linux/fs/kernfs/dir.c
Linus Torvalds 0cbee99269 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull user namespace updates from Eric Biederman:
 "Long ago and far away when user namespaces where young it was realized
  that allowing fresh mounts of proc and sysfs with only user namespace
  permissions could violate the basic rule that only root gets to decide
  if proc or sysfs should be mounted at all.

  Some hacks were put in place to reduce the worst of the damage could
  be done, and the common sense rule was adopted that fresh mounts of
  proc and sysfs should allow no more than bind mounts of proc and
  sysfs.  Unfortunately that rule has not been fully enforced.

  There are two kinds of gaps in that enforcement.  Only filesystems
  mounted on empty directories of proc and sysfs should be ignored but
  the test for empty directories was insufficient.  So in my tree
  directories on proc, sysctl and sysfs that will always be empty are
  created specially.  Every other technique is imperfect as an ordinary
  directory can have entries added even after a readdir returns and
  shows that the directory is empty.  Special creation of directories
  for mount points makes the code in the kernel a smidge clearer about
  it's purpose.  I asked container developers from the various container
  projects to help test this and no holes were found in the set of mount
  points on proc and sysfs that are created specially.

  This set of changes also starts enforcing the mount flags of fresh
  mounts of proc and sysfs are consistent with the existing mount of
  proc and sysfs.  I expected this to be the boring part of the work but
  unfortunately unprivileged userspace winds up mounting fresh copies of
  proc and sysfs with noexec and nosuid clear when root set those flags
  on the previous mount of proc and sysfs.  So for now only the atime,
  read-only and nodev attributes which userspace happens to keep
  consistent are enforced.  Dealing with the noexec and nosuid
  attributes remains for another time.

  This set of changes also addresses an issue with how open file
  descriptors from /proc/<pid>/ns/* are displayed.  Recently readlink of
  /proc/<pid>/fd has been triggering a WARN_ON that has not been
  meaningful since it was added (as all of the code in the kernel was
  converted) and is not now actively wrong.

  There is also a short list of issues that have not been fixed yet that
  I will mention briefly.

  It is possible to rename a directory from below to above a bind mount.
  At which point any directory pointers below the renamed directory can
  be walked up to the root directory of the filesystem.  With user
  namespaces enabled a bind mount of the bind mount can be created
  allowing the user to pick a directory whose children they can rename
  to outside of the bind mount.  This is challenging to fix and doubly
  so because all obvious solutions must touch code that is in the
  performance part of pathname resolution.

  As mentioned above there is also a question of how to ensure that
  developers by accident or with purpose do not introduce exectuable
  files on sysfs and proc and in doing so introduce security regressions
  in the current userspace that will not be immediately obvious and as
  such are likely to require breaking userspace in painful ways once
  they are recognized"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  vfs: Remove incorrect debugging WARN in prepend_path
  mnt: Update fs_fully_visible to test for permanently empty directories
  sysfs: Create mountpoints with sysfs_create_mount_point
  sysfs: Add support for permanently empty directories to serve as mount points.
  kernfs: Add support for always empty directories.
  proc: Allow creating permanently empty directories that serve as mount points
  sysctl: Allow creating permanently empty directories that serve as mountpoints.
  fs: Add helper functions for permanently empty directories.
  vfs: Ignore unlocked mounts in fs_fully_visible
  mnt: Modify fs_fully_visible to deal with locked ro nodev and atime
  mnt: Refactor the logic for mounting sysfs and proc in a user namespace
2015-07-03 15:20:57 -07:00

1465 lines
36 KiB
C

/*
* fs/kernfs/dir.c - kernfs directory implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
*
* This file is released under the GPLv2.
*/
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/idr.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/hash.h>
#include "kernfs-internal.h"
DEFINE_MUTEX(kernfs_mutex);
static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */
#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
static bool kernfs_active(struct kernfs_node *kn)
{
lockdep_assert_held(&kernfs_mutex);
return atomic_read(&kn->active) >= 0;
}
static bool kernfs_lockdep(struct kernfs_node *kn)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
return kn->flags & KERNFS_LOCKDEP;
#else
return false;
#endif
}
static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
{
return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
}
static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf,
size_t buflen)
{
char *p = buf + buflen;
int len;
*--p = '\0';
do {
len = strlen(kn->name);
if (p - buf < len + 1) {
buf[0] = '\0';
p = NULL;
break;
}
p -= len;
memcpy(p, kn->name, len);
*--p = '/';
kn = kn->parent;
} while (kn && kn->parent);
return p;
}
/**
* kernfs_name - obtain the name of a given node
* @kn: kernfs_node of interest
* @buf: buffer to copy @kn's name into
* @buflen: size of @buf
*
* Copies the name of @kn into @buf of @buflen bytes. The behavior is
* similar to strlcpy(). It returns the length of @kn's name and if @buf
* isn't long enough, it's filled upto @buflen-1 and nul terminated.
*
* This function can be called from any context.
