4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * Some corrections by tytso.
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/export.h>
19 #include <linux/slab.h>
21 #include <linux/namei.h>
22 #include <linux/pagemap.h>
23 #include <linux/fsnotify.h>
24 #include <linux/personality.h>
25 #include <linux/security.h>
26 #include <linux/ima.h>
27 #include <linux/syscalls.h>
28 #include <linux/mount.h>
29 #include <linux/audit.h>
30 #include <linux/capability.h>
31 #include <linux/file.h>
32 #include <linux/fcntl.h>
33 #include <linux/device_cgroup.h>
34 #include <linux/fs_struct.h>
35 #include <linux/posix_acl.h>
36 #include <asm/uaccess.h>
41 /* [Feb-1997 T. Schoebel-Theuer]
42 * Fundamental changes in the pathname lookup mechanisms (namei)
43 * were necessary because of omirr. The reason is that omirr needs
44 * to know the _real_ pathname, not the user-supplied one, in case
45 * of symlinks (and also when transname replacements occur).
47 * The new code replaces the old recursive symlink resolution with
48 * an iterative one (in case of non-nested symlink chains). It does
49 * this with calls to <fs>_follow_link().
50 * As a side effect, dir_namei(), _namei() and follow_link() are now
51 * replaced with a single function lookup_dentry() that can handle all
52 * the special cases of the former code.
54 * With the new dcache, the pathname is stored at each inode, at least as
55 * long as the refcount of the inode is positive. As a side effect, the
56 * size of the dcache depends on the inode cache and thus is dynamic.
58 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
59 * resolution to correspond with current state of the code.
61 * Note that the symlink resolution is not *completely* iterative.
62 * There is still a significant amount of tail- and mid- recursion in
63 * the algorithm. Also, note that <fs>_readlink() is not used in
64 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
65 * may return different results than <fs>_follow_link(). Many virtual
66 * filesystems (including /proc) exhibit this behavior.
69 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
70 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
71 * and the name already exists in form of a symlink, try to create the new
72 * name indicated by the symlink. The old code always complained that the
73 * name already exists, due to not following the symlink even if its target
74 * is nonexistent. The new semantics affects also mknod() and link() when
75 * the name is a symlink pointing to a non-existent name.
77 * I don't know which semantics is the right one, since I have no access
78 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
79 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
80 * "old" one. Personally, I think the new semantics is much more logical.
81 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
82 * file does succeed in both HP-UX and SunOs, but not in Solaris
83 * and in the old Linux semantics.
86 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
87 * semantics. See the comments in "open_namei" and "do_link" below.
89 * [10-Sep-98 Alan Modra] Another symlink change.
92 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
93 * inside the path - always follow.
94 * in the last component in creation/removal/renaming - never follow.
95 * if LOOKUP_FOLLOW passed - follow.
96 * if the pathname has trailing slashes - follow.
97 * otherwise - don't follow.
98 * (applied in that order).
100 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
101 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
102 * During the 2.4 we need to fix the userland stuff depending on it -
103 * hopefully we will be able to get rid of that wart in 2.5. So far only
104 * XEmacs seems to be relying on it...
107 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
108 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
109 * any extra contention...
112 /* In order to reduce some races, while at the same time doing additional
113 * checking and hopefully speeding things up, we copy filenames to the
114 * kernel data space before using them..
116 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
117 * PATH_MAX includes the nul terminator --RR.
119 static int do_getname(const char __user
*filename
, char *page
)
122 unsigned long len
= PATH_MAX
;
124 if (!segment_eq(get_fs(), KERNEL_DS
)) {
125 if ((unsigned long) filename
>= TASK_SIZE
)
127 if (TASK_SIZE
- (unsigned long) filename
< PATH_MAX
)
128 len
= TASK_SIZE
- (unsigned long) filename
;
131 retval
= strncpy_from_user(page
, filename
, len
);
135 return -ENAMETOOLONG
;
141 static char *getname_flags(const char __user
*filename
, int flags
, int *empty
)
143 char *result
= __getname();
147 return ERR_PTR(-ENOMEM
);
149 retval
= do_getname(filename
, result
);
151 if (retval
== -ENOENT
&& empty
)
153 if (retval
!= -ENOENT
|| !(flags
& LOOKUP_EMPTY
)) {
155 return ERR_PTR(retval
);
158 audit_getname(result
);
162 char *getname(const char __user
* filename
)
164 return getname_flags(filename
, 0, NULL
);
167 #ifdef CONFIG_AUDITSYSCALL
168 void putname(const char *name
)
170 if (unlikely(!audit_dummy_context()))
175 EXPORT_SYMBOL(putname
);
178 static int check_acl(struct inode
*inode
, int mask
)
180 #ifdef CONFIG_FS_POSIX_ACL
181 struct posix_acl
*acl
;
183 if (mask
& MAY_NOT_BLOCK
) {
184 acl
= get_cached_acl_rcu(inode
, ACL_TYPE_ACCESS
);
187 /* no ->get_acl() calls in RCU mode... */
188 if (acl
== ACL_NOT_CACHED
)
190 return posix_acl_permission(inode
, acl
, mask
& ~MAY_NOT_BLOCK
);
193 acl
= get_cached_acl(inode
, ACL_TYPE_ACCESS
);
196 * A filesystem can force a ACL callback by just never filling the
197 * ACL cache. But normally you'd fill the cache either at inode
198 * instantiation time, or on the first ->get_acl call.
200 * If the filesystem doesn't have a get_acl() function at all, we'll
201 * just create the negative cache entry.
203 if (acl
== ACL_NOT_CACHED
) {
204 if (inode
->i_op
->get_acl
) {
205 acl
= inode
->i_op
->get_acl(inode
, ACL_TYPE_ACCESS
);
209 set_cached_acl(inode
, ACL_TYPE_ACCESS
, NULL
);
215 int error
= posix_acl_permission(inode
, acl
, mask
);
216 posix_acl_release(acl
);
225 * This does the basic permission checking
227 static int acl_permission_check(struct inode
*inode
, int mask
)
229 unsigned int mode
= inode
->i_mode
;
231 if (likely(current_fsuid() == inode
->i_uid
))
234 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
)) {
235 int error
= check_acl(inode
, mask
);
236 if (error
!= -EAGAIN
)
240 if (in_group_p(inode
->i_gid
))
245 * If the DACs are ok we don't need any capability check.
247 if ((mask
& ~mode
& (MAY_READ
| MAY_WRITE
| MAY_EXEC
)) == 0)
253 * generic_permission - check for access rights on a Posix-like filesystem
254 * @inode: inode to check access rights for
255 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
257 * Used to check for read/write/execute permissions on a file.
258 * We use "fsuid" for this, letting us set arbitrary permissions
259 * for filesystem access without changing the "normal" uids which
260 * are used for other things.
262 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
263 * request cannot be satisfied (eg. requires blocking or too much complexity).
264 * It would then be called again in ref-walk mode.
266 int generic_permission(struct inode
*inode
, int mask
)
271 * Do the basic permission checks.
273 ret
= acl_permission_check(inode
, mask
);
277 if (S_ISDIR(inode
->i_mode
)) {
278 /* DACs are overridable for directories */
279 if (inode_capable(inode
, CAP_DAC_OVERRIDE
))
281 if (!(mask
& MAY_WRITE
))
282 if (inode_capable(inode
, CAP_DAC_READ_SEARCH
))
287 * Read/write DACs are always overridable.
288 * Executable DACs are overridable when there is
289 * at least one exec bit set.
291 if (!(mask
& MAY_EXEC
) || (inode
->i_mode
& S_IXUGO
))
292 if (inode_capable(inode
, CAP_DAC_OVERRIDE
))
296 * Searching includes executable on directories, else just read.
298 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
299 if (mask
== MAY_READ
)
300 if (inode_capable(inode
, CAP_DAC_READ_SEARCH
))
307 * We _really_ want to just do "generic_permission()" without
308 * even looking at the inode->i_op values. So we keep a cache
309 * flag in inode->i_opflags, that says "this has not special
310 * permission function, use the fast case".
312 static inline int do_inode_permission(struct inode
*inode
, int mask
)
314 if (unlikely(!(inode
->i_opflags
& IOP_FASTPERM
))) {
315 if (likely(inode
->i_op
->permission
))
316 return inode
->i_op
->permission(inode
, mask
);
318 /* This gets set once for the inode lifetime */
319 spin_lock(&inode
->i_lock
);
320 inode
->i_opflags
|= IOP_FASTPERM
;
321 spin_unlock(&inode
->i_lock
);
323 return generic_permission(inode
, mask
);
327 * inode_permission - check for access rights to a given inode
328 * @inode: inode to check permission on
329 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
331 * Used to check for read/write/execute permissions on an inode.
332 * We use "fsuid" for this, letting us set arbitrary permissions
333 * for filesystem access without changing the "normal" uids which
334 * are used for other things.
336 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
338 int inode_permission(struct inode
*inode
, int mask
)
342 if (unlikely(mask
& MAY_WRITE
)) {
343 umode_t mode
= inode
->i_mode
;
346 * Nobody gets write access to a read-only fs.
348 if (IS_RDONLY(inode
) &&
349 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
353 * Nobody gets write access to an immutable file.
355 if (IS_IMMUTABLE(inode
))
359 retval
= do_inode_permission(inode
, mask
);
363 retval
= devcgroup_inode_permission(inode
, mask
);
367 return security_inode_permission(inode
, mask
);
371 * path_get - get a reference to a path
372 * @path: path to get the reference to
374 * Given a path increment the reference count to the dentry and the vfsmount.
376 void path_get(struct path
*path
)
381 EXPORT_SYMBOL(path_get
);
384 * path_put - put a reference to a path
385 * @path: path to put the reference to
387 * Given a path decrement the reference count to the dentry and the vfsmount.
