// SPDX-License-Identifier: GPL-2.0-only
/*
* inode.c - part of tracefs, a pseudo file system for activating tracing
*
* Based on debugfs by: Greg Kroah-Hartman <[email protected]>
*
* Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <[email protected]>
*
* tracefs is the file system that is used by the tracing infrastructure.
*/
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/tracefs.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include <linux/seq_file.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include "internal.h"
#define TRACEFS_DEFAULT_MODE 0700
static struct kmem_cache *tracefs_inode_cachep __ro_after_init;
static struct vfsmount *tracefs_mount;
static int tracefs_mount_count;
static bool tracefs_registered;
/*
* Keep track of all tracefs_inodes in order to update their
* flags if necessary on a remount.
*/
static DEFINE_SPINLOCK(tracefs_inode_lock);
static LIST_HEAD(tracefs_inodes);
static struct inode *tracefs_alloc_inode(struct super_block *sb)
{
struct tracefs_inode *ti;
unsigned long flags;
ti = alloc_inode_sb(sb, tracefs_inode_cachep, GFP_KERNEL);
if (!ti)
return NULL;
spin_lock_irqsave(&tracefs_inode_lock, flags);
list_add_rcu(&ti->list, &tracefs_inodes);
spin_unlock_irqrestore(&tracefs_inode_lock, flags);
return &ti->vfs_inode;
}
static void tracefs_free_inode(struct inode *inode)
{
struct tracefs_inode *ti = get_tracefs(inode);
kmem_cache_free(tracefs_inode_cachep, ti);
}
static void tracefs_destroy_inode(struct inode *inode)
{
struct tracefs_inode *ti = get_tracefs(inode);
unsigned long flags;
spin_lock_irqsave(&tracefs_inode_lock, flags);
list_del_rcu(&ti->list);
spin_unlock_irqrestore(&tracefs_inode_lock, flags);
}
static ssize_t default_read_file(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
return 0;
}
static ssize_t default_write_file(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
return count;
}
static const struct file_operations tracefs_file_operations = {
.read = default_read_file,
.write = default_write_file,
.open = simple_open,
.llseek = noop_llseek,
};
static struct tracefs_dir_ops {
int (*mkdir)(const char *name);
int (*rmdir)(const char *name);
} tracefs_ops __ro_after_init;
static char *get_dname(struct dentry *dentry)
{
const char *dname;
char *name;
int len = dentry->d_name.len;
dname = dentry->d_name.name;
name = kmalloc(len + 1, GFP_KERNEL);
if (!name)
return NULL;
memcpy(name, dname, len);
name[len] = 0;
return name;
}
static int tracefs_syscall_mkdir(struct mnt_idmap *idmap,
struct inode *inode, struct dentry *dentry,
umode_t mode)
{
struct tracefs_inode *ti;
char *name;
int ret;
name = get_dname(dentry);
if (!name)
return -ENOMEM;
/*
* This is a new directory that does not take the default of
* the rootfs. It becomes the default permissions for all the
* files and directories underneath it.
*/
ti = get_tracefs(inode);
ti->flags |= TRACEFS_INSTANCE_INODE;
ti->private = inode;
/*
* The mkdir call can call the generic functions that create
* the files within the tracefs system. It is up to the individual
* mkdir routine to handle races.
*/
inode_unlock(inode);
ret = tracefs_ops.mkdir(name);
inode_lock(inode);
kfree(name);
return ret;
}
static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
{
char *name;
int ret;
name = get_dname(dentry);
if (!name)
return -ENOMEM;
/*
* The rmdir call can call the generic functions that create
* the files within the tracefs system. It is up to the individual
* rmdir routine to handle races.
* This time we need to unlock not only the parent (inode) but
* also the directory that is being deleted.
*/
inode_unlock(inode);
inode_unlock(d_inode(dentry));
ret = tracefs_ops.rmdir(name);
inode_lock_nested(inode, I_MUTEX_PARENT);
inode_lock(d_inode(dentry));
kfree(name);
return ret;
}
static void set_tracefs_inode_owner(struct inode *inode)
{
struct tracefs_inode *ti = get_tracefs(inode);
struct inode *root_inode = ti->private;
kuid_t uid;
kgid_t gid;
uid = root_inode->i_uid;
gid = root_inode->i_gid;
/*
* If the root is not the mount point, then check the root's
* permissions. If it was never set, then default to the
* mount point.