*/
int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
{
unsigned long flags;
int ret;
spin_lock_irqsave(&kernfs_rename_lock, flags);
ret = kernfs_name_locked(kn, buf, buflen);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
return ret;
}
/**
* kernfs_path - build full path of a given node
* @kn: kernfs_node of interest
* @buf: buffer to copy @kn's name into
* @buflen: size of @buf
*
* Builds and returns the full path of @kn in @buf of @buflen bytes. The
* path is built from the end of @buf so the returned pointer usually
* doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
* and %NULL is returned.
*/
char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
{
unsigned long flags;
char *p;
spin_lock_irqsave(&kernfs_rename_lock, flags);
p = kernfs_path_locked(kn, buf, buflen);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
return p;
}
EXPORT_SYMBOL_GPL(kernfs_path);
/**
* pr_cont_kernfs_name - pr_cont name of a kernfs_node
* @kn: kernfs_node of interest
*
* This function can be called from any context.
*/
void pr_cont_kernfs_name(struct kernfs_node *kn)
{
unsigned long flags;
spin_lock_irqsave(&kernfs_rename_lock, flags);
kernfs_name_locked(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
pr_cont("%s", kernfs_pr_cont_buf);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
}
/**
* pr_cont_kernfs_path - pr_cont path of a kernfs_node
* @kn: kernfs_node of interest
*
* This function can be called from any context.
*/
void pr_cont_kernfs_path(struct kernfs_node *kn)
{
unsigned long flags;
char *p;
spin_lock_irqsave(&kernfs_rename_lock, flags);
p = kernfs_path_locked(kn, kernfs_pr_cont_buf,
sizeof(kernfs_pr_cont_buf));
if (p)
pr_cont("%s", p);
else
pr_cont("<name too long>");
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
}
/**
* kernfs_get_parent - determine the parent node and pin it
* @kn: kernfs_node of interest
*
* Determines @kn's parent, pins and returns it. This function can be
* called from any context.
*/
struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
{
struct kernfs_node *parent;
unsigned long flags;
spin_lock_irqsave(&kernfs_rename_lock, flags);
parent = kn->parent;
kernfs_get(parent);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
return parent;
}
/**
* kernfs_name_hash
* @name: Null terminated string to hash
* @ns: Namespace tag to hash
*
* Returns 31 bit hash of ns + name (so it fits in an off_t )
*/
static unsigned int kernfs_name_hash(const char *name, const void *ns)
{
unsigned long hash = init_name_hash();
unsigned int len = strlen(name);
while (len--)
hash = partial_name_hash(*name++, hash);
hash = (end_name_hash(hash) ^ hash_ptr((void *)ns, 31));
hash &= 0x7fffffffU;
/* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
if (hash < 2)
hash += 2;
if (hash >= INT_MAX)
hash = INT_MAX - 1;
return hash;
}
static int kernfs_name_compare(unsigned int hash, const char *name,
const void *ns, const struct kernfs_node *kn)
{
if (hash < kn->hash)
return -1;
if (hash > kn->hash)
return 1;
if (ns < kn->ns)
return -1;
if (ns > kn->ns)
return 1;
return strcmp(name, kn->name);
}
static int kernfs_sd_compare(const struct kernfs_node *left,
const struct kernfs_node *right)
{
return kernfs_name_compare(left->hash, left->name, left->ns, right);
}
/**
* kernfs_link_sibling - link kernfs_node into sibling rbtree
* @kn: kernfs_node of interest
*
* Link @kn into its sibling rbtree which starts from
* @kn->parent->dir.children.
*
* Locking:
* mutex_lock(kernfs_mutex)
*
* RETURNS:
* 0 on susccess -EEXIST on failure.
*/
static int kernfs_link_sibling(struct kernfs_node *kn)
{
struct rb_node **node = &kn->parent->dir.children.rb_node;
struct rb_node *parent = NULL;
while (*node) {
struct kernfs_node *pos;
int result;
pos = rb_to_kn(*node);
parent = *node;
result = kernfs_sd_compare(kn, pos);
if (result < 0)
node = &pos->rb.rb_left;
else if (result > 0)
node = &pos->rb.rb_right;
else
return -EEXIST;
}
/* add new node and rebalance the tree */
rb_link_node(&kn->rb, parent, node);
rb_insert_color(&kn->rb, &kn->parent->dir.children);
/* successfully added, account subdir number */
if (kernfs_type(kn) == KERNFS_DIR)
kn->parent->dir.subdirs++;
return 0;
}
/**
* kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
* @kn: kernfs_node of interest
*
* Try to unlink @kn from its sibling rbtree which starts from
* kn->parent->dir.children. Returns %true if @kn was actually
* removed, %false if @kn wasn't on the rbtree.
