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linux/fs/namei.c
Tim Chen c1530019e3 vfs: Fix absolute RCU path walk failures due to uninitialized seq number 
During RCU walk in path_lookupat and path_openat, the rcu lookup
frequently failed if looking up an absolute path, because when root
directory was looked up, seq number was not properly set in nameidata.

We dropped out of RCU walk in nameidata_drop_rcu due to mismatch in
directory entry's seq number.  We reverted to slow path walk that need
to take references.

With the following patch, I saw a 50% increase in an exim mail server
benchmark throughput on a 4-socket Nehalem-EX system.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: stable@kernel.org (v2.6.38)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-04-15 15:28:12 -07:00

3450 lines
84 KiB
C
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/*
* linux/fs/namei.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* Some corrections by tytso.
*/
/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
* lookup logic.
*/
/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/fsnotify.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/ima.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fcntl.h>
#include <linux/device_cgroup.h>
#include <linux/fs_struct.h>
#include <asm/uaccess.h>
#include "internal.h"
/* [Feb-1997 T. Schoebel-Theuer]
* Fundamental changes in the pathname lookup mechanisms (namei)
* were necessary because of omirr. The reason is that omirr needs
* to know the _real_ pathname, not the user-supplied one, in case
* of symlinks (and also when transname replacements occur).
*
* The new code replaces the old recursive symlink resolution with
* an iterative one (in case of non-nested symlink chains). It does
* this with calls to <fs>_follow_link().
* As a side effect, dir_namei(), _namei() and follow_link() are now
* replaced with a single function lookup_dentry() that can handle all
* the special cases of the former code.
*
* With the new dcache, the pathname is stored at each inode, at least as
* long as the refcount of the inode is positive. As a side effect, the
* size of the dcache depends on the inode cache and thus is dynamic.
*
* [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
* resolution to correspond with current state of the code.
*
* Note that the symlink resolution is not *completely* iterative.
* There is still a significant amount of tail- and mid- recursion in
* the algorithm. Also, note that <fs>_readlink() is not used in
* lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
* may return different results than <fs>_follow_link(). Many virtual
* filesystems (including /proc) exhibit this behavior.
*/
/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
* New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
* and the name already exists in form of a symlink, try to create the new
* name indicated by the symlink. The old code always complained that the
* name already exists, due to not following the symlink even if its target
* is nonexistent. The new semantics affects also mknod() and link() when
* the name is a symlink pointing to a non-existent name.
*
* I don't know which semantics is the right one, since I have no access
* to standards. But I found by trial that HP-UX 9.0 has the full "new"
* semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
* "old" one. Personally, I think the new semantics is much more logical.
* Note that "ln old new" where "new" is a symlink pointing to a non-existing
* file does succeed in both HP-UX and SunOs, but not in Solaris
* and in the old Linux semantics.
*/
/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
* semantics. See the comments in "open_namei" and "do_link" below.
*
* [10-Sep-98 Alan Modra] Another symlink change.
*/
/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
* inside the path - always follow.
* in the last component in creation/removal/renaming - never follow.
* if LOOKUP_FOLLOW passed - follow.
* if the pathname has trailing slashes - follow.
* otherwise - don't follow.
* (applied in that order).
*
* [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
* restored for 2.4. This is the last surviving part of old 4.2BSD bug.
* During the 2.4 we need to fix the userland stuff depending on it -
* hopefully we will be able to get rid of that wart in 2.5. So far only
* XEmacs seems to be relying on it...
*/
/*
* [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
* implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
* any extra contention...
*/
/* In order to reduce some races, while at the same time doing additional
* checking and hopefully speeding things up, we copy filenames to the
* kernel data space before using them..
*
* POSIX.1 2.4: an empty pathname is invalid (ENOENT).
* PATH_MAX includes the nul terminator --RR.
*/
static int do_getname(const char __user *filename, char *page)
{
int retval;
unsigned long len = PATH_MAX;
if (!segment_eq(get_fs(), KERNEL_DS)) {
if ((unsigned long) filename >= TASK_SIZE)
return -EFAULT;
if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
len = TASK_SIZE - (unsigned long) filename;
}
retval = strncpy_from_user(page, filename, len);
if (retval > 0) {
if (retval < len)
return 0;
return -ENAMETOOLONG;
} else if (!retval)
retval = -ENOENT;
return retval;
}
static char *getname_flags(const char __user * filename, int flags)
{
char *tmp, *result;
result = ERR_PTR(-ENOMEM);
tmp = __getname();
if (tmp) {
int retval = do_getname(filename, tmp);
result = tmp;
if (retval < 0) {
if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
__putname(tmp);
result = ERR_PTR(retval);
}
}
}
audit_getname(result);
return result;
}
char *getname(const char __user * filename)
{
return getname_flags(filename, 0);
}
#ifdef CONFIG_AUDITSYSCALL
void putname(const char *name)
{
if (unlikely(!audit_dummy_context()))
audit_putname(name);
else
__putname(name);
}
EXPORT_SYMBOL(putname);
#endif
/*
* This does basic POSIX ACL permission checking
*/
static int acl_permission_check(struct inode *inode, int mask, unsigned int flags,
int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
{
umode_t mode = inode->i_mode;
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (current_user_ns() != inode_userns(inode))
goto other_perms;
if (current_fsuid() == inode->i_uid)
mode >>= 6;
else {
if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
int error = check_acl(inode, mask, flags);
if (error != -EAGAIN)
return error;
}
if (in_group_p(inode->i_gid))
mode >>= 3;
}
other_perms:
/*
* If the DACs are ok we don't need any capability check.
*/
if ((mask & ~mode) == 0)
return 0;
return -EACCES;
}
/**
* generic_permission - check for access rights on a Posix-like filesystem
* @inode: inode to check access rights for
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
* @check_acl: optional callback to check for Posix ACLs
* @flags: IPERM_FLAG_ flags.
*
* Used to check for read/write/execute permissions on a file.
* We use "fsuid" for this, letting us set arbitrary permissions
* for filesystem access without changing the "normal" uids which
* are used for other things.
*
* generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
* request cannot be satisfied (eg. requires blocking or too much complexity).
* It would then be called again in ref-walk mode.
*/
int generic_permission(struct inode *inode, int mask, unsigned int flags,
int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
{
int ret;
/*
* Do the basic POSIX ACL permission checks.
*/
ret = acl_permission_check(inode, mask, flags, check_acl);
if (ret != -EACCES)
return ret;
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable if at least one exec bit is set.
*/
if (!(mask & MAY_EXEC) || execute_ok(inode))
if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
return 0;
/*
* Searching includes executable on directories, else just read.
*/
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
return 0;
return -EACCES;
}
/**
* inode_permission - check for access rights to a given inode
* @inode: inode to check permission on
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Used to check for read/write/execute permissions on an inode.
* We use "fsuid" for this, letting us set arbitrary permissions
* for filesystem access without changing the "normal" uids which
* are used for other things.
*/
int inode_permission(struct inode *inode, int mask)
{
int retval;
if (mask & MAY_WRITE) {
umode_t mode = inode->i_mode;
/*
* Nobody gets write access to a read-only fs.
*/
if (IS_RDONLY(inode) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
return -EROFS;
/*
* Nobody gets write access to an immutable file.
*/
if (IS_IMMUTABLE(inode))
return -EACCES;
}
if (inode->i_op->permission)
retval = inode->i_op->permission(inode, mask, 0);
else
retval = generic_permission(inode, mask, 0,
inode->i_op->check_acl);
if (retval)
return retval;
retval = devcgroup_inode_permission(inode, mask);
if (retval)
return retval;
return security_inode_permission(inode, mask);
}
/**
* file_permission - check for additional access rights to a given file
* @file: file to check access rights for
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Used to check for read/write/execute permissions on an already opened
* file.
*
* Note:
* Do not use this function in new code. All access checks should
* be done using inode_permission().
*/
int file_permission(struct file *file, int mask)
{
return inode_permission(file->f_path.dentry->d_inode, mask);
}
/*
* get_write_access() gets write permission for a file.
* put_write_access() releases this write permission.
* This is used for regular files.
* We cannot support write (and maybe mmap read-write shared) accesses and
* MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
* can have the following values:
* 0: no writers, no VM_DENYWRITE mappings
* < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
* > 0: (i_writecount) users are writing to the file.
*
* Normally we operate on that counter with atomic_{inc,dec} and it's safe
* except for the cases where we don't hold i_writecount yet. Then we need to
* use {get,deny}_write_access() - these functions check the sign and refuse
* to do the change if sign is wrong. Exclusion between them is provided by
* the inode->i_lock spinlock.
*/
int get_write_access(struct inode * inode)
{
spin_lock(&inode->i_lock);
if (atomic_read(&inode->i_writecount) < 0) {
spin_unlock(&inode->i_lock);
return -ETXTBSY;
}
atomic_inc(&inode->i_writecount);
spin_unlock(&inode->i_lock);
return 0;
}
int deny_write_access(struct file * file)
{
struct inode *inode = file->f_path.dentry->d_inode;
spin_lock(&inode->i_lock);
if (atomic_read(&inode->i_writecount) > 0) {
spin_unlock(&inode->i_lock);
return -ETXTBSY;
}
atomic_dec(&inode->i_writecount);
spin_unlock(&inode->i_lock);
return 0;
}
/**
* path_get - get a reference to a path
* @path: path to get the reference to
*
* Given a path increment the reference count to the dentry and the vfsmount.
*/
void path_get(struct path *path)
{
mntget(path->mnt);
dget(path->dentry);
}
EXPORT_SYMBOL(path_get);
/**
* path_put - put a reference to a path
* @path: path to put the reference to
*
* Given a path decrement the reference count to the dentry and the vfsmount.
