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/kernel.h>
20 #include <linux/slab.h>
22 #include <linux/namei.h>
23 #include <linux/pagemap.h>
24 #include <linux/fsnotify.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/ima.h>
28 #include <linux/syscalls.h>
29 #include <linux/mount.h>
30 #include <linux/audit.h>
31 #include <linux/capability.h>
32 #include <linux/file.h>
33 #include <linux/fcntl.h>
34 #include <linux/device_cgroup.h>
35 #include <linux/fs_struct.h>
36 #include <linux/posix_acl.h>
37 #include <linux/hash.h>
38 #include <asm/uaccess.h>
43 /* [Feb-1997 T. Schoebel-Theuer]
44 * Fundamental changes in the pathname lookup mechanisms (namei)
45 * were necessary because of omirr. The reason is that omirr needs
46 * to know the _real_ pathname, not the user-supplied one, in case
47 * of symlinks (and also when transname replacements occur).
49 * The new code replaces the old recursive symlink resolution with
50 * an iterative one (in case of non-nested symlink chains). It does
51 * this with calls to <fs>_follow_link().
52 * As a side effect, dir_namei(), _namei() and follow_link() are now
53 * replaced with a single function lookup_dentry() that can handle all
54 * the special cases of the former code.
56 * With the new dcache, the pathname is stored at each inode, at least as
57 * long as the refcount of the inode is positive. As a side effect, the
58 * size of the dcache depends on the inode cache and thus is dynamic.
60 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
61 * resolution to correspond with current state of the code.
63 * Note that the symlink resolution is not *completely* iterative.
64 * There is still a significant amount of tail- and mid- recursion in
65 * the algorithm. Also, note that <fs>_readlink() is not used in
66 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
67 * may return different results than <fs>_follow_link(). Many virtual
68 * filesystems (including /proc) exhibit this behavior.
71 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
72 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
73 * and the name already exists in form of a symlink, try to create the new
74 * name indicated by the symlink. The old code always complained that the
75 * name already exists, due to not following the symlink even if its target
76 * is nonexistent. The new semantics affects also mknod() and link() when
77 * the name is a symlink pointing to a non-existent name.
79 * I don't know which semantics is the right one, since I have no access
80 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
81 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
82 * "old" one. Personally, I think the new semantics is much more logical.
83 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
84 * file does succeed in both HP-UX and SunOs, but not in Solaris
85 * and in the old Linux semantics.
88 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
89 * semantics. See the comments in "open_namei" and "do_link" below.
91 * [10-Sep-98 Alan Modra] Another symlink change.
94 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
95 * inside the path - always follow.
96 * in the last component in creation/removal/renaming - never follow.
97 * if LOOKUP_FOLLOW passed - follow.
98 * if the pathname has trailing slashes - follow.
99 * otherwise - don't follow.
100 * (applied in that order).
102 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
103 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
104 * During the 2.4 we need to fix the userland stuff depending on it -
105 * hopefully we will be able to get rid of that wart in 2.5. So far only
106 * XEmacs seems to be relying on it...
109 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
110 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
111 * any extra contention...
114 /* In order to reduce some races, while at the same time doing additional
115 * checking and hopefully speeding things up, we copy filenames to the
116 * kernel data space before using them..
118 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
119 * PATH_MAX includes the nul terminator --RR.
122 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
125 getname_flags(const char __user
*filename
, int flags
, int *empty
)
127 struct filename
*result
;
131 result
= audit_reusename(filename
);
135 result
= __getname();
136 if (unlikely(!result
))
137 return ERR_PTR(-ENOMEM
);
140 * First, try to embed the struct filename inside the names_cache
143 kname
= (char *)result
->iname
;
144 result
->name
= kname
;
146 len
= strncpy_from_user(kname
, filename
, EMBEDDED_NAME_MAX
);
147 if (unlikely(len
< 0)) {
153 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
154 * separate struct filename so we can dedicate the entire
155 * names_cache allocation for the pathname, and re-do the copy from
158 if (unlikely(len
== EMBEDDED_NAME_MAX
)) {
159 const size_t size
= offsetof(struct filename
, iname
[1]);
160 kname
= (char *)result
;
163 * size is chosen that way we to guarantee that
164 * result->iname[0] is within the same object and that
165 * kname can't be equal to result->iname, no matter what.
167 result
= kzalloc(size
, GFP_KERNEL
);
168 if (unlikely(!result
)) {
170 return ERR_PTR(-ENOMEM
);
172 result
->name
= kname
;
173 len
= strncpy_from_user(kname
, filename
, PATH_MAX
);
174 if (unlikely(len
< 0)) {
179 if (unlikely(len
== PATH_MAX
)) {
182 return ERR_PTR(-ENAMETOOLONG
);
187 /* The empty path is special. */
188 if (unlikely(!len
)) {
191 if (!(flags
& LOOKUP_EMPTY
)) {
193 return ERR_PTR(-ENOENT
);
197 result
->uptr
= filename
;
198 result
->aname
= NULL
;
199 audit_getname(result
);
204 getname(const char __user
* filename
)
206 return getname_flags(filename
, 0, NULL
);
210 getname_kernel(const char * filename
)
212 struct filename
*result
;
213 int len
= strlen(filename
) + 1;
215 result
= __getname();
216 if (unlikely(!result
))
217 return ERR_PTR(-ENOMEM
);
219 if (len
<= EMBEDDED_NAME_MAX
) {
220 result
->name
= (char *)result
->iname
;
221 } else if (len
<= PATH_MAX
) {
222 struct filename
*tmp
;
224 tmp
= kmalloc(sizeof(*tmp
), GFP_KERNEL
);
225 if (unlikely(!tmp
)) {
227 return ERR_PTR(-ENOMEM
);
229 tmp
->name
= (char *)result
;
233 return ERR_PTR(-ENAMETOOLONG
);
235 memcpy((char *)result
->name
, filename
, len
);
237 result
->aname
= NULL
;
239 audit_getname(result
);
244 void putname(struct filename
*name
)
246 BUG_ON(name
->refcnt
<= 0);
248 if (--name
->refcnt
> 0)
251 if (name
->name
!= name
->iname
) {
252 __putname(name
->name
);
258 static int check_acl(struct inode
*inode
, int mask
)
260 #ifdef CONFIG_FS_POSIX_ACL
261 struct posix_acl
*acl
;
263 if (mask
& MAY_NOT_BLOCK
) {
264 acl
= get_cached_acl_rcu(inode
, ACL_TYPE_ACCESS
);
267 /* no ->get_acl() calls in RCU mode... */
268 if (acl
== ACL_NOT_CACHED
)
270 return posix_acl_permission(inode
, acl
, mask
& ~MAY_NOT_BLOCK
);
273 acl
= get_acl(inode
, ACL_TYPE_ACCESS
);
277 int error
= posix_acl_permission(inode
, acl
, mask
);
278 posix_acl_release(acl
);
287 * This does the basic permission checking
289 static int acl_permission_check(struct inode
*inode
, int mask
)
291 unsigned int mode
= inode
->i_mode
;
293 if (likely(uid_eq(current_fsuid(), inode
->i_uid
)))
296 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
)) {
297 int error
= check_acl(inode
, mask
);
298 if (error
!= -EAGAIN
)
302 if (in_group_p(inode
->i_gid
))
307 * If the DACs are ok we don't need any capability check.
309 if ((mask
& ~mode
& (MAY_READ
| MAY_WRITE
| MAY_EXEC
)) == 0)
315 * generic_permission - check for access rights on a Posix-like filesystem
316 * @inode: inode to check access rights for
317 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
319 * Used to check for read/write/execute permissions on a file.
320 * We use "fsuid" for this, letting us set arbitrary permissions
321 * for filesystem access without changing the "normal" uids which
322 * are used for other things.
324 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
325 * request cannot be satisfied (eg. requires blocking or too much complexity).
326 * It would then be called again in ref-walk mode.
328 int generic_permission(struct inode
*inode
, int mask
)
333 * Do the basic permission checks.
335 ret
= acl_permission_check(inode
, mask
);
339 if (S_ISDIR(inode
->i_mode
)) {
340 /* DACs are overridable for directories */
341 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
343 if (!(mask
& MAY_WRITE
))
344 if (capable_wrt_inode_uidgid(inode
,
345 CAP_DAC_READ_SEARCH
))
350 * Read/write DACs are always overridable.
351 * Executable DACs are overridable when there is
352 * at least one exec bit set.
354 if (!(mask
& MAY_EXEC
) || (inode
->i_mode
& S_IXUGO
))
355 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
359 * Searching includes executable on directories, else just read.