389 void path_put(struct path
*path
)
394 EXPORT_SYMBOL(path_put
);
397 * Path walking has 2 modes, rcu-walk and ref-walk (see
398 * Documentation/filesystems/path-lookup.txt). In situations when we can't
399 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
400 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
401 * mode. Refcounts are grabbed at the last known good point before rcu-walk
402 * got stuck, so ref-walk may continue from there. If this is not successful
403 * (eg. a seqcount has changed), then failure is returned and it's up to caller
404 * to restart the path walk from the beginning in ref-walk mode.
408 * unlazy_walk - try to switch to ref-walk mode.
409 * @nd: nameidata pathwalk data
410 * @dentry: child of nd->path.dentry or NULL
411 * Returns: 0 on success, -ECHILD on failure
413 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
414 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
415 * @nd or NULL. Must be called from rcu-walk context.
417 static int unlazy_walk(struct nameidata
*nd
, struct dentry
*dentry
)
419 struct fs_struct
*fs
= current
->fs
;
420 struct dentry
*parent
= nd
->path
.dentry
;
423 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
424 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
426 spin_lock(&fs
->lock
);
427 if (nd
->root
.mnt
!= fs
->root
.mnt
||
428 nd
->root
.dentry
!= fs
->root
.dentry
)
431 spin_lock(&parent
->d_lock
);
433 if (!__d_rcu_to_refcount(parent
, nd
->seq
))
435 BUG_ON(nd
->inode
!= parent
->d_inode
);
437 if (dentry
->d_parent
!= parent
)
439 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
440 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
443 * If the sequence check on the child dentry passed, then
444 * the child has not been removed from its parent. This
445 * means the parent dentry must be valid and able to take
446 * a reference at this point.
448 BUG_ON(!IS_ROOT(dentry
) && dentry
->d_parent
!= parent
);
449 BUG_ON(!parent
->d_count
);
451 spin_unlock(&dentry
->d_lock
);
453 spin_unlock(&parent
->d_lock
);
456 spin_unlock(&fs
->lock
);
458 mntget(nd
->path
.mnt
);
461 br_read_unlock(vfsmount_lock
);
462 nd
->flags
&= ~LOOKUP_RCU
;
466 spin_unlock(&dentry
->d_lock
);
468 spin_unlock(&parent
->d_lock
);
471 spin_unlock(&fs
->lock
);
476 * release_open_intent - free up open intent resources
477 * @nd: pointer to nameidata
479 void release_open_intent(struct nameidata
*nd
)
481 struct file
*file
= nd
->intent
.open
.file
;
483 if (file
&& !IS_ERR(file
)) {
484 if (file
->f_path
.dentry
== NULL
)
491 static inline int d_revalidate(struct dentry
*dentry
, struct nameidata
*nd
)
493 return dentry
->d_op
->d_revalidate(dentry
, nd
);
497 * complete_walk - successful completion of path walk
498 * @nd: pointer nameidata
500 * If we had been in RCU mode, drop out of it and legitimize nd->path.
501 * Revalidate the final result, unless we'd already done that during
502 * the path walk or the filesystem doesn't ask for it. Return 0 on
503 * success, -error on failure. In case of failure caller does not
504 * need to drop nd->path.
506 static int complete_walk(struct nameidata
*nd
)
508 struct dentry
*dentry
= nd
->path
.dentry
;
511 if (nd
->flags
& LOOKUP_RCU
) {
512 nd
->flags
&= ~LOOKUP_RCU
;
513 if (!(nd
->flags
& LOOKUP_ROOT
))
515 spin_lock(&dentry
->d_lock
);
516 if (unlikely(!__d_rcu_to_refcount(dentry
, nd
->seq
))) {
517 spin_unlock(&dentry
->d_lock
);
519 br_read_unlock(vfsmount_lock
);
522 BUG_ON(nd
->inode
!= dentry
->d_inode
);
523 spin_unlock(&dentry
->d_lock
);
524 mntget(nd
->path
.mnt
);
526 br_read_unlock(vfsmount_lock
);
529 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
532 if (likely(!(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)))
535 if (likely(!(dentry
->d_sb
->s_type
->fs_flags
& FS_REVAL_DOT
)))
538 /* Note: we do not d_invalidate() */
539 status
= d_revalidate(dentry
, nd
);
550 static __always_inline
void set_root(struct nameidata
*nd
)
553 get_fs_root(current
->fs
, &nd
->root
);
556 static int link_path_walk(const char *, struct nameidata
*);
558 static __always_inline
void set_root_rcu(struct nameidata
*nd
)
561 struct fs_struct
*fs
= current
->fs
;
565 seq
= read_seqcount_begin(&fs
->seq
);
567 nd
->seq
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
568 } while (read_seqcount_retry(&fs
->seq
, seq
));
572 static __always_inline
int __vfs_follow_link(struct nameidata
*nd
, const char *link
)
584 nd
->flags
|= LOOKUP_JUMPED
;
586 nd
->inode
= nd
->path
.dentry
->d_inode
;
588 ret
= link_path_walk(link
, nd
);
592 return PTR_ERR(link
);
595 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
598 if (path
->mnt
!= nd
->path
.mnt
)
602 static inline void path_to_nameidata(const struct path
*path
,
603 struct nameidata
*nd
)
605 if (!(nd
->flags
& LOOKUP_RCU
)) {
606 dput(nd
->path
.dentry
);
607 if (nd
->path
.mnt
!= path
->mnt
)
608 mntput(nd
->path
.mnt
);
610 nd
->path
.mnt
= path
->mnt
;
611 nd
->path
.dentry
= path
->dentry
;
614 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
616 struct inode
*inode
= link
->dentry
->d_inode
;
617 if (!IS_ERR(cookie
) && inode
->i_op
->put_link
)
618 inode
->i_op
->put_link(link
->dentry
, nd
, cookie
);
622 static __always_inline
int
623 follow_link(struct path
*link
, struct nameidata
*nd
, void **p
)
626 struct dentry
*dentry
= link
->dentry
;
628 BUG_ON(nd
->flags
& LOOKUP_RCU
);
630 if (link
->mnt
== nd
->path
.mnt
)
633 if (unlikely(current
->total_link_count
>= 40)) {
634 *p
= ERR_PTR(-ELOOP
); /* no ->put_link(), please */
639 current
->total_link_count
++;
642 nd_set_link(nd
, NULL
);
644 error
= security_inode_follow_link(link
->dentry
, nd
);
646 *p
= ERR_PTR(error
); /* no ->put_link(), please */
651 nd
->last_type
= LAST_BIND
;
652 *p
= dentry
->d_inode
->i_op
->follow_link(dentry
, nd
);
655 char *s
= nd_get_link(nd
);
658 error
= __vfs_follow_link(nd
, s
);
659 else if (nd
->last_type
== LAST_BIND
) {
660 nd
->flags
|= LOOKUP_JUMPED
;
661 nd
->inode
= nd
->path
.dentry
->d_inode
;
662 if (nd
->inode
->i_op
->follow_link
) {
663 /* stepped on a _really_ weird one */
672 static int follow_up_rcu(struct path
*path
)
674 struct mount
*mnt
= real_mount(path
->mnt
);
675 struct mount
*parent
;
676 struct dentry
*mountpoint
;
678 parent
= mnt
->mnt_parent
;
679 if (&parent
->mnt
== path
->mnt
)
681 mountpoint
= mnt
->mnt_mountpoint
;
682 path
->dentry
= mountpoint
;
683 path
->mnt
= &parent
->mnt
;
687 int follow_up(struct path
*path
)
689 struct mount
*mnt
= real_mount(path
->mnt
);
690 struct mount
*parent
;
691 struct dentry
*mountpoint
;
693 br_read_lock(vfsmount_lock
);
694 parent
= mnt
->mnt_parent
;
695 if (&parent
->mnt
== path
->mnt
) {
696 br_read_unlock(vfsmount_lock
);
699 mntget(&parent
->mnt
);
700 mountpoint
= dget(mnt
->mnt_mountpoint
);
701 br_read_unlock(vfsmount_lock
);
703 path
->dentry
= mountpoint
;
705 path
->mnt
= &parent
->mnt
;
710 * Perform an automount
711 * - return -EISDIR to tell follow_managed() to stop and return the path we
714 static int follow_automount(struct path
*path
, unsigned flags
,
717 struct vfsmount
*mnt
;
720 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
723 /* We don't want to mount if someone's just doing a stat -
724 * unless they're stat'ing a directory and appended a '/' to
727 * We do, however, want to mount if someone wants to open or
728 * create a file of any type under the mountpoint, wants to
729 * traverse through the mountpoint or wants to open the
730 * mounted directory. Also, autofs may mark negative dentries
731 * as being automount points. These will need the attentions
732 * of the daemon to instantiate them before they can be used.
734 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
735 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
736 path
->dentry
->d_inode
)
739 current
->total_link_count
++;
740 if (current
->total_link_count
>= 40)
743 mnt
= path
->dentry
->d_op
->d_automount(path
);
746 * The filesystem is allowed to return -EISDIR here to indicate
747 * it doesn't want to automount. For instance, autofs would do
748 * this so that its userspace daemon can mount on this dentry.
750 * However, we can only permit this if it's a terminal point in
751 * the path being looked up; if it wasn't then the remainder of
752 * the path is inaccessible and we should say so.
754 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
759 if (!mnt
) /* mount collision */
763 /* lock_mount() may release path->mnt on error */
767 err
= finish_automount(mnt
, path
);
771 /* Someone else made a mount here whilst we were busy */
776 path
->dentry
= dget(mnt
->mnt_root
);
785 * Handle a dentry that is managed in some way.
786 * - Flagged for transit management (autofs)
787 * - Flagged as mountpoint
788 * - Flagged as automount point
790 * This may only be called in refwalk mode.