*/
if (root_inode != d_inode(root_inode->i_sb->s_root)) {
struct tracefs_inode *rti;
rti = get_tracefs(root_inode);
root_inode = d_inode(root_inode->i_sb->s_root);
if (!(rti->flags & TRACEFS_UID_PERM_SET))
uid = root_inode->i_uid;
if (!(rti->flags & TRACEFS_GID_PERM_SET))
gid = root_inode->i_gid;
}
/*
* If this inode has never been referenced, then update
* the permissions to the superblock.
*/
if (!(ti->flags & TRACEFS_UID_PERM_SET))
inode->i_uid = uid;
if (!(ti->flags & TRACEFS_GID_PERM_SET))
inode->i_gid = gid;
}
static int tracefs_permission(struct mnt_idmap *idmap,
struct inode *inode, int mask)
{
set_tracefs_inode_owner(inode);
return generic_permission(idmap, inode, mask);
}
static int tracefs_getattr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int flags)
{
struct inode *inode = d_backing_inode(path->dentry);
set_tracefs_inode_owner(inode);
generic_fillattr(idmap, request_mask, inode, stat);
return 0;
}
static int tracefs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
struct iattr *attr)
{
unsigned int ia_valid = attr->ia_valid;
struct inode *inode = d_inode(dentry);
struct tracefs_inode *ti = get_tracefs(inode);
if (ia_valid & ATTR_UID)
ti->flags |= TRACEFS_UID_PERM_SET;
if (ia_valid & ATTR_GID)
ti->flags |= TRACEFS_GID_PERM_SET;
return simple_setattr(idmap, dentry, attr);
}
static const struct inode_operations tracefs_instance_dir_inode_operations = {
.lookup = simple_lookup,
.mkdir = tracefs_syscall_mkdir,
.rmdir = tracefs_syscall_rmdir,
.permission = tracefs_permission,
.getattr = tracefs_getattr,
.setattr = tracefs_setattr,
};
static const struct inode_operations tracefs_dir_inode_operations = {
.lookup = simple_lookup,
.permission = tracefs_permission,
.getattr = tracefs_getattr,
.setattr = tracefs_setattr,
};
static const struct inode_operations tracefs_file_inode_operations = {
.permission = tracefs_permission,
.getattr = tracefs_getattr,
.setattr = tracefs_setattr,
};
struct inode *tracefs_get_inode(struct super_block *sb)
{
struct inode *inode = new_inode(sb);
if (inode) {
inode->i_ino = get_next_ino();
simple_inode_init_ts(inode);
}
return inode;
}
struct tracefs_fs_info {
kuid_t uid;
kgid_t gid;
umode_t mode;
/* Opt_* bitfield. */
unsigned int opts;
};
enum {
Opt_uid,
Opt_gid,
Opt_mode,
};
static const struct fs_parameter_spec tracefs_param_specs[] = {
fsparam_gid ("gid", Opt_gid),
fsparam_u32oct ("mode", Opt_mode),
fsparam_uid ("uid", Opt_uid),
{}
};
static int tracefs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct tracefs_fs_info *opts = fc->s_fs_info;
struct fs_parse_result result;
int opt;
opt = fs_parse(fc, tracefs_param_specs, param, &result);
if (opt < 0)
return opt;
switch (opt) {
case Opt_uid:
opts->uid = result.uid;
break;
case Opt_gid:
opts->gid = result.gid;
break;
case Opt_mode:
opts->mode = result.uint_32 & S_IALLUGO;
break;
/*
* We might like to report bad mount options here;
* but traditionally tracefs has ignored all mount options
*/
}
opts->opts |= BIT(opt);
return 0;
}
static int tracefs_apply_options(struct super_block *sb, bool remount)
{
struct tracefs_fs_info *fsi = sb->s_fs_info;
struct inode *inode = d_inode(sb->s_root);
struct tracefs_inode *ti;
bool update_uid, update_gid;
umode_t tmp_mode;
/*
* On remount, only reset mode/uid/gid if they were provided as mount
* options.
