// SPDX-License-Identifier: GPL-2.0
/*
* /proc/sys support
*/
#include <linux/init.h>
#include <linux/sysctl.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/printk.h>
#include <linux/security.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/namei.h>
#include <linux/mm.h>
#include <linux/uio.h>
#include <linux/module.h>
#include <linux/bpf-cgroup.h>
#include <linux/mount.h>
#include <linux/kmemleak.h>
#include "internal.h"
#define list_for_each_table_entry(entry, header) \
entry = header->ctl_table; \
for (size_t i = 0 ; i < header->ctl_table_size; ++i, entry++)
static const struct dentry_operations proc_sys_dentry_operations;
static const struct file_operations proc_sys_file_operations;
static const struct inode_operations proc_sys_inode_operations;
static const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_operations;
/*
* Support for permanently empty directories.
* Must be non-empty to avoid sharing an address with other tables.
*/
static struct ctl_table sysctl_mount_point[] = {
{ }
};
/**
* register_sysctl_mount_point() - registers a sysctl mount point
* @path: path for the mount point
*
* Used to create a permanently empty directory to serve as mount point.
* There are some subtle but important permission checks this allows in the
* case of unprivileged mounts.
*/
struct ctl_table_header *register_sysctl_mount_point(const char *path)
{
return register_sysctl_sz(path, sysctl_mount_point, 0);
}
EXPORT_SYMBOL(register_sysctl_mount_point);
#define sysctl_is_perm_empty_ctl_header(hptr) \
(hptr->type == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
#define sysctl_set_perm_empty_ctl_header(hptr) \
(hptr->type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
#define sysctl_clear_perm_empty_ctl_header(hptr) \
(hptr->type = SYSCTL_TABLE_TYPE_DEFAULT)
void proc_sys_poll_notify(struct ctl_table_poll *poll)
{
if (!poll)
return;
atomic_inc(&poll->event);
wake_up_interruptible(&poll->wait);
}
static struct ctl_table root_table[] = {
{
.procname = "",
.mode = S_IFDIR|S_IRUGO|S_IXUGO,
},
};
static struct ctl_table_root sysctl_table_root = {
.default_set.dir.header = {
{{.count = 1,
.nreg = 1,
.ctl_table = root_table }},
.ctl_table_arg = root_table,
.root = &sysctl_table_root,
.set = &sysctl_table_root.default_set,
},
};
static DEFINE_SPINLOCK(sysctl_lock);
static void drop_sysctl_table(struct ctl_table_header *header);
static int sysctl_follow_link(struct ctl_table_header **phead,
struct ctl_table **pentry);
static int insert_links(struct ctl_table_header *head);
static void put_links(struct ctl_table_header *header);
static void sysctl_print_dir(struct ctl_dir *dir)
{
if (dir->header.parent)
sysctl_print_dir(dir->header.parent);
pr_cont("%s/", dir->header.ctl_table[0].procname);
}
static int namecmp(const char *name1, int len1, const char *name2, int len2)
{
int cmp;
cmp = memcmp(name1, name2, min(len1, len2));
if (cmp == 0)
cmp = len1 - len2;
return cmp;
}
/* Called under sysctl_lock */
static struct ctl_table *find_entry(struct ctl_table_header **phead,
struct ctl_dir *dir, const char *name, int namelen)
{
struct ctl_table_header *head;
struct ctl_table *entry;
struct rb_node *node = dir->root.rb_node;
while (node)
{
struct ctl_node *ctl_node;
const char *procname;
int cmp;
ctl_node = rb_entry(node, struct ctl_node, node);
head = ctl_node->header;
entry = &head->ctl_table[ctl_node - head->node];
procname = entry->procname;
cmp = namecmp(name, namelen, procname, strlen(procname));
if (cmp < 0)
node = node->rb_left;
else if (cmp > 0)
node = node->rb_right;
else {
*phead = head;
return entry;
}
}
return NULL;
}
static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
{
struct rb_node *node = &head->node[entry - head->ctl_table].node;
struct rb_node **p = &head->parent->root.rb_node;
struct rb_node *parent = NULL;
const char *name = entry->procname;
int namelen = strlen(name);
while (*p) {
struct ctl_table_header *parent_head;
struct ctl_table *parent_entry;
struct ctl_node *parent_node;
const char *parent_name;
int cmp;
parent = *p;
parent_node = rb_entry(parent, struct ctl_node, node);
parent_head = parent_node->header;
parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
parent_name = parent_entry->procname;
cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
if (cmp < 0)
p = &(*p)->rb_left;
else if (cmp > 0)
p = &(*p)->rb_right;
else {
pr_err("sysctl duplicate entry: ");
sysctl_print_dir(head->parent);
pr_cont("%s\n", entry->procname);
return -EEXIST;
}
}
rb_link_node(node, parent, p);
rb_insert_color(node, &head->parent->root);
return 0;
}
static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
{
struct rb_node *node = &head->node[entry - head->ctl_table].node;
rb_erase(node, &head->parent->root);
}
static void init_header(struct ctl_table_header *head,
struct ctl_table_root *root, struct ctl_table_set *set,
struct ctl_node *node, struct ctl_table *table, size_t table_size)
{