792 * Serialization is taken care of in namespace.c
794 static int follow_managed(struct path
*path
, unsigned flags
)
796 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
798 bool need_mntput
= false;
801 /* Given that we're not holding a lock here, we retain the value in a
802 * local variable for each dentry as we look at it so that we don't see
803 * the components of that value change under us */
804 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
805 managed
&= DCACHE_MANAGED_DENTRY
,
806 unlikely(managed
!= 0)) {
807 /* Allow the filesystem to manage the transit without i_mutex
809 if (managed
& DCACHE_MANAGE_TRANSIT
) {
810 BUG_ON(!path
->dentry
->d_op
);
811 BUG_ON(!path
->dentry
->d_op
->d_manage
);
812 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
817 /* Transit to a mounted filesystem. */
818 if (managed
& DCACHE_MOUNTED
) {
819 struct vfsmount
*mounted
= lookup_mnt(path
);
825 path
->dentry
= dget(mounted
->mnt_root
);
830 /* Something is mounted on this dentry in another
831 * namespace and/or whatever was mounted there in this
832 * namespace got unmounted before we managed to get the
836 /* Handle an automount point */
837 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
838 ret
= follow_automount(path
, flags
, &need_mntput
);
844 /* We didn't change the current path point */
848 if (need_mntput
&& path
->mnt
== mnt
)
852 return ret
< 0 ? ret
: need_mntput
;
855 int follow_down_one(struct path
*path
)
857 struct vfsmount
*mounted
;
859 mounted
= lookup_mnt(path
);
864 path
->dentry
= dget(mounted
->mnt_root
);
870 static inline bool managed_dentry_might_block(struct dentry
*dentry
)
872 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
&&
873 dentry
->d_op
->d_manage(dentry
, true) < 0);
877 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
878 * we meet a managed dentry that would need blocking.
880 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
881 struct inode
**inode
)
884 struct mount
*mounted
;
886 * Don't forget we might have a non-mountpoint managed dentry
887 * that wants to block transit.
889 if (unlikely(managed_dentry_might_block(path
->dentry
)))
892 if (!d_mountpoint(path
->dentry
))
895 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
, 1);
898 path
->mnt
= &mounted
->mnt
;
899 path
->dentry
= mounted
->mnt
.mnt_root
;
900 nd
->flags
|= LOOKUP_JUMPED
;
901 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
903 * Update the inode too. We don't need to re-check the
904 * dentry sequence number here after this d_inode read,
905 * because a mount-point is always pinned.
907 *inode
= path
->dentry
->d_inode
;
912 static void follow_mount_rcu(struct nameidata
*nd
)
914 while (d_mountpoint(nd
->path
.dentry
)) {
915 struct mount
*mounted
;
916 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
, 1);
919 nd
->path
.mnt
= &mounted
->mnt
;
920 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
921 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
925 static int follow_dotdot_rcu(struct nameidata
*nd
)
930 if (nd
->path
.dentry
== nd
->root
.dentry
&&
931 nd
->path
.mnt
== nd
->root
.mnt
) {
934 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
935 struct dentry
*old
= nd
->path
.dentry
;
936 struct dentry
*parent
= old
->d_parent
;
939 seq
= read_seqcount_begin(&parent
->d_seq
);
940 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
942 nd
->path
.dentry
= parent
;
946 if (!follow_up_rcu(&nd
->path
))
948 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
950 follow_mount_rcu(nd
);
951 nd
->inode
= nd
->path
.dentry
->d_inode
;
955 nd
->flags
&= ~LOOKUP_RCU
;
956 if (!(nd
->flags
& LOOKUP_ROOT
))
959 br_read_unlock(vfsmount_lock
);
964 * Follow down to the covering mount currently visible to userspace. At each
965 * point, the filesystem owning that dentry may be queried as to whether the
966 * caller is permitted to proceed or not.
968 int follow_down(struct path
*path
)
973 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
974 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
975 /* Allow the filesystem to manage the transit without i_mutex
978 * We indicate to the filesystem if someone is trying to mount
979 * something here. This gives autofs the chance to deny anyone
980 * other than its daemon the right to mount on its
983 * The filesystem may sleep at this point.
985 if (managed
& DCACHE_MANAGE_TRANSIT
) {
986 BUG_ON(!path
->dentry
->d_op
);
987 BUG_ON(!path
->dentry
->d_op
->d_manage
);
988 ret
= path
->dentry
->d_op
->d_manage(
989 path
->dentry
, false);
991 return ret
== -EISDIR
? 0 : ret
;
994 /* Transit to a mounted filesystem. */
995 if (managed
& DCACHE_MOUNTED
) {
996 struct vfsmount
*mounted
= lookup_mnt(path
);
1001 path
->mnt
= mounted
;
1002 path
->dentry
= dget(mounted
->mnt_root
);
1006 /* Don't handle automount points here */
1013 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1015 static void follow_mount(struct path
*path
)
1017 while (d_mountpoint(path
->dentry
)) {
1018 struct vfsmount
*mounted
= lookup_mnt(path
);
1023 path
->mnt
= mounted
;
1024 path
->dentry
= dget(mounted
->mnt_root
);
1028 static void follow_dotdot(struct nameidata
*nd
)
1033 struct dentry
*old
= nd
->path
.dentry
;
1035 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1036 nd
->path
.mnt
== nd
->root
.mnt
) {
1039 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1040 /* rare case of legitimate dget_parent()... */
1041 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1045 if (!follow_up(&nd
->path
))
1048 follow_mount(&nd
->path
);
1049 nd
->inode
= nd
->path
.dentry
->d_inode
;
1053 * This looks up the name in dcache, possibly revalidates the old dentry and
1054 * allocates a new one if not found or not valid. In the need_lookup argument
1055 * returns whether i_op->lookup is necessary.
1057 * dir->d_inode->i_mutex must be held
1059 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1060 struct nameidata
*nd
, bool *need_lookup
)
1062 struct dentry
*dentry
;
1065 *need_lookup
= false;
1066 dentry
= d_lookup(dir
, name
);
1068 if (d_need_lookup(dentry
)) {
1069 *need_lookup
= true;
1070 } else if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1071 error
= d_revalidate(dentry
, nd
);
1072 if (unlikely(error
<= 0)) {
1075 return ERR_PTR(error
);
1076 } else if (!d_invalidate(dentry
)) {
1085 dentry
= d_alloc(dir
, name
);
1086 if (unlikely(!dentry
))
1087 return ERR_PTR(-ENOMEM
);
1089 *need_lookup
= true;
1095 * Call i_op->lookup on the dentry. The dentry must be negative but may be
1096 * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1098 * dir->d_inode->i_mutex must be held
1100 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1101 struct nameidata
*nd
)
1105 /* Don't create child dentry for a dead directory. */
1106 if (unlikely(IS_DEADDIR(dir
))) {
1108 return ERR_PTR(-ENOENT
);
1111 old
= dir
->i_op
->lookup(dir
, dentry
, nd
);
1112 if (unlikely(old
)) {
1119 static struct dentry
*__lookup_hash(struct qstr
*name
,
1120 struct dentry
*base
, struct nameidata
*nd
)
1123 struct dentry
*dentry
;
1125 dentry
= lookup_dcache(name
, base
, nd
, &need_lookup
);
1129 return lookup_real(base
->d_inode
, dentry
, nd
);
1133 * It's more convoluted than I'd like it to be, but... it's still fairly
1134 * small and for now I'd prefer to have fast path as straight as possible.
1135 * It _is_ time-critical.
1137 static int do_lookup(struct nameidata
*nd
, struct qstr
*name
,
1138 struct path
*path
, struct inode
**inode
)
1140 struct vfsmount
*mnt
= nd
->path
.mnt
;
1141 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1147 * Rename seqlock is not required here because in the off chance
1148 * of a false negative due to a concurrent rename, we're going to
1149 * do the non-racy lookup, below.
1151 if (nd
->flags
& LOOKUP_RCU
) {
1154 dentry
= __d_lookup_rcu(parent
, name
, &seq
, inode
);
1158 /* Memory barrier in read_seqcount_begin of child is enough */
1159 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1163 if (unlikely(d_need_lookup(dentry
)))
1165 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1166 status
= d_revalidate(dentry
, nd
);
1167 if (unlikely(status
<= 0)) {
1168 if (status
!= -ECHILD
)
1174 path
->dentry
= dentry
;
1175 if (unlikely(!__follow_mount_rcu(nd
, path
, inode
)))
1177 if (unlikely(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
))
1181 if (unlazy_walk(nd
, dentry
))
1184 dentry
= __d_lookup(parent
, name
);
1187 if (unlikely(!dentry
))
1190 if (unlikely(d_need_lookup(dentry
))) {
1195 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1196 status
= d_revalidate(dentry
, nd
);
1197 if (unlikely(status
<= 0)) {
1202 if (!d_invalidate(dentry
)) {
1209 path
->dentry
= dentry
;
1210 err
= follow_managed(path
, nd
->flags
);
1211 if (unlikely(err
< 0)) {
1212 path_put_conditional(path
, nd
);
1216 nd
->flags
|= LOOKUP_JUMPED
;
1217 *inode
= path
->dentry
->d_inode
;
1221 BUG_ON(nd
->inode
!= parent
->d_inode
);
1223 mutex_lock(&parent
->d_inode
->i_mutex
);
1224 dentry
= __lookup_hash(name
, parent
, nd
);
1225 mutex_unlock(&parent
->d_inode
->i_mutex
);
1227 return PTR_ERR(dentry
);
1231 static inline int may_lookup(struct nameidata
*nd
)
1233 if (nd
->flags
& LOOKUP_RCU
) {
1234 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1237 if (unlazy_walk(nd
, NULL
))
1240 return inode_permission(nd
->inode
, MAY_EXEC
);
1243 static inline int handle_dots(struct nameidata
*nd
, int type
)
1245 if (type
== LAST_DOTDOT
) {
1246 if (nd
->flags
& LOOKUP_RCU
) {
1247 if (follow_dotdot_rcu(nd
))
1255 static void terminate_walk(struct nameidata
*nd
)
1257 if (!(nd
->flags
& LOOKUP_RCU
)) {
1258 path_put(&nd
->path
);
1260 nd
->flags
&= ~LOOKUP_RCU
;
1261 if (!(nd
->flags
& LOOKUP_ROOT
))
1262 nd
->root
.mnt
= NULL
;
1264 br_read_unlock(vfsmount_lock
);
1269 * Do we need to follow links? We _really_ want to be able
1270 * to do this check without having to look at inode->i_op,
1271 * so we keep a cache of "no, this doesn't need follow_link"
1272 * for the common case.