*
* Locking:
* mutex_lock(kernfs_mutex)
*/
static bool kernfs_unlink_sibling(struct kernfs_node *kn)
{
if (RB_EMPTY_NODE(&kn->rb))
return false;
if (kernfs_type(kn) == KERNFS_DIR)
kn->parent->dir.subdirs--;
rb_erase(&kn->rb, &kn->parent->dir.children);
RB_CLEAR_NODE(&kn->rb);
return true;
}
/**
* kernfs_get_active - get an active reference to kernfs_node
* @kn: kernfs_node to get an active reference to
*
* Get an active reference of @kn. This function is noop if @kn
* is NULL.
*
* RETURNS:
* Pointer to @kn on success, NULL on failure.
*/
struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
{
if (unlikely(!kn))
return NULL;
if (!atomic_inc_unless_negative(&kn->active))
return NULL;
if (kernfs_lockdep(kn))
rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
return kn;
}
/**
* kernfs_put_active - put an active reference to kernfs_node
* @kn: kernfs_node to put an active reference to
*
* Put an active reference to @kn. This function is noop if @kn
* is NULL.
*/
void kernfs_put_active(struct kernfs_node *kn)
{
struct kernfs_root *root = kernfs_root(kn);
int v;
if (unlikely(!kn))
return;
if (kernfs_lockdep(kn))
rwsem_release(&kn->dep_map, 1, _RET_IP_);
v = atomic_dec_return(&kn->active);
if (likely(v != KN_DEACTIVATED_BIAS))
return;
wake_up_all(&root->deactivate_waitq);
}
/**
* kernfs_drain - drain kernfs_node
* @kn: kernfs_node to drain
*
* Drain existing usages and nuke all existing mmaps of @kn. Mutiple
* removers may invoke this function concurrently on @kn and all will
* return after draining is complete.
*/
static void kernfs_drain(struct kernfs_node *kn)
__releases(&kernfs_mutex) __acquires(&kernfs_mutex)
{
struct kernfs_root *root = kernfs_root(kn);
lockdep_assert_held(&kernfs_mutex);
WARN_ON_ONCE(kernfs_active(kn));
mutex_unlock(&kernfs_mutex);
if (kernfs_lockdep(kn)) {
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
lock_contended(&kn->dep_map, _RET_IP_);
}
/* but everyone should wait for draining */
wait_event(root->deactivate_waitq,
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
if (kernfs_lockdep(kn)) {
lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_);
}
kernfs_unmap_bin_file(kn);
mutex_lock(&kernfs_mutex);
}
/**
* kernfs_get - get a reference count on a kernfs_node
* @kn: the target kernfs_node
*/
void kernfs_get(struct kernfs_node *kn)
{
if (kn) {
WARN_ON(!atomic_read(&kn->count));
atomic_inc(&kn->count);
}
}
EXPORT_SYMBOL_GPL(kernfs_get);
/**
* kernfs_put - put a reference count on a kernfs_node
* @kn: the target kernfs_node
*
* Put a reference count of @kn and destroy it if it reached zero.
*/
void kernfs_put(struct kernfs_node *kn)
{
struct kernfs_node *parent;
struct kernfs_root *root;
if (!kn || !atomic_dec_and_test(&kn->count))
return;
root = kernfs_root(kn);
repeat:
/*
* Moving/renaming is always done while holding reference.
* kn->parent won't change beneath us.
*/
parent = kn->parent;
WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
"kernfs_put: %s/%s: released with incorrect active_ref %d\n",
parent ? parent->name : "", kn->name, atomic_read(&kn->active));
if (kernfs_type(kn) == KERNFS_LINK)
kernfs_put(kn->symlink.target_kn);
kfree_const(kn->name);
if (kn->iattr) {
if (kn->iattr->ia_secdata)
security_release_secctx(kn->iattr->ia_secdata,
kn->iattr->ia_secdata_len);
simple_xattrs_free(&kn->iattr->xattrs);
}
kfree(kn->iattr);
ida_simple_remove(&root->ino_ida, kn->ino);
kmem_cache_free(kernfs_node_cache, kn);
kn = parent;
if (kn) {
if (atomic_dec_and_test(&kn->count))
goto repeat;
} else {
/* just released the root kn, free @root too */
ida_destroy(&root->ino_ida);
kfree(root);
}
}
EXPORT_SYMBOL_GPL(kernfs_put);
static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
{
struct kernfs_node *kn;
if (flags & LOOKUP_RCU)
return -ECHILD;
/* Always perform fresh lookup for negatives */
if (d_really_is_negative(dentry))
goto out_bad_unlocked;
kn = dentry->d_fsdata;
mutex_lock(&kernfs_mutex);
/* The kernfs node has been deactivated */
if (!kernfs_active(kn))
goto out_bad;
/* The kernfs node has been moved? */
if (dentry->d_parent->d_fsdata != kn->parent)
goto out_bad;
/* The kernfs node has been renamed */
if (strcmp(dentry->d_name.name, kn->name) != 0)
goto out_bad;
/* The kernfs node has been moved to a different namespace */
if (kn->parent && kernfs_ns_enabled(kn->parent) &&
kernfs_info(dentry->d_sb)->ns != kn->ns)
goto out_bad;
mutex_unlock(&kernfs_mutex);
return 1;
out_bad:
mutex_unlock(&kernfs_mutex);
out_bad_unlocked:
return 0;
}
static void kernfs_dop_release(struct dentry *dentry)
{
kernfs_put(dentry->d_fsdata);
}
const struct dentry_operations kernfs_dops = {
.d_revalidate = kernfs_dop_revalidate,
.d_release = kernfs_dop_release,
};
/**
* kernfs_node_from_dentry - determine kernfs_node associated with a dentry
* @dentry: the dentry in question
*
* Return the kernfs_node associated with @dentry. If @dentry is not a
* kernfs one, %NULL is returned.