head->ctl_table = table;
head->ctl_table_size = table_size;
head->ctl_table_arg = table;
head->used = 0;
head->count = 1;
head->nreg = 1;
head->unregistering = NULL;
head->root = root;
head->set = set;
head->parent = NULL;
head->node = node;
INIT_HLIST_HEAD(&head->inodes);
if (node) {
struct ctl_table *entry;
list_for_each_table_entry(entry, head) {
node->header = head;
node++;
}
}
if (table == sysctl_mount_point)
sysctl_set_perm_empty_ctl_header(head);
}
static void erase_header(struct ctl_table_header *head)
{
struct ctl_table *entry;
list_for_each_table_entry(entry, head)
erase_entry(head, entry);
}
static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
{
struct ctl_table *entry;
struct ctl_table_header *dir_h = &dir->header;
int err;
/* Is this a permanently empty directory? */
if (sysctl_is_perm_empty_ctl_header(dir_h))
return -EROFS;
/* Am I creating a permanently empty directory? */
if (sysctl_is_perm_empty_ctl_header(header)) {
if (!RB_EMPTY_ROOT(&dir->root))
return -EINVAL;
sysctl_set_perm_empty_ctl_header(dir_h);
}
dir_h->nreg++;
header->parent = dir;
err = insert_links(header);
if (err)
goto fail_links;
list_for_each_table_entry(entry, header) {
err = insert_entry(header, entry);
if (err)
goto fail;
}
return 0;
fail:
erase_header(header);
put_links(header);
fail_links:
if (header->ctl_table == sysctl_mount_point)
sysctl_clear_perm_empty_ctl_header(dir_h);
header->parent = NULL;
drop_sysctl_table(dir_h);
return err;
}
/* called under sysctl_lock */
static int use_table(struct ctl_table_header *p)
{
if (unlikely(p->unregistering))
return 0;
p->used++;
return 1;
}
/* called under sysctl_lock */
static void unuse_table(struct ctl_table_header *p)
{
if (!--p->used)
if (unlikely(p->unregistering))
complete(p->unregistering);
}
static void proc_sys_invalidate_dcache(struct ctl_table_header *head)
{
proc_invalidate_siblings_dcache(&head->inodes, &sysctl_lock);
}
/* called under sysctl_lock, will reacquire if has to wait */
static void start_unregistering(struct ctl_table_header *p)
{
/*
* if p->used is 0, nobody will ever touch that entry again;
* we'll eliminate all paths to it before dropping sysctl_lock
*/
if (unlikely(p->used)) {
struct completion wait;
init_completion(&wait);
p->unregistering = &wait;
spin_unlock(&sysctl_lock);
wait_for_completion(&wait);
} else {
/* anything non-NULL; we'll never dereference it */
p->unregistering = ERR_PTR(-EINVAL);
spin_unlock(&sysctl_lock);
}
/*
* Invalidate dentries for unregistered sysctls: namespaced sysctls
* can have duplicate names and contaminate dcache very badly.
*/
proc_sys_invalidate_dcache(p);
/*
* do not remove from the list until nobody holds it; walking the
* list in do_sysctl() relies on that.
*/
spin_lock(&sysctl_lock);
erase_header(p);
}
static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
{
BUG_ON(!head);
spin_lock(&sysctl_lock);
if (!use_table(head))
head = ERR_PTR(-ENOENT);
spin_unlock(&sysctl_lock);
return head;
}
static void sysctl_head_finish(struct ctl_table_header *head)
{
if (!head)
return;
spin_lock(&sysctl_lock);
unuse_table(head);
spin_unlock(&sysctl_lock);
}
static struct ctl_table_set *
lookup_header_set(struct ctl_table_root *root)
{
struct ctl_table_set *set = &root->default_set;
if (root->lookup)
set = root->lookup(root);
return set;
}
static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
struct ctl_dir *dir,
const char *name, int namelen)
{
struct ctl_table_header *head;
struct ctl_table *entry;
spin_lock(&sysctl_lock);
entry = find_entry(&head, dir, name, namelen);
if (entry && use_table(head))
*phead = head;
else
entry = NULL;
spin_unlock(&sysctl_lock);
return entry;
}
static struct ctl_node *first_usable_entry(struct rb_node *node)
{
struct ctl_node *ctl_node;
for (;node; node = rb_next(node)) {
ctl_node = rb_entry(node, struct ctl_node, node);
if (use_table(ctl_node->header))
return ctl_node;
}
return NULL;
}
static void first_entry(struct ctl_dir *dir,
struct ctl_table_header **phead, struct ctl_table **pentry)
{
struct ctl_table_header *head = NULL;
struct ctl_table *entry = NULL;
struct ctl_node *ctl_node;
spin_lock(&sysctl_lock);
ctl_node = first_usable_entry(rb_first(&dir->root));
spin_unlock(&sysctl_lock);
if (ctl_node) {
head = ctl_node->header;
entry = &head->ctl_table[ctl_node - head->node];
}
*phead = head;
*pentry = entry;
}
static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
{
struct ctl_table_header *head = *phead;
struct ctl_table *entry = *pentry;
struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
spin_lock(&sysctl_lock);
unuse_table(head);
ctl_node = first_usable_entry(rb_next(&ctl_node->node));
spin_unlock(&sysctl_lock);
head = NULL;
if (ctl_node) {
head = ctl_node->header;
entry = &head->ctl_table[ctl_node - head->node];
}
*phead = head;
*pentry = entry;
}
/*
* sysctl_perm does NOT grant the superuser all rights automatically, because
* some sysctl variables are readonly even to root.