*/
void path_put(struct path *path)
{
dput(path->dentry);
mntput(path->mnt);
}
EXPORT_SYMBOL(path_put);
/**
* nameidata_drop_rcu - drop this nameidata out of rcu-walk
* @nd: nameidata pathwalk data to drop
* Returns: 0 on success, -ECHILD on failure
*
* Path walking has 2 modes, rcu-walk and ref-walk (see
* Documentation/filesystems/path-lookup.txt). __drop_rcu* functions attempt
* to drop out of rcu-walk mode and take normal reference counts on dentries
* and vfsmounts to transition to rcu-walk mode. __drop_rcu* functions take
* refcounts at the last known good point before rcu-walk got stuck, so
* ref-walk may continue from there. If this is not successful (eg. a seqcount
* has changed), then failure is returned and path walk restarts from the
* beginning in ref-walk mode.
*
* nameidata_drop_rcu attempts to drop the current nd->path and nd->root into
* ref-walk. Must be called from rcu-walk context.
*/
static int nameidata_drop_rcu(struct nameidata *nd)
{
struct fs_struct *fs = current->fs;
struct dentry *dentry = nd->path.dentry;
int want_root = 0;
BUG_ON(!(nd->flags & LOOKUP_RCU));
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
want_root = 1;
spin_lock(&fs->lock);
if (nd->root.mnt != fs->root.mnt ||
nd->root.dentry != fs->root.dentry)
goto err_root;
}
spin_lock(&dentry->d_lock);
if (!__d_rcu_to_refcount(dentry, nd->seq))
goto err;
BUG_ON(nd->inode != dentry->d_inode);
spin_unlock(&dentry->d_lock);
if (want_root) {
path_get(&nd->root);
spin_unlock(&fs->lock);
}
mntget(nd->path.mnt);
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
nd->flags &= ~LOOKUP_RCU;
return 0;
err:
spin_unlock(&dentry->d_lock);
err_root:
if (want_root)
spin_unlock(&fs->lock);
return -ECHILD;
}
/* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
static inline int nameidata_drop_rcu_maybe(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU)
return nameidata_drop_rcu(nd);
return 0;
}
/**
* nameidata_dentry_drop_rcu - drop nameidata and dentry out of rcu-walk
* @nd: nameidata pathwalk data to drop
* @dentry: dentry to drop
* Returns: 0 on success, -ECHILD on failure
*
* nameidata_dentry_drop_rcu attempts to drop the current nd->path and nd->root,
* and dentry into ref-walk. @dentry must be a path found by a do_lookup call on
* @nd. Must be called from rcu-walk context.
*/
static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry)
{
struct fs_struct *fs = current->fs;
struct dentry *parent = nd->path.dentry;
int want_root = 0;
BUG_ON(!(nd->flags & LOOKUP_RCU));
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
want_root = 1;
spin_lock(&fs->lock);
if (nd->root.mnt != fs->root.mnt ||
nd->root.dentry != fs->root.dentry)
goto err_root;
}
spin_lock(&parent->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
if (!__d_rcu_to_refcount(dentry, nd->seq))
goto err;
/*
* If the sequence check on the child dentry passed, then the child has
* not been removed from its parent. This means the parent dentry must
* be valid and able to take a reference at this point.
*/
BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
BUG_ON(!parent->d_count);
parent->d_count++;
spin_unlock(&dentry->d_lock);
spin_unlock(&parent->d_lock);
if (want_root) {
path_get(&nd->root);
spin_unlock(&fs->lock);
}
mntget(nd->path.mnt);
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
nd->flags &= ~LOOKUP_RCU;
return 0;
err:
spin_unlock(&dentry->d_lock);
spin_unlock(&parent->d_lock);
err_root:
if (want_root)
spin_unlock(&fs->lock);
return -ECHILD;
}
/* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata *nd, struct dentry *dentry)
{
if (nd->flags & LOOKUP_RCU) {
if (unlikely(nameidata_dentry_drop_rcu(nd, dentry))) {
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
return -ECHILD;
}
}
return 0;
}
/**
* nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
* @nd: nameidata pathwalk data to drop
* Returns: 0 on success, -ECHILD on failure
*
* nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
* nd->path should be the final element of the lookup, so nd->root is discarded.
* Must be called from rcu-walk context.
*/
static int nameidata_drop_rcu_last(struct nameidata *nd)
{
struct dentry *dentry = nd->path.dentry;
BUG_ON(!(nd->flags & LOOKUP_RCU));
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
spin_lock(&dentry->d_lock);
if (!__d_rcu_to_refcount(dentry, nd->seq))
goto err_unlock;
BUG_ON(nd->inode != dentry->d_inode);
spin_unlock(&dentry->d_lock);
mntget(nd->path.mnt);
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
return 0;
err_unlock:
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
return -ECHILD;
}
/**
* release_open_intent - free up open intent resources
* @nd: pointer to nameidata
*/
void release_open_intent(struct nameidata *nd)
{
struct file *file = nd->intent.open.file;
if (file && !IS_ERR(file)) {
if (file->f_path.dentry == NULL)
put_filp(file);
else
fput(file);
}
}
static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
{
return dentry->d_op->d_revalidate(dentry, nd);
}
static struct dentry *
do_revalidate(struct dentry *dentry, struct nameidata *nd)
{
int status = d_revalidate(dentry, nd);
if (unlikely(status <= 0)) {
/*
* The dentry failed validation.
* If d_revalidate returned 0 attempt to invalidate
* the dentry otherwise d_revalidate is asking us
* to return a fail status.
*/
if (status < 0) {
dput(dentry);
dentry = ERR_PTR(status);
} else if (!d_invalidate(dentry)) {
dput(dentry);
dentry = NULL;
}
}
return dentry;
}
/*
* handle_reval_path - force revalidation of a dentry
*
* In some situations the path walking code will trust dentries without
* revalidating them. This causes problems for filesystems that depend on
* d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
* (which indicates that it's possible for the dentry to go stale), force
* a d_revalidate call before proceeding.
*
* Returns 0 if the revalidation was successful. If the revalidation fails,
* either return the error returned by d_revalidate or -ESTALE if the
* revalidation it just returned 0. If d_revalidate returns 0, we attempt to
* invalidate the dentry. It's up to the caller to handle putting references
* to the path if necessary.
*/
static inline int handle_reval_path(struct nameidata *nd)
{
struct dentry *dentry = nd->path.dentry;
int status;
if (likely(!(nd->flags & LOOKUP_JUMPED)))
return 0;
if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
return 0;
if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
return 0;
/* Note: we do not d_invalidate() */
status = d_revalidate(dentry, nd);
if (status > 0)
return 0;
if (!status)
status = -ESTALE;
return status;
}
/*
* Short-cut version of permission(), for calling on directories
* during pathname resolution. Combines parts of permission()
* and generic_permission(), and tests ONLY for MAY_EXEC permission.
*
* If appropriate, check DAC only. If not appropriate, or
* short-cut DAC fails, then call ->permission() to do more
* complete permission check.
*/
static inline int exec_permission(struct inode *inode, unsigned int flags)
{
int ret;
struct user_namespace *ns = inode_userns(inode);
if (inode->i_op->permission) {
ret = inode->i_op->permission(inode, MAY_EXEC, flags);
} else {
ret = acl_permission_check(inode, MAY_EXEC, flags,
inode->i_op->check_acl);
}
if (likely(!ret))
goto ok;
if (ret == -ECHILD)
return ret;
if (ns_capable(ns, CAP_DAC_OVERRIDE) ||
ns_capable(ns, CAP_DAC_READ_SEARCH))
goto ok;
return ret;
ok:
return security_inode_exec_permission(inode, flags);
}
static __always_inline void set_root(struct nameidata *nd)
{
if (!nd->root.mnt)
get_fs_root(current->fs, &nd->root);
}
static int link_path_walk(const char *, struct nameidata *);
static __always_inline void set_root_rcu(struct nameidata *nd)
{
if (!nd->root.mnt) {
struct fs_struct *fs = current->fs;
unsigned seq;
do {
seq = read_seqcount_begin(&fs->seq);
nd->root = fs->root;
nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
}
}
static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
{
int ret;
if (IS_ERR(link))
goto fail;
if (*link == '/') {
set_root(nd);
path_put(&nd->path);
nd->path = nd->root;
path_get(&nd->root);
nd->flags |= LOOKUP_JUMPED;
}
nd->inode = nd->path.dentry->d_inode;
ret = link_path_walk(link, nd);
return ret;
fail:
path_put(&nd->path);
return PTR_ERR(link);
}
static void path_put_conditional(struct path *path, struct nameidata *nd)
{
dput(path->dentry);
if (path->mnt != nd->path.mnt)
mntput(path->mnt);
}
static inline void path_to_nameidata(const struct path *path,
struct nameidata *nd)
{
if (!(nd->flags & LOOKUP_RCU)) {
dput(nd->path.dentry);
if (nd->path.mnt != path->mnt)
mntput(nd->path.mnt);
}
nd->path.mnt = path->mnt;
nd->path.dentry = path->dentry;
}
static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
{
struct inode *inode = link->dentry->d_inode;
if (!IS_ERR(cookie) && inode->i_op->put_link)
inode->i_op->put_link(link->dentry, nd, cookie);
path_put(link);
}
static __always_inline int
follow_link(struct path *link, struct nameidata *nd, void **p)
{
int error;
struct dentry *dentry = link->dentry;
BUG_ON(nd->flags & LOOKUP_RCU);
if (link->mnt == nd->path.mnt)
mntget(link->mnt);
if (unlikely(current->total_link_count >= 40)) {
*p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
path_put(&nd->path);
return -ELOOP;
}
cond_resched();
current->total_link_count++;
touch_atime(link->mnt, dentry);
nd_set_link(nd, NULL);
error = security_inode_follow_link(link->dentry, nd);
if (error) {
*p = ERR_PTR(error); /* no ->put_link(), please */
path_put(&nd->path);
return error;
}
nd->last_type = LAST_BIND;
*p = dentry->d_inode->i_op->follow_link(dentry, nd);
error = PTR_ERR(*p);
if (!IS_ERR(*p)) {
char *s = nd_get_link(nd);
error = 0;
if (s)
error = __vfs_follow_link(nd, s);
else if (nd->last_type == LAST_BIND) {
nd->flags |= LOOKUP_JUMPED;
nd->inode = nd->path.dentry->d_inode;
if (nd->inode->i_op->follow_link) {
/* stepped on a _really_ weird one */
path_put(&nd->path);
error = -ELOOP;
}
}
}
return error;
}
static int follow_up_rcu(struct path *path)
{
struct vfsmount *parent;
struct dentry *mountpoint;
parent = path->mnt->mnt_parent;
if (parent == path->mnt)
return 0;
mountpoint = path->mnt->mnt_mountpoint;
path->dentry = mountpoint;
path->mnt = parent;
return 1;
}
int follow_up(struct path *path)
{
struct vfsmount *parent;
struct dentry *mountpoint;
br_read_lock(vfsmount_lock);
parent = path->mnt->mnt_parent;
if (parent == path->mnt) {
br_read_unlock(vfsmount_lock);
return 0;
}
mntget(parent);
mountpoint = dget(path->mnt->mnt_mountpoint);
br_read_unlock(vfsmount_lock);
dput(path->dentry);
path->dentry = mountpoint;
mntput(path->mnt);
path->mnt = parent;
return 1;
}
/*
* Perform an automount
* - return -EISDIR to tell follow_managed() to stop and return the path we
* were called with.