1274 static inline int should_follow_link(struct inode
*inode
, int follow
)
1276 if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1277 if (likely(inode
->i_op
->follow_link
))
1280 /* This gets set once for the inode lifetime */
1281 spin_lock(&inode
->i_lock
);
1282 inode
->i_opflags
|= IOP_NOFOLLOW
;
1283 spin_unlock(&inode
->i_lock
);
1288 static inline int walk_component(struct nameidata
*nd
, struct path
*path
,
1289 struct qstr
*name
, int type
, int follow
)
1291 struct inode
*inode
;
1294 * "." and ".." are special - ".." especially so because it has
1295 * to be able to know about the current root directory and
1296 * parent relationships.
1298 if (unlikely(type
!= LAST_NORM
))
1299 return handle_dots(nd
, type
);
1300 err
= do_lookup(nd
, name
, path
, &inode
);
1301 if (unlikely(err
)) {
1306 path_to_nameidata(path
, nd
);
1310 if (should_follow_link(inode
, follow
)) {
1311 if (nd
->flags
& LOOKUP_RCU
) {
1312 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
1317 BUG_ON(inode
!= path
->dentry
->d_inode
);
1320 path_to_nameidata(path
, nd
);
1326 * This limits recursive symlink follows to 8, while
1327 * limiting consecutive symlinks to 40.
1329 * Without that kind of total limit, nasty chains of consecutive
1330 * symlinks can cause almost arbitrarily long lookups.
1332 static inline int nested_symlink(struct path
*path
, struct nameidata
*nd
)
1336 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1337 path_put_conditional(path
, nd
);
1338 path_put(&nd
->path
);
1341 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1344 current
->link_count
++;
1347 struct path link
= *path
;
1350 res
= follow_link(&link
, nd
, &cookie
);
1352 res
= walk_component(nd
, path
, &nd
->last
,
1353 nd
->last_type
, LOOKUP_FOLLOW
);
1354 put_link(nd
, &link
, cookie
);
1357 current
->link_count
--;
1363 * We really don't want to look at inode->i_op->lookup
1364 * when we don't have to. So we keep a cache bit in
1365 * the inode ->i_opflags field that says "yes, we can
1366 * do lookup on this inode".
1368 static inline int can_lookup(struct inode
*inode
)
1370 if (likely(inode
->i_opflags
& IOP_LOOKUP
))
1372 if (likely(!inode
->i_op
->lookup
))
1375 /* We do this once for the lifetime of the inode */
1376 spin_lock(&inode
->i_lock
);
1377 inode
->i_opflags
|= IOP_LOOKUP
;
1378 spin_unlock(&inode
->i_lock
);
1383 * We can do the critical dentry name comparison and hashing
1384 * operations one word at a time, but we are limited to:
1386 * - Architectures with fast unaligned word accesses. We could
1387 * do a "get_unaligned()" if this helps and is sufficiently
1390 * - Little-endian machines (so that we can generate the mask
1391 * of low bytes efficiently). Again, we *could* do a byte
1392 * swapping load on big-endian architectures if that is not
1393 * expensive enough to make the optimization worthless.
1395 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1396 * do not trap on the (extremely unlikely) case of a page
1397 * crossing operation.
1399 * - Furthermore, we need an efficient 64-bit compile for the
1400 * 64-bit case in order to generate the "number of bytes in
1401 * the final mask". Again, that could be replaced with a
1402 * efficient population count instruction or similar.
1404 #ifdef CONFIG_DCACHE_WORD_ACCESS
1409 * Jan Achrenius on G+: microoptimized version of
1410 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
1411 * that works for the bytemasks without having to
1414 static inline long count_masked_bytes(unsigned long mask
)
1416 return mask
*0x0001020304050608ul
>> 56;
1419 static inline unsigned int fold_hash(unsigned long hash
)
1421 hash
+= hash
>> (8*sizeof(int));
1425 #else /* 32-bit case */
1427 /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
1428 static inline long count_masked_bytes(long mask
)
1430 /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
1431 long a
= (0x0ff0001+mask
) >> 23;
1432 /* Fix the 1 for 00 case */
1436 #define fold_hash(x) (x)
1440 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1442 unsigned long a
, mask
;
1443 unsigned long hash
= 0;
1446 a
= *(unsigned long *)name
;
1447 if (len
< sizeof(unsigned long))
1451 name
+= sizeof(unsigned long);
1452 len
-= sizeof(unsigned long);
1456 mask
= ~(~0ul << len
*8);
1459 return fold_hash(hash
);
1461 EXPORT_SYMBOL(full_name_hash
);
1463 #define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
1464 #define ONEBYTES REPEAT_BYTE(0x01)
1465 #define SLASHBYTES REPEAT_BYTE('/')
1466 #define HIGHBITS REPEAT_BYTE(0x80)
1468 /* Return the high bit set in the first byte that is a zero */
1469 static inline unsigned long has_zero(unsigned long a
)
1471 return ((a
- ONEBYTES
) & ~a
) & HIGHBITS
;
1475 * Calculate the length and hash of the path component, and
1476 * return the length of the component;
1478 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1480 unsigned long a
, mask
, hash
, len
;
1483 len
= -sizeof(unsigned long);
1485 hash
= (hash
+ a
) * 9;
1486 len
+= sizeof(unsigned long);
1487 a
= *(unsigned long *)(name
+len
);
1488 /* Do we have any NUL or '/' bytes in this word? */
1489 mask
= has_zero(a
) | has_zero(a
^ SLASHBYTES
);
1492 /* The mask *below* the first high bit set */
1493 mask
= (mask
- 1) & ~mask
;
1496 *hashp
= fold_hash(hash
);
1498 return len
+ count_masked_bytes(mask
);
1503 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1505 unsigned long hash
= init_name_hash();
1507 hash
= partial_name_hash(*name
++, hash
);
1508 return end_name_hash(hash
);
1510 EXPORT_SYMBOL(full_name_hash
);
1513 * We know there's a real path component here of at least
1516 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1518 unsigned long hash
= init_name_hash();
1519 unsigned long len
= 0, c
;
1521 c
= (unsigned char)*name
;
1524 hash
= partial_name_hash(c
, hash
);
1525 c
= (unsigned char)name
[len
];
1526 } while (c
&& c
!= '/');
1527 *hashp
= end_name_hash(hash
);
1535 * This is the basic name resolution function, turning a pathname into
1536 * the final dentry. We expect 'base' to be positive and a directory.
1538 * Returns 0 and nd will have valid dentry and mnt on success.
1539 * Returns error and drops reference to input namei data on failure.
1541 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1551 /* At this point we know we have a real path component. */
1557 err
= may_lookup(nd
);
1561 len
= hash_name(name
, &this.hash
);
1566 if (name
[0] == '.') switch (len
) {
1568 if (name
[1] == '.') {
1570 nd
->flags
|= LOOKUP_JUMPED
;
1576 if (likely(type
== LAST_NORM
)) {
1577 struct dentry
*parent
= nd
->path
.dentry
;
1578 nd
->flags
&= ~LOOKUP_JUMPED
;
1579 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1580 err
= parent
->d_op
->d_hash(parent
, nd
->inode
,
1588 goto last_component
;
1590 * If it wasn't NUL, we know it was '/'. Skip that
1591 * slash, and continue until no more slashes.
1595 } while (unlikely(name
[len
] == '/'));
1597 goto last_component
;
1600 err
= walk_component(nd
, &next
, &this, type
, LOOKUP_FOLLOW
);
1605 err
= nested_symlink(&next
, nd
);
1609 if (can_lookup(nd
->inode
))
1613 /* here ends the main loop */
1617 nd
->last_type
= type
;
1624 static int path_init(int dfd
, const char *name
, unsigned int flags
,
1625 struct nameidata
*nd
, struct file
**fp
)
1631 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1632 nd
->flags
= flags
| LOOKUP_JUMPED
;
1634 if (flags
& LOOKUP_ROOT
) {
1635 struct inode
*inode
= nd
->root
.dentry
->d_inode
;
1637 if (!inode
->i_op
->lookup
)
1639 retval
= inode_permission(inode
, MAY_EXEC
);
1643 nd
->path
= nd
->root
;
1645 if (flags
& LOOKUP_RCU
) {
1646 br_read_lock(vfsmount_lock
);
1648 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1650 path_get(&nd
->path
);
1655 nd
->root
.mnt
= NULL
;
1658 if (flags
& LOOKUP_RCU
) {
1659 br_read_lock(vfsmount_lock
);
1664 path_get(&nd
->root
);
1666 nd
->path
= nd
->root
;
1667 } else if (dfd
== AT_FDCWD
) {
1668 if (flags
& LOOKUP_RCU
) {
1669 struct fs_struct
*fs
= current
->fs
;
1672 br_read_lock(vfsmount_lock
);
1676 seq
= read_seqcount_begin(&fs
->seq
);
1678 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1679 } while (read_seqcount_retry(&fs
->seq
, seq
));
1681 get_fs_pwd(current
->fs
, &nd
->path
);
1684 struct dentry
*dentry
;
1686 file
= fget_raw_light(dfd
, &fput_needed
);
1691 dentry
= file
->f_path
.dentry
;
1695 if (!S_ISDIR(dentry
->d_inode
->i_mode
))
1698 retval
= inode_permission(dentry
->d_inode
, MAY_EXEC
);
1703 nd
->path
= file
->f_path
;
1704 if (flags
& LOOKUP_RCU
) {
1707 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1708 br_read_lock(vfsmount_lock
);
1711 path_get(&file
->f_path
);
1712 fput_light(file
, fput_needed
);
1716 nd
->inode
= nd
->path
.dentry
->d_inode
;
1720 fput_light(file
, fput_needed
);
1725 static inline int lookup_last(struct nameidata
*nd
, struct path
*path
)
1727 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1728 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1730 nd
->flags
&= ~LOOKUP_PARENT
;
1731 return walk_component(nd
, path
, &nd
->last
, nd
->last_type
,
1732 nd
->flags
& LOOKUP_FOLLOW
);
1735 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1736 static int path_lookupat(int dfd
, const char *name
,
1737 unsigned int flags
, struct nameidata
*nd
)
1739 struct file
*base
= NULL
;
1744 * Path walking is largely split up into 2 different synchronisation
1745 * schemes, rcu-walk and ref-walk (explained in
1746 * Documentation/filesystems/path-lookup.txt). These share much of the
1747 * path walk code, but some things particularly setup, cleanup, and
1748 * following mounts are sufficiently divergent that functions are
1749 * duplicated. Typically there is a function foo(), and its RCU
1750 * analogue, foo_rcu().