*/
static int test_perm(int mode, int op)
{
if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
mode >>= 6;
else if (in_egroup_p(GLOBAL_ROOT_GID))
mode >>= 3;
if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
return 0;
return -EACCES;
}
static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
{
struct ctl_table_root *root = head->root;
int mode;
if (root->permissions)
mode = root->permissions(head, table);
else
mode = table->mode;
return test_perm(mode, op);
}
static struct inode *proc_sys_make_inode(struct super_block *sb,
struct ctl_table_header *head, struct ctl_table *table)
{
struct ctl_table_root *root = head->root;
struct inode *inode;
struct proc_inode *ei;
inode = new_inode(sb);
if (!inode)
return ERR_PTR(-ENOMEM);
inode->i_ino = get_next_ino();
ei = PROC_I(inode);
spin_lock(&sysctl_lock);
if (unlikely(head->unregistering)) {
spin_unlock(&sysctl_lock);
iput(inode);
return ERR_PTR(-ENOENT);
}
ei->sysctl = head;
ei->sysctl_entry = table;
hlist_add_head_rcu(&ei->sibling_inodes, &head->inodes);
head->count++;
spin_unlock(&sysctl_lock);
simple_inode_init_ts(inode);
inode->i_mode = table->mode;
if (!S_ISDIR(table->mode)) {
inode->i_mode |= S_IFREG;
inode->i_op = &proc_sys_inode_operations;
inode->i_fop = &proc_sys_file_operations;
} else {
inode->i_mode |= S_IFDIR;
inode->i_op = &proc_sys_dir_operations;
inode->i_fop = &proc_sys_dir_file_operations;
if (sysctl_is_perm_empty_ctl_header(head))
make_empty_dir_inode(inode);
}
inode->i_uid = GLOBAL_ROOT_UID;
inode->i_gid = GLOBAL_ROOT_GID;
if (root->set_ownership)
root->set_ownership(head, &inode->i_uid, &inode->i_gid);
return inode;
}
void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
{
spin_lock(&sysctl_lock);
hlist_del_init_rcu(&PROC_I(inode)->sibling_inodes);
if (!--head->count)
kfree_rcu(head, rcu);
spin_unlock(&sysctl_lock);
}
static struct ctl_table_header *grab_header(struct inode *inode)
{
struct ctl_table_header *head = PROC_I(inode)->sysctl;
if (!head)
head = &sysctl_table_root.default_set.dir.header;
return sysctl_head_grab(head);
}
static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct ctl_table_header *head = grab_header(dir);
struct ctl_table_header *h = NULL;
const struct qstr *name = &dentry->d_name;
struct ctl_table *p;
struct inode *inode;
struct dentry *err = ERR_PTR(-ENOENT);
struct ctl_dir *ctl_dir;
int ret;
if (IS_ERR(head))
return ERR_CAST(head);
ctl_dir = container_of(head, struct ctl_dir, header);
p = lookup_entry(&h, ctl_dir, name->name, name->len);
if (!p)
goto out;
if (S_ISLNK(p->mode)) {
ret = sysctl_follow_link(&h, &p);
err = ERR_PTR(ret);
if (ret)
goto out;
}
d_set_d_op(dentry, &proc_sys_dentry_operations);
inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
err = d_splice_alias(inode, dentry);
out:
if (h)
sysctl_head_finish(h);
sysctl_head_finish(head);
return err;
}
static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
int write)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
size_t count = iov_iter_count(iter);
char *kbuf;
ssize_t error;
if (IS_ERR(head))
return PTR_ERR(head);
/*
* At this point we know that the sysctl was not unregistered
* and won't be until we finish.
*/
error = -EPERM;
if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
goto out;
/* if that can happen at all, it should be -EINVAL, not -EISDIR */
error = -EINVAL;
if (!table->proc_handler)
goto out;
/* don't even try if the size is too large */
error = -ENOMEM;
if (count >= KMALLOC_MAX_SIZE)
goto out;
kbuf = kvzalloc(count + 1, GFP_KERNEL);
if (!kbuf)
goto out;
if (write) {
error = -EFAULT;
if (!copy_from_iter_full(kbuf, count, iter))
goto out_free_buf;
kbuf[count] = '\0';
}
error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
&iocb->ki_pos);
if (error)
goto out_free_buf;
/* careful: calling conventions are nasty here */
error = table->proc_handler(table, write, kbuf, &count, &iocb->ki_pos);
if (error)
goto out_free_buf;
if (!write) {
error = -EFAULT;
if (copy_to_iter(kbuf, count, iter) < count)
goto out_free_buf;
}
error = count;
out_free_buf:
kvfree(kbuf);
out:
sysctl_head_finish(head);
return error;
}
static ssize_t proc_sys_read(struct kiocb *iocb, struct iov_iter *iter)
{
return proc_sys_call_handler(iocb, iter, 0);
}
static ssize_t proc_sys_write(struct kiocb *iocb, struct iov_iter *iter)
{
return proc_sys_call_handler(iocb, iter, 1);
}
static int proc_sys_open(struct inode *inode, struct file *filp)
{
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
/* sysctl was unregistered */
if (IS_ERR(head))
return PTR_ERR(head);
if (table->poll)
filp->private_data = proc_sys_poll_event(table->poll);
sysctl_head_finish(head);
return 0;
}
static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
{
struct inode *inode = file_inode(filp);
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
__poll_t ret = DEFAULT_POLLMASK;
unsigned long event;
/* sysctl was unregistered */
if (IS_ERR(head))
return EPOLLERR | EPOLLHUP;
if (!table->proc_handler)
goto out;
if (!table->poll)
goto out;
event = (unsigned long)filp->private_data;
poll_wait(filp, &table->poll->wait, wait);
if (event != atomic_read(&table->poll->event)) {
filp->private_data = proc_sys_poll_event(table->poll);
ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
}
out:
sysctl_head_finish(head);
return ret;
}
static bool proc_sys_fill_cache(struct file *file,
struct dir_context *ctx,
struct ctl_table_header *head,
struct ctl_table *table)
{
struct dentry *child, *dir = file->f_path.dentry;
struct inode *inode;
struct qstr qname;
ino_t ino = 0;
unsigned type = DT_UNKNOWN;
qname.name = table->procname;
qname.len = strlen(table->procname);
qname.hash = full_name_hash(dir, qname.name, qname.len);
child = d_lookup(dir, &qname);
if (!child) {
DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
child = d_alloc_parallel(dir, &qname, &wq);
if (IS_ERR(child))
return false;
if (d_in_lookup(child)) {
struct dentry *res;
d_set_d_op(child, &proc_sys_dentry_operations);
inode = proc_sys_make_inode(dir->d_sb, head, table);
res = d_splice_alias(inode, child);
d_lookup_done(child);
if (unlikely(res)) {