*/
static int follow_automount(struct path *path, unsigned flags,
bool *need_mntput)
{
struct vfsmount *mnt;
int err;
if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
return -EREMOTE;
/* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
* and this is the terminal part of the path.
*/
if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
return -EISDIR; /* we actually want to stop here */
/* We want to mount if someone is trying to open/create a file of any
* type under the mountpoint, wants to traverse through the mountpoint
* or wants to open the mounted directory.
*
* We don't want to mount if someone's just doing a stat and they've
* set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
* appended a '/' to the name.
*/
if (!(flags & LOOKUP_FOLLOW) &&
!(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
LOOKUP_OPEN | LOOKUP_CREATE)))
return -EISDIR;
current->total_link_count++;
if (current->total_link_count >= 40)
return -ELOOP;
mnt = path->dentry->d_op->d_automount(path);
if (IS_ERR(mnt)) {
/*
* The filesystem is allowed to return -EISDIR here to indicate
* it doesn't want to automount. For instance, autofs would do
* this so that its userspace daemon can mount on this dentry.
*
* However, we can only permit this if it's a terminal point in
* the path being looked up; if it wasn't then the remainder of
* the path is inaccessible and we should say so.
*/
if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_CONTINUE))
return -EREMOTE;
return PTR_ERR(mnt);
}
if (!mnt) /* mount collision */
return 0;
err = finish_automount(mnt, path);
switch (err) {
case -EBUSY:
/* Someone else made a mount here whilst we were busy */
return 0;
case 0:
dput(path->dentry);
if (*need_mntput)
mntput(path->mnt);
path->mnt = mnt;
path->dentry = dget(mnt->mnt_root);
*need_mntput = true;
return 0;
default:
return err;
}
}
/*
* Handle a dentry that is managed in some way.
* - Flagged for transit management (autofs)
* - Flagged as mountpoint
* - Flagged as automount point
*
* This may only be called in refwalk mode.
*
* Serialization is taken care of in namespace.c
*/
static int follow_managed(struct path *path, unsigned flags)
{
unsigned managed;
bool need_mntput = false;
int ret;
/* Given that we're not holding a lock here, we retain the value in a
* local variable for each dentry as we look at it so that we don't see
* the components of that value change under us */
while (managed = ACCESS_ONCE(path->dentry->d_flags),
managed &= DCACHE_MANAGED_DENTRY,
unlikely(managed != 0)) {
/* Allow the filesystem to manage the transit without i_mutex
* being held. */
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
ret = path->dentry->d_op->d_manage(path->dentry, false);
if (ret < 0)
return ret == -EISDIR ? 0 : ret;
}
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
if (mounted) {
dput(path->dentry);
if (need_mntput)
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
need_mntput = true;
continue;
}
/* Something is mounted on this dentry in another
* namespace and/or whatever was mounted there in this
* namespace got unmounted before we managed to get the
* vfsmount_lock */
}
/* Handle an automount point */
if (managed & DCACHE_NEED_AUTOMOUNT) {
ret = follow_automount(path, flags, &need_mntput);
if (ret < 0)
return ret == -EISDIR ? 0 : ret;
continue;
}
/* We didn't change the current path point */
break;
}
return 0;
}
int follow_down_one(struct path *path)
{
struct vfsmount *mounted;
mounted = lookup_mnt(path);
if (mounted) {
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
return 1;
}
return 0;
}
static inline bool managed_dentry_might_block(struct dentry *dentry)
{
return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
dentry->d_op->d_manage(dentry, true) < 0);
}
/*
* Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
* meet a managed dentry and we're not walking to "..". True is returned to
* continue, false to abort.
*/
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode, bool reverse_transit)
{
for (;;) {
struct vfsmount *mounted;
/*
* Don't forget we might have a non-mountpoint managed dentry
* that wants to block transit.
*/
*inode = path->dentry->d_inode;
if (!reverse_transit &&
unlikely(managed_dentry_might_block(path->dentry)))
return false;
if (!d_mountpoint(path->dentry))
break;
mounted = __lookup_mnt(path->mnt, path->dentry, 1);
if (!mounted)
break;
path->mnt = mounted;
path->dentry = mounted->mnt_root;
nd->seq = read_seqcount_begin(&path->dentry->d_seq);
}
if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
return reverse_transit;
return true;
}
static int follow_dotdot_rcu(struct nameidata *nd)
{
struct inode *inode = nd->inode;
set_root_rcu(nd);
while (1) {
if (nd->path.dentry == nd->root.dentry &&
nd->path.mnt == nd->root.mnt) {
break;
}
if (nd->path.dentry != nd->path.mnt->mnt_root) {
struct dentry *old = nd->path.dentry;
struct dentry *parent = old->d_parent;
unsigned seq;
seq = read_seqcount_begin(&parent->d_seq);
if (read_seqcount_retry(&old->d_seq, nd->seq))
goto failed;
inode = parent->d_inode;
nd->path.dentry = parent;
nd->seq = seq;
break;
}
if (!follow_up_rcu(&nd->path))
break;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
inode = nd->path.dentry->d_inode;
}
__follow_mount_rcu(nd, &nd->path, &inode, true);
nd->inode = inode;
return 0;
failed:
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
return -ECHILD;
}
/*
* Follow down to the covering mount currently visible to userspace. At each
* point, the filesystem owning that dentry may be queried as to whether the
* caller is permitted to proceed or not.
*
* Care must be taken as namespace_sem may be held (indicated by mounting_here
* being true).
*/
int follow_down(struct path *path)
{
unsigned managed;
int ret;
while (managed = ACCESS_ONCE(path->dentry->d_flags),
unlikely(managed & DCACHE_MANAGED_DENTRY)) {
/* Allow the filesystem to manage the transit without i_mutex
* being held.
*
* We indicate to the filesystem if someone is trying to mount
* something here. This gives autofs the chance to deny anyone
* other than its daemon the right to mount on its
* superstructure.
*
* The filesystem may sleep at this point.
*/
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
ret = path->dentry->d_op->d_manage(
path->dentry, false);
if (ret < 0)
return ret == -EISDIR ? 0 : ret;
}
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
if (!mounted)
break;
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
continue;
}
/* Don't handle automount points here */
break;
}
return 0;
}
/*
* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
*/
static void follow_mount(struct path *path)
{
while (d_mountpoint(path->dentry)) {
struct vfsmount *mounted = lookup_mnt(path);
if (!mounted)
break;
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
}
}
static void follow_dotdot(struct nameidata *nd)
{
set_root(nd);
while(1) {
struct dentry *old = nd->path.dentry;
if (nd->path.dentry == nd->root.dentry &&
nd->path.mnt == nd->root.mnt) {
break;
}
if (nd->path.dentry != nd->path.mnt->mnt_root) {
/* rare case of legitimate dget_parent()... */
nd->path.dentry = dget_parent(nd->path.dentry);
dput(old);
break;
}
if (!follow_up(&nd->path))
break;
}
follow_mount(&nd->path);
nd->inode = nd->path.dentry->d_inode;
}
/*
* Allocate a dentry with name and parent, and perform a parent
* directory ->lookup on it. Returns the new dentry, or ERR_PTR
* on error. parent->d_inode->i_mutex must be held. d_lookup must
* have verified that no child exists while under i_mutex.
*/
static struct dentry *d_alloc_and_lookup(struct dentry *parent,
struct qstr *name, struct nameidata *nd)
{
struct inode *inode = parent->d_inode;
struct dentry *dentry;
struct dentry *old;
/* Don't create child dentry for a dead directory. */
if (unlikely(IS_DEADDIR(inode)))
return ERR_PTR(-ENOENT);
dentry = d_alloc(parent, name);
if (unlikely(!dentry))
return ERR_PTR(-ENOMEM);
old = inode->i_op->lookup(inode, dentry, nd);
if (unlikely(old)) {
dput(dentry);
dentry = old;
}
return dentry;
}
/*
* It's more convoluted than I'd like it to be, but... it's still fairly
* small and for now I'd prefer to have fast path as straight as possible.
* It _is_ time-critical.
*/
static int do_lookup(struct nameidata *nd, struct qstr *name,
struct path *path, struct inode **inode)
{
struct vfsmount *mnt = nd->path.mnt;
struct dentry *dentry, *parent = nd->path.dentry;
int need_reval = 1;
int status = 1;
int err;
/*
* Rename seqlock is not required here because in the off chance
* of a false negative due to a concurrent rename, we're going to
* do the non-racy lookup, below.