*/
if (!remount || fsi->opts & BIT(Opt_mode)) {
tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;
tmp_mode |= fsi->mode;
WRITE_ONCE(inode->i_mode, tmp_mode);
}
if (!remount || fsi->opts & BIT(Opt_uid))
inode->i_uid = fsi->uid;
if (!remount || fsi->opts & BIT(Opt_gid))
inode->i_gid = fsi->gid;
if (remount && (fsi->opts & BIT(Opt_uid) || fsi->opts & BIT(Opt_gid))) {
update_uid = fsi->opts & BIT(Opt_uid);
update_gid = fsi->opts & BIT(Opt_gid);
rcu_read_lock();
list_for_each_entry_rcu(ti, &tracefs_inodes, list) {
if (update_uid) {
ti->flags &= ~TRACEFS_UID_PERM_SET;
ti->vfs_inode.i_uid = fsi->uid;
}
if (update_gid) {
ti->flags &= ~TRACEFS_GID_PERM_SET;
ti->vfs_inode.i_gid = fsi->gid;
}
/*
* Note, the above ti->vfs_inode updates are
* used in eventfs_remount() so they must come
* before calling it.
*/
if (ti->flags & TRACEFS_EVENT_INODE)
eventfs_remount(ti, update_uid, update_gid);
}
rcu_read_unlock();
}
return 0;
}
static int tracefs_reconfigure(struct fs_context *fc)
{
struct super_block *sb = fc->root->d_sb;
struct tracefs_fs_info *sb_opts = sb->s_fs_info;
struct tracefs_fs_info *new_opts = fc->s_fs_info;
sync_filesystem(sb);
/* structure copy of new mount options to sb */
*sb_opts = *new_opts;
return tracefs_apply_options(sb, true);
}
static int tracefs_show_options(struct seq_file *m, struct dentry *root)
{
struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
seq_printf(m, ",uid=%u",
from_kuid_munged(&init_user_ns, fsi->uid));
if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
seq_printf(m, ",gid=%u",
from_kgid_munged(&init_user_ns, fsi->gid));
if (fsi->mode != TRACEFS_DEFAULT_MODE)
seq_printf(m, ",mode=%o", fsi->mode);
return 0;
}
static int tracefs_drop_inode(struct inode *inode)
{
struct tracefs_inode *ti = get_tracefs(inode);
/*
* This inode is being freed and cannot be used for
* eventfs. Clear the flag so that it doesn't call into
* eventfs during the remount flag updates. The eventfs_inode
* gets freed after an RCU cycle, so the content will still
* be safe if the iteration is going on now.
*/
ti->flags &= ~TRACEFS_EVENT_INODE;
return 1;
}
static const struct super_operations tracefs_super_operations = {
.alloc_inode = tracefs_alloc_inode,
.free_inode = tracefs_free_inode,
.destroy_inode = tracefs_destroy_inode,
.drop_inode = tracefs_drop_inode,
.statfs = simple_statfs,
.show_options = tracefs_show_options,
};
/*
* It would be cleaner if eventfs had its own dentry ops.
*
* Note that d_revalidate is called potentially under RCU,
* so it can't take the eventfs mutex etc. It's fine - if
* we open a file just as it's marked dead, things will
* still work just fine, and just see the old stale case.
*/
static void tracefs_d_release(struct dentry *dentry)
{
if (dentry->d_fsdata)
eventfs_d_release(dentry);
}
static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
{
struct eventfs_inode *ei = dentry->d_fsdata;
return !(ei && ei->is_freed);
}
static const struct dentry_operations tracefs_dentry_operations = {
.d_revalidate = tracefs_d_revalidate,
.d_release = tracefs_d_release,
};
static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc)
{
static const struct tree_descr trace_files[] = {{""}};
int err;
err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
if (err)
return err;
sb->s_op = &tracefs_super_operations;
sb->s_d_op = &tracefs_dentry_operations;
tracefs_apply_options(sb, false);
return 0;
}
static int tracefs_get_tree(struct fs_context *fc)
{
return get_tree_single(fc, tracefs_fill_super);
}
static void tracefs_free_fc(struct fs_context *fc)
{
kfree(fc->s_fs_info);
}
static const struct fs_context_operations tracefs_context_ops = {
.free = tracefs_free_fc,
.parse_param = tracefs_parse_param,
.get_tree = tracefs_get_tree,
.reconfigure = tracefs_reconfigure,
};
static int tracefs_init_fs_context(struct fs_context *fc)
{
struct tracefs_fs_info *fsi;
fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
if (!fsi)
return -ENOMEM;
fsi->mode = TRACEFS_DEFAULT_MODE;
fc->s_fs_info = fsi;
fc->ops = &tracefs_context_ops;
return 0;
}
static struct file_system_type trace_fs_type = {
.owner = THIS_MODULE,
.name = "tracefs",
.init_fs_context = tracefs_init_fs_context,
.parameters = tracefs_param_specs,
.kill_sb = kill_litter_super,
};
MODULE_ALIAS_FS("tracefs");
struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
{
struct dentry *dentry;
int error;
pr_debug("tracefs: creating file '%s'\n",name);
error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
&tracefs_mount_count);
if (error)
return ERR_PTR(error);
/* If the parent is not specified, we create it in the root.