*
* While the returned kernfs_node will stay accessible as long as @dentry
* is accessible, the returned node can be in any state and the caller is
* fully responsible for determining what's accessible.
*/
struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
{
if (dentry->d_sb->s_op == &kernfs_sops)
return dentry->d_fsdata;
return NULL;
}
static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
const char *name, umode_t mode,
unsigned flags)
{
struct kernfs_node *kn;
int ret;
name = kstrdup_const(name, GFP_KERNEL);
if (!name)
return NULL;
kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
if (!kn)
goto err_out1;
/*
* If the ino of the sysfs entry created for a kmem cache gets
* allocated from an ida layer, which is accounted to the memcg that
* owns the cache, the memcg will get pinned forever. So do not account
* ino ida allocations.
*/
ret = ida_simple_get(&root->ino_ida, 1, 0,
GFP_KERNEL | __GFP_NOACCOUNT);
if (ret < 0)
goto err_out2;
kn->ino = ret;
atomic_set(&kn->count, 1);
atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
RB_CLEAR_NODE(&kn->rb);
kn->name = name;
kn->mode = mode;
kn->flags = flags;
return kn;
err_out2:
kmem_cache_free(kernfs_node_cache, kn);
err_out1:
kfree_const(name);
return NULL;
}
struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
const char *name, umode_t mode,
unsigned flags)
{
struct kernfs_node *kn;
kn = __kernfs_new_node(kernfs_root(parent), name, mode, flags);
if (kn) {
kernfs_get(parent);
kn->parent = parent;
}
return kn;
}
/**
* kernfs_add_one - add kernfs_node to parent without warning
* @kn: kernfs_node to be added
*
* The caller must already have initialized @kn->parent. This
* function increments nlink of the parent's inode if @kn is a
* directory and link into the children list of the parent.
*
* RETURNS:
* 0 on success, -EEXIST if entry with the given name already
* exists.
*/
int kernfs_add_one(struct kernfs_node *kn)
{
struct kernfs_node *parent = kn->parent;
struct kernfs_iattrs *ps_iattr;
bool has_ns;
int ret;
mutex_lock(&kernfs_mutex);
ret = -EINVAL;
has_ns = kernfs_ns_enabled(parent);
if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
has_ns ? "required" : "invalid", parent->name, kn->name))
goto out_unlock;
if (kernfs_type(parent) != KERNFS_DIR)
goto out_unlock;
ret = -ENOENT;
if (parent->flags & KERNFS_EMPTY_DIR)
goto out_unlock;
if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
goto out_unlock;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
ret = kernfs_link_sibling(kn);
if (ret)
goto out_unlock;
/* Update timestamps on the parent */
ps_iattr = parent->iattr;
if (ps_iattr) {
struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
}
mutex_unlock(&kernfs_mutex);
/*
* Activate the new node unless CREATE_DEACTIVATED is requested.
* If not activated here, the kernfs user is responsible for
* activating the node with kernfs_activate(). A node which hasn't
* been activated is not visible to userland and its removal won't
* trigger deactivation.
*/
if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
kernfs_activate(kn);
return 0;
out_unlock:
mutex_unlock(&kernfs_mutex);
return ret;
}
/**
* kernfs_find_ns - find kernfs_node with the given name
* @parent: kernfs_node to search under
* @name: name to look for
* @ns: the namespace tag to use
*
* Look for kernfs_node with name @name under @parent. Returns pointer to
* the found kernfs_node on success, %NULL on failure.
*/
static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
const unsigned char *name,
const void *ns)
{
struct rb_node *node = parent->dir.children.rb_node;
bool has_ns = kernfs_ns_enabled(parent);
unsigned int hash;
lockdep_assert_held(&kernfs_mutex);
if (has_ns != (bool)ns) {
WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
has_ns ? "required" : "invalid", parent->name, name);
return NULL;
}
hash = kernfs_name_hash(name, ns);
while (node) {
struct kernfs_node *kn;
int result;
kn = rb_to_kn(node);
result = kernfs_name_compare(hash, name, ns, kn);
if (result < 0)
node = node->rb_left;
else if (result > 0)
node = node->rb_right;
else
return kn;
}
return NULL;
}
/**
* kernfs_find_and_get_ns - find and get kernfs_node with the given name
* @parent: kernfs_node to search under
* @name: name to look for
* @ns: the namespace tag to use
*
* Look for kernfs_node with name @name under @parent and get a reference
* if found. This function may sleep and returns pointer to the found
* kernfs_node on success, %NULL on failure.