*/
if (nd->flags & LOOKUP_RCU) {
unsigned seq;
*inode = nd->inode;
dentry = __d_lookup_rcu(parent, name, &seq, inode);
if (!dentry)
goto unlazy;
/* Memory barrier in read_seqcount_begin of child is enough */
if (__read_seqcount_retry(&parent->d_seq, nd->seq))
return -ECHILD;
nd->seq = seq;
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
status = d_revalidate(dentry, nd);
if (unlikely(status <= 0)) {
if (status != -ECHILD)
need_reval = 0;
goto unlazy;
}
}
path->mnt = mnt;
path->dentry = dentry;
if (likely(__follow_mount_rcu(nd, path, inode, false)))
return 0;
unlazy:
if (dentry) {
if (nameidata_dentry_drop_rcu(nd, dentry))
return -ECHILD;
} else {
if (nameidata_drop_rcu(nd))
return -ECHILD;
}
} else {
dentry = __d_lookup(parent, name);
}
retry:
if (unlikely(!dentry)) {
struct inode *dir = parent->d_inode;
BUG_ON(nd->inode != dir);
mutex_lock(&dir->i_mutex);
dentry = d_lookup(parent, name);
if (likely(!dentry)) {
dentry = d_alloc_and_lookup(parent, name, nd);
if (IS_ERR(dentry)) {
mutex_unlock(&dir->i_mutex);
return PTR_ERR(dentry);
}
/* known good */
need_reval = 0;
status = 1;
}
mutex_unlock(&dir->i_mutex);
}
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
status = d_revalidate(dentry, nd);
if (unlikely(status <= 0)) {
if (status < 0) {
dput(dentry);
return status;
}
if (!d_invalidate(dentry)) {
dput(dentry);
dentry = NULL;
need_reval = 1;
goto retry;
}
}
path->mnt = mnt;
path->dentry = dentry;
err = follow_managed(path, nd->flags);
if (unlikely(err < 0)) {
path_put_conditional(path, nd);
return err;
}
*inode = path->dentry->d_inode;
return 0;
}
static inline int may_lookup(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU) {
int err = exec_permission(nd->inode, IPERM_FLAG_RCU);
if (err != -ECHILD)
return err;
if (nameidata_drop_rcu(nd))
return -ECHILD;
}
return exec_permission(nd->inode, 0);
}
static inline int handle_dots(struct nameidata *nd, int type)
{
if (type == LAST_DOTDOT) {
if (nd->flags & LOOKUP_RCU) {
if (follow_dotdot_rcu(nd))
return -ECHILD;
} else
follow_dotdot(nd);
}
return 0;
}
static void terminate_walk(struct nameidata *nd)
{
if (!(nd->flags & LOOKUP_RCU)) {
path_put(&nd->path);
} else {
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
}
}
static inline int walk_component(struct nameidata *nd, struct path *path,
struct qstr *name, int type, int follow)
{
struct inode *inode;
int err;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
* parent relationships.
*/
if (unlikely(type != LAST_NORM))
return handle_dots(nd, type);
err = do_lookup(nd, name, path, &inode);
if (unlikely(err)) {
terminate_walk(nd);
return err;
}
if (!inode) {
path_to_nameidata(path, nd);
terminate_walk(nd);
return -ENOENT;
}
if (unlikely(inode->i_op->follow_link) && follow) {
if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
return -ECHILD;
BUG_ON(inode != path->dentry->d_inode);
return 1;
}
path_to_nameidata(path, nd);
nd->inode = inode;
return 0;
}
/*
* This limits recursive symlink follows to 8, while
* limiting consecutive symlinks to 40.
*
* Without that kind of total limit, nasty chains of consecutive
* symlinks can cause almost arbitrarily long lookups.
*/
static inline int nested_symlink(struct path *path, struct nameidata *nd)
{
int res;
BUG_ON(nd->depth >= MAX_NESTED_LINKS);
if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
path_put_conditional(path, nd);
path_put(&nd->path);
return -ELOOP;
}
nd->depth++;
current->link_count++;
do {
struct path link = *path;
void *cookie;
res = follow_link(&link, nd, &cookie);
if (!res)
res = walk_component(nd, path, &nd->last,
nd->last_type, LOOKUP_FOLLOW);
put_link(nd, &link, cookie);
} while (res > 0);
current->link_count--;
nd->depth--;
return res;
}
/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
* the final dentry. We expect 'base' to be positive and a directory.
*
* Returns 0 and nd will have valid dentry and mnt on success.
* Returns error and drops reference to input namei data on failure.
*/
static int link_path_walk(const char *name, struct nameidata *nd)
{
struct path next;
int err;
unsigned int lookup_flags = nd->flags;
while (*name=='/')
name++;
if (!*name)
return 0;
/* At this point we know we have a real path component. */
for(;;) {
unsigned long hash;
struct qstr this;
unsigned int c;
int type;
nd->flags |= LOOKUP_CONTINUE;
err = may_lookup(nd);
if (err)
break;
this.name = name;
c = *(const unsigned char *)name;
hash = init_name_hash();
do {
name++;
hash = partial_name_hash(c, hash);
c = *(const unsigned char *)name;
} while (c && (c != '/'));
this.len = name - (const char *) this.name;
this.hash = end_name_hash(hash);
type = LAST_NORM;
if (this.name[0] == '.') switch (this.len) {
case 2:
if (this.name[1] == '.') {
type = LAST_DOTDOT;
nd->flags |= LOOKUP_JUMPED;
}
break;
case 1:
type = LAST_DOT;
}
if (likely(type == LAST_NORM)) {
struct dentry *parent = nd->path.dentry;
nd->flags &= ~LOOKUP_JUMPED;
if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
err = parent->d_op->d_hash(parent, nd->inode,
&this);
if (err < 0)
break;
}
}
/* remove trailing slashes? */
if (!c)
goto last_component;
while (*++name == '/');
if (!*name)
goto last_component;
err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
if (err < 0)
return err;
if (err) {
err = nested_symlink(&next, nd);
if (err)
return err;
}
err = -ENOTDIR;
if (!nd->inode->i_op->lookup)
break;
continue;
/* here ends the main loop */
last_component:
/* Clear LOOKUP_CONTINUE iff it was previously unset */
nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
nd->last = this;
nd->last_type = type;
return 0;
}
terminate_walk(nd);
return err;
}
static int path_init(int dfd, const char *name, unsigned int flags,
struct nameidata *nd, struct file **fp)
{
int retval = 0;
int fput_needed;
struct file *file;
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags | LOOKUP_JUMPED;
nd->depth = 0;
if (flags & LOOKUP_ROOT) {
struct inode *inode = nd->root.dentry->d_inode;
if (*name) {
if (!inode->i_op->lookup)
return -ENOTDIR;
retval = inode_permission(inode, MAY_EXEC);
if (retval)
return retval;
}
nd->path = nd->root;
nd->inode = inode;
if (flags & LOOKUP_RCU) {
br_read_lock(vfsmount_lock);
rcu_read_lock();
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
} else {
path_get(&nd->path);
}
return 0;
}
nd->root.mnt = NULL;
if (*name=='/') {
if (flags & LOOKUP_RCU) {
br_read_lock(vfsmount_lock);
rcu_read_lock();
set_root_rcu(nd);
} else {
set_root(nd);
path_get(&nd->root);
}
nd->path = nd->root;
} else if (dfd == AT_FDCWD) {
if (flags & LOOKUP_RCU) {
struct fs_struct *fs = current->fs;
unsigned seq;
br_read_lock(vfsmount_lock);
rcu_read_lock();
do {
seq = read_seqcount_begin(&fs->seq);
nd->path = fs->pwd;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
} else {
get_fs_pwd(current->fs, &nd->path);
}
} else {
struct dentry *dentry;
file = fget_raw_light(dfd, &fput_needed);
retval = -EBADF;
if (!file)
goto out_fail;
dentry = file->f_path.dentry;
if (*name) {
retval = -ENOTDIR;
if (!S_ISDIR(dentry->d_inode->i_mode))
goto fput_fail;
retval = file_permission(file, MAY_EXEC);
if (retval)
goto fput_fail;
}
nd->path = file->f_path;
if (flags & LOOKUP_RCU) {
if (fput_needed)
*fp = file;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
br_read_lock(vfsmount_lock);
rcu_read_lock();
} else {
path_get(&file->f_path);
fput_light(file, fput_needed);
}
}
nd->inode = nd->path.dentry->d_inode;
return 0;
fput_fail:
fput_light(file, fput_needed);
out_fail:
return retval;
}
static inline int lookup_last(struct nameidata *nd, struct path *path)
{
if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
nd->flags &= ~LOOKUP_PARENT;
return walk_component(nd, path, &nd->last, nd->last_type,
nd->flags & LOOKUP_FOLLOW);
}
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int path_lookupat(int dfd, const char *name,
unsigned int flags, struct nameidata *nd)
{
struct file *base = NULL;
struct path path;
int err;
/*
* Path walking is largely split up into 2 different synchronisation
* schemes, rcu-walk and ref-walk (explained in
* Documentation/filesystems/path-lookup.txt). These share much of the
* path walk code, but some things particularly setup, cleanup, and
* following mounts are sufficiently divergent that functions are
* duplicated. Typically there is a function foo(), and its RCU
* analogue, foo_rcu().
*
* -ECHILD is the error number of choice (just to avoid clashes) that
* is returned if some aspect of an rcu-walk fails. Such an error must
* be handled by restarting a traditional ref-walk (which will always
* be able to complete).