if (IS_ERR(res)) {
dput(child);
return false;
}
dput(child);
child = res;
}
}
}
inode = d_inode(child);
ino = inode->i_ino;
type = inode->i_mode >> 12;
dput(child);
return dir_emit(ctx, qname.name, qname.len, ino, type);
}
static bool proc_sys_link_fill_cache(struct file *file,
struct dir_context *ctx,
struct ctl_table_header *head,
struct ctl_table *table)
{
bool ret = true;
head = sysctl_head_grab(head);
if (IS_ERR(head))
return false;
/* It is not an error if we can not follow the link ignore it */
if (sysctl_follow_link(&head, &table))
goto out;
ret = proc_sys_fill_cache(file, ctx, head, table);
out:
sysctl_head_finish(head);
return ret;
}
static int scan(struct ctl_table_header *head, struct ctl_table *table,
unsigned long *pos, struct file *file,
struct dir_context *ctx)
{
bool res;
if ((*pos)++ < ctx->pos)
return true;
if (unlikely(S_ISLNK(table->mode)))
res = proc_sys_link_fill_cache(file, ctx, head, table);
else
res = proc_sys_fill_cache(file, ctx, head, table);
if (res)
ctx->pos = *pos;
return res;
}
static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
{
struct ctl_table_header *head = grab_header(file_inode(file));
struct ctl_table_header *h = NULL;
struct ctl_table *entry;
struct ctl_dir *ctl_dir;
unsigned long pos;
if (IS_ERR(head))
return PTR_ERR(head);
ctl_dir = container_of(head, struct ctl_dir, header);
if (!dir_emit_dots(file, ctx))
goto out;
pos = 2;
for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
if (!scan(h, entry, &pos, file, ctx)) {
sysctl_head_finish(h);
break;
}
}
out:
sysctl_head_finish(head);
return 0;
}
static int proc_sys_permission(struct mnt_idmap *idmap,
struct inode *inode, int mask)
{
/*
* sysctl entries that are not writeable,
* are _NOT_ writeable, capabilities or not.
*/
struct ctl_table_header *head;
struct ctl_table *table;
int error;
/* Executable files are not allowed under /proc/sys/ */
if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
return -EACCES;
head = grab_header(inode);
if (IS_ERR(head))
return PTR_ERR(head);
table = PROC_I(inode)->sysctl_entry;
if (!table) /* global root - r-xr-xr-x */
error = mask & MAY_WRITE ? -EACCES : 0;
else /* Use the permissions on the sysctl table entry */
error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
sysctl_head_finish(head);
return error;
}
static int proc_sys_setattr(struct mnt_idmap *idmap,
struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = d_inode(dentry);
int error;
if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
return -EPERM;
error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
if (error)
return error;
setattr_copy(&nop_mnt_idmap, inode, attr);
return 0;
}
static int proc_sys_getattr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
struct inode *inode = d_inode(path->dentry);
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
if (IS_ERR(head))
return PTR_ERR(head);
generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
if (table)
stat->mode = (stat->mode & S_IFMT) | table->mode;
sysctl_head_finish(head);
return 0;
}
static const struct file_operations proc_sys_file_operations = {
.open = proc_sys_open,
.poll = proc_sys_poll,
.read_iter = proc_sys_read,
.write_iter = proc_sys_write,
.splice_read = copy_splice_read,
.splice_write = iter_file_splice_write,
.llseek = default_llseek,
};
static const struct file_operations proc_sys_dir_file_operations = {
.read = generic_read_dir,
.iterate_shared = proc_sys_readdir,
.llseek = generic_file_llseek,
};
static const struct inode_operations proc_sys_inode_operations = {
.permission = proc_sys_permission,
.setattr = proc_sys_setattr,
.getattr = proc_sys_getattr,
};
static const struct inode_operations proc_sys_dir_operations = {
.lookup = proc_sys_lookup,
.permission = proc_sys_permission,
.setattr = proc_sys_setattr,
.getattr = proc_sys_getattr,
};
static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
{
if (flags & LOOKUP_RCU)
return -ECHILD;
return !PROC_I(d_inode(dentry))->sysctl->unregistering;
}
static int proc_sys_delete(const struct dentry *dentry)
{
return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
}
static int sysctl_is_seen(struct ctl_table_header *p)
{
struct ctl_table_set *set = p->set;
int res;
spin_lock(&sysctl_lock);
if (p->unregistering)
res = 0;
else if (!set->is_seen)
res = 1;
else
res = set->is_seen(set);
spin_unlock(&sysctl_lock);
return res;
}
static int proc_sys_compare(const struct dentry *dentry,
unsigned int len, const char *str, const struct qstr *name)
{
struct ctl_table_header *head;
struct inode *inode;
/* Although proc doesn't have negative dentries, rcu-walk means
* that inode here can be NULL */
/* AV: can it, indeed? */
inode = d_inode_rcu(dentry);
if (!inode)
return 1;
if (name->len != len)
return 1;
if (memcmp(name->name, str, len))
return 1;
head = rcu_dereference(PROC_I(inode)->sysctl);
return !head || !sysctl_is_seen(head);
}
static const struct dentry_operations proc_sys_dentry_operations = {
.d_revalidate = proc_sys_revalidate,
.d_delete = proc_sys_delete,
.d_compare = proc_sys_compare,
};
static struct ctl_dir *find_subdir(struct ctl_dir *dir,
const char *name, int namelen)
{
struct ctl_table_header *head;
struct ctl_table *entry;
entry = find_entry(&head, dir, name, namelen);
if (!entry)
return ERR_PTR(-ENOENT);
if (!S_ISDIR(entry->mode))
return ERR_PTR(-ENOTDIR);
return container_of(head, struct ctl_dir, header);
}
static struct ctl_dir *new_dir(struct ctl_table_set *set,
const char *name, int namelen)
{
struct ctl_table *table;
struct ctl_dir *new;
struct ctl_node *node;
char *new_name;
new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
sizeof(struct ctl_table) + namelen + 1,
GFP_KERNEL);
if (!new)
return NULL;
node = (struct ctl_node *)(new + 1);
table = (struct ctl_table *)(node + 1);
new_name = (char *)(table + 1);
memcpy(new_name, name, namelen);
table[0].procname = new_name;
table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
init_header(&new->header, set->dir.header.root, set, node, table, 1);
return new;
}
/**
* get_subdir - find or create a subdir with the specified name.
