPTY_ROOT(&ns->mounts))
return -ENOENT;
s->mnt = lookup_mnt_in_ns(mnt_id, ns);
if (!s->mnt)
return -ENOENT;
err = grab_requested_root(ns, &root);
if (err)
return err;
/*
* Don't trigger audit denials. We just want to determine what
* mounts to show users.
*/
m = real_mount(s->mnt);
if (!is_path_reachable(m, m->mnt.mnt_root, &root) &&
!ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN))
return -EPERM;
err = security_sb_statfs(s->mnt->mnt_root);
if (err)
return err;
s->root = root;
if (s->mask & STATMOUNT_SB_BASIC)
statmount_sb_basic(s);
if (s->mask & STATMOUNT_MNT_BASIC)
statmount_mnt_basic(s);
if (s->mask & STATMOUNT_PROPAGATE_FROM)
statmount_propagate_from(s);
if (s->mask & STATMOUNT_FS_TYPE)
err = statmount_string(s, STATMOUNT_FS_TYPE);
if (!err && s->mask & STATMOUNT_MNT_ROOT)
err = statmount_string(s, STATMOUNT_MNT_ROOT);
if (!err && s->mask & STATMOUNT_MNT_POINT)
err = statmount_string(s, STATMOUNT_MNT_POINT);
if (!err && s->mask & STATMOUNT_MNT_OPTS)
err = statmount_string(s, STATMOUNT_MNT_OPTS);
if (!err && s->mask & STATMOUNT_MNT_NS_ID)
statmount_mnt_ns_id(s, ns);
if (err)
return err;
return 0;
}
static inline bool retry_statmount(const long ret, size_t *seq_size)
{
if (likely(ret != -EAGAIN))
return false;
if (unlikely(check_mul_overflow(*seq_size, 2, seq_size)))
return false;
if (unlikely(*seq_size > MAX_RW_COUNT))
return false;
return true;
}
#define STATMOUNT_STRING_REQ (STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | \
STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS)
static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
struct statmount __user *buf, size_t bufsize,
size_t seq_size)
{
if (!access_ok(buf, bufsize))
return -EFAULT;
memset(ks, 0, sizeof(*ks));
ks->mask = kreq->param;
ks->buf = buf;
ks->bufsize = bufsize;
if (ks->mask & STATMOUNT_STRING_REQ) {
if (bufsize == sizeof(ks->sm))
return -EOVERFLOW;
ks->seq.buf = kvmalloc(seq_size, GFP_KERNEL_ACCOUNT);
if (!ks->seq.buf)
return -ENOMEM;
ks->seq.size = seq_size;
}
return 0;
}
static int copy_mnt_id_req(const struct mnt_id_req __user *req,
struct mnt_id_req *kreq)
{
int ret;
size_t usize;
BUILD_BUG_ON(sizeof(struct mnt_id_req) != MNT_ID_REQ_SIZE_VER1);
ret = get_user(usize, &req->size);
if (ret)
return -EFAULT;
if (unlikely(usize > PAGE_SIZE))
return -E2BIG;
if (unlikely(usize < MNT_ID_REQ_SIZE_VER0))
return -EINVAL;
memset(kreq, 0, sizeof(*kreq));
ret = copy_struct_from_user(kreq, sizeof(*kreq), req, usize);
if (ret)
return ret;
if (kreq->spare != 0)
return -EINVAL;
/* The first valid unique mount id is MNT_UNIQUE_ID_OFFSET + 1. */
if (kreq->mnt_id <= MNT_UNIQUE_ID_OFFSET)
return -EINVAL;
return 0;
}
/*
* If the user requested a specific mount namespace id, look that up and return
* that, or if not simply grab a passive reference on our mount namespace and
* return that.