361 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
362 if (mask
== MAY_READ
)
363 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_READ_SEARCH
))
368 EXPORT_SYMBOL(generic_permission
);
371 * We _really_ want to just do "generic_permission()" without
372 * even looking at the inode->i_op values. So we keep a cache
373 * flag in inode->i_opflags, that says "this has not special
374 * permission function, use the fast case".
376 static inline int do_inode_permission(struct inode
*inode
, int mask
)
378 if (unlikely(!(inode
->i_opflags
& IOP_FASTPERM
))) {
379 if (likely(inode
->i_op
->permission
))
380 return inode
->i_op
->permission(inode
, mask
);
382 /* This gets set once for the inode lifetime */
383 spin_lock(&inode
->i_lock
);
384 inode
->i_opflags
|= IOP_FASTPERM
;
385 spin_unlock(&inode
->i_lock
);
387 return generic_permission(inode
, mask
);
391 * __inode_permission - Check for access rights to a given inode
392 * @inode: Inode to check permission on
393 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
395 * Check for read/write/execute permissions on an inode.
397 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
399 * This does not check for a read-only file system. You probably want
400 * inode_permission().
402 int __inode_permission(struct inode
*inode
, int mask
)
406 if (unlikely(mask
& MAY_WRITE
)) {
408 * Nobody gets write access to an immutable file.
410 if (IS_IMMUTABLE(inode
))
414 retval
= do_inode_permission(inode
, mask
);
418 retval
= devcgroup_inode_permission(inode
, mask
);
422 return security_inode_permission(inode
, mask
);
424 EXPORT_SYMBOL(__inode_permission
);
427 * sb_permission - Check superblock-level permissions
428 * @sb: Superblock of inode to check permission on
429 * @inode: Inode to check permission on
430 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
432 * Separate out file-system wide checks from inode-specific permission checks.
434 static int sb_permission(struct super_block
*sb
, struct inode
*inode
, int mask
)
436 if (unlikely(mask
& MAY_WRITE
)) {
437 umode_t mode
= inode
->i_mode
;
439 /* Nobody gets write access to a read-only fs. */
440 if ((sb
->s_flags
& MS_RDONLY
) &&
441 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
448 * inode_permission - Check for access rights to a given inode
449 * @inode: Inode to check permission on
450 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
452 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
453 * this, letting us set arbitrary permissions for filesystem access without
454 * changing the "normal" UIDs which are used for other things.
456 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
458 int inode_permission(struct inode
*inode
, int mask
)
462 retval
= sb_permission(inode
->i_sb
, inode
, mask
);
465 return __inode_permission(inode
, mask
);
467 EXPORT_SYMBOL(inode_permission
);
470 * path_get - get a reference to a path
471 * @path: path to get the reference to
473 * Given a path increment the reference count to the dentry and the vfsmount.
475 void path_get(const struct path
*path
)
480 EXPORT_SYMBOL(path_get
);
483 * path_put - put a reference to a path
484 * @path: path to put the reference to
486 * Given a path decrement the reference count to the dentry and the vfsmount.
488 void path_put(const struct path
*path
)
493 EXPORT_SYMBOL(path_put
);
502 struct inode
*inode
; /* path.dentry.d_inode */
511 * Path walking has 2 modes, rcu-walk and ref-walk (see
512 * Documentation/filesystems/path-lookup.txt). In situations when we can't
513 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
514 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
515 * mode. Refcounts are grabbed at the last known good point before rcu-walk
516 * got stuck, so ref-walk may continue from there. If this is not successful
517 * (eg. a seqcount has changed), then failure is returned and it's up to caller
518 * to restart the path walk from the beginning in ref-walk mode.
522 * unlazy_walk - try to switch to ref-walk mode.
523 * @nd: nameidata pathwalk data
524 * @dentry: child of nd->path.dentry or NULL
525 * Returns: 0 on success, -ECHILD on failure
527 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
528 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
529 * @nd or NULL. Must be called from rcu-walk context.
531 static int unlazy_walk(struct nameidata
*nd
, struct dentry
*dentry
)
533 struct fs_struct
*fs
= current
->fs
;
534 struct dentry
*parent
= nd
->path
.dentry
;
536 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
539 * After legitimizing the bastards, terminate_walk()
540 * will do the right thing for non-RCU mode, and all our
541 * subsequent exit cases should rcu_read_unlock()
542 * before returning. Do vfsmount first; if dentry
543 * can't be legitimized, just set nd->path.dentry to NULL
544 * and rely on dput(NULL) being a no-op.
546 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
))
548 nd
->flags
&= ~LOOKUP_RCU
;
550 if (!lockref_get_not_dead(&parent
->d_lockref
)) {
551 nd
->path
.dentry
= NULL
;
556 * For a negative lookup, the lookup sequence point is the parents
557 * sequence point, and it only needs to revalidate the parent dentry.
559 * For a positive lookup, we need to move both the parent and the
560 * dentry from the RCU domain to be properly refcounted. And the
561 * sequence number in the dentry validates *both* dentry counters,
562 * since we checked the sequence number of the parent after we got
563 * the child sequence number. So we know the parent must still
564 * be valid if the child sequence number is still valid.
567 if (read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
569 BUG_ON(nd
->inode
!= parent
->d_inode
);
571 if (!lockref_get_not_dead(&dentry
->d_lockref
))
573 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
))
578 * Sequence counts matched. Now make sure that the root is
579 * still valid and get it if required.
581 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
582 spin_lock(&fs
->lock
);
583 if (nd
->root
.mnt
!= fs
->root
.mnt
|| nd
->root
.dentry
!= fs
->root
.dentry
)
584 goto unlock_and_drop_dentry
;
586 spin_unlock(&fs
->lock
);
592 unlock_and_drop_dentry
:
593 spin_unlock(&fs
->lock
);
601 if (!(nd
->flags
& LOOKUP_ROOT
))
606 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
608 return dentry
->d_op
->d_revalidate(dentry
, flags
);
612 * complete_walk - successful completion of path walk
613 * @nd: pointer nameidata
615 * If we had been in RCU mode, drop out of it and legitimize nd->path.
616 * Revalidate the final result, unless we'd already done that during
617 * the path walk or the filesystem doesn't ask for it. Return 0 on
618 * success, -error on failure. In case of failure caller does not
619 * need to drop nd->path.
621 static int complete_walk(struct nameidata
*nd
)
623 struct dentry
*dentry
= nd
->path
.dentry
;
626 if (nd
->flags
& LOOKUP_RCU
) {
627 nd
->flags
&= ~LOOKUP_RCU
;
628 if (!(nd
->flags
& LOOKUP_ROOT
))
631 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
)) {
635 if (unlikely(!lockref_get_not_dead(&dentry
->d_lockref
))) {
637 mntput(nd
->path
.mnt
);
640 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
)) {
643 mntput(nd
->path
.mnt
);
649 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
652 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
655 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
666 static __always_inline
void set_root(struct nameidata
*nd
)
668 get_fs_root(current
->fs
, &nd
->root
);
671 static __always_inline
unsigned set_root_rcu(struct nameidata
*nd
)
673 struct fs_struct
*fs
= current
->fs
;
677 seq
= read_seqcount_begin(&fs
->seq
);
679 res
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
680 } while (read_seqcount_retry(&fs
->seq
, seq
));
684 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
687 if (path
->mnt
!= nd
->path
.mnt
)
691 static inline void path_to_nameidata(const struct path
*path
,
692 struct nameidata
*nd
)
694 if (!(nd
->flags
& LOOKUP_RCU
)) {
695 dput(nd
->path
.dentry
);
696 if (nd
->path
.mnt
!= path
->mnt
)
697 mntput(nd
->path
.mnt
);
699 nd
->path
.mnt
= path
->mnt
;
700 nd
->path
.dentry
= path
->dentry
;
704 * Helper to directly jump to a known parsed path from ->follow_link,
705 * caller must have taken a reference to path beforehand.
707 void nd_jump_link(struct nameidata
*nd
, struct path
*path
)
712 nd
->inode
= nd
->path
.dentry
->d_inode
;
713 nd
->flags
|= LOOKUP_JUMPED
;
716 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
718 struct inode
*inode
= link
->dentry
->d_inode
;
719 if (cookie
&& inode
->i_op
->put_link
)
720 inode
->i_op
->put_link(link
->dentry
, cookie
);
724 int sysctl_protected_symlinks __read_mostly
= 0;
725 int sysctl_protected_hardlinks __read_mostly
= 0;
728 * may_follow_link - Check symlink following for unsafe situations
729 * @link: The path of the symlink
730 * @nd: nameidata pathwalk data
732 * In the case of the sysctl_protected_symlinks sysctl being enabled,
733 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
734 * in a sticky world-writable directory. This is to protect privileged
735 * processes from failing races against path names that may change out
736 * from under them by way of other users creating malicious symlinks.