* @dir: Directory to create the subdirectory in
* @name: The name of the subdirectory to find or create
* @namelen: The length of name
*
* Takes a directory with an elevated reference count so we know that
* if we drop the lock the directory will not go away. Upon success
* the reference is moved from @dir to the returned subdirectory.
* Upon error an error code is returned and the reference on @dir is
* simply dropped.
*/
static struct ctl_dir *get_subdir(struct ctl_dir *dir,
const char *name, int namelen)
{
struct ctl_table_set *set = dir->header.set;
struct ctl_dir *subdir, *new = NULL;
int err;
spin_lock(&sysctl_lock);
subdir = find_subdir(dir, name, namelen);
if (!IS_ERR(subdir))
goto found;
if (PTR_ERR(subdir) != -ENOENT)
goto failed;
spin_unlock(&sysctl_lock);
new = new_dir(set, name, namelen);
spin_lock(&sysctl_lock);
subdir = ERR_PTR(-ENOMEM);
if (!new)
goto failed;
/* Was the subdir added while we dropped the lock? */
subdir = find_subdir(dir, name, namelen);
if (!IS_ERR(subdir))
goto found;
if (PTR_ERR(subdir) != -ENOENT)
goto failed;
/* Nope. Use the our freshly made directory entry. */
err = insert_header(dir, &new->header);
subdir = ERR_PTR(err);
if (err)
goto failed;
subdir = new;
found:
subdir->header.nreg++;
failed:
if (IS_ERR(subdir)) {
pr_err("sysctl could not get directory: ");
sysctl_print_dir(dir);
pr_cont("%*.*s %ld\n", namelen, namelen, name,
PTR_ERR(subdir));
}
drop_sysctl_table(&dir->header);
if (new)
drop_sysctl_table(&new->header);
spin_unlock(&sysctl_lock);
return subdir;
}
static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
{
struct ctl_dir *parent;
const char *procname;
if (!dir->header.parent)
return &set->dir;
parent = xlate_dir(set, dir->header.parent);
if (IS_ERR(parent))
return parent;
procname = dir->header.ctl_table[0].procname;
return find_subdir(parent, procname, strlen(procname));
}
static int sysctl_follow_link(struct ctl_table_header **phead,
struct ctl_table **pentry)
{
struct ctl_table_header *head;
struct ctl_table_root *root;
struct ctl_table_set *set;
struct ctl_table *entry;
struct ctl_dir *dir;
int ret;
spin_lock(&sysctl_lock);
root = (*pentry)->data;
set = lookup_header_set(root);
dir = xlate_dir(set, (*phead)->parent);
if (IS_ERR(dir))
ret = PTR_ERR(dir);
else {
const char *procname = (*pentry)->procname;
head = NULL;
entry = find_entry(&head, dir, procname, strlen(procname));
ret = -ENOENT;
if (entry && use_table(head)) {
unuse_table(*phead);
*phead = head;
*pentry = entry;
ret = 0;
}
}
spin_unlock(&sysctl_lock);
return ret;
}
static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
{
struct va_format vaf;
va_list args;
va_start(args, fmt);
vaf.fmt = fmt;
vaf.va = &args;
pr_err("sysctl table check failed: %s/%s %pV\n",
path, table->procname, &vaf);
va_end(args);
return -EINVAL;
}
static int sysctl_check_table_array(const char *path, struct ctl_table *table)
{
unsigned int extra;
int err = 0;
if ((table->proc_handler == proc_douintvec) ||
(table->proc_handler == proc_douintvec_minmax)) {
if (table->maxlen != sizeof(unsigned int))
err |= sysctl_err(path, table, "array not allowed");
}
if (table->proc_handler == proc_dou8vec_minmax) {
if (table->maxlen != sizeof(u8))
err |= sysctl_err(path, table, "array not allowed");
if (table->extra1) {
extra = *(unsigned int *) table->extra1;
if (extra > 255U)
err |= sysctl_err(path, table,
"range value too large for proc_dou8vec_minmax");
}
if (table->extra2) {
extra = *(unsigned int *) table->extra2;
if (extra > 255U)
err |= sysctl_err(path, table,
"range value too large for proc_dou8vec_minmax");
}
}
if (table->proc_handler == proc_dobool) {
if (table->maxlen != sizeof(bool))
err |= sysctl_err(path, table, "array not allowed");
}
return err;
}
static int sysctl_check_table(const char *path, struct ctl_table_header *header)
{
struct ctl_table *entry;
int err = 0;
list_for_each_table_entry(entry, header) {
if (!entry->procname)
err |= sysctl_err(path, entry, "procname is null");
if ((entry->proc_handler == proc_dostring) ||
(entry->proc_handler == proc_dobool) ||
(entry->proc_handler == proc_dointvec) ||
(entry->proc_handler == proc_douintvec) ||
(entry->proc_handler == proc_douintvec_minmax) ||
(entry->proc_handler == proc_dointvec_minmax) ||
(entry->proc_handler == proc_dou8vec_minmax) ||
(entry->proc_handler == proc_dointvec_jiffies) ||
(entry->proc_handler == proc_dointvec_userhz_jiffies) ||