*/
err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
if (unlikely(err))
return err;
current->total_link_count = 0;
err = link_path_walk(name, nd);
if (!err && !(flags & LOOKUP_PARENT)) {
err = lookup_last(nd, &path);
while (err > 0) {
void *cookie;
struct path link = path;
nd->flags |= LOOKUP_PARENT;
err = follow_link(&link, nd, &cookie);
if (!err)
err = lookup_last(nd, &path);
put_link(nd, &link, cookie);
}
}
if (nd->flags & LOOKUP_RCU) {
/* went all way through without dropping RCU */
BUG_ON(err);
if (nameidata_drop_rcu_last(nd))
err = -ECHILD;
}
if (!err) {
err = handle_reval_path(nd);
if (err)
path_put(&nd->path);
}
if (!err && nd->flags & LOOKUP_DIRECTORY) {
if (!nd->inode->i_op->lookup) {
path_put(&nd->path);
err = -ENOTDIR;
}
}
if (base)
fput(base);
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
path_put(&nd->root);
nd->root.mnt = NULL;
}
return err;
}
static int do_path_lookup(int dfd, const char *name,
unsigned int flags, struct nameidata *nd)
{
int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
if (unlikely(retval == -ECHILD))
retval = path_lookupat(dfd, name, flags, nd);
if (unlikely(retval == -ESTALE))
retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
if (likely(!retval)) {
if (unlikely(!audit_dummy_context())) {
if (nd->path.dentry && nd->inode)
audit_inode(name, nd->path.dentry);
}
}
return retval;
}
int kern_path_parent(const char *name, struct nameidata *nd)
{
return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
}
int kern_path(const char *name, unsigned int flags, struct path *path)
{
struct nameidata nd;
int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
if (!res)
*path = nd.path;
return res;
}
/**
* vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
* @dentry: pointer to dentry of the base directory
* @mnt: pointer to vfs mount of the base directory
* @name: pointer to file name
* @flags: lookup flags
* @nd: pointer to nameidata
*/
int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
const char *name, unsigned int flags,
struct nameidata *nd)
{
nd->root.dentry = dentry;
nd->root.mnt = mnt;
/* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
return do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, nd);
}
static struct dentry *__lookup_hash(struct qstr *name,
struct dentry *base, struct nameidata *nd)
{
struct inode *inode = base->d_inode;
struct dentry *dentry;
int err;
err = exec_permission(inode, 0);
if (err)
return ERR_PTR(err);
/*
* Don't bother with __d_lookup: callers are for creat as
* well as unlink, so a lot of the time it would cost
* a double lookup.
*/
dentry = d_lookup(base, name);
if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
dentry = do_revalidate(dentry, nd);
if (!dentry)
dentry = d_alloc_and_lookup(base, name, nd);
return dentry;
}
/*
* Restricted form of lookup. Doesn't follow links, single-component only,
* needs parent already locked. Doesn't follow mounts.
* SMP-safe.
*/
static struct dentry *lookup_hash(struct nameidata *nd)
{
return __lookup_hash(&nd->last, nd->path.dentry, nd);
}
/**
* lookup_one_len - filesystem helper to lookup single pathname component
* @name: pathname component to lookup
* @base: base directory to lookup from
* @len: maximum length @len should be interpreted to
*
* Note that this routine is purely a helper for filesystem usage and should
* not be called by generic code. Also note that by using this function the
* nameidata argument is passed to the filesystem methods and a filesystem
* using this helper needs to be prepared for that.
*/
struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
struct qstr this;
unsigned long hash;
unsigned int c;
WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
this.name = name;
this.len = len;
if (!len)
return ERR_PTR(-EACCES);
hash = init_name_hash();
while (len--) {
c = *(const unsigned char *)name++;
if (c == '/' || c == '\0')
return ERR_PTR(-EACCES);
hash = partial_name_hash(c, hash);
}
this.hash = end_name_hash(hash);
/*
* See if the low-level filesystem might want
* to use its own hash..
*/
if (base->d_flags & DCACHE_OP_HASH) {
int err = base->d_op->d_hash(base, base->d_inode, &this);
if (err < 0)
return ERR_PTR(err);
}
return __lookup_hash(&this, base, NULL);
}
int user_path_at(int dfd, const char __user *name, unsigned flags,
struct path *path)
{
struct nameidata nd;
char *tmp = getname_flags(name, flags);
int err = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
BUG_ON(flags & LOOKUP_PARENT);
err = do_path_lookup(dfd, tmp, flags, &nd);
putname(tmp);
if (!err)
*path = nd.path;
}
return err;
}
static int user_path_parent(int dfd, const char __user *path,
struct nameidata *nd, char **name)
{
char *s = getname(path);
int error;
if (IS_ERR(s))
return PTR_ERR(s);
error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
if (error)
putname(s);
else
*name = s;
return error;
}
/*
* It's inline, so penalty for filesystems that don't use sticky bit is
* minimal.
*/
static inline int check_sticky(struct inode *dir, struct inode *inode)
{
uid_t fsuid = current_fsuid();
if (!(dir->i_mode & S_ISVTX))
return 0;
if (current_user_ns() != inode_userns(inode))
goto other_userns;
if (inode->i_uid == fsuid)
return 0;
if (dir->i_uid == fsuid)
return 0;
other_userns:
return !ns_capable(inode_userns(inode), CAP_FOWNER);
}
/*
* Check whether we can remove a link victim from directory dir, check
* whether the type of victim is right.
* 1. We can't do it if dir is read-only (done in permission())
* 2. We should have write and exec permissions on dir
* 3. We can't remove anything from append-only dir
* 4. We can't do anything with immutable dir (done in permission())
* 5. If the sticky bit on dir is set we should either
* a. be owner of dir, or
* b. be owner of victim, or
* c. have CAP_FOWNER capability
* 6. If the victim is append-only or immutable we can't do antyhing with
* links pointing to it.
* 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
* 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
* 9. We can't remove a root or mountpoint.
* 10. We don't allow removal of NFS sillyrenamed files; it's handled by
* nfs_async_unlink().
*/
static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
{
int error;
if (!victim->d_inode)
return -ENOENT;
BUG_ON(victim->d_parent->d_inode != dir);
audit_inode_child(victim, dir);
error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
if (error)
return error;
if (IS_APPEND(dir))
return -EPERM;
if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
return -EPERM;
if (isdir) {
if (!S_ISDIR(victim->d_inode->i_mode))
return -ENOTDIR;
if (IS_ROOT(victim))
return -EBUSY;
} else if (S_ISDIR(victim->d_inode->i_mode))
return -EISDIR;
if (IS_DEADDIR(dir))
return -ENOENT;
if (victim->d_flags & DCACHE_NFSFS_RENAMED)
return -EBUSY;
return 0;
}
/* Check whether we can create an object with dentry child in directory
* dir.
* 1. We can't do it if child already exists (open has special treatment for
* this case, but since we are inlined it's OK)
* 2. We can't do it if dir is read-only (done in permission())
* 3. We should have write and exec permissions on dir
* 4. We can't do it if dir is immutable (done in permission())
*/
static inline int may_create(struct inode *dir, struct dentry *child)
{
if (child->d_inode)
return -EEXIST;
if (IS_DEADDIR(dir))
return -ENOENT;
return inode_permission(dir, MAY_WRITE | MAY_EXEC);
}
/*
* p1 and p2 should be directories on the same fs.
*/
struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
if (p1 == p2) {
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
return NULL;
}
mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
p = d_ancestor(p2, p1);
if (p) {
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
return p;
}
p = d_ancestor(p1, p2);
if (p) {
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
return p;
}
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
return NULL;
}
void unlock_rename(struct dentry *p1, struct dentry *p2)
{
mutex_unlock(&p1->d_inode->i_mutex);
if (p1 != p2) {
mutex_unlock(&p2->d_inode->i_mutex);
mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
}
}
int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
struct nameidata *nd)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->create)
return -EACCES; /* shouldn't it be ENOSYS? */
mode &= S_IALLUGO;
mode |= S_IFREG;
error = security_inode_create(dir, dentry, mode);
if (error)
return error;
error = dir->i_op->create(dir, dentry, mode, nd);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
static int may_open(struct path *path, int acc_mode, int flag)
{
struct dentry *dentry = path->dentry;
struct inode *inode = dentry->d_inode;
int error;
/* O_PATH? */
if (!acc_mode)
return 0;
if (!inode)
return -ENOENT;
switch (inode->i_mode & S_IFMT) {
case S_IFLNK:
return -ELOOP;
case S_IFDIR:
if (acc_mode & MAY_WRITE)
return -EISDIR;
break;
case S_IFBLK:
case S_IFCHR:
if (path->mnt->mnt_flags & MNT_NODEV)
return -EACCES;
/*FALLTHRU*/
case S_IFIFO:
case S_IFSOCK:
flag &= ~O_TRUNC;
break;
}
error = inode_permission(inode, acc_mode);
if (error)
return error;
/*
* An append-only file must be opened in append mode for writing.
*/
if (IS_APPEND(inode)) {
if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
return -EPERM;
if (flag & O_TRUNC)
return -EPERM;
}
/* O_NOATIME can only be set by the owner or superuser */
if (flag & O_NOATIME && !inode_owner_or_capable(inode))
return -EPERM;
/*
* Ensure there are no outstanding leases on the file.
*/
return break_lease(inode, flag);
}
static int handle_truncate(struct file *filp)
{
struct path *path = &filp->f_path;
struct inode *inode = path->dentry->d_inode;
int error = get_write_access(inode);
if (error)
return error;
/*
* Refuse to truncate files with mandatory locks held on them.
*/
error = locks_verify_locked(inode);
if (!error)
error = security_path_truncate(path);
if (!error) {
error = do_truncate(path->dentry, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
filp);
}
put_write_access(inode);
return error;
}
/*
* Note that while the flag value (low two bits) for sys_open means:
* 00 - read-only
* 01 - write-only
* 10 - read-write
* 11 - special
* it is changed into
* 00 - no permissions needed
* 01 - read-permission
* 10 - write-permission
* 11 - read-write
* for the internal routines (ie open_namei()/follow_link() etc)
* This is more logical, and also allows the 00 "no perm needed"
* to be used for symlinks (where the permissions are checked
* later).