737 * It will permit symlinks to be followed only when outside a sticky
738 * world-writable directory, or when the uid of the symlink and follower
739 * match, or when the directory owner matches the symlink's owner.
741 * Returns 0 if following the symlink is allowed, -ve on error.
743 static inline int may_follow_link(struct path
*link
, struct nameidata
*nd
)
745 const struct inode
*inode
;
746 const struct inode
*parent
;
748 if (!sysctl_protected_symlinks
)
751 /* Allowed if owner and follower match. */
752 inode
= link
->dentry
->d_inode
;
753 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
756 /* Allowed if parent directory not sticky and world-writable. */
757 parent
= nd
->path
.dentry
->d_inode
;
758 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
761 /* Allowed if parent directory and link owner match. */
762 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
765 audit_log_link_denied("follow_link", link
);
766 path_put_conditional(link
, nd
);
772 * safe_hardlink_source - Check for safe hardlink conditions
773 * @inode: the source inode to hardlink from
775 * Return false if at least one of the following conditions:
776 * - inode is not a regular file
778 * - inode is setgid and group-exec
779 * - access failure for read and write
781 * Otherwise returns true.
783 static bool safe_hardlink_source(struct inode
*inode
)
785 umode_t mode
= inode
->i_mode
;
787 /* Special files should not get pinned to the filesystem. */
791 /* Setuid files should not get pinned to the filesystem. */
795 /* Executable setgid files should not get pinned to the filesystem. */
796 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
799 /* Hardlinking to unreadable or unwritable sources is dangerous. */
800 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
807 * may_linkat - Check permissions for creating a hardlink
808 * @link: the source to hardlink from
810 * Block hardlink when all of:
811 * - sysctl_protected_hardlinks enabled
812 * - fsuid does not match inode
813 * - hardlink source is unsafe (see safe_hardlink_source() above)
816 * Returns 0 if successful, -ve on error.
818 static int may_linkat(struct path
*link
)
820 const struct cred
*cred
;
823 if (!sysctl_protected_hardlinks
)
826 cred
= current_cred();
827 inode
= link
->dentry
->d_inode
;
829 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
830 * otherwise, it must be a safe source.
832 if (uid_eq(cred
->fsuid
, inode
->i_uid
) || safe_hardlink_source(inode
) ||
836 audit_log_link_denied("linkat", link
);
840 static __always_inline
const char *
841 get_link(struct path
*link
, struct nameidata
*nd
, void **p
)
843 struct dentry
*dentry
= link
->dentry
;
844 struct inode
*inode
= dentry
->d_inode
;
848 BUG_ON(nd
->flags
& LOOKUP_RCU
);
850 if (link
->mnt
== nd
->path
.mnt
)
853 res
= ERR_PTR(-ELOOP
);
854 if (unlikely(current
->total_link_count
>= 40))
858 current
->total_link_count
++;
862 error
= security_inode_follow_link(dentry
);
863 res
= ERR_PTR(error
);
867 nd
->last_type
= LAST_BIND
;
871 res
= inode
->i_op
->follow_link(dentry
, p
, nd
);
881 static int follow_up_rcu(struct path
*path
)
883 struct mount
*mnt
= real_mount(path
->mnt
);
884 struct mount
*parent
;
885 struct dentry
*mountpoint
;
887 parent
= mnt
->mnt_parent
;
888 if (&parent
->mnt
== path
->mnt
)
890 mountpoint
= mnt
->mnt_mountpoint
;
891 path
->dentry
= mountpoint
;
892 path
->mnt
= &parent
->mnt
;
897 * follow_up - Find the mountpoint of path's vfsmount
899 * Given a path, find the mountpoint of its source file system.
900 * Replace @path with the path of the mountpoint in the parent mount.
903 * Return 1 if we went up a level and 0 if we were already at the
906 int follow_up(struct path
*path
)
908 struct mount
*mnt
= real_mount(path
->mnt
);
909 struct mount
*parent
;
910 struct dentry
*mountpoint
;
912 read_seqlock_excl(&mount_lock
);
913 parent
= mnt
->mnt_parent
;
915 read_sequnlock_excl(&mount_lock
);
918 mntget(&parent
->mnt
);
919 mountpoint
= dget(mnt
->mnt_mountpoint
);
920 read_sequnlock_excl(&mount_lock
);
922 path
->dentry
= mountpoint
;
924 path
->mnt
= &parent
->mnt
;
927 EXPORT_SYMBOL(follow_up
);
930 * Perform an automount
931 * - return -EISDIR to tell follow_managed() to stop and return the path we
934 static int follow_automount(struct path
*path
, unsigned flags
,
937 struct vfsmount
*mnt
;
940 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
943 /* We don't want to mount if someone's just doing a stat -
944 * unless they're stat'ing a directory and appended a '/' to
947 * We do, however, want to mount if someone wants to open or
948 * create a file of any type under the mountpoint, wants to
949 * traverse through the mountpoint or wants to open the
950 * mounted directory. Also, autofs may mark negative dentries
951 * as being automount points. These will need the attentions
952 * of the daemon to instantiate them before they can be used.
954 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
955 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
956 path
->dentry
->d_inode
)
959 current
->total_link_count
++;
960 if (current
->total_link_count
>= 40)
963 mnt
= path
->dentry
->d_op
->d_automount(path
);
966 * The filesystem is allowed to return -EISDIR here to indicate
967 * it doesn't want to automount. For instance, autofs would do
968 * this so that its userspace daemon can mount on this dentry.
970 * However, we can only permit this if it's a terminal point in
971 * the path being looked up; if it wasn't then the remainder of
972 * the path is inaccessible and we should say so.
974 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
979 if (!mnt
) /* mount collision */
983 /* lock_mount() may release path->mnt on error */
987 err
= finish_automount(mnt
, path
);
991 /* Someone else made a mount here whilst we were busy */
996 path
->dentry
= dget(mnt
->mnt_root
);
1005 * Handle a dentry that is managed in some way.
1006 * - Flagged for transit management (autofs)
1007 * - Flagged as mountpoint
1008 * - Flagged as automount point
1010 * This may only be called in refwalk mode.
1012 * Serialization is taken care of in namespace.c
1014 static int follow_managed(struct path
*path
, unsigned flags
)
1016 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1018 bool need_mntput
= false;
1021 /* Given that we're not holding a lock here, we retain the value in a
1022 * local variable for each dentry as we look at it so that we don't see
1023 * the components of that value change under us */
1024 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1025 managed
&= DCACHE_MANAGED_DENTRY
,
1026 unlikely(managed
!= 0)) {
1027 /* Allow the filesystem to manage the transit without i_mutex
1029 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1030 BUG_ON(!path
->dentry
->d_op
);
1031 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1032 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1037 /* Transit to a mounted filesystem. */
1038 if (managed
& DCACHE_MOUNTED
) {
1039 struct vfsmount
*mounted
= lookup_mnt(path
);
1044 path
->mnt
= mounted
;
1045 path
->dentry
= dget(mounted
->mnt_root
);
1050 /* Something is mounted on this dentry in another
1051 * namespace and/or whatever was mounted there in this
1052 * namespace got unmounted before lookup_mnt() could
1056 /* Handle an automount point */
1057 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1058 ret
= follow_automount(path
, flags
, &need_mntput
);
1064 /* We didn't change the current path point */
1068 if (need_mntput
&& path
->mnt
== mnt
)
1072 return ret
< 0 ? ret
: need_mntput
;
1075 int follow_down_one(struct path
*path
)
1077 struct vfsmount
*mounted
;
1079 mounted
= lookup_mnt(path
);
1083 path
->mnt
= mounted
;
1084 path
->dentry
= dget(mounted
->mnt_root
);
1089 EXPORT_SYMBOL(follow_down_one
);
1091 static inline int managed_dentry_rcu(struct dentry
*dentry
)
1093 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) ?
1094 dentry
->d_op
->d_manage(dentry
, true) : 0;
1098 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1099 * we meet a managed dentry that would need blocking.
1101 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1102 struct inode
**inode
)
1105 struct mount
*mounted
;
1107 * Don't forget we might have a non-mountpoint managed dentry
1108 * that wants to block transit.
1110 switch (managed_dentry_rcu(path
->dentry
)) {
1120 if (!d_mountpoint(path
->dentry
))
1121 return !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1123 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1126 path
->mnt
= &mounted
->mnt
;
1127 path
->dentry
= mounted
->mnt
.mnt_root
;
1128 nd
->flags
|= LOOKUP_JUMPED
;
1129 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1131 * Update the inode too. We don't need to re-check the
1132 * dentry sequence number here after this d_inode read,
1133 * because a mount-point is always pinned.