*/
static struct mnt_namespace *grab_requested_mnt_ns(const struct mnt_id_req *kreq)
{
struct mnt_namespace *mnt_ns;
if (kreq->mnt_ns_id && kreq->spare)
return ERR_PTR(-EINVAL);
if (kreq->mnt_ns_id)
return lookup_mnt_ns(kreq->mnt_ns_id);
if (kreq->spare) {
struct ns_common *ns;
CLASS(fd, f)(kreq->spare);
if (fd_empty(f))
return ERR_PTR(-EBADF);
if (!proc_ns_file(fd_file(f)))
return ERR_PTR(-EINVAL);
ns = get_proc_ns(file_inode(fd_file(f)));
if (ns->ops->type != CLONE_NEWNS)
return ERR_PTR(-EINVAL);
mnt_ns = to_mnt_ns(ns);
} else {
mnt_ns = current->nsproxy->mnt_ns;
}
refcount_inc(&mnt_ns->passive);
return mnt_ns;
}
SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req,
struct statmount __user *, buf, size_t, bufsize,
unsigned int, flags)
{
struct mnt_namespace *ns __free(mnt_ns_release) = NULL;
struct kstatmount *ks __free(kfree) = NULL;
struct mnt_id_req kreq;
/* We currently support retrieval of 3 strings. */
size_t seq_size = 3 * PATH_MAX;
int ret;
if (flags)
return -EINVAL;
ret = copy_mnt_id_req(req, &kreq);
if (ret)
return ret;
ns = grab_requested_mnt_ns(&kreq);
if (!ns)
return -ENOENT;
if (kreq.mnt_ns_id && (ns != current->nsproxy->mnt_ns) &&
!ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN))
return -ENOENT;
ks = kmalloc(sizeof(*ks), GFP_KERNEL_ACCOUNT);
if (!ks)
return -ENOMEM;
retry:
ret = prepare_kstatmount(ks, &kreq, buf, bufsize, seq_size);
if (ret)
return ret;
scoped_guard(rwsem_read, &namespace_sem)
ret = do_statmount(ks, kreq.mnt_id, kreq.mnt_ns_id, ns);
if (!ret)
ret = copy_statmount_to_user(ks);
kvfree(ks->seq.buf);
if (retry_statmount(ret, &seq_size))
goto retry;
return ret;
}
static ssize_t do_listmount(struct mnt_namespace *ns, u64 mnt_parent_id,
u64 last_mnt_id, u64 *mnt_ids, size_t nr_mnt_ids,
bool reverse)
{
struct path root __free(path_put) = {};
struct path orig;
struct mount *r, *first;
ssize_t ret;
rwsem_assert_held(&namespace_sem);
ret = grab_requested_root(ns, &root);
if (ret)
return ret;
if (mnt_parent_id == LSMT_ROOT) {
orig = root;
} else {
orig.mnt = lookup_mnt_in_ns(mnt_parent_id, ns);
if (!orig.mnt)
return -ENOENT;
orig.dentry = orig.mnt->mnt_root;
}
/*
* Don't trigger audit denials. We just want to determine what
* mounts to show users.
*/
if (!is_path_reachable(real_mount(orig.mnt), orig.dentry, &root) &&
!ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN))
return -EPERM;
ret = security_sb_statfs(orig.dentry);
if (ret)
return ret;
if (!last_mnt_id) {
if (reverse)
first = node_to_mount(rb_last(&ns->mounts));
else
first = node_to_mount(rb_first(&ns->mounts));
} else {
if (reverse)
first = mnt_find_id_at_reverse(ns, last_mnt_id - 1);
else
first = mnt_find_id_at(ns, last_mnt_id + 1);
}
for (ret = 0, r = first; r && nr_mnt_ids; r = listmnt_next(r, reverse)) {
if (r->mnt_id_unique == mnt_parent_id)
continue;
if (!is_path_reachable(r, r->mnt.mnt_root, &orig))
continue;
*mnt_ids = r->mnt_id_unique;
mnt_ids++;
nr_mnt_ids--;
ret++;
}
return ret;
}
SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req,
u64 __user *, mnt_ids, size_t, nr_mnt_ids, unsigned int, flags)
{
u64 *kmnt_ids __free(kvfree) = NULL;
const size_t maxcount = 1000000;
struct mnt_namespace *ns __free(mnt_ns_release) = NULL;
struct mnt_id_req kreq;
u64 last_mnt_id;
ssize_t ret;
if (flags & ~LISTMOUNT_REVERSE)
return -EINVAL;
/*
* If the mount namespace really has more than 1 million mounts the
* caller must iterate over the mount namespace (and reconsider their
* system design...).