*
*/
static inline int open_to_namei_flags(int flag)
{
if ((flag+1) & O_ACCMODE)
flag++;
return flag;
}
/*
* Handle the last step of open()
*/
static struct file *do_last(struct nameidata *nd, struct path *path,
const struct open_flags *op, const char *pathname)
{
struct dentry *dir = nd->path.dentry;
struct dentry *dentry;
int open_flag = op->open_flag;
int will_truncate = open_flag & O_TRUNC;
int want_write = 0;
int acc_mode = op->acc_mode;
struct file *filp;
int error;
nd->flags &= ~LOOKUP_PARENT;
nd->flags |= op->intent;
switch (nd->last_type) {
case LAST_DOTDOT:
case LAST_DOT:
error = handle_dots(nd, nd->last_type);
if (error)
return ERR_PTR(error);
/* fallthrough */
case LAST_ROOT:
if (nd->flags & LOOKUP_RCU) {
if (nameidata_drop_rcu_last(nd))
return ERR_PTR(-ECHILD);
}
error = handle_reval_path(nd);
if (error)
goto exit;
audit_inode(pathname, nd->path.dentry);
if (open_flag & O_CREAT) {
error = -EISDIR;
goto exit;
}
goto ok;
case LAST_BIND:
/* can't be RCU mode here */
error = handle_reval_path(nd);
if (error)
goto exit;
audit_inode(pathname, dir);
goto ok;
}
if (!(open_flag & O_CREAT)) {
int symlink_ok = 0;
if (nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
symlink_ok = 1;
/* we _can_ be in RCU mode here */
error = walk_component(nd, path, &nd->last, LAST_NORM,
!symlink_ok);
if (error < 0)
return ERR_PTR(error);
if (error) /* symlink */
return NULL;
/* sayonara */
if (nd->flags & LOOKUP_RCU) {
if (nameidata_drop_rcu_last(nd))
return ERR_PTR(-ECHILD);
}
error = -ENOTDIR;
if (nd->flags & LOOKUP_DIRECTORY) {
if (!nd->inode->i_op->lookup)
goto exit;
}
audit_inode(pathname, nd->path.dentry);
goto ok;
}
/* create side of things */
if (nd->flags & LOOKUP_RCU) {
if (nameidata_drop_rcu_last(nd))
return ERR_PTR(-ECHILD);
}
audit_inode(pathname, dir);
error = -EISDIR;
/* trailing slashes? */
if (nd->last.name[nd->last.len])
goto exit;
mutex_lock(&dir->d_inode->i_mutex);
dentry = lookup_hash(nd);
error = PTR_ERR(dentry);
if (IS_ERR(dentry)) {
mutex_unlock(&dir->d_inode->i_mutex);
goto exit;
}
path->dentry = dentry;
path->mnt = nd->path.mnt;
/* Negative dentry, just create the file */
if (!dentry->d_inode) {
int mode = op->mode;
if (!IS_POSIXACL(dir->d_inode))
mode &= ~current_umask();
/*
* This write is needed to ensure that a
* rw->ro transition does not occur between
* the time when the file is created and when
* a permanent write count is taken through
* the 'struct file' in nameidata_to_filp().
*/
error = mnt_want_write(nd->path.mnt);
if (error)
goto exit_mutex_unlock;
want_write = 1;
/* Don't check for write permission, don't truncate */
open_flag &= ~O_TRUNC;
will_truncate = 0;
acc_mode = MAY_OPEN;
error = security_path_mknod(&nd->path, dentry, mode, 0);
if (error)
goto exit_mutex_unlock;
error = vfs_create(dir->d_inode, dentry, mode, nd);
if (error)
goto exit_mutex_unlock;
mutex_unlock(&dir->d_inode->i_mutex);
dput(nd->path.dentry);
nd->path.dentry = dentry;
goto common;
}
/*
* It already exists.
*/
mutex_unlock(&dir->d_inode->i_mutex);
audit_inode(pathname, path->dentry);
error = -EEXIST;
if (open_flag & O_EXCL)
goto exit_dput;
error = follow_managed(path, nd->flags);
if (error < 0)
goto exit_dput;
error = -ENOENT;
if (!path->dentry->d_inode)
goto exit_dput;
if (path->dentry->d_inode->i_op->follow_link)
return NULL;
path_to_nameidata(path, nd);
nd->inode = path->dentry->d_inode;
error = -EISDIR;
if (S_ISDIR(nd->inode->i_mode))
goto exit;
ok:
if (!S_ISREG(nd->inode->i_mode))
will_truncate = 0;
if (will_truncate) {
error = mnt_want_write(nd->path.mnt);
if (error)
goto exit;
want_write = 1;
}
common:
error = may_open(&nd->path, acc_mode, open_flag);
if (error)
goto exit;
filp = nameidata_to_filp(nd);
if (!IS_ERR(filp)) {
error = ima_file_check(filp, op->acc_mode);
if (error) {
fput(filp);
filp = ERR_PTR(error);
}
}
if (!IS_ERR(filp)) {
if (will_truncate) {
error = handle_truncate(filp);
if (error) {
fput(filp);
filp = ERR_PTR(error);
}
}
}
out:
if (want_write)
mnt_drop_write(nd->path.mnt);
path_put(&nd->path);
return filp;
exit_mutex_unlock:
mutex_unlock(&dir->d_inode->i_mutex);
exit_dput:
path_put_conditional(path, nd);
exit:
filp = ERR_PTR(error);
goto out;
}
static struct file *path_openat(int dfd, const char *pathname,
struct nameidata *nd, const struct open_flags *op, int flags)
{
struct file *base = NULL;
struct file *filp;
struct path path;
int error;
filp = get_empty_filp();
if (!filp)
return ERR_PTR(-ENFILE);
filp->f_flags = op->open_flag;
nd->intent.open.file = filp;
nd->intent.open.flags = open_to_namei_flags(op->open_flag);
nd->intent.open.create_mode = op->mode;
error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
if (unlikely(error))
goto out_filp;
current->total_link_count = 0;
error = link_path_walk(pathname, nd);
if (unlikely(error))
goto out_filp;
filp = do_last(nd, &path, op, pathname);
while (unlikely(!filp)) { /* trailing symlink */
struct path link = path;
void *cookie;
if (!(nd->flags & LOOKUP_FOLLOW)) {
path_put_conditional(&path, nd);
path_put(&nd->path);
filp = ERR_PTR(-ELOOP);
break;
}
nd->flags |= LOOKUP_PARENT;
nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
error = follow_link(&link, nd, &cookie);
if (unlikely(error))
filp = ERR_PTR(error);
else
filp = do_last(nd, &path, op, pathname);
put_link(nd, &link, cookie);
}
out:
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
path_put(&nd->root);
if (base)
fput(base);
release_open_intent(nd);
return filp;
out_filp:
filp = ERR_PTR(error);
goto out;
}
struct file *do_filp_open(int dfd, const char *pathname,
const struct open_flags *op, int flags)
{
struct nameidata nd;
struct file *filp;
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
if (unlikely(filp == ERR_PTR(-ECHILD)))
filp = path_openat(dfd, pathname, &nd, op, flags);
if (unlikely(filp == ERR_PTR(-ESTALE)))
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
return filp;
}
struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
const char *name, const struct open_flags *op, int flags)
{
struct nameidata nd;
struct file *file;
nd.root.mnt = mnt;
nd.root.dentry = dentry;
flags |= LOOKUP_ROOT;
if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
return ERR_PTR(-ELOOP);
file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
if (unlikely(file == ERR_PTR(-ECHILD)))
file = path_openat(-1, name, &nd, op, flags);
if (unlikely(file == ERR_PTR(-ESTALE)))
file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
return file;
}
/**
* lookup_create - lookup a dentry, creating it if it doesn't exist
* @nd: nameidata info
* @is_dir: directory flag
*
* Simple function to lookup and return a dentry and create it
* if it doesn't exist. Is SMP-safe.
*
* Returns with nd->path.dentry->d_inode->i_mutex locked.
*/
struct dentry *lookup_create(struct nameidata *nd, int is_dir)
{
struct dentry *dentry = ERR_PTR(-EEXIST);
mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
/*
* Yucky last component or no last component at all?
* (foo/., foo/.., /////)
*/
if (nd->last_type != LAST_NORM)
goto fail;
nd->flags &= ~LOOKUP_PARENT;
nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
nd->intent.open.flags = O_EXCL;
/*
* Do the final lookup.
*/
dentry = lookup_hash(nd);
if (IS_ERR(dentry))
goto fail;
if (dentry->d_inode)
goto eexist;
/*
* Special case - lookup gave negative, but... we had foo/bar/
* From the vfs_mknod() POV we just have a negative dentry -
* all is fine. Let's be bastards - you had / on the end, you've
* been asking for (non-existent) directory. -ENOENT for you.