1135 *inode
= path
->dentry
->d_inode
;
1137 return !read_seqretry(&mount_lock
, nd
->m_seq
) &&
1138 !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1141 static int follow_dotdot_rcu(struct nameidata
*nd
)
1143 struct inode
*inode
= nd
->inode
;
1148 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1149 nd
->path
.mnt
== nd
->root
.mnt
) {
1152 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1153 struct dentry
*old
= nd
->path
.dentry
;
1154 struct dentry
*parent
= old
->d_parent
;
1157 inode
= parent
->d_inode
;
1158 seq
= read_seqcount_begin(&parent
->d_seq
);
1159 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1161 nd
->path
.dentry
= parent
;
1165 if (!follow_up_rcu(&nd
->path
))
1167 inode
= nd
->path
.dentry
->d_inode
;
1168 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1170 while (d_mountpoint(nd
->path
.dentry
)) {
1171 struct mount
*mounted
;
1172 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1175 nd
->path
.mnt
= &mounted
->mnt
;
1176 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1177 inode
= nd
->path
.dentry
->d_inode
;
1178 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1179 if (read_seqretry(&mount_lock
, nd
->m_seq
))
1186 nd
->flags
&= ~LOOKUP_RCU
;
1187 if (!(nd
->flags
& LOOKUP_ROOT
))
1188 nd
->root
.mnt
= NULL
;
1194 * Follow down to the covering mount currently visible to userspace. At each
1195 * point, the filesystem owning that dentry may be queried as to whether the
1196 * caller is permitted to proceed or not.
1198 int follow_down(struct path
*path
)
1203 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1204 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1205 /* Allow the filesystem to manage the transit without i_mutex
1208 * We indicate to the filesystem if someone is trying to mount
1209 * something here. This gives autofs the chance to deny anyone
1210 * other than its daemon the right to mount on its
1213 * The filesystem may sleep at this point.
1215 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1216 BUG_ON(!path
->dentry
->d_op
);
1217 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1218 ret
= path
->dentry
->d_op
->d_manage(
1219 path
->dentry
, false);
1221 return ret
== -EISDIR
? 0 : ret
;
1224 /* Transit to a mounted filesystem. */
1225 if (managed
& DCACHE_MOUNTED
) {
1226 struct vfsmount
*mounted
= lookup_mnt(path
);
1231 path
->mnt
= mounted
;
1232 path
->dentry
= dget(mounted
->mnt_root
);
1236 /* Don't handle automount points here */
1241 EXPORT_SYMBOL(follow_down
);
1244 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1246 static void follow_mount(struct path
*path
)
1248 while (d_mountpoint(path
->dentry
)) {
1249 struct vfsmount
*mounted
= lookup_mnt(path
);
1254 path
->mnt
= mounted
;
1255 path
->dentry
= dget(mounted
->mnt_root
);
1259 static void follow_dotdot(struct nameidata
*nd
)
1265 struct dentry
*old
= nd
->path
.dentry
;
1267 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1268 nd
->path
.mnt
== nd
->root
.mnt
) {
1271 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1272 /* rare case of legitimate dget_parent()... */
1273 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1277 if (!follow_up(&nd
->path
))
1280 follow_mount(&nd
->path
);
1281 nd
->inode
= nd
->path
.dentry
->d_inode
;
1285 * This looks up the name in dcache, possibly revalidates the old dentry and
1286 * allocates a new one if not found or not valid. In the need_lookup argument
1287 * returns whether i_op->lookup is necessary.
1289 * dir->d_inode->i_mutex must be held
1291 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1292 unsigned int flags
, bool *need_lookup
)
1294 struct dentry
*dentry
;
1297 *need_lookup
= false;
1298 dentry
= d_lookup(dir
, name
);
1300 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1301 error
= d_revalidate(dentry
, flags
);
1302 if (unlikely(error
<= 0)) {
1305 return ERR_PTR(error
);
1307 d_invalidate(dentry
);
1316 dentry
= d_alloc(dir
, name
);
1317 if (unlikely(!dentry
))
1318 return ERR_PTR(-ENOMEM
);
1320 *need_lookup
= true;
1326 * Call i_op->lookup on the dentry. The dentry must be negative and
1329 * dir->d_inode->i_mutex must be held
1331 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1336 /* Don't create child dentry for a dead directory. */
1337 if (unlikely(IS_DEADDIR(dir
))) {
1339 return ERR_PTR(-ENOENT
);
1342 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1343 if (unlikely(old
)) {
1350 static struct dentry
*__lookup_hash(struct qstr
*name
,
1351 struct dentry
*base
, unsigned int flags
)
1354 struct dentry
*dentry
;
1356 dentry
= lookup_dcache(name
, base
, flags
, &need_lookup
);
1360 return lookup_real(base
->d_inode
, dentry
, flags
);
1364 * It's more convoluted than I'd like it to be, but... it's still fairly
1365 * small and for now I'd prefer to have fast path as straight as possible.
1366 * It _is_ time-critical.
1368 static int lookup_fast(struct nameidata
*nd
,
1369 struct path
*path
, struct inode
**inode
)
1371 struct vfsmount
*mnt
= nd
->path
.mnt
;
1372 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1378 * Rename seqlock is not required here because in the off chance
1379 * of a false negative due to a concurrent rename, we're going to
1380 * do the non-racy lookup, below.
1382 if (nd
->flags
& LOOKUP_RCU
) {
1385 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1390 * This sequence count validates that the inode matches
1391 * the dentry name information from lookup.
1393 *inode
= dentry
->d_inode
;
1394 negative
= d_is_negative(dentry
);
1395 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
1401 * This sequence count validates that the parent had no
1402 * changes while we did the lookup of the dentry above.
1404 * The memory barrier in read_seqcount_begin of child is
1405 * enough, we can use __read_seqcount_retry here.
1407 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1411 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1412 status
= d_revalidate(dentry
, nd
->flags
);
1413 if (unlikely(status
<= 0)) {
1414 if (status
!= -ECHILD
)
1420 path
->dentry
= dentry
;
1421 if (likely(__follow_mount_rcu(nd
, path
, inode
)))
1424 if (unlazy_walk(nd
, dentry
))
1427 dentry
= __d_lookup(parent
, &nd
->last
);
1430 if (unlikely(!dentry
))
1433 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1434 status
= d_revalidate(dentry
, nd
->flags
);
1435 if (unlikely(status
<= 0)) {
1440 d_invalidate(dentry
);
1445 if (unlikely(d_is_negative(dentry
))) {
1450 path
->dentry
= dentry
;
1451 err
= follow_managed(path
, nd
->flags
);
1452 if (unlikely(err
< 0)) {
1453 path_put_conditional(path
, nd
);
1457 nd
->flags
|= LOOKUP_JUMPED
;
1458 *inode
= path
->dentry
->d_inode
;
1465 /* Fast lookup failed, do it the slow way */
1466 static int lookup_slow(struct nameidata
*nd
, struct path
*path
)
1468 struct dentry
*dentry
, *parent
;
1471 parent
= nd
->path
.dentry
;
1472 BUG_ON(nd
->inode
!= parent
->d_inode
);
1474 mutex_lock(&parent
->d_inode
->i_mutex
);
1475 dentry
= __lookup_hash(&nd
->last
, parent
, nd
->flags
);
1476 mutex_unlock(&parent
->d_inode
->i_mutex
);
1478 return PTR_ERR(dentry
);
1479 path
->mnt
= nd
->path
.mnt
;
1480 path
->dentry
= dentry
;
1481 err
= follow_managed(path
, nd
->flags
);
1482 if (unlikely(err
< 0)) {
1483 path_put_conditional(path
, nd
);
1487 nd
->flags
|= LOOKUP_JUMPED
;
1491 static inline int may_lookup(struct nameidata
*nd
)
1493 if (nd
->flags
& LOOKUP_RCU
) {
1494 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1497 if (unlazy_walk(nd
, NULL
))
1500 return inode_permission(nd
->inode
, MAY_EXEC
);
1503 static inline int handle_dots(struct nameidata
*nd
, int type
)
1505 if (type
== LAST_DOTDOT
) {
1506 if (nd
->flags
& LOOKUP_RCU
) {
1507 if (follow_dotdot_rcu(nd
))
1515 static void terminate_walk(struct nameidata
*nd
)
1517 if (!(nd
->flags
& LOOKUP_RCU
)) {
1518 path_put(&nd
->path
);
1520 nd
->flags
&= ~LOOKUP_RCU
;
1521 if (!(nd
->flags
& LOOKUP_ROOT
))
1522 nd
->root
.mnt
= NULL
;
1528 * Do we need to follow links? We _really_ want to be able
1529 * to do this check without having to look at inode->i_op,
1530 * so we keep a cache of "no, this doesn't need follow_link"
1531 * for the common case.