*/
if (unlikely(nr_mnt_ids > maxcount))
return -EOVERFLOW;
if (!access_ok(mnt_ids, nr_mnt_ids * sizeof(*mnt_ids)))
return -EFAULT;
ret = copy_mnt_id_req(req, &kreq);
if (ret)
return ret;
last_mnt_id = kreq.param;
/* The first valid unique mount id is MNT_UNIQUE_ID_OFFSET + 1. */
if (last_mnt_id != 0 && last_mnt_id <= MNT_UNIQUE_ID_OFFSET)
return -EINVAL;
kmnt_ids = kvmalloc_array(nr_mnt_ids, sizeof(*kmnt_ids),
GFP_KERNEL_ACCOUNT);
if (!kmnt_ids)
return -ENOMEM;
ns = grab_requested_mnt_ns(&kreq);
if (!ns)
return -ENOENT;
if (kreq.mnt_ns_id && (ns != current->nsproxy->mnt_ns) &&
!ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN))
return -ENOENT;
scoped_guard(rwsem_read, &namespace_sem)
ret = do_listmount(ns, kreq.mnt_id, last_mnt_id, kmnt_ids,
nr_mnt_ids, (flags & LISTMOUNT_REVERSE));
if (ret <= 0)
return ret;
if (copy_to_user(mnt_ids, kmnt_ids, ret * sizeof(*mnt_ids)))
return -EFAULT;
return ret;
}
static void __init init_mount_tree(void)
{
struct vfsmount *mnt;
struct mount *m;
struct mnt_namespace *ns;
struct path root;
mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
if (IS_ERR(mnt))
panic("Can't create rootfs");
ns = alloc_mnt_ns(&init_user_ns, false);
if (IS_ERR(ns))
panic("Can't allocate initial namespace");
m = real_mount(mnt);
ns->root = m;
ns->nr_mounts = 1;
mnt_add_to_ns(ns, m);
init_task.nsproxy->mnt_ns = ns;
get_mnt_ns(ns);
root.mnt = mnt;
root.dentry = mnt->mnt_root;
mnt->mnt_flags |= MNT_LOCKED;
set_fs_pwd(current->fs, &root);
set_fs_root(current->fs, &root);
mnt_ns_tree_add(ns);
}
void __init mnt_init(void)
{
int err;
mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
mount_hashtable = alloc_large_system_hash("Mount-cache",
sizeof(struct hlist_head),
mhash_entries, 19,
HASH_ZERO,
&m_hash_shift, &m_hash_mask, 0, 0);
mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
sizeof(struct hlist_head),
mphash_entries, 19,
HASH_ZERO,
&mp_hash_shift, &mp_hash_mask, 0, 0);
if (!mount_hashtable || !mountpoint_hashtable)
panic("Failed to allocate mount hash table\n");
kernfs_init();
err = sysfs_init();
if (err)
printk(KERN_WARNING "%s: sysfs_init error: %d\n",
__func__, err);
fs_kobj = kobject_create_and_add("fs", NULL);
if (!fs_kobj)
printk(KERN_WARNING "%s: kobj create error\n", __func__);
shmem_init();
init_rootfs();
init_mount_tree();
}
void put_mnt_ns(struct mnt_namespace *ns)
{
if (!refcount_dec_and_test(&ns->ns.count))
return;
drop_collected_mounts(&ns->root->mnt);
free_mnt_ns(ns);
}
struct vfsmount *kern_mount(struct file_system_type *type)
{
struct vfsmount *mnt;
mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
if (!IS_ERR(mnt)) {
/*
* it is a longterm mount, don't release mnt until
* we unmount before file sys is unregistered
*/
real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
}
return mnt;
}
EXPORT_SYMBOL_GPL(kern_mount);
void kern_unmount(struct vfsmount *mnt)
{
/* release long term mount so mount point can be released */
if (!IS_ERR(mnt)) {
mnt_make_shortterm(mnt);
synchronize_rcu(); /* yecchhh... */
mntput(mnt);
}
}
EXPORT_SYMBOL(kern_unmount);
void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
{
unsigned int i;
for (i = 0; i < num; i++)
mnt_make_shortterm(mnt[i]);
synchronize_rcu_expedited();
for (i = 0; i < num; i++)
mntput(mnt[i]);
}
EXPORT_SYMBOL(kern_unmount_array);
bool our_mnt(struct vfsmount *mnt)
{
return check_mnt(real_mount(mnt));
}
bool current_chrooted(void)
{
/* Does the current process have a non-standard root */
struct path ns_root;
struct path fs_root;
bool chrooted;
/* Find the namespace root */
ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
ns_root.dentry = ns_root.mnt->mnt_root;
path_get(&ns_root);
while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
;
get_fs_root(current->fs, &fs_root);
chrooted = !path_equal(&fs_root, &ns_root);
path_put(&fs_root);
path_put(&ns_root);
return chrooted;
}
static bool mnt_already_visible(struct mnt_namespace *ns,
const struct super_block *sb,
int *new_mnt_flags)
{
int new_flags = *new_mnt_flags;
struct mount *mnt, *n;
bool visible = false;
down_read(&namespace_sem);
rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) {
struct mount *child;
int mnt_flags;
if (mnt->mnt.mnt_sb->s_type != sb->s_type)
continue;
/* This mount is not fully visible if it's root directory
* is not the root directory of the filesystem.