1752 * -ECHILD is the error number of choice (just to avoid clashes) that
1753 * is returned if some aspect of an rcu-walk fails. Such an error must
1754 * be handled by restarting a traditional ref-walk (which will always
1755 * be able to complete).
1757 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, nd
, &base
);
1762 current
->total_link_count
= 0;
1763 err
= link_path_walk(name
, nd
);
1765 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
1766 err
= lookup_last(nd
, &path
);
1769 struct path link
= path
;
1770 nd
->flags
|= LOOKUP_PARENT
;
1771 err
= follow_link(&link
, nd
, &cookie
);
1773 err
= lookup_last(nd
, &path
);
1774 put_link(nd
, &link
, cookie
);
1779 err
= complete_walk(nd
);
1781 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
1782 if (!nd
->inode
->i_op
->lookup
) {
1783 path_put(&nd
->path
);
1791 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1792 path_put(&nd
->root
);
1793 nd
->root
.mnt
= NULL
;
1798 static int do_path_lookup(int dfd
, const char *name
,
1799 unsigned int flags
, struct nameidata
*nd
)
1801 int retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_RCU
, nd
);
1802 if (unlikely(retval
== -ECHILD
))
1803 retval
= path_lookupat(dfd
, name
, flags
, nd
);
1804 if (unlikely(retval
== -ESTALE
))
1805 retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_REVAL
, nd
);
1807 if (likely(!retval
)) {
1808 if (unlikely(!audit_dummy_context())) {
1809 if (nd
->path
.dentry
&& nd
->inode
)
1810 audit_inode(name
, nd
->path
.dentry
);
1816 int kern_path_parent(const char *name
, struct nameidata
*nd
)
1818 return do_path_lookup(AT_FDCWD
, name
, LOOKUP_PARENT
, nd
);
1821 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
1823 struct nameidata nd
;
1824 int res
= do_path_lookup(AT_FDCWD
, name
, flags
, &nd
);
1831 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1832 * @dentry: pointer to dentry of the base directory
1833 * @mnt: pointer to vfs mount of the base directory
1834 * @name: pointer to file name
1835 * @flags: lookup flags
1836 * @path: pointer to struct path to fill
1838 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
1839 const char *name
, unsigned int flags
,
1842 struct nameidata nd
;
1844 nd
.root
.dentry
= dentry
;
1846 BUG_ON(flags
& LOOKUP_PARENT
);
1847 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1848 err
= do_path_lookup(AT_FDCWD
, name
, flags
| LOOKUP_ROOT
, &nd
);
1855 * Restricted form of lookup. Doesn't follow links, single-component only,
1856 * needs parent already locked. Doesn't follow mounts.
1859 static struct dentry
*lookup_hash(struct nameidata
*nd
)
1861 return __lookup_hash(&nd
->last
, nd
->path
.dentry
, nd
);
1865 * lookup_one_len - filesystem helper to lookup single pathname component
1866 * @name: pathname component to lookup
1867 * @base: base directory to lookup from
1868 * @len: maximum length @len should be interpreted to
1870 * Note that this routine is purely a helper for filesystem usage and should
1871 * not be called by generic code. Also note that by using this function the
1872 * nameidata argument is passed to the filesystem methods and a filesystem
1873 * using this helper needs to be prepared for that.
1875 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
1881 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
1885 this.hash
= full_name_hash(name
, len
);
1887 return ERR_PTR(-EACCES
);
1890 c
= *(const unsigned char *)name
++;
1891 if (c
== '/' || c
== '\0')
1892 return ERR_PTR(-EACCES
);
1895 * See if the low-level filesystem might want
1896 * to use its own hash..
1898 if (base
->d_flags
& DCACHE_OP_HASH
) {
1899 int err
= base
->d_op
->d_hash(base
, base
->d_inode
, &this);
1901 return ERR_PTR(err
);
1904 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
1906 return ERR_PTR(err
);
1908 return __lookup_hash(&this, base
, NULL
);
1911 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
1912 struct path
*path
, int *empty
)
1914 struct nameidata nd
;
1915 char *tmp
= getname_flags(name
, flags
, empty
);
1916 int err
= PTR_ERR(tmp
);
1919 BUG_ON(flags
& LOOKUP_PARENT
);
1921 err
= do_path_lookup(dfd
, tmp
, flags
, &nd
);
1929 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
1932 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
1935 static int user_path_parent(int dfd
, const char __user
*path
,
1936 struct nameidata
*nd
, char **name
)
1938 char *s
= getname(path
);
1944 error
= do_path_lookup(dfd
, s
, LOOKUP_PARENT
, nd
);
1954 * It's inline, so penalty for filesystems that don't use sticky bit is
1957 static inline int check_sticky(struct inode
*dir
, struct inode
*inode
)
1959 uid_t fsuid
= current_fsuid();
1961 if (!(dir
->i_mode
& S_ISVTX
))
1963 if (inode
->i_uid
== fsuid
)
1965 if (dir
->i_uid
== fsuid
)
1967 return !inode_capable(inode
, CAP_FOWNER
);
1971 * Check whether we can remove a link victim from directory dir, check
1972 * whether the type of victim is right.
1973 * 1. We can't do it if dir is read-only (done in permission())
1974 * 2. We should have write and exec permissions on dir
1975 * 3. We can't remove anything from append-only dir
1976 * 4. We can't do anything with immutable dir (done in permission())
1977 * 5. If the sticky bit on dir is set we should either
1978 * a. be owner of dir, or
1979 * b. be owner of victim, or
1980 * c. have CAP_FOWNER capability
1981 * 6. If the victim is append-only or immutable we can't do antyhing with
1982 * links pointing to it.
1983 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1984 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1985 * 9. We can't remove a root or mountpoint.
1986 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1987 * nfs_async_unlink().
1989 static int may_delete(struct inode
*dir
,struct dentry
*victim
,int isdir
)
1993 if (!victim
->d_inode
)
1996 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
1997 audit_inode_child(victim
, dir
);
1999 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2004 if (check_sticky(dir
, victim
->d_inode
)||IS_APPEND(victim
->d_inode
)||
2005 IS_IMMUTABLE(victim
->d_inode
) || IS_SWAPFILE(victim
->d_inode
))
2008 if (!S_ISDIR(victim
->d_inode
->i_mode
))
2010 if (IS_ROOT(victim
))
2012 } else if (S_ISDIR(victim
->d_inode
->i_mode
))
2014 if (IS_DEADDIR(dir
))
2016 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2021 /* Check whether we can create an object with dentry child in directory
2023 * 1. We can't do it if child already exists (open has special treatment for
2024 * this case, but since we are inlined it's OK)
2025 * 2. We can't do it if dir is read-only (done in permission())
2026 * 3. We should have write and exec permissions on dir
2027 * 4. We can't do it if dir is immutable (done in permission())
2029 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2033 if (IS_DEADDIR(dir
))
2035 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2039 * p1 and p2 should be directories on the same fs.
2041 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2046 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2050 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2052 p
= d_ancestor(p2
, p1
);
2054 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2055 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2059 p
= d_ancestor(p1
, p2
);
2061 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2062 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2066 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2067 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2071 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2073 mutex_unlock(&p1
->d_inode
->i_mutex
);
2075 mutex_unlock(&p2
->d_inode
->i_mutex
);
2076 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2080 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2081 struct nameidata
*nd
)
2083 int error
= may_create(dir
, dentry
);
2088 if (!dir
->i_op
->create
)
2089 return -EACCES
; /* shouldn't it be ENOSYS? */
2092 error
= security_inode_create(dir
, dentry
, mode
);
2095 error
= dir
->i_op
->create(dir
, dentry
, mode
, nd
);
2097 fsnotify_create(dir
, dentry
);
2101 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2103 struct dentry
*dentry
= path
->dentry
;
2104 struct inode
*inode
= dentry
->d_inode
;
2114 switch (inode
->i_mode
& S_IFMT
) {
2118 if (acc_mode
& MAY_WRITE
)
2123 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2132 error
= inode_permission(inode
, acc_mode
);
2137 * An append-only file must be opened in append mode for writing.
2139 if (IS_APPEND(inode
)) {
2140 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2146 /* O_NOATIME can only be set by the owner or superuser */
2147 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2153 static int handle_truncate(struct file
*filp
)
2155 struct path
*path
= &filp
->f_path
;
2156 struct inode
*inode
= path
->dentry
->d_inode
;
2157 int error
= get_write_access(inode
);
2161 * Refuse to truncate files with mandatory locks held on them.