1533 static inline int should_follow_link(struct dentry
*dentry
, int follow
)
1535 return unlikely(d_is_symlink(dentry
)) ? follow
: 0;
1538 static int walk_component(struct nameidata
*nd
, int follow
)
1541 struct inode
*inode
;
1544 * "." and ".." are special - ".." especially so because it has
1545 * to be able to know about the current root directory and
1546 * parent relationships.
1548 if (unlikely(nd
->last_type
!= LAST_NORM
))
1549 return handle_dots(nd
, nd
->last_type
);
1550 err
= lookup_fast(nd
, &path
, &inode
);
1551 if (unlikely(err
)) {
1555 err
= lookup_slow(nd
, &path
);
1559 inode
= path
.dentry
->d_inode
;
1561 if (d_is_negative(path
.dentry
))
1565 if (should_follow_link(path
.dentry
, follow
)) {
1566 if (nd
->flags
& LOOKUP_RCU
) {
1567 if (unlikely(nd
->path
.mnt
!= path
.mnt
||
1568 unlazy_walk(nd
, path
.dentry
))) {
1573 BUG_ON(inode
!= path
.dentry
->d_inode
);
1577 path_to_nameidata(&path
, nd
);
1582 path_to_nameidata(&path
, nd
);
1589 * We can do the critical dentry name comparison and hashing
1590 * operations one word at a time, but we are limited to:
1592 * - Architectures with fast unaligned word accesses. We could
1593 * do a "get_unaligned()" if this helps and is sufficiently
1596 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1597 * do not trap on the (extremely unlikely) case of a page
1598 * crossing operation.
1600 * - Furthermore, we need an efficient 64-bit compile for the
1601 * 64-bit case in order to generate the "number of bytes in
1602 * the final mask". Again, that could be replaced with a
1603 * efficient population count instruction or similar.
1605 #ifdef CONFIG_DCACHE_WORD_ACCESS
1607 #include <asm/word-at-a-time.h>
1611 static inline unsigned int fold_hash(unsigned long hash
)
1613 return hash_64(hash
, 32);
1616 #else /* 32-bit case */
1618 #define fold_hash(x) (x)
1622 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1624 unsigned long a
, mask
;
1625 unsigned long hash
= 0;
1628 a
= load_unaligned_zeropad(name
);
1629 if (len
< sizeof(unsigned long))
1633 name
+= sizeof(unsigned long);
1634 len
-= sizeof(unsigned long);
1638 mask
= bytemask_from_count(len
);
1641 return fold_hash(hash
);
1643 EXPORT_SYMBOL(full_name_hash
);
1646 * Calculate the length and hash of the path component, and
1647 * return the "hash_len" as the result.
1649 static inline u64
hash_name(const char *name
)
1651 unsigned long a
, b
, adata
, bdata
, mask
, hash
, len
;
1652 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1655 len
= -sizeof(unsigned long);
1657 hash
= (hash
+ a
) * 9;
1658 len
+= sizeof(unsigned long);
1659 a
= load_unaligned_zeropad(name
+len
);
1660 b
= a
^ REPEAT_BYTE('/');
1661 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1663 adata
= prep_zero_mask(a
, adata
, &constants
);
1664 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1666 mask
= create_zero_mask(adata
| bdata
);
1668 hash
+= a
& zero_bytemask(mask
);
1669 len
+= find_zero(mask
);
1670 return hashlen_create(fold_hash(hash
), len
);
1675 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1677 unsigned long hash
= init_name_hash();
1679 hash
= partial_name_hash(*name
++, hash
);
1680 return end_name_hash(hash
);
1682 EXPORT_SYMBOL(full_name_hash
);
1685 * We know there's a real path component here of at least
1688 static inline u64
hash_name(const char *name
)
1690 unsigned long hash
= init_name_hash();
1691 unsigned long len
= 0, c
;
1693 c
= (unsigned char)*name
;
1696 hash
= partial_name_hash(c
, hash
);
1697 c
= (unsigned char)name
[len
];
1698 } while (c
&& c
!= '/');
1699 return hashlen_create(end_name_hash(hash
), len
);
1706 * This is the basic name resolution function, turning a pathname into
1707 * the final dentry. We expect 'base' to be positive and a directory.
1709 * Returns 0 and nd will have valid dentry and mnt on success.
1710 * Returns error and drops reference to input namei data on failure.
1712 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1718 } stack
[MAX_NESTED_LINKS
], *last
= stack
+ nd
->depth
- 1;
1726 /* At this point we know we have a real path component. */
1731 err
= may_lookup(nd
);
1735 hash_len
= hash_name(name
);
1738 if (name
[0] == '.') switch (hashlen_len(hash_len
)) {
1740 if (name
[1] == '.') {
1742 nd
->flags
|= LOOKUP_JUMPED
;
1748 if (likely(type
== LAST_NORM
)) {
1749 struct dentry
*parent
= nd
->path
.dentry
;
1750 nd
->flags
&= ~LOOKUP_JUMPED
;
1751 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1752 struct qstr
this = { { .hash_len
= hash_len
}, .name
= name
};
1753 err
= parent
->d_op
->d_hash(parent
, &this);
1756 hash_len
= this.hash_len
;
1761 nd
->last
.hash_len
= hash_len
;
1762 nd
->last
.name
= name
;
1763 nd
->last_type
= type
;
1765 name
+= hashlen_len(hash_len
);
1769 * If it wasn't NUL, we know it was '/'. Skip that
1770 * slash, and continue until no more slashes.
1774 } while (unlikely(*name
== '/'));
1778 err
= walk_component(nd
, LOOKUP_FOLLOW
);
1786 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1787 path_put_conditional(&nd
->link
, nd
);
1788 path_put(&nd
->path
);
1792 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1795 current
->link_count
++;
1798 last
->link
= nd
->link
;
1799 s
= get_link(&last
->link
, nd
, &last
->cookie
);
1801 if (unlikely(IS_ERR(s
))) {
1803 current
->link_count
--;
1811 put_link(nd
, &last
->link
, last
->cookie
);
1812 current
->link_count
--;
1819 path_put(&nd
->path
);
1820 nd
->path
= nd
->root
;
1821 path_get(&nd
->root
);
1822 nd
->flags
|= LOOKUP_JUMPED
;
1823 while (unlikely(*++s
== '/'))
1826 nd
->inode
= nd
->path
.dentry
->d_inode
;
1834 if (!d_can_lookup(nd
->path
.dentry
)) {
1841 while (unlikely(nd
->depth
)) {
1842 put_link(nd
, &last
->link
, last
->cookie
);
1843 current
->link_count
--;
1849 if (unlikely(nd
->depth
)) {
1851 err
= walk_component(nd
, LOOKUP_FOLLOW
);
1852 put_link(nd
, &last
->link
, last
->cookie
);
1853 current
->link_count
--;
1861 static int path_init(int dfd
, const struct filename
*name
, unsigned int flags
,
1862 struct nameidata
*nd
)
1865 const char *s
= name
->name
;
1867 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1868 nd
->flags
= flags
| LOOKUP_JUMPED
| LOOKUP_PARENT
;
1871 if (flags
& LOOKUP_ROOT
) {
1872 struct dentry
*root
= nd
->root
.dentry
;
1873 struct inode
*inode
= root
->d_inode
;
1875 if (!d_can_lookup(root
))
1877 retval
= inode_permission(inode
, MAY_EXEC
);
1881 nd
->path
= nd
->root
;
1883 if (flags
& LOOKUP_RCU
) {
1885 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1886 nd
->m_seq
= read_seqbegin(&mount_lock
);
1888 path_get(&nd
->path
);
1893 nd
->root
.mnt
= NULL
;
1895 nd
->m_seq
= read_seqbegin(&mount_lock
);
1897 if (flags
& LOOKUP_RCU
) {
1899 nd
->seq
= set_root_rcu(nd
);
1902 path_get(&nd
->root
);
1904 nd
->path
= nd
->root
;
1905 } else if (dfd
== AT_FDCWD
) {
1906 if (flags
& LOOKUP_RCU
) {
1907 struct fs_struct
*fs
= current
->fs
;
1913 seq
= read_seqcount_begin(&fs
->seq
);
1915 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1916 } while (read_seqcount_retry(&fs
->seq
, seq
));
1918 get_fs_pwd(current
->fs
, &nd
->path
);
1921 /* Caller must check execute permissions on the starting path component */
1922 struct fd f
= fdget_raw(dfd
);
1923 struct dentry
*dentry
;
1928 dentry
= f
.file
->f_path
.dentry
;
1931 if (!d_can_lookup(dentry
)) {
1937 nd
->path
= f
.file
->f_path
;
1938 if (flags
& LOOKUP_RCU
) {
1939 if (f
.flags
& FDPUT_FPUT
)
1941 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1944 path_get(&nd
->path
);
1949 nd
->inode
= nd
->path
.dentry
->d_inode
;
1950 if (!(flags
& LOOKUP_RCU
))
1952 if (likely(!read_seqcount_retry(&nd
->path
.dentry
->d_seq
, nd
->seq
)))
1954 if (!(nd
->flags
& LOOKUP_ROOT
))
1955 nd
->root
.mnt
= NULL
;
1959 current
->total_link_count
= 0;
1960 return link_path_walk(s
, nd
);
1963 static void path_cleanup(struct nameidata
*nd
)
1965 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1966 path_put(&nd
->root
);
1967 nd
->root
.mnt
= NULL
;
1969 if (unlikely(nd
->base
))
1973 static int trailing_symlink(struct path
*link
, struct nameidata
*nd
, void **p
)
1976 int error
= may_follow_link(link
, nd
);
1977 if (unlikely(error
))
1979 nd
->flags
|= LOOKUP_PARENT
;
1980 s
= get_link(link
, nd
, p
);
1981 if (unlikely(IS_ERR(s
)))
1988 path_put(&nd
->path
);
1989 nd
->path
= nd
->root
;
1990 path_get(&nd
->root
);
1991 nd
->flags
|= LOOKUP_JUMPED
;
1993 nd
->inode
= nd
->path
.dentry
->d_inode
;
1994 error
= link_path_walk(s
, nd
);
1995 if (unlikely(error
))
1996 put_link(nd
, link
, *p
);
2000 static inline int lookup_last(struct nameidata
*nd
)
2002 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
2003 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2005 nd
->flags
&= ~LOOKUP_PARENT
;
2006 return walk_component(nd
, nd
->flags
& LOOKUP_FOLLOW
);
2009 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2010 static int path_lookupat(int dfd
, const struct filename
*name
,
2011 unsigned int flags
, struct nameidata
*nd
)
2016 * Path walking is largely split up into 2 different synchronisation
2017 * schemes, rcu-walk and ref-walk (explained in
2018 * Documentation/filesystems/path-lookup.txt). These share much of the
2019 * path walk code, but some things particularly setup, cleanup, and
2020 * following mounts are sufficiently divergent that functions are
2021 * duplicated. Typically there is a function foo(), and its RCU
2022 * analogue, foo_rcu().