* We need the root dentry to do this, which is in the super
* block. A pointer to that is in the struct vfsmount that we
* have around.
*/
if (!parent)
parent = tracefs_mount->mnt_root;
inode_lock(d_inode(parent));
if (unlikely(IS_DEADDIR(d_inode(parent))))
dentry = ERR_PTR(-ENOENT);
else
dentry = lookup_one_len(name, parent, strlen(name));
if (!IS_ERR(dentry) && d_inode(dentry)) {
dput(dentry);
dentry = ERR_PTR(-EEXIST);
}
if (IS_ERR(dentry)) {
inode_unlock(d_inode(parent));
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}
return dentry;
}
struct dentry *tracefs_failed_creating(struct dentry *dentry)
{
inode_unlock(d_inode(dentry->d_parent));
dput(dentry);
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
return NULL;
}
struct dentry *tracefs_end_creating(struct dentry *dentry)
{
inode_unlock(d_inode(dentry->d_parent));
return dentry;
}
/* Find the inode that this will use for default */
static struct inode *instance_inode(struct dentry *parent, struct inode *inode)
{
struct tracefs_inode *ti;
/* If parent is NULL then use root inode */
if (!parent)
return d_inode(inode->i_sb->s_root);
/* Find the inode that is flagged as an instance or the root inode */
while (!IS_ROOT(parent)) {
ti = get_tracefs(d_inode(parent));
if (ti->flags & TRACEFS_INSTANCE_INODE)
break;
parent = parent->d_parent;
}
return d_inode(parent);
}
/**
* tracefs_create_file - create a file in the tracefs filesystem
* @name: a pointer to a string containing the name of the file to create.
* @mode: the permission that the file should have.
* @parent: a pointer to the parent dentry for this file. This should be a
* directory dentry if set. If this parameter is NULL, then the
* file will be created in the root of the tracefs filesystem.
* @data: a pointer to something that the caller will want to get to later
* on. The inode.i_private pointer will point to this value on
* the open() call.
* @fops: a pointer to a struct file_operations that should be used for
* this file.
*
* This is the basic "create a file" function for tracefs. It allows for a
* wide range of flexibility in creating a file, or a directory (if you want
* to create a directory, the tracefs_create_dir() function is
* recommended to be used instead.)
*
* This function will return a pointer to a dentry if it succeeds. This
* pointer must be passed to the tracefs_remove() function when the file is
* to be removed (no automatic cleanup happens if your module is unloaded,
* you are responsible here.) If an error occurs, %NULL will be returned.
*
* If tracefs is not enabled in the kernel, the value -%ENODEV will be
* returned.