2163 error
= locks_verify_locked(inode
);
2165 error
= security_path_truncate(path
);
2167 error
= do_truncate(path
->dentry
, 0,
2168 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2171 put_write_access(inode
);
2175 static inline int open_to_namei_flags(int flag
)
2177 if ((flag
& O_ACCMODE
) == 3)
2183 * Handle the last step of open()
2185 static struct file
*do_last(struct nameidata
*nd
, struct path
*path
,
2186 const struct open_flags
*op
, const char *pathname
)
2188 struct dentry
*dir
= nd
->path
.dentry
;
2189 struct dentry
*dentry
;
2190 int open_flag
= op
->open_flag
;
2191 int will_truncate
= open_flag
& O_TRUNC
;
2193 int acc_mode
= op
->acc_mode
;
2197 nd
->flags
&= ~LOOKUP_PARENT
;
2198 nd
->flags
|= op
->intent
;
2200 switch (nd
->last_type
) {
2203 error
= handle_dots(nd
, nd
->last_type
);
2205 return ERR_PTR(error
);
2208 error
= complete_walk(nd
);
2210 return ERR_PTR(error
);
2211 audit_inode(pathname
, nd
->path
.dentry
);
2212 if (open_flag
& O_CREAT
) {
2218 error
= complete_walk(nd
);
2220 return ERR_PTR(error
);
2221 audit_inode(pathname
, dir
);
2225 if (!(open_flag
& O_CREAT
)) {
2227 if (nd
->last
.name
[nd
->last
.len
])
2228 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2229 if (open_flag
& O_PATH
&& !(nd
->flags
& LOOKUP_FOLLOW
))
2231 /* we _can_ be in RCU mode here */
2232 error
= walk_component(nd
, path
, &nd
->last
, LAST_NORM
,
2235 return ERR_PTR(error
);
2236 if (error
) /* symlink */
2239 error
= complete_walk(nd
);
2241 return ERR_PTR(error
);
2244 if (nd
->flags
& LOOKUP_DIRECTORY
) {
2245 if (!nd
->inode
->i_op
->lookup
)
2248 audit_inode(pathname
, nd
->path
.dentry
);
2252 /* create side of things */
2254 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been
2255 * cleared when we got to the last component we are about to look up
2257 error
= complete_walk(nd
);
2259 return ERR_PTR(error
);
2261 audit_inode(pathname
, dir
);
2263 /* trailing slashes? */
2264 if (nd
->last
.name
[nd
->last
.len
])
2267 mutex_lock(&dir
->d_inode
->i_mutex
);
2269 dentry
= lookup_hash(nd
);
2270 error
= PTR_ERR(dentry
);
2271 if (IS_ERR(dentry
)) {
2272 mutex_unlock(&dir
->d_inode
->i_mutex
);
2276 path
->dentry
= dentry
;
2277 path
->mnt
= nd
->path
.mnt
;
2279 /* Negative dentry, just create the file */
2280 if (!dentry
->d_inode
) {
2281 umode_t mode
= op
->mode
;
2282 if (!IS_POSIXACL(dir
->d_inode
))
2283 mode
&= ~current_umask();
2285 * This write is needed to ensure that a
2286 * rw->ro transition does not occur between
2287 * the time when the file is created and when
2288 * a permanent write count is taken through
2289 * the 'struct file' in nameidata_to_filp().
2291 error
= mnt_want_write(nd
->path
.mnt
);
2293 goto exit_mutex_unlock
;
2295 /* Don't check for write permission, don't truncate */
2296 open_flag
&= ~O_TRUNC
;
2298 acc_mode
= MAY_OPEN
;
2299 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2301 goto exit_mutex_unlock
;
2302 error
= vfs_create(dir
->d_inode
, dentry
, mode
, nd
);
2304 goto exit_mutex_unlock
;
2305 mutex_unlock(&dir
->d_inode
->i_mutex
);
2306 dput(nd
->path
.dentry
);
2307 nd
->path
.dentry
= dentry
;
2312 * It already exists.
2314 mutex_unlock(&dir
->d_inode
->i_mutex
);
2315 audit_inode(pathname
, path
->dentry
);
2318 if (open_flag
& O_EXCL
)
2321 error
= follow_managed(path
, nd
->flags
);
2326 nd
->flags
|= LOOKUP_JUMPED
;
2329 if (!path
->dentry
->d_inode
)
2332 if (path
->dentry
->d_inode
->i_op
->follow_link
)
2335 path_to_nameidata(path
, nd
);
2336 nd
->inode
= path
->dentry
->d_inode
;
2337 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
2338 error
= complete_walk(nd
);
2340 return ERR_PTR(error
);
2342 if (S_ISDIR(nd
->inode
->i_mode
))
2345 if (!S_ISREG(nd
->inode
->i_mode
))
2348 if (will_truncate
) {
2349 error
= mnt_want_write(nd
->path
.mnt
);
2355 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
2358 filp
= nameidata_to_filp(nd
);
2359 if (!IS_ERR(filp
)) {
2360 error
= ima_file_check(filp
, op
->acc_mode
);
2363 filp
= ERR_PTR(error
);
2366 if (!IS_ERR(filp
)) {
2367 if (will_truncate
) {
2368 error
= handle_truncate(filp
);
2371 filp
= ERR_PTR(error
);
2377 mnt_drop_write(nd
->path
.mnt
);
2378 path_put(&nd
->path
);
2382 mutex_unlock(&dir
->d_inode
->i_mutex
);
2384 path_put_conditional(path
, nd
);
2386 filp
= ERR_PTR(error
);
2390 static struct file
*path_openat(int dfd
, const char *pathname
,
2391 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
2393 struct file
*base
= NULL
;
2398 filp
= get_empty_filp();
2400 return ERR_PTR(-ENFILE
);
2402 filp
->f_flags
= op
->open_flag
;
2403 nd
->intent
.open
.file
= filp
;
2404 nd
->intent
.open
.flags
= open_to_namei_flags(op
->open_flag
);
2405 nd
->intent
.open
.create_mode
= op
->mode
;
2407 error
= path_init(dfd
, pathname
, flags
| LOOKUP_PARENT
, nd
, &base
);
2408 if (unlikely(error
))
2411 current
->total_link_count
= 0;
2412 error
= link_path_walk(pathname
, nd
);
2413 if (unlikely(error
))
2416 filp
= do_last(nd
, &path
, op
, pathname
);
2417 while (unlikely(!filp
)) { /* trailing symlink */
2418 struct path link
= path
;
2420 if (!(nd
->flags
& LOOKUP_FOLLOW
)) {
2421 path_put_conditional(&path
, nd
);
2422 path_put(&nd
->path
);
2423 filp
= ERR_PTR(-ELOOP
);
2426 nd
->flags
|= LOOKUP_PARENT
;
2427 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
2428 error
= follow_link(&link
, nd
, &cookie
);
2429 if (unlikely(error
))
2430 filp
= ERR_PTR(error
);
2432 filp
= do_last(nd
, &path
, op
, pathname
);
2433 put_link(nd
, &link
, cookie
);
2436 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
))
2437 path_put(&nd
->root
);
2440 release_open_intent(nd
);
2444 filp
= ERR_PTR(error
);
2448 struct file
*do_filp_open(int dfd
, const char *pathname
,
2449 const struct open_flags
*op
, int flags
)
2451 struct nameidata nd
;
2454 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
2455 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
2456 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
2457 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
2458 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
2462 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
2463 const char *name
, const struct open_flags
*op
, int flags
)
2465 struct nameidata nd
;
2469 nd
.root
.dentry
= dentry
;
2471 flags
|= LOOKUP_ROOT
;
2473 if (dentry
->d_inode
->i_op
->follow_link
&& op
->intent
& LOOKUP_OPEN
)
2474 return ERR_PTR(-ELOOP
);
2476 file
= path_openat(-1, name
, &nd
, op
, flags
| LOOKUP_RCU
);
2477 if (unlikely(file
== ERR_PTR(-ECHILD
)))
2478 file
= path_openat(-1, name
, &nd
, op
, flags
);
2479 if (unlikely(file
== ERR_PTR(-ESTALE
)))
2480 file
= path_openat(-1, name
, &nd
, op
, flags
| LOOKUP_REVAL
);
2484 struct dentry
*kern_path_create(int dfd
, const char *pathname
, struct path
*path
, int is_dir
)
2486 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
2487 struct nameidata nd
;
2488 int error
= do_path_lookup(dfd
, pathname
, LOOKUP_PARENT
, &nd
);
2490 return ERR_PTR(error
);
2493 * Yucky last component or no last component at all?
2494 * (foo/., foo/.., /////)
2496 if (nd
.last_type
!= LAST_NORM
)
2498 nd
.flags
&= ~LOOKUP_PARENT
;
2499 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
2500 nd
.intent
.open
.flags
= O_EXCL
;
2503 * Do the final lookup.
2505 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2506 dentry
= lookup_hash(&nd
);
2510 if (dentry
->d_inode
)
2513 * Special case - lookup gave negative, but... we had foo/bar/
2514 * From the vfs_mknod() POV we just have a negative dentry -
2515 * all is fine. Let's be bastards - you had / on the end, you've
2516 * been asking for (non-existent) directory. -ENOENT for you.