2024 * -ECHILD is the error number of choice (just to avoid clashes) that
2025 * is returned if some aspect of an rcu-walk fails. Such an error must
2026 * be handled by restarting a traditional ref-walk (which will always
2027 * be able to complete).
2029 err
= path_init(dfd
, name
, flags
, nd
);
2030 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
2031 err
= lookup_last(nd
);
2034 struct path link
= nd
->link
;
2035 err
= trailing_symlink(&link
, nd
, &cookie
);
2038 err
= lookup_last(nd
);
2039 put_link(nd
, &link
, cookie
);
2044 err
= complete_walk(nd
);
2046 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
2047 if (!d_can_lookup(nd
->path
.dentry
)) {
2048 path_put(&nd
->path
);
2057 static int filename_lookup(int dfd
, struct filename
*name
,
2058 unsigned int flags
, struct nameidata
*nd
)
2060 int retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_RCU
, nd
);
2061 if (unlikely(retval
== -ECHILD
))
2062 retval
= path_lookupat(dfd
, name
, flags
, nd
);
2063 if (unlikely(retval
== -ESTALE
))
2064 retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_REVAL
, nd
);
2066 if (likely(!retval
))
2067 audit_inode(name
, nd
->path
.dentry
, flags
& LOOKUP_PARENT
);
2071 /* does lookup, returns the object with parent locked */
2072 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2074 struct filename
*filename
= getname_kernel(name
);
2075 struct nameidata nd
;
2079 if (IS_ERR(filename
))
2080 return ERR_CAST(filename
);
2082 err
= filename_lookup(AT_FDCWD
, filename
, LOOKUP_PARENT
, &nd
);
2087 if (nd
.last_type
!= LAST_NORM
) {
2089 d
= ERR_PTR(-EINVAL
);
2092 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2093 d
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, 0);
2095 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2105 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2107 struct nameidata nd
;
2108 struct filename
*filename
= getname_kernel(name
);
2109 int res
= PTR_ERR(filename
);
2111 if (!IS_ERR(filename
)) {
2112 res
= filename_lookup(AT_FDCWD
, filename
, flags
, &nd
);
2119 EXPORT_SYMBOL(kern_path
);
2122 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2123 * @dentry: pointer to dentry of the base directory
2124 * @mnt: pointer to vfs mount of the base directory
2125 * @name: pointer to file name
2126 * @flags: lookup flags
2127 * @path: pointer to struct path to fill
2129 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2130 const char *name
, unsigned int flags
,
2133 struct filename
*filename
= getname_kernel(name
);
2134 int err
= PTR_ERR(filename
);
2136 BUG_ON(flags
& LOOKUP_PARENT
);
2138 /* the first argument of filename_lookup() is ignored with LOOKUP_ROOT */
2139 if (!IS_ERR(filename
)) {
2140 struct nameidata nd
;
2141 nd
.root
.dentry
= dentry
;
2143 err
= filename_lookup(AT_FDCWD
, filename
,
2144 flags
| LOOKUP_ROOT
, &nd
);
2151 EXPORT_SYMBOL(vfs_path_lookup
);
2154 * lookup_one_len - filesystem helper to lookup single pathname component
2155 * @name: pathname component to lookup
2156 * @base: base directory to lookup from
2157 * @len: maximum length @len should be interpreted to
2159 * Note that this routine is purely a helper for filesystem usage and should
2160 * not be called by generic code.
2162 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2168 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
2172 this.hash
= full_name_hash(name
, len
);
2174 return ERR_PTR(-EACCES
);
2176 if (unlikely(name
[0] == '.')) {
2177 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2178 return ERR_PTR(-EACCES
);
2182 c
= *(const unsigned char *)name
++;
2183 if (c
== '/' || c
== '\0')
2184 return ERR_PTR(-EACCES
);
2187 * See if the low-level filesystem might want
2188 * to use its own hash..
2190 if (base
->d_flags
& DCACHE_OP_HASH
) {
2191 int err
= base
->d_op
->d_hash(base
, &this);
2193 return ERR_PTR(err
);
2196 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2198 return ERR_PTR(err
);
2200 return __lookup_hash(&this, base
, 0);
2202 EXPORT_SYMBOL(lookup_one_len
);
2204 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2205 struct path
*path
, int *empty
)
2207 struct nameidata nd
;
2208 struct filename
*tmp
= getname_flags(name
, flags
, empty
);
2209 int err
= PTR_ERR(tmp
);
2212 BUG_ON(flags
& LOOKUP_PARENT
);
2214 err
= filename_lookup(dfd
, tmp
, flags
, &nd
);
2222 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
2225 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
2227 EXPORT_SYMBOL(user_path_at
);
2230 * NB: most callers don't do anything directly with the reference to the
2231 * to struct filename, but the nd->last pointer points into the name string
2232 * allocated by getname. So we must hold the reference to it until all
2233 * path-walking is complete.
2235 static struct filename
*
2236 user_path_parent(int dfd
, const char __user
*path
,
2237 struct path
*parent
,
2242 struct nameidata nd
;
2243 struct filename
*s
= getname(path
);
2246 /* only LOOKUP_REVAL is allowed in extra flags */
2247 flags
&= LOOKUP_REVAL
;
2252 error
= filename_lookup(dfd
, s
, flags
| LOOKUP_PARENT
, &nd
);
2255 return ERR_PTR(error
);
2259 *type
= nd
.last_type
;
2265 * mountpoint_last - look up last component for umount
2266 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2267 * @path: pointer to container for result
2269 * This is a special lookup_last function just for umount. In this case, we
2270 * need to resolve the path without doing any revalidation.
2272 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2273 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2274 * in almost all cases, this lookup will be served out of the dcache. The only
2275 * cases where it won't are if nd->last refers to a symlink or the path is
2276 * bogus and it doesn't exist.
2279 * -error: if there was an error during lookup. This includes -ENOENT if the
2280 * lookup found a negative dentry. The nd->path reference will also be
2283 * 0: if we successfully resolved nd->path and found it to not to be a
2284 * symlink that needs to be followed. "path" will also be populated.
2285 * The nd->path reference will also be put.
2287 * 1: if we successfully resolved nd->last and found it to be a symlink
2288 * that needs to be followed. "path" will be populated with the path
2289 * to the link, and nd->path will *not* be put.