(entry->proc_handler == proc_dointvec_ms_jiffies) ||
(entry->proc_handler == proc_doulongvec_minmax) ||
(entry->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
if (!entry->data)
err |= sysctl_err(path, entry, "No data");
if (!entry->maxlen)
err |= sysctl_err(path, entry, "No maxlen");
else
err |= sysctl_check_table_array(path, entry);
}
if (!entry->proc_handler)
err |= sysctl_err(path, entry, "No proc_handler");
if ((entry->mode & (S_IRUGO|S_IWUGO)) != entry->mode)
err |= sysctl_err(path, entry, "bogus .mode 0%o",
entry->mode);
}
return err;
}
static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_header *head)
{
struct ctl_table *link_table, *entry, *link;
struct ctl_table_header *links;
struct ctl_node *node;
char *link_name;
int name_bytes;
name_bytes = 0;
list_for_each_table_entry(entry, head) {
name_bytes += strlen(entry->procname) + 1;
}
links = kzalloc(sizeof(struct ctl_table_header) +
sizeof(struct ctl_node)*head->ctl_table_size +
sizeof(struct ctl_table)*head->ctl_table_size +
name_bytes,
GFP_KERNEL);
if (!links)
return NULL;
node = (struct ctl_node *)(links + 1);
link_table = (struct ctl_table *)(node + head->ctl_table_size);
link_name = (char *)(link_table + head->ctl_table_size);
link = link_table;
list_for_each_table_entry(entry, head) {
int len = strlen(entry->procname) + 1;
memcpy(link_name, entry->procname, len);
link->procname = link_name;
link->mode = S_IFLNK|S_IRWXUGO;
link->data = head->root;
link_name += len;
link++;
}
init_header(links, dir->header.root, dir->header.set, node, link_table,
head->ctl_table_size);
links->nreg = head->ctl_table_size;
return links;
}
static bool get_links(struct ctl_dir *dir,
struct ctl_table_header *header,
struct ctl_table_root *link_root)
{
struct ctl_table_header *tmp_head;
struct ctl_table *entry, *link;
if (header->ctl_table_size == 0 ||
sysctl_is_perm_empty_ctl_header(header))
return true;
/* Are there links available for every entry in table? */
list_for_each_table_entry(entry, header) {
const char *procname = entry->procname;
link = find_entry(&tmp_head, dir, procname, strlen(procname));
if (!link)
return false;
if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
continue;
if (S_ISLNK(link->mode) && (link->data == link_root))
continue;
return false;
}
/* The checks passed. Increase the registration count on the links */
list_for_each_table_entry(entry, header) {
const char *procname = entry->procname;
link = find_entry(&tmp_head, dir, procname, strlen(procname));
tmp_head->nreg++;
}
return true;
}
static int insert_links(struct ctl_table_header *head)
{
struct ctl_table_set *root_set = &sysctl_table_root.default_set;
struct ctl_dir *core_parent;
struct ctl_table_header *links;
int err;
if (head->set == root_set)
return 0;
core_parent = xlate_dir(root_set, head->parent);
if (IS_ERR(core_parent))
return 0;
if (get_links(core_parent, head, head->root))
return 0;
core_parent->header.nreg++;
spin_unlock(&sysctl_lock);
links = new_links(core_parent, head);
spin_lock(&sysctl_lock);
err = -ENOMEM;
if (!links)
goto out;
err = 0;
if (get_links(core_parent, head, head->root)) {
kfree(links);
goto out;
}
err = insert_header(core_parent, links);
if (err)
kfree(links);
out:
drop_sysctl_table(&core_parent->header);
return err;
}
/* Find the directory for the ctl_table. If one is not found create it. */
static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
{
const char *name, *nextname;
for (name = path; name; name = nextname) {
int namelen;
nextname = strchr(name, '/');
if (nextname) {
namelen = nextname - name;
nextname++;
} else {
namelen = strlen(name);
}
if (namelen == 0)
continue;
/*
* namelen ensures if name is "foo/bar/yay" only foo is
* registered first. We traverse as if using mkdir -p and
* return a ctl_dir for the last directory entry.
*/
dir = get_subdir(dir, name, namelen);
if (IS_ERR(dir))
break;
}
return dir;
}
/**
* __register_sysctl_table - register a leaf sysctl table
* @set: Sysctl tree to register on
* @path: The path to the directory the sysctl table is in.
*
* @table: the top-level table structure. This table should not be free'd
* after registration. So it should not be used on stack. It can either
* be a global or dynamically allocated by the caller and free'd later
* after sysctl unregistration.
* @table_size : The number of elements in table
*
* Register a sysctl table hierarchy. @table should be a filled in ctl_table
* array.