2518 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
2520 dentry
= ERR_PTR(-ENOENT
);
2527 dentry
= ERR_PTR(-EEXIST
);
2529 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2534 EXPORT_SYMBOL(kern_path_create
);
2536 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
, struct path
*path
, int is_dir
)
2538 char *tmp
= getname(pathname
);
2541 return ERR_CAST(tmp
);
2542 res
= kern_path_create(dfd
, tmp
, path
, is_dir
);
2546 EXPORT_SYMBOL(user_path_create
);
2548 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
2550 int error
= may_create(dir
, dentry
);
2555 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
2558 if (!dir
->i_op
->mknod
)
2561 error
= devcgroup_inode_mknod(mode
, dev
);
2565 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
2569 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
2571 fsnotify_create(dir
, dentry
);
2575 static int may_mknod(umode_t mode
)
2577 switch (mode
& S_IFMT
) {
2583 case 0: /* zero mode translates to S_IFREG */
2592 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
2595 struct dentry
*dentry
;
2602 dentry
= user_path_create(dfd
, filename
, &path
, 0);
2604 return PTR_ERR(dentry
);
2606 if (!IS_POSIXACL(path
.dentry
->d_inode
))
2607 mode
&= ~current_umask();
2608 error
= may_mknod(mode
);
2611 error
= mnt_want_write(path
.mnt
);
2614 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
2616 goto out_drop_write
;
2617 switch (mode
& S_IFMT
) {
2618 case 0: case S_IFREG
:
2619 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,NULL
);
2621 case S_IFCHR
: case S_IFBLK
:
2622 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
2623 new_decode_dev(dev
));
2625 case S_IFIFO
: case S_IFSOCK
:
2626 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
2630 mnt_drop_write(path
.mnt
);
2633 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
2639 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
2641 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
2644 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
2646 int error
= may_create(dir
, dentry
);
2647 unsigned max_links
= dir
->i_sb
->s_max_links
;
2652 if (!dir
->i_op
->mkdir
)
2655 mode
&= (S_IRWXUGO
|S_ISVTX
);
2656 error
= security_inode_mkdir(dir
, dentry
, mode
);
2660 if (max_links
&& dir
->i_nlink
>= max_links
)
2663 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
2665 fsnotify_mkdir(dir
, dentry
);
2669 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
2671 struct dentry
*dentry
;
2675 dentry
= user_path_create(dfd
, pathname
, &path
, 1);
2677 return PTR_ERR(dentry
);
2679 if (!IS_POSIXACL(path
.dentry
->d_inode
))
2680 mode
&= ~current_umask();
2681 error
= mnt_want_write(path
.mnt
);
2684 error
= security_path_mkdir(&path
, dentry
, mode
);
2686 goto out_drop_write
;
2687 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
2689 mnt_drop_write(path
.mnt
);
2692 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
2697 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
2699 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
2703 * The dentry_unhash() helper will try to drop the dentry early: we
2704 * should have a usage count of 1 if we're the only user of this
2705 * dentry, and if that is true (possibly after pruning the dcache),
2706 * then we drop the dentry now.
2708 * A low-level filesystem can, if it choses, legally
2711 * if (!d_unhashed(dentry))
2714 * if it cannot handle the case of removing a directory
2715 * that is still in use by something else..
2717 void dentry_unhash(struct dentry
*dentry
)
2719 shrink_dcache_parent(dentry
);
2720 spin_lock(&dentry
->d_lock
);
2721 if (dentry
->d_count
== 1)
2723 spin_unlock(&dentry
->d_lock
);
2726 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
2728 int error
= may_delete(dir
, dentry
, 1);
2733 if (!dir
->i_op
->rmdir
)
2737 mutex_lock(&dentry
->d_inode
->i_mutex
);
2740 if (d_mountpoint(dentry
))
2743 error
= security_inode_rmdir(dir
, dentry
);
2747 shrink_dcache_parent(dentry
);
2748 error
= dir
->i_op
->rmdir(dir
, dentry
);
2752 dentry
->d_inode
->i_flags
|= S_DEAD
;
2756 mutex_unlock(&dentry
->d_inode
->i_mutex
);
2763 static long do_rmdir(int dfd
, const char __user
*pathname
)
2767 struct dentry
*dentry
;
2768 struct nameidata nd
;
2770 error
= user_path_parent(dfd
, pathname
, &nd
, &name
);
2774 switch(nd
.last_type
) {
2786 nd
.flags
&= ~LOOKUP_PARENT
;
2788 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2789 dentry
= lookup_hash(&nd
);
2790 error
= PTR_ERR(dentry
);
2793 if (!dentry
->d_inode
) {
2797 error
= mnt_want_write(nd
.path
.mnt
);
2800 error
= security_path_rmdir(&nd
.path
, dentry
);
2803 error
= vfs_rmdir(nd
.path
.dentry
->d_inode
, dentry
);
2805 mnt_drop_write(nd
.path
.mnt
);
2809 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2816 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
2818 return do_rmdir(AT_FDCWD
, pathname
);
2821 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
)
2823 int error
= may_delete(dir
, dentry
, 0);
2828 if (!dir
->i_op
->unlink
)
2831 mutex_lock(&dentry
->d_inode
->i_mutex
);
2832 if (d_mountpoint(dentry
))
2835 error
= security_inode_unlink(dir
, dentry
);
2837 error
= dir
->i_op
->unlink(dir
, dentry
);
2842 mutex_unlock(&dentry
->d_inode
->i_mutex
);
2844 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2845 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
2846 fsnotify_link_count(dentry
->d_inode
);
2854 * Make sure that the actual truncation of the file will occur outside its
2855 * directory's i_mutex. Truncate can take a long time if there is a lot of
2856 * writeout happening, and we don't want to prevent access to the directory
2857 * while waiting on the I/O.
2859 static long do_unlinkat(int dfd
, const char __user
*pathname
)
2863 struct dentry
*dentry
;
2864 struct nameidata nd
;
2865 struct inode
*inode
= NULL
;
2867 error
= user_path_parent(dfd
, pathname
, &nd
, &name
);
2872 if (nd
.last_type
!= LAST_NORM
)
2875 nd
.flags
&= ~LOOKUP_PARENT
;
2877 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2878 dentry
= lookup_hash(&nd
);
2879 error
= PTR_ERR(dentry
);
2880 if (!IS_ERR(dentry
)) {
2881 /* Why not before? Because we want correct error value */
2882 if (nd
.last
.name
[nd
.last
.len
])
2884 inode
= dentry
->d_inode
;
2888 error
= mnt_want_write(nd
.path
.mnt
);
2891 error
= security_path_unlink(&nd
.path
, dentry
);
2894 error
= vfs_unlink(nd
.path
.dentry
->d_inode
, dentry
);
2896 mnt_drop_write(nd
.path
.mnt
);
2900 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2902 iput(inode
); /* truncate the inode here */
2909 error
= !dentry
->d_inode
? -ENOENT
:
2910 S_ISDIR(dentry
->d_inode
->i_mode
) ? -EISDIR
: -ENOTDIR
;
2914 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
2916 if ((flag
& ~AT_REMOVEDIR
) != 0)
2919 if (flag
& AT_REMOVEDIR
)
2920 return do_rmdir(dfd
, pathname
);
2922 return do_unlinkat(dfd
, pathname
);
2925 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
2927 return do_unlinkat(AT_FDCWD
, pathname
);
2930 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
2932 int error
= may_create(dir
, dentry
);
2937 if (!dir
->i_op
->symlink
)
2940 error
= security_inode_symlink(dir
, dentry
, oldname
);
2944 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
2946 fsnotify_create(dir
, dentry
);
2950 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
2951 int, newdfd
, const char __user
*, newname
)
2955 struct dentry
*dentry
;
2958 from
= getname(oldname
);
2960 return PTR_ERR(from
);
2962 dentry
= user_path_create(newdfd
, newname
, &path
, 0);
2963 error
= PTR_ERR(dentry
);
2967 error
= mnt_want_write(path
.mnt
);
2970 error
= security_path_symlink(&path
, dentry
, from
);
2972 goto out_drop_write
;
2973 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
);
2975 mnt_drop_write(path
.mnt
);
2978 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
2985 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
2987 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
2990 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
)
2992 struct inode
*inode
= old_dentry
->d_inode
;
2993 unsigned max_links
= dir
->i_sb
->s_max_links
;
2999 error
= may_create(dir
, new_dentry
);
3003 if (dir
->i_sb
!= inode
->i_sb
)
3007 * A link to an append-only or immutable file cannot be created.
3009 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3011 if (!dir
->i_op
->link
)
3013 if (S_ISDIR(inode
->i_mode
))
3016 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3020 mutex_lock(&inode
->i_mutex
);
3021 /* Make sure we don't allow creating hardlink to an unlinked file */
3022 if (inode
->i_nlink
== 0)
3024 else if (max_links
&& inode
->i_nlink
>= max_links
)
3027 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3028 mutex_unlock(&inode
->i_mutex
);
3030 fsnotify_link(dir
, inode
, new_dentry
);
3035 * Hardlinks are often used in delicate situations. We avoid
3036 * security-related surprises by not following symlinks on the
3039 * We don't follow them on the oldname either to be compatible
3040 * with linux 2.0, and to avoid hard-linking to directories
3041 * and other special files. --ADM
3043 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
3044 int, newdfd
, const char __user
*, newname
, int, flags
)
3046 struct dentry
*new_dentry
;
3047 struct path old_path
, new_path
;
3051 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
3054 * To use null names we require CAP_DAC_READ_SEARCH
3055 * This ensures that not everyone will be able to create
3056 * handlink using the passed filedescriptor.
3058 if (flags
& AT_EMPTY_PATH
) {
3059 if (!capable(CAP_DAC_READ_SEARCH
))
3064 if (flags
& AT_SYMLINK_FOLLOW
)
3065 how
|= LOOKUP_FOLLOW
;
3067 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
3071 new_dentry
= user_path_create(newdfd
, newname
, &new_path
, 0);
3072 error
= PTR_ERR(new_dentry
);
3073 if (IS_ERR(new_dentry
))
3077 if (old_path
.mnt
!= new_path
.mnt
)
3079 error
= mnt_want_write(new_path
.mnt
);
3082 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
3084 goto out_drop_write
;
3085 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
);
3087 mnt_drop_write(new_path
.mnt
);
3090 mutex_unlock(&new_path
.dentry
->d_inode
->i_mutex
);
3091 path_put(&new_path
);
3093 path_put(&old_path
);
3098 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
3100 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
3104 * The worst of all namespace operations - renaming directory. "Perverted"
3105 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3107 * a) we can get into loop creation. Check is done in is_subdir().
3108 * b) race potential - two innocent renames can create a loop together.
3109 * That's where 4.4 screws up. Current fix: serialization on
3110 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3112 * c) we have to lock _three_ objects - parents and victim (if it exists).