2292 mountpoint_last(struct nameidata
*nd
, struct path
*path
)
2295 struct dentry
*dentry
;
2296 struct dentry
*dir
= nd
->path
.dentry
;
2298 /* If we're in rcuwalk, drop out of it to handle last component */
2299 if (nd
->flags
& LOOKUP_RCU
) {
2300 if (unlazy_walk(nd
, NULL
)) {
2306 nd
->flags
&= ~LOOKUP_PARENT
;
2308 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2309 error
= handle_dots(nd
, nd
->last_type
);
2312 dentry
= dget(nd
->path
.dentry
);
2316 mutex_lock(&dir
->d_inode
->i_mutex
);
2317 dentry
= d_lookup(dir
, &nd
->last
);
2320 * No cached dentry. Mounted dentries are pinned in the cache,
2321 * so that means that this dentry is probably a symlink or the
2322 * path doesn't actually point to a mounted dentry.
2324 dentry
= d_alloc(dir
, &nd
->last
);
2327 mutex_unlock(&dir
->d_inode
->i_mutex
);
2330 dentry
= lookup_real(dir
->d_inode
, dentry
, nd
->flags
);
2331 error
= PTR_ERR(dentry
);
2332 if (IS_ERR(dentry
)) {
2333 mutex_unlock(&dir
->d_inode
->i_mutex
);
2337 mutex_unlock(&dir
->d_inode
->i_mutex
);
2340 if (d_is_negative(dentry
)) {
2345 path
->dentry
= dentry
;
2346 path
->mnt
= nd
->path
.mnt
;
2347 if (should_follow_link(dentry
, nd
->flags
& LOOKUP_FOLLOW
)) {
2360 * path_mountpoint - look up a path to be umounted
2361 * @dfd: directory file descriptor to start walk from
2362 * @name: full pathname to walk
2363 * @path: pointer to container for result
2364 * @flags: lookup flags
2366 * Look up the given name, but don't attempt to revalidate the last component.
2367 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2370 path_mountpoint(int dfd
, const struct filename
*name
, struct path
*path
,
2371 struct nameidata
*nd
, unsigned int flags
)
2373 int err
= path_init(dfd
, name
, flags
, nd
);
2377 err
= mountpoint_last(nd
, path
);
2380 struct path link
= *path
;
2381 err
= trailing_symlink(&link
, nd
, &cookie
);
2384 err
= mountpoint_last(nd
, path
);
2385 put_link(nd
, &link
, cookie
);
2393 filename_mountpoint(int dfd
, struct filename
*name
, struct path
*path
,
2396 struct nameidata nd
;
2399 return PTR_ERR(name
);
2400 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
| LOOKUP_RCU
);
2401 if (unlikely(error
== -ECHILD
))
2402 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
);
2403 if (unlikely(error
== -ESTALE
))
2404 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
| LOOKUP_REVAL
);
2406 audit_inode(name
, path
->dentry
, 0);
2412 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2413 * @dfd: directory file descriptor
2414 * @name: pathname from userland
2415 * @flags: lookup flags
2416 * @path: pointer to container to hold result
2418 * A umount is a special case for path walking. We're not actually interested
2419 * in the inode in this situation, and ESTALE errors can be a problem. We
2420 * simply want track down the dentry and vfsmount attached at the mountpoint
2421 * and avoid revalidating the last component.
2423 * Returns 0 and populates "path" on success.
2426 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2429 return filename_mountpoint(dfd
, getname(name
), path
, flags
);
2433 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2436 return filename_mountpoint(dfd
, getname_kernel(name
), path
, flags
);
2438 EXPORT_SYMBOL(kern_path_mountpoint
);
2440 int __check_sticky(struct inode
*dir
, struct inode
*inode
)
2442 kuid_t fsuid
= current_fsuid();
2444 if (uid_eq(inode
->i_uid
, fsuid
))
2446 if (uid_eq(dir
->i_uid
, fsuid
))
2448 return !capable_wrt_inode_uidgid(inode
, CAP_FOWNER
);
2450 EXPORT_SYMBOL(__check_sticky
);
2453 * Check whether we can remove a link victim from directory dir, check
2454 * whether the type of victim is right.
2455 * 1. We can't do it if dir is read-only (done in permission())
2456 * 2. We should have write and exec permissions on dir
2457 * 3. We can't remove anything from append-only dir
2458 * 4. We can't do anything with immutable dir (done in permission())
2459 * 5. If the sticky bit on dir is set we should either
2460 * a. be owner of dir, or
2461 * b. be owner of victim, or
2462 * c. have CAP_FOWNER capability
2463 * 6. If the victim is append-only or immutable we can't do antyhing with
2464 * links pointing to it.
2465 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2466 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2467 * 9. We can't remove a root or mountpoint.
2468 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2469 * nfs_async_unlink().
2471 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2473 struct inode
*inode
= victim
->d_inode
;
2476 if (d_is_negative(victim
))
2480 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2481 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2483 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2489 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2490 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
))
2493 if (!d_is_dir(victim
))
2495 if (IS_ROOT(victim
))
2497 } else if (d_is_dir(victim
))
2499 if (IS_DEADDIR(dir
))
2501 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2506 /* Check whether we can create an object with dentry child in directory
2508 * 1. We can't do it if child already exists (open has special treatment for
2509 * this case, but since we are inlined it's OK)
2510 * 2. We can't do it if dir is read-only (done in permission())
2511 * 3. We should have write and exec permissions on dir
2512 * 4. We can't do it if dir is immutable (done in permission())
2514 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2516 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2519 if (IS_DEADDIR(dir
))
2521 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2525 * p1 and p2 should be directories on the same fs.
2527 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2532 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2536 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2538 p
= d_ancestor(p2
, p1
);
2540 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2541 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2545 p
= d_ancestor(p1
, p2
);
2547 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2548 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2552 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2553 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT2
);
2556 EXPORT_SYMBOL(lock_rename
);
2558 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2560 mutex_unlock(&p1
->d_inode
->i_mutex
);
2562 mutex_unlock(&p2
->d_inode
->i_mutex
);
2563 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2566 EXPORT_SYMBOL(unlock_rename
);
2568 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2571 int error
= may_create(dir
, dentry
);
2575 if (!dir
->i_op
->create
)
2576 return -EACCES
; /* shouldn't it be ENOSYS? */
2579 error
= security_inode_create(dir
, dentry
, mode
);
2582 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2584 fsnotify_create(dir
, dentry
);
2587 EXPORT_SYMBOL(vfs_create
);
2589 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2591 struct dentry
*dentry
= path
->dentry
;
2592 struct inode
*inode
= dentry
->d_inode
;
2602 switch (inode
->i_mode
& S_IFMT
) {
2606 if (acc_mode
& MAY_WRITE
)
2611 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2620 error
= inode_permission(inode
, acc_mode
);
2625 * An append-only file must be opened in append mode for writing.
2627 if (IS_APPEND(inode
)) {
2628 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2634 /* O_NOATIME can only be set by the owner or superuser */
2635 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2641 static int handle_truncate(struct file
*filp
)
2643 struct path
*path
= &filp
->f_path
;
2644 struct inode
*inode
= path
->dentry
->d_inode
;
2645 int error
= get_write_access(inode
);
2649 * Refuse to truncate files with mandatory locks held on them.
2651 error
= locks_verify_locked(filp
);
2653 error
= security_path_truncate(path
);
2655 error
= do_truncate(path
->dentry
, 0,
2656 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2659 put_write_access(inode
);
2663 static inline int open_to_namei_flags(int flag
)
2665 if ((flag
& O_ACCMODE
) == 3)
2670 static int may_o_create(struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2672 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2676 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2680 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2684 * Attempt to atomically look up, create and open a file from a negative
2687 * Returns 0 if successful. The file will have been created and attached to
2688 * @file by the filesystem calling finish_open().
2690 * Returns 1 if the file was looked up only or didn't need creating. The
2691 * caller will need to perform the open themselves. @path will have been
2692 * updated to point to the new dentry. This may be negative.
2694 * Returns an error code otherwise.
2696 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2697 struct path
*path
, struct file
*file
,
2698 const struct open_flags
*op
,
2699 bool got_write
, bool need_lookup
,
2702 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2703 unsigned open_flag
= open_to_namei_flags(op
->open_flag
);
2707 int create_error
= 0;
2708 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2711 BUG_ON(dentry
->d_inode
);
2713 /* Don't create child dentry for a dead directory. */
2714 if (unlikely(IS_DEADDIR(dir
))) {
2720 if ((open_flag
& O_CREAT
) && !IS_POSIXACL(dir
))
2721 mode
&= ~current_umask();
2723 excl
= (open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
);
2725 open_flag
&= ~O_TRUNC
;
2728 * Checking write permission is tricky, bacuse we don't know if we are
2729 * going to actually need it: O_CREAT opens should work as long as the
2730 * file exists. But checking existence breaks atomicity. The trick is
2731 * to check access and if not granted clear O_CREAT from the flags.