*/
struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
const char *name, const void *ns)
{
struct kernfs_node *kn;
mutex_lock(&kernfs_mutex);
kn = kernfs_find_ns(parent, name, ns);
kernfs_get(kn);
mutex_unlock(&kernfs_mutex);
return kn;
}
EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
/**
* kernfs_create_root - create a new kernfs hierarchy
* @scops: optional syscall operations for the hierarchy
* @flags: KERNFS_ROOT_* flags
* @priv: opaque data associated with the new directory
*
* Returns the root of the new hierarchy on success, ERR_PTR() value on
* failure.
*/
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
unsigned int flags, void *priv)
{
struct kernfs_root *root;
struct kernfs_node *kn;
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root)
return ERR_PTR(-ENOMEM);
ida_init(&root->ino_ida);
INIT_LIST_HEAD(&root->supers);
kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
KERNFS_DIR);
if (!kn) {
ida_destroy(&root->ino_ida);
kfree(root);
return ERR_PTR(-ENOMEM);
}
kn->priv = priv;
kn->dir.root = root;
root->syscall_ops = scops;
root->flags = flags;
root->kn = kn;
init_waitqueue_head(&root->deactivate_waitq);
if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
kernfs_activate(kn);
return root;
}
/**
* kernfs_destroy_root - destroy a kernfs hierarchy
* @root: root of the hierarchy to destroy
*
* Destroy the hierarchy anchored at @root by removing all existing
* directories and destroying @root.
*/
void kernfs_destroy_root(struct kernfs_root *root)
{
kernfs_remove(root->kn); /* will also free @root */
}
/**
* kernfs_create_dir_ns - create a directory
* @parent: parent in which to create a new directory
* @name: name of the new directory
* @mode: mode of the new directory
* @priv: opaque data associated with the new directory
* @ns: optional namespace tag of the directory
*
* Returns the created node on success, ERR_PTR() value on failure.
*/
struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
const char *name, umode_t mode,
void *priv, const void *ns)
{
struct kernfs_node *kn;
int rc;
/* allocate */
kn = kernfs_new_node(parent, name, mode | S_IFDIR, KERNFS_DIR);
if (!kn)
return ERR_PTR(-ENOMEM);
kn->dir.root = parent->dir.root;
kn->ns = ns;
kn->priv = priv;
/* link in */
rc = kernfs_add_one(kn);
if (!rc)
return kn;
kernfs_put(kn);
return ERR_PTR(rc);
}
/**
* kernfs_create_empty_dir - create an always empty directory
* @parent: parent in which to create a new directory
* @name: name of the new directory
*
* Returns the created node on success, ERR_PTR() value on failure.
*/
struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
const char *name)
{
struct kernfs_node *kn;
int rc;
/* allocate */
kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR, KERNFS_DIR);
if (!kn)
return ERR_PTR(-ENOMEM);
kn->flags |= KERNFS_EMPTY_DIR;
kn->dir.root = parent->dir.root;
kn->ns = NULL;
kn->priv = NULL;
/* link in */
rc = kernfs_add_one(kn);
if (!rc)
return kn;
kernfs_put(kn);
return ERR_PTR(rc);
}
static struct dentry *kernfs_iop_lookup(struct inode *dir,
struct dentry *dentry,
unsigned int flags)
{
struct dentry *ret;
struct kernfs_node *parent = dentry->d_parent->d_fsdata;
struct kernfs_node *kn;
struct inode *inode;
const void *ns = NULL;
mutex_lock(&kernfs_mutex);
if (kernfs_ns_enabled(parent))
ns = kernfs_info(dir->i_sb)->ns;
kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
/* no such entry */
if (!kn || !kernfs_active(kn)) {
ret = NULL;
goto out_unlock;
}
kernfs_get(kn);
dentry->d_fsdata = kn;
/* attach dentry and inode */
inode = kernfs_get_inode(dir->i_sb, kn);
if (!inode) {
ret = ERR_PTR(-ENOMEM);
goto out_unlock;
}
/* instantiate and hash dentry */
ret = d_splice_alias(inode, dentry);
out_unlock:
mutex_unlock(&kernfs_mutex);
return ret;
}
static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
umode_t mode)
{
struct kernfs_node *parent = dir->i_private;
struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
int ret;
if (!scops || !scops->mkdir)
return -EPERM;
if (!kernfs_get_active(parent))
return -ENODEV;
ret = scops->mkdir(parent, dentry->d_name.name, mode);
kernfs_put_active(parent);
return ret;
}
static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
int ret;
if (!scops || !scops->rmdir)
return -EPERM;
if (!kernfs_get_active(kn))
return -ENODEV;
ret = scops->rmdir(kn);
kernfs_put_active(kn);
return ret;
}
static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
struct kernfs_node *kn = old_dentry->d_fsdata;
struct kernfs_node *new_parent = new_dir->i_private;
struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
int ret;
if (!scops || !scops->rename)
return -EPERM;