*/
struct dentry *tracefs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)
{
struct tracefs_inode *ti;
struct dentry *dentry;
struct inode *inode;
if (security_locked_down(LOCKDOWN_TRACEFS))
return NULL;
if (!(mode & S_IFMT))
mode |= S_IFREG;
BUG_ON(!S_ISREG(mode));
dentry = tracefs_start_creating(name, parent);
if (IS_ERR(dentry))
return NULL;
inode = tracefs_get_inode(dentry->d_sb);
if (unlikely(!inode))
return tracefs_failed_creating(dentry);
ti = get_tracefs(inode);
ti->private = instance_inode(parent, inode);
inode->i_mode = mode;
inode->i_op = &tracefs_file_inode_operations;
inode->i_fop = fops ? fops : &tracefs_file_operations;
inode->i_private = data;
inode->i_uid = d_inode(dentry->d_parent)->i_uid;
inode->i_gid = d_inode(dentry->d_parent)->i_gid;
d_instantiate(dentry, inode);
fsnotify_create(d_inode(dentry->d_parent), dentry);
return tracefs_end_creating(dentry);
}
static struct dentry *__create_dir(const char *name, struct dentry *parent,
const struct inode_operations *ops)
{
struct tracefs_inode *ti;
struct dentry *dentry = tracefs_start_creating(name, parent);
struct inode *inode;
if (IS_ERR(dentry))
return NULL;
inode = tracefs_get_inode(dentry->d_sb);
if (unlikely(!inode))
return tracefs_failed_creating(dentry);
/* Do not set bits for OTH */
inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
inode->i_op = ops;
inode->i_fop = &simple_dir_operations;
inode->i_uid = d_inode(dentry->d_parent)->i_uid;
inode->i_gid = d_inode(dentry->d_parent)->i_gid;
ti = get_tracefs(inode);
ti->private = instance_inode(parent, inode);
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
d_instantiate(dentry, inode);
inc_nlink(d_inode(dentry->d_parent));
fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
return tracefs_end_creating(dentry);
}
/**
* tracefs_create_dir - create a directory in the tracefs filesystem
* @name: a pointer to a string containing the name of the directory to
* create.
* @parent: a pointer to the parent dentry for this file. This should be a
* directory dentry if set. If this parameter is NULL, then the
* directory will be created in the root of the tracefs filesystem.
*
* This function creates a directory in tracefs with the given name.
*
* This function will return a pointer to a dentry if it succeeds. This
* pointer must be passed to the tracefs_remove() function when the file is
* to be removed. If an error occurs, %NULL will be returned.
*
* If tracing is not enabled in the kernel, the value -%ENODEV will be
* returned.
*/
struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
{
if (security_locked_down(LOCKDOWN_TRACEFS))
return NULL;
return __create_dir(name, parent, &tracefs_dir_inode_operations);
}
/**
* tracefs_create_instance_dir - create the tracing instances directory
* @name: The name of the instances directory to create
* @parent: The parent directory that the instances directory will exist
* @mkdir: The function to call when a mkdir is performed.
* @rmdir: The function to call when a rmdir is performed.
*
* Only one instances directory is allowed.
*
* The instances directory is special as it allows for mkdir and rmdir
* to be done by userspace. When a mkdir or rmdir is performed, the inode
* locks are released and the methods passed in (@mkdir and @rmdir) are
* called without locks and with the name of the directory being created
* within the instances directory.
*
* Returns the dentry of the instances directory.
*/
__init struct dentry *tracefs_create_instance_dir(const char *name,
struct dentry *parent,
int (*mkdir)(const char *name),
int (*rmdir)(const char *name))
{
struct dentry *dentry;
/* Only allow one instance of the instances directory. */
if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
return NULL;
dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations);
if (!dentry)
return NULL;
tracefs_ops.mkdir = mkdir;
tracefs_ops.rmdir = rmdir;
return dentry;
}
static void remove_one(struct dentry *victim)
{
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}
/**
* tracefs_remove - recursively removes a directory
* @dentry: a pointer to a the dentry of the directory to be removed.
*
* This function recursively removes a directory tree in tracefs that
* was previously created with a call to another tracefs function
* (like tracefs_create_file() or variants thereof.)
*/
void tracefs_remove(struct dentry *dentry)
{
if (IS_ERR_OR_NULL(dentry))
return;
simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
simple_recursive_removal(dentry, remove_one);
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}
/**
* tracefs_initialized - Tells whether tracefs has been registered
*/
bool tracefs_initialized(void)
{
return tracefs_registered;
}
static void init_once(void *foo)
{
struct tracefs_inode *ti = (struct tracefs_inode *) foo;
/* inode_init_once() calls memset() on the vfs_inode portion */
inode_init_once(&ti->vfs_inode);
/* Zero out the rest */
memset_after(ti, 0, vfs_inode);
}
static int __init tracefs_init(void)
{
int retval;
tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",
sizeof(struct tracefs_inode),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_ACCOUNT),
init_once);
if (!tracefs_inode_cachep)
return -ENOMEM;
retval = sysfs_create_mount_point(kernel_kobj, "tracing");
if (retval)
return -EINVAL;
retval = register_filesystem(&trace_fs_type);
if (!retval)
tracefs_registered = true;
return retval;
}
core_initcall(tracefs_init);
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