*/
if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
dput(dentry);
dentry = ERR_PTR(-ENOENT);
}
return dentry;
eexist:
dput(dentry);
dentry = ERR_PTR(-EEXIST);
fail:
return dentry;
}
EXPORT_SYMBOL_GPL(lookup_create);
int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
int error = may_create(dir, dentry);
if (error)
return error;
if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
!ns_capable(inode_userns(dir), CAP_MKNOD))
return -EPERM;
if (!dir->i_op->mknod)
return -EPERM;
error = devcgroup_inode_mknod(mode, dev);
if (error)
return error;
error = security_inode_mknod(dir, dentry, mode, dev);
if (error)
return error;
error = dir->i_op->mknod(dir, dentry, mode, dev);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
static int may_mknod(mode_t mode)
{
switch (mode & S_IFMT) {
case S_IFREG:
case S_IFCHR:
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
case 0: /* zero mode translates to S_IFREG */
return 0;
case S_IFDIR:
return -EPERM;
default:
return -EINVAL;
}
}
SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
unsigned, dev)
{
int error;
char *tmp;
struct dentry *dentry;
struct nameidata nd;
if (S_ISDIR(mode))
return -EPERM;
error = user_path_parent(dfd, filename, &nd, &tmp);
if (error)
return error;
dentry = lookup_create(&nd, 0);
if (IS_ERR(dentry)) {
error = PTR_ERR(dentry);
goto out_unlock;
}
if (!IS_POSIXACL(nd.path.dentry->d_inode))
mode &= ~current_umask();
error = may_mknod(mode);
if (error)
goto out_dput;
error = mnt_want_write(nd.path.mnt);
if (error)
goto out_dput;
error = security_path_mknod(&nd.path, dentry, mode, dev);
if (error)
goto out_drop_write;
switch (mode & S_IFMT) {
case 0: case S_IFREG:
error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
break;
case S_IFCHR: case S_IFBLK:
error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
new_decode_dev(dev));
break;
case S_IFIFO: case S_IFSOCK:
error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
break;
}
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
dput(dentry);
out_unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
path_put(&nd.path);
putname(tmp);
return error;
}
SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
{
return sys_mknodat(AT_FDCWD, filename, mode, dev);
}
int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->mkdir)
return -EPERM;
mode &= (S_IRWXUGO|S_ISVTX);
error = security_inode_mkdir(dir, dentry, mode);
if (error)
return error;
error = dir->i_op->mkdir(dir, dentry, mode);
if (!error)
fsnotify_mkdir(dir, dentry);
return error;
}
SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
{
int error = 0;
char * tmp;
struct dentry *dentry;
struct nameidata nd;
error = user_path_parent(dfd, pathname, &nd, &tmp);
if (error)
goto out_err;
dentry = lookup_create(&nd, 1);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto out_unlock;
if (!IS_POSIXACL(nd.path.dentry->d_inode))
mode &= ~current_umask();
error = mnt_want_write(nd.path.mnt);
if (error)
goto out_dput;
error = security_path_mkdir(&nd.path, dentry, mode);
if (error)
goto out_drop_write;
error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
dput(dentry);
out_unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
path_put(&nd.path);
putname(tmp);
out_err:
return error;
}
SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
{
return sys_mkdirat(AT_FDCWD, pathname, mode);
}
/*
* We try to drop the dentry early: we should have
* a usage count of 2 if we're the only user of this
* dentry, and if that is true (possibly after pruning
* the dcache), then we drop the dentry now.
*
* A low-level filesystem can, if it choses, legally
* do a
*
* if (!d_unhashed(dentry))
* return -EBUSY;
*
* if it cannot handle the case of removing a directory
* that is still in use by something else..
*/
void dentry_unhash(struct dentry *dentry)
{
dget(dentry);
shrink_dcache_parent(dentry);
spin_lock(&dentry->d_lock);
if (dentry->d_count == 2)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
int vfs_rmdir(struct inode *dir, struct dentry *dentry)
{
int error = may_delete(dir, dentry, 1);
if (error)
return error;
if (!dir->i_op->rmdir)
return -EPERM;
mutex_lock(&dentry->d_inode->i_mutex);
dentry_unhash(dentry);
if (d_mountpoint(dentry))
error = -EBUSY;
else {
error = security_inode_rmdir(dir, dentry);
if (!error) {
error = dir->i_op->rmdir(dir, dentry);
if (!error) {
dentry->d_inode->i_flags |= S_DEAD;
dont_mount(dentry);
}
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
if (!error) {
d_delete(dentry);
}
dput(dentry);
return error;
}
static long do_rmdir(int dfd, const char __user *pathname)
{
int error = 0;
char * name;
struct dentry *dentry;
struct nameidata nd;
error = user_path_parent(dfd, pathname, &nd, &name);
if (error)
return error;
switch(nd.last_type) {
case LAST_DOTDOT:
error = -ENOTEMPTY;
goto exit1;
case LAST_DOT:
error = -EINVAL;
goto exit1;
case LAST_ROOT:
error = -EBUSY;
goto exit1;
}
nd.flags &= ~LOOKUP_PARENT;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto exit2;
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit3;
error = security_path_rmdir(&nd.path, dentry);
if (error)
goto exit4;
error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
exit4:
mnt_drop_write(nd.path.mnt);
exit3:
dput(dentry);
exit2:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
exit1:
path_put(&nd.path);
putname(name);
return error;
}
SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
{
return do_rmdir(AT_FDCWD, pathname);
}
int vfs_unlink(struct inode *dir, struct dentry *dentry)
{
int error = may_delete(dir, dentry, 0);
if (error)
return error;
if (!dir->i_op->unlink)
return -EPERM;
mutex_lock(&dentry->d_inode->i_mutex);
if (d_mountpoint(dentry))
error = -EBUSY;
else {
error = security_inode_unlink(dir, dentry);
if (!error) {
error = dir->i_op->unlink(dir, dentry);
if (!error)
dont_mount(dentry);
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
/* We don't d_delete() NFS sillyrenamed files--they still exist. */
if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
fsnotify_link_count(dentry->d_inode);
d_delete(dentry);
}
return error;
}
/*
* Make sure that the actual truncation of the file will occur outside its
* directory's i_mutex. Truncate can take a long time if there is a lot of
* writeout happening, and we don't want to prevent access to the directory
* while waiting on the I/O.
*/
static long do_unlinkat(int dfd, const char __user *pathname)
{
int error;
char *name;
struct dentry *dentry;
struct nameidata nd;
struct inode *inode = NULL;
error = user_path_parent(dfd, pathname, &nd, &name);
if (error)
return error;
error = -EISDIR;
if (nd.last_type != LAST_NORM)
goto exit1;
nd.flags &= ~LOOKUP_PARENT;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
/* Why not before? Because we want correct error value */
if (nd.last.name[nd.last.len])
goto slashes;
inode = dentry->d_inode;
if (inode)
ihold(inode);
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit2;
error = security_path_unlink(&nd.path, dentry);
if (error)
goto exit3;
error = vfs_unlink(nd.path.dentry->d_inode, dentry);
exit3:
mnt_drop_write(nd.path.mnt);
exit2:
dput(dentry);
}
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
if (inode)
iput(inode); /* truncate the inode here */
exit1:
path_put(&nd.path);
putname(name);
return error;
slashes:
error = !dentry->d_inode ? -ENOENT :
S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
goto exit2;
}
SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
{
if ((flag & ~AT_REMOVEDIR) != 0)
return -EINVAL;
if (flag & AT_REMOVEDIR)
return do_rmdir(dfd, pathname);
return do_unlinkat(dfd, pathname);
}
SYSCALL_DEFINE1(unlink, const char __user *, pathname)
{
return do_unlinkat(AT_FDCWD, pathname);
}
int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->symlink)
return -EPERM;
error = security_inode_symlink(dir, dentry, oldname);
if (error)
return error;
error = dir->i_op->symlink(dir, dentry, oldname);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
int, newdfd, const char __user *, newname)
{
int error;
char *from;
char *to;
struct dentry *dentry;
struct nameidata nd;
from = getname(oldname);
if (IS_ERR(from))
return PTR_ERR(from);
error = user_path_parent(newdfd, newname, &nd, &to);
if (error)
goto out_putname;
dentry = lookup_create(&nd, 0);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto out_unlock;
error = mnt_want_write(nd.path.mnt);
if (error)
goto out_dput;
error = security_path_symlink(&nd.path, dentry, from);
if (error)
goto out_drop_write;
error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
dput(dentry);
out_unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
path_put(&nd.path);
putname(to);
out_putname:
putname(from);
return error;
}
SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
{
return sys_symlinkat(oldname, AT_FDCWD, newname);
}
int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
{
struct inode *inode = old_dentry->d_inode;
int error;
if (!inode)
return -ENOENT;
error = may_create(dir, new_dentry);
if (error)
return error;
if (dir->i_sb != inode->i_sb)
return -EXDEV;
/*
* A link to an append-only or immutable file cannot be created.
*/
if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
return -EPERM;
if (!dir->i_op->link)
return -EPERM;
if (S_ISDIR(inode->i_mode))
return -EPERM;
error = security_inode_link(old_dentry, dir, new_dentry);
if (error)
return error;
mutex_lock(&inode->i_mutex);
/* Make sure we don't allow creating hardlink to an unlinked file */
if (inode->i_nlink == 0)
error = -ENOENT;
else
error = dir->i_op->link(old_dentry, dir, new_dentry);
mutex_unlock(&inode->i_mutex);
if (!error)
fsnotify_link(dir, inode, new_dentry);
return error;
}
/*
* Hardlinks are often used in delicate situations. We avoid
* security-related surprises by not following symlinks on the
* newname. --KAB
*
* We don't follow them on the oldname either to be compatible
* with linux 2.0, and to avoid hard-linking to directories
* and other special files. --ADM
*/
SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname, int, flags)
{
struct dentry *new_dentry;
struct nameidata nd;
struct path old_path;
int how = 0;
int error;
char *to;
if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
return -EINVAL;
/*
* To use null names we require CAP_DAC_READ_SEARCH
* This ensures that not everyone will be able to create
* handlink using the passed filedescriptor.
*/
if (flags & AT_EMPTY_PATH) {
if (!capable(CAP_DAC_READ_SEARCH))
return -ENOENT;
how = LOOKUP_EMPTY;
}
if (flags & AT_SYMLINK_FOLLOW)
how |= LOOKUP_FOLLOW;
error = user_path_at(olddfd, oldname, how, &old_path);
if (error)
return error;
error = user_path_parent(newdfd, newname, &nd, &to);
if (error)
goto out;
error = -EXDEV;
if (old_path.mnt != nd.path.mnt)
goto out_release;
new_dentry = lookup_create(&nd, 0);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto out_unlock;
error = mnt_want_write(nd.path.mnt);
if (error)
goto out_dput;
error = security_path_link(old_path.dentry, &nd.path, new_dentry);
if (error)
goto out_drop_write;
error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
dput(new_dentry);
out_unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
out_release:
path_put(&nd.path);
putname(to);
out:
path_put(&old_path);
return error;
}
SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
{
return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
}
/*
* The worst of all namespace operations - renaming directory. "Perverted"
* doesn't even start to describe it. Somebody in UCB had a heck of a trip...
* Problems:
* a) we can get into loop creation. Check is done in is_subdir().