if (!kernfs_get_active(kn))
return -ENODEV;
if (!kernfs_get_active(new_parent)) {
kernfs_put_active(kn);
return -ENODEV;
}
ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
kernfs_put_active(new_parent);
kernfs_put_active(kn);
return ret;
}
const struct inode_operations kernfs_dir_iops = {
.lookup = kernfs_iop_lookup,
.permission = kernfs_iop_permission,
.setattr = kernfs_iop_setattr,
.getattr = kernfs_iop_getattr,
.setxattr = kernfs_iop_setxattr,
.removexattr = kernfs_iop_removexattr,
.getxattr = kernfs_iop_getxattr,
.listxattr = kernfs_iop_listxattr,
.mkdir = kernfs_iop_mkdir,
.rmdir = kernfs_iop_rmdir,
.rename = kernfs_iop_rename,
};
static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos)
{
struct kernfs_node *last;
while (true) {
struct rb_node *rbn;
last = pos;
if (kernfs_type(pos) != KERNFS_DIR)
break;
rbn = rb_first(&pos->dir.children);
if (!rbn)
break;
pos = rb_to_kn(rbn);
}
return last;
}
/**
* kernfs_next_descendant_post - find the next descendant for post-order walk
* @pos: the current position (%NULL to initiate traversal)
* @root: kernfs_node whose descendants to walk
*
* Find the next descendant to visit for post-order traversal of @root's
* descendants. @root is included in the iteration and the last node to be
* visited.
*/
static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
struct kernfs_node *root)
{
struct rb_node *rbn;
lockdep_assert_held(&kernfs_mutex);
/* if first iteration, visit leftmost descendant which may be root */
if (!pos)
return kernfs_leftmost_descendant(root);
/* if we visited @root, we're done */
if (pos == root)
return NULL;
/* if there's an unvisited sibling, visit its leftmost descendant */
rbn = rb_next(&pos->rb);
if (rbn)
return kernfs_leftmost_descendant(rb_to_kn(rbn));
/* no sibling left, visit parent */
return pos->parent;
}
/**
* kernfs_activate - activate a node which started deactivated
* @kn: kernfs_node whose subtree is to be activated
*
* If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
* needs to be explicitly activated. A node which hasn't been activated
* isn't visible to userland and deactivation is skipped during its
* removal. This is useful to construct atomic init sequences where
* creation of multiple nodes should either succeed or fail atomically.
*
* The caller is responsible for ensuring that this function is not called
* after kernfs_remove*() is invoked on @kn.
*/
void kernfs_activate(struct kernfs_node *kn)
{
struct kernfs_node *pos;
mutex_lock(&kernfs_mutex);
pos = NULL;
while ((pos = kernfs_next_descendant_post(pos, kn))) {
if (!pos || (pos->flags & KERNFS_ACTIVATED))
continue;
WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb));
WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS);
atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
pos->flags |= KERNFS_ACTIVATED;
}
mutex_unlock(&kernfs_mutex);
}
static void __kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_node *pos;
lockdep_assert_held(&kernfs_mutex);
/*
* Short-circuit if non-root @kn has already finished removal.
* This is for kernfs_remove_self() which plays with active ref
* after removal.
*/
if (!kn || (kn->parent && RB_EMPTY_NODE(&kn->rb)))
return;
pr_debug("kernfs %s: removing\n", kn->name);
/* prevent any new usage under @kn by deactivating all nodes */
pos = NULL;
while ((pos = kernfs_next_descendant_post(pos, kn)))
if (kernfs_active(pos))
atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
/* deactivate and unlink the subtree node-by-node */
do {
pos = kernfs_leftmost_descendant(kn);
/*
* kernfs_drain() drops kernfs_mutex temporarily and @pos's
* base ref could have been put by someone else by the time
* the function returns. Make sure it doesn't go away
* underneath us.
*/
kernfs_get(pos);
/*
* Drain iff @kn was activated. This avoids draining and
* its lockdep annotations for nodes which have never been
* activated and allows embedding kernfs_remove() in create
* error paths without worrying about draining.
*/
if (kn->flags & KERNFS_ACTIVATED)
kernfs_drain(pos);
else
WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
/*
* kernfs_unlink_sibling() succeeds once per node. Use it
* to decide who's responsible for cleanups.
*/
if (!pos->parent || kernfs_unlink_sibling(pos)) {
struct kernfs_iattrs *ps_iattr =
pos->parent ? pos->parent->iattr : NULL;
/* update timestamps on the parent */
if (ps_iattr) {
ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
}
kernfs_put(pos);
}
kernfs_put(pos);
} while (pos != kn);
}
/**
* kernfs_remove - remove a kernfs_node recursively
* @kn: the kernfs_node to remove
*
* Remove @kn along with all its subdirectories and files.