3113 * And that - after we got ->i_mutex on parents (until then we don't know
3114 * whether the target exists). Solution: try to be smart with locking
3115 * order for inodes. We rely on the fact that tree topology may change
3116 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3117 * move will be locked. Thus we can rank directories by the tree
3118 * (ancestors first) and rank all non-directories after them.
3119 * That works since everybody except rename does "lock parent, lookup,
3120 * lock child" and rename is under ->s_vfs_rename_mutex.
3121 * HOWEVER, it relies on the assumption that any object with ->lookup()
3122 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3123 * we'd better make sure that there's no link(2) for them.
3124 * d) conversion from fhandle to dentry may come in the wrong moment - when
3125 * we are removing the target. Solution: we will have to grab ->i_mutex
3126 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3127 * ->i_mutex on parents, which works but leads to some truly excessive
3130 static int vfs_rename_dir(struct inode
*old_dir
, struct dentry
*old_dentry
,
3131 struct inode
*new_dir
, struct dentry
*new_dentry
)
3134 struct inode
*target
= new_dentry
->d_inode
;
3135 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
3138 * If we are going to change the parent - check write permissions,
3139 * we'll need to flip '..'.
3141 if (new_dir
!= old_dir
) {
3142 error
= inode_permission(old_dentry
->d_inode
, MAY_WRITE
);
3147 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3153 mutex_lock(&target
->i_mutex
);
3156 if (d_mountpoint(old_dentry
) || d_mountpoint(new_dentry
))
3160 if (max_links
&& !target
&& new_dir
!= old_dir
&&
3161 new_dir
->i_nlink
>= max_links
)
3165 shrink_dcache_parent(new_dentry
);
3166 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3171 target
->i_flags
|= S_DEAD
;
3172 dont_mount(new_dentry
);
3176 mutex_unlock(&target
->i_mutex
);
3179 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3180 d_move(old_dentry
,new_dentry
);
3184 static int vfs_rename_other(struct inode
*old_dir
, struct dentry
*old_dentry
,
3185 struct inode
*new_dir
, struct dentry
*new_dentry
)
3187 struct inode
*target
= new_dentry
->d_inode
;
3190 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3196 mutex_lock(&target
->i_mutex
);
3199 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
3202 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3207 dont_mount(new_dentry
);
3208 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3209 d_move(old_dentry
, new_dentry
);
3212 mutex_unlock(&target
->i_mutex
);
3217 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
3218 struct inode
*new_dir
, struct dentry
*new_dentry
)
3221 int is_dir
= S_ISDIR(old_dentry
->d_inode
->i_mode
);
3222 const unsigned char *old_name
;
3224 if (old_dentry
->d_inode
== new_dentry
->d_inode
)
3227 error
= may_delete(old_dir
, old_dentry
, is_dir
);
3231 if (!new_dentry
->d_inode
)
3232 error
= may_create(new_dir
, new_dentry
);
3234 error
= may_delete(new_dir
, new_dentry
, is_dir
);
3238 if (!old_dir
->i_op
->rename
)
3241 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
3244 error
= vfs_rename_dir(old_dir
,old_dentry
,new_dir
,new_dentry
);
3246 error
= vfs_rename_other(old_dir
,old_dentry
,new_dir
,new_dentry
);
3248 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
3249 new_dentry
->d_inode
, old_dentry
);
3250 fsnotify_oldname_free(old_name
);
3255 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
3256 int, newdfd
, const char __user
*, newname
)
3258 struct dentry
*old_dir
, *new_dir
;
3259 struct dentry
*old_dentry
, *new_dentry
;
3260 struct dentry
*trap
;
3261 struct nameidata oldnd
, newnd
;
3266 error
= user_path_parent(olddfd
, oldname
, &oldnd
, &from
);
3270 error
= user_path_parent(newdfd
, newname
, &newnd
, &to
);
3275 if (oldnd
.path
.mnt
!= newnd
.path
.mnt
)
3278 old_dir
= oldnd
.path
.dentry
;
3280 if (oldnd
.last_type
!= LAST_NORM
)
3283 new_dir
= newnd
.path
.dentry
;
3284 if (newnd
.last_type
!= LAST_NORM
)
3287 oldnd
.flags
&= ~LOOKUP_PARENT
;
3288 newnd
.flags
&= ~LOOKUP_PARENT
;
3289 newnd
.flags
|= LOOKUP_RENAME_TARGET
;
3291 trap
= lock_rename(new_dir
, old_dir
);
3293 old_dentry
= lookup_hash(&oldnd
);
3294 error
= PTR_ERR(old_dentry
);
3295 if (IS_ERR(old_dentry
))
3297 /* source must exist */
3299 if (!old_dentry
->d_inode
)
3301 /* unless the source is a directory trailing slashes give -ENOTDIR */
3302 if (!S_ISDIR(old_dentry
->d_inode
->i_mode
)) {
3304 if (oldnd
.last
.name
[oldnd
.last
.len
])
3306 if (newnd
.last
.name
[newnd
.last
.len
])
3309 /* source should not be ancestor of target */
3311 if (old_dentry
== trap
)
3313 new_dentry
= lookup_hash(&newnd
);
3314 error
= PTR_ERR(new_dentry
);
3315 if (IS_ERR(new_dentry
))
3317 /* target should not be an ancestor of source */
3319 if (new_dentry
== trap
)
3322 error
= mnt_want_write(oldnd
.path
.mnt
);
3325 error
= security_path_rename(&oldnd
.path
, old_dentry
,
3326 &newnd
.path
, new_dentry
);
3329 error
= vfs_rename(old_dir
->d_inode
, old_dentry
,
3330 new_dir
->d_inode
, new_dentry
);
3332 mnt_drop_write(oldnd
.path
.mnt
);
3338 unlock_rename(new_dir
, old_dir
);
3340 path_put(&newnd
.path
);
3343 path_put(&oldnd
.path
);
3349 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
3351 return sys_renameat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
);
3354 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
, const char *link
)
3358 len
= PTR_ERR(link
);
3363 if (len
> (unsigned) buflen
)
3365 if (copy_to_user(buffer
, link
, len
))
3372 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3373 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3374 * using) it for any given inode is up to filesystem.
3376 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3378 struct nameidata nd
;
3383 cookie
= dentry
->d_inode
->i_op
->follow_link(dentry
, &nd
);
3385 return PTR_ERR(cookie
);
3387 res
= vfs_readlink(dentry
, buffer
, buflen
, nd_get_link(&nd
));
3388 if (dentry
->d_inode
->i_op
->put_link
)
3389 dentry
->d_inode
->i_op
->put_link(dentry
, &nd
, cookie
);
3393 int vfs_follow_link(struct nameidata
*nd
, const char *link
)
3395 return __vfs_follow_link(nd
, link
);
3398 /* get the link contents into pagecache */
3399 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
3403 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
3404 page
= read_mapping_page(mapping
, 0, NULL
);
3409 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
3413 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3415 struct page
*page
= NULL
;
3416 char *s
= page_getlink(dentry
, &page
);
3417 int res
= vfs_readlink(dentry
,buffer
,buflen
,s
);
3420 page_cache_release(page
);
3425 void *page_follow_link_light(struct dentry
*dentry
, struct nameidata
*nd
)
3427 struct page
*page
= NULL
;
3428 nd_set_link(nd
, page_getlink(dentry
, &page
));
3432 void page_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
3434 struct page
*page
= cookie
;
3438 page_cache_release(page
);
3443 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3445 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
3447 struct address_space
*mapping
= inode
->i_mapping
;
3452 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
3454 flags
|= AOP_FLAG_NOFS
;
3457 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
3458 flags
, &page
, &fsdata
);
3462 kaddr
= kmap_atomic(page
);
3463 memcpy(kaddr
, symname
, len
-1);
3464 kunmap_atomic(kaddr
);
3466 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
3473 mark_inode_dirty(inode
);
3479 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
3481 return __page_symlink(inode
, symname
, len
,
3482 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
3485 const struct inode_operations page_symlink_inode_operations
= {
3486 .readlink
= generic_readlink
,
3487 .follow_link
= page_follow_link_light
,
3488 .put_link
= page_put_link
,
3491 EXPORT_SYMBOL(user_path_at
);
3492 EXPORT_SYMBOL(follow_down_one
);
3493 EXPORT_SYMBOL(follow_down
);
3494 EXPORT_SYMBOL(follow_up
);
3495 EXPORT_SYMBOL(get_write_access
); /* binfmt_aout */
3496 EXPORT_SYMBOL(getname
);
3497 EXPORT_SYMBOL(lock_rename
);
3498 EXPORT_SYMBOL(lookup_one_len
);
3499 EXPORT_SYMBOL(page_follow_link_light
);
3500 EXPORT_SYMBOL(page_put_link
);
3501 EXPORT_SYMBOL(page_readlink
);
3502 EXPORT_SYMBOL(__page_symlink
);
3503 EXPORT_SYMBOL(page_symlink
);
3504 EXPORT_SYMBOL(page_symlink_inode_operations
);
3505 EXPORT_SYMBOL(kern_path
);
3506 EXPORT_SYMBOL(vfs_path_lookup
);
3507 EXPORT_SYMBOL(inode_permission
);
3508 EXPORT_SYMBOL(unlock_rename
);
3509 EXPORT_SYMBOL(vfs_create
);
3510 EXPORT_SYMBOL(vfs_follow_link
);
3511 EXPORT_SYMBOL(vfs_link
);
3512 EXPORT_SYMBOL(vfs_mkdir
);
3513 EXPORT_SYMBOL(vfs_mknod
);
3514 EXPORT_SYMBOL(generic_permission
);
3515 EXPORT_SYMBOL(vfs_readlink
);
3516 EXPORT_SYMBOL(vfs_rename
);
3517 EXPORT_SYMBOL(vfs_rmdir
);
3518 EXPORT_SYMBOL(vfs_symlink
);
3519 EXPORT_SYMBOL(vfs_unlink
);
3520 EXPORT_SYMBOL(dentry_unhash
);
3521 EXPORT_SYMBOL(generic_readlink
);