* b) race potential - two innocent renames can create a loop together.
* That's where 4.4 screws up. Current fix: serialization on
* sb->s_vfs_rename_mutex. We might be more accurate, but that's another
* story.
* c) we have to lock _three_ objects - parents and victim (if it exists).
* And that - after we got ->i_mutex on parents (until then we don't know
* whether the target exists). Solution: try to be smart with locking
* order for inodes. We rely on the fact that tree topology may change
* only under ->s_vfs_rename_mutex _and_ that parent of the object we
* move will be locked. Thus we can rank directories by the tree
* (ancestors first) and rank all non-directories after them.
* That works since everybody except rename does "lock parent, lookup,
* lock child" and rename is under ->s_vfs_rename_mutex.
* HOWEVER, it relies on the assumption that any object with ->lookup()
* has no more than 1 dentry. If "hybrid" objects will ever appear,
* we'd better make sure that there's no link(2) for them.
* d) some filesystems don't support opened-but-unlinked directories,
* either because of layout or because they are not ready to deal with
* all cases correctly. The latter will be fixed (taking this sort of
* stuff into VFS), but the former is not going away. Solution: the same
* trick as in rmdir().
* e) conversion from fhandle to dentry may come in the wrong moment - when
* we are removing the target. Solution: we will have to grab ->i_mutex
* in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
* ->i_mutex on parents, which works but leads to some truly excessive
* locking].
*/
static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
int error = 0;
struct inode *target;
/*
* If we are going to change the parent - check write permissions,
* we'll need to flip '..'.
*/
if (new_dir != old_dir) {
error = inode_permission(old_dentry->d_inode, MAY_WRITE);
if (error)
return error;
}
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
return error;
target = new_dentry->d_inode;
if (target)
mutex_lock(&target->i_mutex);
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
error = -EBUSY;
else {
if (target)
dentry_unhash(new_dentry);
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
}
if (target) {
if (!error) {
target->i_flags |= S_DEAD;
dont_mount(new_dentry);
}
mutex_unlock(&target->i_mutex);
if (d_unhashed(new_dentry))
d_rehash(new_dentry);
dput(new_dentry);
}
if (!error)
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
d_move(old_dentry,new_dentry);
return error;
}
static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
struct inode *target;
int error;
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
return error;
dget(new_dentry);
target = new_dentry->d_inode;
if (target)
mutex_lock(&target->i_mutex);
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
error = -EBUSY;
else
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
if (!error) {
if (target)
dont_mount(new_dentry);
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
d_move(old_dentry, new_dentry);
}
if (target)
mutex_unlock(&target->i_mutex);
dput(new_dentry);
return error;
}
int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
int error;
int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
const unsigned char *old_name;
if (old_dentry->d_inode == new_dentry->d_inode)
return 0;
error = may_delete(old_dir, old_dentry, is_dir);
if (error)
return error;
if (!new_dentry->d_inode)
error = may_create(new_dir, new_dentry);
else
error = may_delete(new_dir, new_dentry, is_dir);
if (error)
return error;
if (!old_dir->i_op->rename)
return -EPERM;
old_name = fsnotify_oldname_init(old_dentry->d_name.name);
if (is_dir)
error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
else
error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
if (!error)
fsnotify_move(old_dir, new_dir, old_name, is_dir,
new_dentry->d_inode, old_dentry);
fsnotify_oldname_free(old_name);
return error;
}
SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname)
{
struct dentry *old_dir, *new_dir;
struct dentry *old_dentry, *new_dentry;
struct dentry *trap;
struct nameidata oldnd, newnd;
char *from;
char *to;
int error;
error = user_path_parent(olddfd, oldname, &oldnd, &from);
if (error)
goto exit;
error = user_path_parent(newdfd, newname, &newnd, &to);
if (error)
goto exit1;
error = -EXDEV;
if (oldnd.path.mnt != newnd.path.mnt)
goto exit2;
old_dir = oldnd.path.dentry;
error = -EBUSY;
if (oldnd.last_type != LAST_NORM)
goto exit2;
new_dir = newnd.path.dentry;
if (newnd.last_type != LAST_NORM)
goto exit2;
oldnd.flags &= ~LOOKUP_PARENT;
newnd.flags &= ~LOOKUP_PARENT;
newnd.flags |= LOOKUP_RENAME_TARGET;
trap = lock_rename(new_dir, old_dir);
old_dentry = lookup_hash(&oldnd);
error = PTR_ERR(old_dentry);
if (IS_ERR(old_dentry))
goto exit3;
/* source must exist */
error = -ENOENT;
if (!old_dentry->d_inode)
goto exit4;
/* unless the source is a directory trailing slashes give -ENOTDIR */
if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
error = -ENOTDIR;
if (oldnd.last.name[oldnd.last.len])
goto exit4;
if (newnd.last.name[newnd.last.len])
goto exit4;
}
/* source should not be ancestor of target */
error = -EINVAL;
if (old_dentry == trap)
goto exit4;
new_dentry = lookup_hash(&newnd);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto exit4;
/* target should not be an ancestor of source */
error = -ENOTEMPTY;
if (new_dentry == trap)
goto exit5;
error = mnt_want_write(oldnd.path.mnt);
if (error)
goto exit5;
error = security_path_rename(&oldnd.path, old_dentry,
&newnd.path, new_dentry);
if (error)
goto exit6;
error = vfs_rename(old_dir->d_inode, old_dentry,
new_dir->d_inode, new_dentry);
exit6:
mnt_drop_write(oldnd.path.mnt);
exit5:
dput(new_dentry);
exit4:
dput(old_dentry);
exit3:
unlock_rename(new_dir, old_dir);
exit2:
path_put(&newnd.path);
putname(to);
exit1:
path_put(&oldnd.path);
putname(from);
exit:
return error;
}
SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
{
return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
}
int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
{
int len;
len = PTR_ERR(link);
if (IS_ERR(link))
goto out;
len = strlen(link);
if (len > (unsigned) buflen)
len = buflen;
if (copy_to_user(buffer, link, len))
len = -EFAULT;
out:
return len;
}
/*
* A helper for ->readlink(). This should be used *ONLY* for symlinks that
* have ->follow_link() touching nd only in nd_set_link(). Using (or not
* using) it for any given inode is up to filesystem.
*/
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct nameidata nd;
void *cookie;
int res;
nd.depth = 0;
cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
if (IS_ERR(cookie))
return PTR_ERR(cookie);
res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
if (dentry->d_inode->i_op->put_link)
dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
return res;
}
int vfs_follow_link(struct nameidata *nd, const char *link)
{
return __vfs_follow_link(nd, link);
}
/* get the link contents into pagecache */
static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
char *kaddr;
struct page *page;
struct address_space *mapping = dentry->d_inode->i_mapping;
page = read_mapping_page(mapping, 0, NULL);
if (IS_ERR(page))
return (char*)page;
*ppage = page;
kaddr = kmap(page);
nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
return kaddr;
}
int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct page *page = NULL;
char *s = page_getlink(dentry, &page);
int res = vfs_readlink(dentry,buffer,buflen,s);
if (page) {
kunmap(page);
page_cache_release(page);
}
return res;
}
void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
{
struct page *page = NULL;
nd_set_link(nd, page_getlink(dentry, &page));
return page;
}
void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
struct page *page = cookie;
if (page) {
kunmap(page);
page_cache_release(page);
}
}
/*
* The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
*/
int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
{
struct address_space *mapping = inode->i_mapping;
struct page *page;
void *fsdata;
int err;
char *kaddr;
unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
if (nofs)
flags |= AOP_FLAG_NOFS;
retry:
err = pagecache_write_begin(NULL, mapping, 0, len-1,
flags, &page, &fsdata);
if (err)
goto fail;
kaddr = kmap_atomic(page, KM_USER0);
memcpy(kaddr, symname, len-1);
kunmap_atomic(kaddr, KM_USER0);
err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
page, fsdata);
if (err < 0)
goto fail;
if (err < len-1)
goto retry;
mark_inode_dirty(inode);
return 0;
fail:
return err;
}
int page_symlink(struct inode *inode, const char *symname, int len)
{
return __page_symlink(inode, symname, len,
!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
}
const struct inode_operations page_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = page_follow_link_light,
.put_link = page_put_link,
};
EXPORT_SYMBOL(user_path_at);
EXPORT_SYMBOL(follow_down_one);
EXPORT_SYMBOL(follow_down);
EXPORT_SYMBOL(follow_up);
EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
EXPORT_SYMBOL(getname);
EXPORT_SYMBOL(lock_rename);
EXPORT_SYMBOL(lookup_one_len);
EXPORT_SYMBOL(page_follow_link_light);
EXPORT_SYMBOL(page_put_link);
EXPORT_SYMBOL(page_readlink);
EXPORT_SYMBOL(__page_symlink);
EXPORT_SYMBOL(page_symlink);
EXPORT_SYMBOL(page_symlink_inode_operations);
EXPORT_SYMBOL(kern_path_parent);
EXPORT_SYMBOL(kern_path);
EXPORT_SYMBOL(vfs_path_lookup);
EXPORT_SYMBOL(inode_permission);
EXPORT_SYMBOL(file_permission);
EXPORT_SYMBOL(unlock_rename);
EXPORT_SYMBOL(vfs_create);
EXPORT_SYMBOL(vfs_follow_link);
EXPORT_SYMBOL(vfs_link);
EXPORT_SYMBOL(vfs_mkdir);
EXPORT_SYMBOL(vfs_mknod);
EXPORT_SYMBOL(generic_permission);
EXPORT_SYMBOL(vfs_readlink);
EXPORT_SYMBOL(vfs_rename);
EXPORT_SYMBOL(vfs_rmdir);
EXPORT_SYMBOL(vfs_symlink);
EXPORT_SYMBOL(vfs_unlink);
EXPORT_SYMBOL(dentry_unhash);
EXPORT_SYMBOL(generic_readlink);
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