*/
void kernfs_remove(struct kernfs_node *kn)
{
mutex_lock(&kernfs_mutex);
__kernfs_remove(kn);
mutex_unlock(&kernfs_mutex);
}
/**
* kernfs_break_active_protection - break out of active protection
* @kn: the self kernfs_node
*
* The caller must be running off of a kernfs operation which is invoked
* with an active reference - e.g. one of kernfs_ops. Each invocation of
* this function must also be matched with an invocation of
* kernfs_unbreak_active_protection().
*
* This function releases the active reference of @kn the caller is
* holding. Once this function is called, @kn may be removed at any point
* and the caller is solely responsible for ensuring that the objects it
* dereferences are accessible.
*/
void kernfs_break_active_protection(struct kernfs_node *kn)
{
/*
* Take out ourself out of the active ref dependency chain. If
* we're called without an active ref, lockdep will complain.
*/
kernfs_put_active(kn);
}
/**
* kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
* @kn: the self kernfs_node
*
* If kernfs_break_active_protection() was called, this function must be
* invoked before finishing the kernfs operation. Note that while this
* function restores the active reference, it doesn't and can't actually
* restore the active protection - @kn may already or be in the process of
* being removed. Once kernfs_break_active_protection() is invoked, that
* protection is irreversibly gone for the kernfs operation instance.
*
* While this function may be called at any point after
* kernfs_break_active_protection() is invoked, its most useful location
* would be right before the enclosing kernfs operation returns.
*/
void kernfs_unbreak_active_protection(struct kernfs_node *kn)
{
/*
* @kn->active could be in any state; however, the increment we do
* here will be undone as soon as the enclosing kernfs operation
* finishes and this temporary bump can't break anything. If @kn
* is alive, nothing changes. If @kn is being deactivated, the
* soon-to-follow put will either finish deactivation or restore
* deactivated state. If @kn is already removed, the temporary
* bump is guaranteed to be gone before @kn is released.
*/
atomic_inc(&kn->active);
if (kernfs_lockdep(kn))
rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
}
/**
* kernfs_remove_self - remove a kernfs_node from its own method
* @kn: the self kernfs_node to remove
*
* The caller must be running off of a kernfs operation which is invoked
* with an active reference - e.g. one of kernfs_ops. This can be used to
* implement a file operation which deletes itself.
*
* For example, the "delete" file for a sysfs device directory can be
* implemented by invoking kernfs_remove_self() on the "delete" file
* itself. This function breaks the circular dependency of trying to
* deactivate self while holding an active ref itself. It isn't necessary
* to modify the usual removal path to use kernfs_remove_self(). The
* "delete" implementation can simply invoke kernfs_remove_self() on self
* before proceeding with the usual removal path. kernfs will ignore later
* kernfs_remove() on self.
*
* kernfs_remove_self() can be called multiple times concurrently on the
* same kernfs_node. Only the first one actually performs removal and
* returns %true. All others will wait until the kernfs operation which
* won self-removal finishes and return %false. Note that the losers wait
* for the completion of not only the winning kernfs_remove_self() but also
* the whole kernfs_ops which won the arbitration. This can be used to
* guarantee, for example, all concurrent writes to a "delete" file to
* finish only after the whole operation is complete.
*/
bool kernfs_remove_self(struct kernfs_node *kn)
{
bool ret;
mutex_lock(&kernfs_mutex);
kernfs_break_active_protection(kn);
/*
* SUICIDAL is used to arbitrate among competing invocations. Only
* the first one will actually perform removal. When the removal
* is complete, SUICIDED is set and the active ref is restored
* while holding kernfs_mutex. The ones which lost arbitration
* waits for SUICDED && drained which can happen only after the
* enclosing kernfs operation which executed the winning instance
* of kernfs_remove_self() finished.
*/
if (!(kn->flags & KERNFS_SUICIDAL)) {
kn->flags |= KERNFS_SUICIDAL;
__kernfs_remove(kn);
kn->flags |= KERNFS_SUICIDED;
ret = true;
} else {
wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
DEFINE_WAIT(wait);
while (true) {
prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
if ((kn->flags & KERNFS_SUICIDED) &&
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
break;
mutex_unlock(&kernfs_mutex);
schedule();
mutex_lock(&kernfs_mutex);
}
finish_wait(waitq, &wait);
WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
ret = false;
}
/*
* This must be done while holding kernfs_mutex; otherwise, waiting
* for SUICIDED && deactivated could finish prematurely.
*/
kernfs_unbreak_active_protection(kn);
mutex_unlock(&kernfs_mutex);
return ret;
}
/**
* kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
* @parent: parent of the target
* @name: name of the kernfs_node to remove
* @ns: namespace tag of the kernfs_node to remove
*
* Look for the kernfs_node with @name and @ns under @parent and remove it.
* Returns 0 on success, -ENOENT if such entry doesn't exist.