*
* The members of the &struct ctl_table structure are used as follows:
* procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
* enter a sysctl file
* data - a pointer to data for use by proc_handler
* maxlen - the maximum size in bytes of the data
* mode - the file permissions for the /proc/sys file
* type - Defines the target type (described in struct definition)
* proc_handler - the text handler routine (described below)
*
* extra1, extra2 - extra pointers usable by the proc handler routines
* XXX: we should eventually modify these to use long min / max [0]
* [0] https://lkml.kernel.org/[email protected]
*
* Leaf nodes in the sysctl tree will be represented by a single file
* under /proc; non-leaf nodes are not allowed.
*
* There must be a proc_handler routine for any terminal nodes.
* Several default handlers are available to cover common cases -
*
* proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
* proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
* proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
*
* It is the handler's job to read the input buffer from user memory
* and process it. The handler should return 0 on success.
*
* This routine returns %NULL on a failure to register, and a pointer
* to the table header on success.
*/
struct ctl_table_header *__register_sysctl_table(
struct ctl_table_set *set,
const char *path, struct ctl_table *table, size_t table_size)
{
struct ctl_table_root *root = set->dir.header.root;
struct ctl_table_header *header;
struct ctl_dir *dir;
struct ctl_node *node;
header = kzalloc(sizeof(struct ctl_table_header) +
sizeof(struct ctl_node)*table_size, GFP_KERNEL_ACCOUNT);
if (!header)
return NULL;
node = (struct ctl_node *)(header + 1);
init_header(header, root, set, node, table, table_size);
if (sysctl_check_table(path, header))
goto fail;
spin_lock(&sysctl_lock);
dir = &set->dir;
/* Reference moved down the directory tree get_subdir */
dir->header.nreg++;
spin_unlock(&sysctl_lock);
dir = sysctl_mkdir_p(dir, path);
if (IS_ERR(dir))
goto fail;
spin_lock(&sysctl_lock);
if (insert_header(dir, header))
goto fail_put_dir_locked;
drop_sysctl_table(&dir->header);
spin_unlock(&sysctl_lock);
return header;
fail_put_dir_locked:
drop_sysctl_table(&dir->header);
spin_unlock(&sysctl_lock);
fail:
kfree(header);
return NULL;
}
/**
* register_sysctl_sz - register a sysctl table
* @path: The path to the directory the sysctl table is in. If the path
* doesn't exist we will create it for you.
* @table: the table structure. The calller must ensure the life of the @table
* will be kept during the lifetime use of the syctl. It must not be freed
* until unregister_sysctl_table() is called with the given returned table
* with this registration. If your code is non modular then you don't need
* to call unregister_sysctl_table() and can instead use something like
* register_sysctl_init() which does not care for the result of the syctl
* registration.
* @table_size: The number of elements in table.
*
* Register a sysctl table. @table should be a filled in ctl_table
* array. A completely 0 filled entry terminates the table.
*
* See __register_sysctl_table for more details.
*/
struct ctl_table_header *register_sysctl_sz(const char *path, struct ctl_table *table,
size_t table_size)
{
return __register_sysctl_table(&sysctl_table_root.default_set,
path, table, table_size);
}
EXPORT_SYMBOL(register_sysctl_sz);
/**
* __register_sysctl_init() - register sysctl table to path
* @path: path name for sysctl base. If that path doesn't exist we will create
* it for you.
* @table: This is the sysctl table that needs to be registered to the path.
* The caller must ensure the life of the @table will be kept during the
* lifetime use of the sysctl.
* @table_name: The name of sysctl table, only used for log printing when
* registration fails
* @table_size: The number of elements in table
*
* The sysctl interface is used by userspace to query or modify at runtime
* a predefined value set on a variable. These variables however have default
* values pre-set. Code which depends on these variables will always work even
* if register_sysctl() fails. If register_sysctl() fails you'd just loose the
* ability to query or modify the sysctls dynamically at run time. Chances of
* register_sysctl() failing on init are extremely low, and so for both reasons
* this function does not return any error as it is used by initialization code.
*
* Context: if your base directory does not exist it will be created for you.
*/
void __init __register_sysctl_init(const char *path, struct ctl_table *table,
const char *table_name, size_t table_size)
{
struct ctl_table_header *hdr = register_sysctl_sz(path, table, table_size);
if (unlikely(!hdr)) {
pr_err("failed when register_sysctl_sz %s to %s\n", table_name, path);
return;
}
kmemleak_not_leak(hdr);
}
static void put_links(struct ctl_table_header *header)
{
struct ctl_table_set *root_set = &sysctl_table_root.default_set;
struct ctl_table_root *root = header->root;
struct ctl_dir *parent = header->parent;
struct ctl_dir *core_parent;
struct ctl_table *entry;
if (header->set == root_set)
return;
core_parent = xlate_dir(root_set, parent);
if (IS_ERR(core_parent))
return;
list_for_each_table_entry(entry, header) {
struct ctl_table_header *link_head;
struct ctl_table *link;
const char *name = entry->procname;
link = find_entry(&link_head, core_parent, name, strlen(name));
if (link &&
((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
(S_ISLNK(link->mode) && (link->data == root)))) {
drop_sysctl_table(link_head);
}
else {
pr_err("sysctl link missing during unregister: ");
sysctl_print_dir(parent);
pr_cont("%s\n", name);
}
}
}
static void drop_sysctl_table(struct ctl_table_header *header)
{
struct ctl_dir *parent = header->parent;
if (--header->nreg)
return;
if (parent) {
put_links(header);
start_unregistering(header);
}
if (!--header->count)
kfree_rcu(header, rcu);
if (parent)
drop_sysctl_table(&parent->header);
}
/**
* unregister_sysctl_table - unregister a sysctl table hierarchy
* @header: the header returned from register_sysctl or __register_sysctl_table
*
* Unregisters the sysctl table and all children. proc entries may not
* actually be removed until they are no longer used by anyone.