*/
if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
continue;
/* A local view of the mount flags */
mnt_flags = mnt->mnt.mnt_flags;
/* Don't miss readonly hidden in the superblock flags */
if (sb_rdonly(mnt->mnt.mnt_sb))
mnt_flags |= MNT_LOCK_READONLY;
/* Verify the mount flags are equal to or more permissive
* than the proposed new mount.
*/
if ((mnt_flags & MNT_LOCK_READONLY) &&
!(new_flags & MNT_READONLY))
continue;
if ((mnt_flags & MNT_LOCK_ATIME) &&
((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
continue;
/* This mount is not fully visible if there are any
* locked child mounts that cover anything except for
* empty directories.
*/
list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
struct inode *inode = child->mnt_mountpoint->d_inode;
/* Only worry about locked mounts */
if (!(child->mnt.mnt_flags & MNT_LOCKED))
continue;
/* Is the directory permanently empty? */
if (!is_empty_dir_inode(inode))
goto next;
}
/* Preserve the locked attributes */
*new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
MNT_LOCK_ATIME);
visible = true;
goto found;
next: ;
}
found:
up_read(&namespace_sem);
return visible;
}
static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
{
const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
unsigned long s_iflags;
if (ns->user_ns == &init_user_ns)
return false;
/* Can this filesystem be too revealing? */
s_iflags = sb->s_iflags;
if (!(s_iflags & SB_I_USERNS_VISIBLE))
return false;
if ((s_iflags & required_iflags) != required_iflags) {
WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
required_iflags);
return true;
}
return !mnt_already_visible(ns, sb, new_mnt_flags);
}
bool mnt_may_suid(struct vfsmount *mnt)
{
/*
* Foreign mounts (accessed via fchdir or through /proc
* symlinks) are always treated as if they are nosuid. This
* prevents namespaces from trusting potentially unsafe
* suid/sgid bits, file caps, or security labels that originate
* in other namespaces.
*/
return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
current_in_userns(mnt->mnt_sb->s_user_ns);
}
static struct ns_common *mntns_get(struct task_struct *task)
{
struct ns_common *ns = NULL;
struct nsproxy *nsproxy;
task_lock(task);
nsproxy = task->nsproxy;
if (nsproxy) {
ns = &nsproxy->mnt_ns->ns;
get_mnt_ns(to_mnt_ns(ns));
}
task_unlock(task);
return ns;
}
static void mntns_put(struct ns_common *ns)
{
put_mnt_ns(to_mnt_ns(ns));
}
static int mntns_install(struct nsset *nsset, struct ns_common *ns)
{
struct nsproxy *nsproxy = nsset->nsproxy;
struct fs_struct *fs = nsset->fs;
struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
struct user_namespace *user_ns = nsset->cred->user_ns;
struct path root;
int err;
if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
!ns_capable(user_ns, CAP_SYS_CHROOT) ||
!ns_capable(user_ns, CAP_SYS_ADMIN))
return -EPERM;
if (is_anon_ns(mnt_ns))
return -EINVAL;
if (fs->users != 1)
return -EINVAL;
get_mnt_ns(mnt_ns);
old_mnt_ns = nsproxy->mnt_ns;
nsproxy->mnt_ns = mnt_ns;
/* Find the root */
err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
"/", LOOKUP_DOWN, &root);
if (err) {
/* revert to old namespace */
nsproxy->mnt_ns = old_mnt_ns;
put_mnt_ns(mnt_ns);
return err;
}
put_mnt_ns(old_mnt_ns);
/* Update the pwd and root */
set_fs_pwd(fs, &root);
set_fs_root(fs, &root);
path_put(&root);
return 0;
}
static struct user_namespace *mntns_owner(struct ns_common *ns)
{
return to_mnt_ns(ns)->user_ns;
}
const struct proc_ns_operations mntns_operations = {
.name = "mnt",
.type = CLONE_NEWNS,
.get = mntns_get,
.put = mntns_put,
.install = mntns_install,
.owner = mntns_owner,
};
#ifdef CONFIG_SYSCTL
static struct ctl_table fs_namespace_sysctls[] = {
{
.procname = "mount-max",
.data = &sysctl_mount_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
},
};
static int __init init_fs_namespace_sysctls(void)
{
register_sysctl_init("fs", fs_namespace_sysctls);
return 0;
}
fs_initcall(init_fs_namespace_sysctls);
#endif /* CONFIG_SYSCTL */
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