*/
int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{
struct kernfs_node *kn;
if (!parent) {
WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
name);
return -ENOENT;
}
mutex_lock(&kernfs_mutex);
kn = kernfs_find_ns(parent, name, ns);
if (kn)
__kernfs_remove(kn);
mutex_unlock(&kernfs_mutex);
if (kn)
return 0;
else
return -ENOENT;
}
/**
* kernfs_rename_ns - move and rename a kernfs_node
* @kn: target node
* @new_parent: new parent to put @sd under
* @new_name: new name
* @new_ns: new namespace tag
*/
int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
const char *new_name, const void *new_ns)
{
struct kernfs_node *old_parent;
const char *old_name = NULL;
int error;
/* can't move or rename root */
if (!kn->parent)
return -EINVAL;
mutex_lock(&kernfs_mutex);
error = -ENOENT;
if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
(new_parent->flags & KERNFS_EMPTY_DIR))
goto out;
error = 0;
if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
(strcmp(kn->name, new_name) == 0))
goto out; /* nothing to rename */
error = -EEXIST;
if (kernfs_find_ns(new_parent, new_name, new_ns))
goto out;
/* rename kernfs_node */
if (strcmp(kn->name, new_name) != 0) {
error = -ENOMEM;
new_name = kstrdup_const(new_name, GFP_KERNEL);
if (!new_name)
goto out;
} else {
new_name = NULL;
}
/*
* Move to the appropriate place in the appropriate directories rbtree.
*/
kernfs_unlink_sibling(kn);
kernfs_get(new_parent);
/* rename_lock protects ->parent and ->name accessors */
spin_lock_irq(&kernfs_rename_lock);
old_parent = kn->parent;
kn->parent = new_parent;
kn->ns = new_ns;
if (new_name) {
old_name = kn->name;
kn->name = new_name;
}
spin_unlock_irq(&kernfs_rename_lock);
kn->hash = kernfs_name_hash(kn->name, kn->ns);
kernfs_link_sibling(kn);
kernfs_put(old_parent);
kfree_const(old_name);
error = 0;
out:
mutex_unlock(&kernfs_mutex);
return error;
}
/* Relationship between s_mode and the DT_xxx types */
static inline unsigned char dt_type(struct kernfs_node *kn)
{
return (kn->mode >> 12) & 15;
}
static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
{
kernfs_put(filp->private_data);
return 0;
}
static struct kernfs_node *kernfs_dir_pos(const void *ns,
struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
{
if (pos) {
int valid = kernfs_active(pos) &&
pos->parent == parent && hash == pos->hash;
kernfs_put(pos);
if (!valid)
pos = NULL;
}
if (!pos && (hash > 1) && (hash < INT_MAX)) {
struct rb_node *node = parent->dir.children.rb_node;
while (node) {
pos = rb_to_kn(node);
if (hash < pos->hash)
node = node->rb_left;
else if (hash > pos->hash)
node = node->rb_right;
else
break;
}
}
/* Skip over entries which are dying/dead or in the wrong namespace */
while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
struct rb_node *node = rb_next(&pos->rb);
if (!node)
pos = NULL;
else
pos = rb_to_kn(node);
}
return pos;
}
static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
{
pos = kernfs_dir_pos(ns, parent, ino, pos);
if (pos) {
do {
struct rb_node *node = rb_next(&pos->rb);
if (!node)
pos = NULL;
else
pos = rb_to_kn(node);
} while (pos && (!kernfs_active(pos) || pos->ns != ns));
}
return pos;
}
static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
{
struct dentry *dentry = file->f_path.dentry;
struct kernfs_node *parent = dentry->d_fsdata;
struct kernfs_node *pos = file->private_data;
const void *ns = NULL;
if (!dir_emit_dots(file, ctx))
return 0;
mutex_lock(&kernfs_mutex);
if (kernfs_ns_enabled(parent))
ns = kernfs_info(dentry->d_sb)->ns;
for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
pos;
pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
const char *name = pos->name;
unsigned int type = dt_type(pos);
int len = strlen(name);
ino_t ino = pos->ino;
ctx->pos = pos->hash;
file->private_data = pos;
kernfs_get(pos);
mutex_unlock(&kernfs_mutex);
if (!dir_emit(ctx, name, len, ino, type))
return 0;
mutex_lock(&kernfs_mutex);
}
mutex_unlock(&kernfs_mutex);
file->private_data = NULL;
ctx->pos = INT_MAX;
return 0;
}
static loff_t kernfs_dir_fop_llseek(struct file *file, loff_t offset,
int whence)
{
struct inode *inode = file_inode(file);
loff_t ret;
mutex_lock(&inode->i_mutex);
ret = generic_file_llseek(file, offset, whence);
mutex_unlock(&inode->i_mutex);
return ret;
}
const struct file_operations kernfs_dir_fops = {
.read = generic_read_dir,
.iterate = kernfs_fop_readdir,
.release = kernfs_dir_fop_release,
.llseek = kernfs_dir_fop_llseek,
};