*/
void unregister_sysctl_table(struct ctl_table_header * header)
{
might_sleep();
if (header == NULL)
return;
spin_lock(&sysctl_lock);
drop_sysctl_table(header);
spin_unlock(&sysctl_lock);
}
EXPORT_SYMBOL(unregister_sysctl_table);
void setup_sysctl_set(struct ctl_table_set *set,
struct ctl_table_root *root,
int (*is_seen)(struct ctl_table_set *))
{
memset(set, 0, sizeof(*set));
set->is_seen = is_seen;
init_header(&set->dir.header, root, set, NULL, root_table, 1);
}
void retire_sysctl_set(struct ctl_table_set *set)
{
WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
}
int __init proc_sys_init(void)
{
struct proc_dir_entry *proc_sys_root;
proc_sys_root = proc_mkdir("sys", NULL);
proc_sys_root->proc_iops = &proc_sys_dir_operations;
proc_sys_root->proc_dir_ops = &proc_sys_dir_file_operations;
proc_sys_root->nlink = 0;
return sysctl_init_bases();
}
struct sysctl_alias {
const char *kernel_param;
const char *sysctl_param;
};
/*
* Historically some settings had both sysctl and a command line parameter.
* With the generic sysctl. parameter support, we can handle them at a single
* place and only keep the historical name for compatibility. This is not meant
* to add brand new aliases. When adding existing aliases, consider whether
* the possibly different moment of changing the value (e.g. from early_param
* to the moment do_sysctl_args() is called) is an issue for the specific
* parameter.
*/
static const struct sysctl_alias sysctl_aliases[] = {
{"hardlockup_all_cpu_backtrace", "kernel.hardlockup_all_cpu_backtrace" },
{"hung_task_panic", "kernel.hung_task_panic" },
{"numa_zonelist_order", "vm.numa_zonelist_order" },
{"softlockup_all_cpu_backtrace", "kernel.softlockup_all_cpu_backtrace" },
{ }
};
static const char *sysctl_find_alias(char *param)
{
const struct sysctl_alias *alias;
for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) {
if (strcmp(alias->kernel_param, param) == 0)
return alias->sysctl_param;
}
return NULL;
}
bool sysctl_is_alias(char *param)
{
const char *alias = sysctl_find_alias(param);
return alias != NULL;
}
/* Set sysctl value passed on kernel command line. */
static int process_sysctl_arg(char *param, char *val,
const char *unused, void *arg)
{
char *path;
struct vfsmount **proc_mnt = arg;
struct file_system_type *proc_fs_type;
struct file *file;
int len;
int err;
loff_t pos = 0;
ssize_t wret;
if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
param += sizeof("sysctl") - 1;
if (param[0] != '/' && param[0] != '.')
return 0;
param++;
} else {
param = (char *) sysctl_find_alias(param);
if (!param)
return 0;
}
if (!val)
return -EINVAL;
len = strlen(val);
if (len == 0)
return -EINVAL;
/*
* To set sysctl options, we use a temporary mount of proc, look up the
* respective sys/ file and write to it. To avoid mounting it when no
* options were given, we mount it only when the first sysctl option is
* found. Why not a persistent mount? There are problems with a
* persistent mount of proc in that it forces userspace not to use any
* proc mount options.
*/
if (!*proc_mnt) {
proc_fs_type = get_fs_type("proc");
if (!proc_fs_type) {
pr_err("Failed to find procfs to set sysctl from command line\n");
return 0;
}
*proc_mnt = kern_mount(proc_fs_type);
put_filesystem(proc_fs_type);
if (IS_ERR(*proc_mnt)) {
pr_err("Failed to mount procfs to set sysctl from command line\n");
return 0;
}
}
path = kasprintf(GFP_KERNEL, "sys/%s", param);
if (!path)
panic("%s: Failed to allocate path for %s\n", __func__, param);
strreplace(path, '.', '/');
file = file_open_root_mnt(*proc_mnt, path, O_WRONLY, 0);
if (IS_ERR(file)) {
err = PTR_ERR(file);
if (err == -ENOENT)
pr_err("Failed to set sysctl parameter '%s=%s': parameter not found\n",
param, val);
else if (err == -EACCES)
pr_err("Failed to set sysctl parameter '%s=%s': permission denied (read-only?)\n",
param, val);
else
pr_err("Error %pe opening proc file to set sysctl parameter '%s=%s'\n",
file, param, val);
goto out;
}
wret = kernel_write(file, val, len, &pos);
if (wret < 0) {
err = wret;
if (err == -EINVAL)
pr_err("Failed to set sysctl parameter '%s=%s': invalid value\n",
param, val);
else
pr_err("Error %pe writing to proc file to set sysctl parameter '%s=%s'\n",
ERR_PTR(err), param, val);
} else if (wret != len) {
pr_err("Wrote only %zd bytes of %d writing to proc file %s to set sysctl parameter '%s=%s\n",
wret, len, path, param, val);
}
err = filp_close(file, NULL);
if (err)
pr_err("Error %pe closing proc file to set sysctl parameter '%s=%s\n",
ERR_PTR(err), param, val);
out:
kfree(path);
return 0;
}
void do_sysctl_args(void)
{
char *command_line;
struct vfsmount *proc_mnt = NULL;
command_line = kstrdup(saved_command_line, GFP_KERNEL);
if (!command_line)
panic("%s: Failed to allocate copy of command line\n", __func__);
parse_args("Setting sysctl args", command_line,
NULL, 0, -1, -1, &proc_mnt, process_sysctl_arg);
if (proc_mnt)
kern_unmount(proc_mnt);
kfree(command_line);
}
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