2733 * Another problem is returing the "right" error value (e.g. for an
2734 * O_EXCL open we want to return EEXIST not EROFS).
2736 if (((open_flag
& (O_CREAT
| O_TRUNC
)) ||
2737 (open_flag
& O_ACCMODE
) != O_RDONLY
) && unlikely(!got_write
)) {
2738 if (!(open_flag
& O_CREAT
)) {
2740 * No O_CREATE -> atomicity not a requirement -> fall
2741 * back to lookup + open
2744 } else if (open_flag
& (O_EXCL
| O_TRUNC
)) {
2745 /* Fall back and fail with the right error */
2746 create_error
= -EROFS
;
2749 /* No side effects, safe to clear O_CREAT */
2750 create_error
= -EROFS
;
2751 open_flag
&= ~O_CREAT
;
2755 if (open_flag
& O_CREAT
) {
2756 error
= may_o_create(&nd
->path
, dentry
, mode
);
2758 create_error
= error
;
2759 if (open_flag
& O_EXCL
)
2761 open_flag
&= ~O_CREAT
;
2765 if (nd
->flags
& LOOKUP_DIRECTORY
)
2766 open_flag
|= O_DIRECTORY
;
2768 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2769 file
->f_path
.mnt
= nd
->path
.mnt
;
2770 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
, open_flag
, mode
,
2773 if (create_error
&& error
== -ENOENT
)
2774 error
= create_error
;
2778 if (error
) { /* returned 1, that is */
2779 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
2783 if (file
->f_path
.dentry
) {
2785 dentry
= file
->f_path
.dentry
;
2787 if (*opened
& FILE_CREATED
)
2788 fsnotify_create(dir
, dentry
);
2789 if (!dentry
->d_inode
) {
2790 WARN_ON(*opened
& FILE_CREATED
);
2792 error
= create_error
;
2796 if (excl
&& !(*opened
& FILE_CREATED
)) {
2805 * We didn't have the inode before the open, so check open permission
2808 acc_mode
= op
->acc_mode
;
2809 if (*opened
& FILE_CREATED
) {
2810 WARN_ON(!(open_flag
& O_CREAT
));
2811 fsnotify_create(dir
, dentry
);
2812 acc_mode
= MAY_OPEN
;
2814 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
2824 dentry
= lookup_real(dir
, dentry
, nd
->flags
);
2826 return PTR_ERR(dentry
);
2829 int open_flag
= op
->open_flag
;
2831 error
= create_error
;
2832 if ((open_flag
& O_EXCL
)) {
2833 if (!dentry
->d_inode
)
2835 } else if (!dentry
->d_inode
) {
2837 } else if ((open_flag
& O_TRUNC
) &&
2841 /* will fail later, go on to get the right error */
2845 path
->dentry
= dentry
;
2846 path
->mnt
= nd
->path
.mnt
;
2851 * Look up and maybe create and open the last component.
2853 * Must be called with i_mutex held on parent.
2855 * Returns 0 if the file was successfully atomically created (if necessary) and
2856 * opened. In this case the file will be returned attached to @file.
2858 * Returns 1 if the file was not completely opened at this time, though lookups
2859 * and creations will have been performed and the dentry returned in @path will
2860 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2861 * specified then a negative dentry may be returned.
2863 * An error code is returned otherwise.
2865 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2866 * cleared otherwise prior to returning.
2868 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
2870 const struct open_flags
*op
,
2871 bool got_write
, int *opened
)
2873 struct dentry
*dir
= nd
->path
.dentry
;
2874 struct inode
*dir_inode
= dir
->d_inode
;
2875 struct dentry
*dentry
;
2879 *opened
&= ~FILE_CREATED
;
2880 dentry
= lookup_dcache(&nd
->last
, dir
, nd
->flags
, &need_lookup
);
2882 return PTR_ERR(dentry
);
2884 /* Cached positive dentry: will open in f_op->open */
2885 if (!need_lookup
&& dentry
->d_inode
)
2888 if ((nd
->flags
& LOOKUP_OPEN
) && dir_inode
->i_op
->atomic_open
) {
2889 return atomic_open(nd
, dentry
, path
, file
, op
, got_write
,
2890 need_lookup
, opened
);
2894 BUG_ON(dentry
->d_inode
);
2896 dentry
= lookup_real(dir_inode
, dentry
, nd
->flags
);
2898 return PTR_ERR(dentry
);
2901 /* Negative dentry, just create the file */
2902 if (!dentry
->d_inode
&& (op
->open_flag
& O_CREAT
)) {
2903 umode_t mode
= op
->mode
;
2904 if (!IS_POSIXACL(dir
->d_inode
))
2905 mode
&= ~current_umask();
2907 * This write is needed to ensure that a
2908 * rw->ro transition does not occur between
2909 * the time when the file is created and when
2910 * a permanent write count is taken through
2911 * the 'struct file' in finish_open().
2917 *opened
|= FILE_CREATED
;
2918 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2921 error
= vfs_create(dir
->d_inode
, dentry
, mode
,
2922 nd
->flags
& LOOKUP_EXCL
);
2927 path
->dentry
= dentry
;
2928 path
->mnt
= nd
->path
.mnt
;
2937 * Handle the last step of open()
2939 static int do_last(struct nameidata
*nd
,
2940 struct file
*file
, const struct open_flags
*op
,
2941 int *opened
, struct filename
*name
)
2943 struct dentry
*dir
= nd
->path
.dentry
;
2944 int open_flag
= op
->open_flag
;
2945 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
2946 bool got_write
= false;
2947 int acc_mode
= op
->acc_mode
;
2948 struct inode
*inode
;
2949 struct path save_parent
= { .dentry
= NULL
, .mnt
= NULL
};
2951 bool retried
= false;
2954 nd
->flags
&= ~LOOKUP_PARENT
;
2955 nd
->flags
|= op
->intent
;
2957 if (nd
->last_type
!= LAST_NORM
) {
2958 error
= handle_dots(nd
, nd
->last_type
);
2964 if (!(open_flag
& O_CREAT
)) {
2965 if (nd
->last
.name
[nd
->last
.len
])
2966 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2967 /* we _can_ be in RCU mode here */
2968 error
= lookup_fast(nd
, &path
, &inode
);
2975 BUG_ON(nd
->inode
!= dir
->d_inode
);
2977 /* create side of things */
2979 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2980 * has been cleared when we got to the last component we are
2983 error
= complete_walk(nd
);
2987 audit_inode(name
, dir
, LOOKUP_PARENT
);
2989 /* trailing slashes? */
2990 if (nd
->last
.name
[nd
->last
.len
])
2995 if (op
->open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
2996 error
= mnt_want_write(nd
->path
.mnt
);
3000 * do _not_ fail yet - we might not need that or fail with
3001 * a different error; let lookup_open() decide; we'll be
3002 * dropping this one anyway.
3005 mutex_lock(&dir
->d_inode
->i_mutex
);
3006 error
= lookup_open(nd
, &path
, file
, op
, got_write
, opened
);
3007 mutex_unlock(&dir
->d_inode
->i_mutex
);
3013 if ((*opened
& FILE_CREATED
) ||
3014 !S_ISREG(file_inode(file
)->i_mode
))
3015 will_truncate
= false;
3017 audit_inode(name
, file
->f_path
.dentry
, 0);
3021 if (*opened
& FILE_CREATED
) {
3022 /* Don't check for write permission, don't truncate */
3023 open_flag
&= ~O_TRUNC
;
3024 will_truncate
= false;
3025 acc_mode
= MAY_OPEN
;
3026 path_to_nameidata(&path
, nd
);
3027 goto finish_open_created
;
3031 * create/update audit record if it already exists.
3033 if (d_is_positive(path
.dentry
))
3034 audit_inode(name
, path
.dentry
, 0);
3037 * If atomic_open() acquired write access it is dropped now due to
3038 * possible mount and symlink following (this might be optimized away if
3042 mnt_drop_write(nd
->path
.mnt
);
3047 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))
3050 error
= follow_managed(&path
, nd
->flags
);
3055 nd
->flags
|= LOOKUP_JUMPED
;
3057 BUG_ON(nd
->flags
& LOOKUP_RCU
);
3058 inode
= path
.dentry
->d_inode
;
3060 if (d_is_negative(path
.dentry
)) {
3061 path_to_nameidata(&path
, nd
);
3065 if (should_follow_link(path
.dentry
, nd
->flags
& LOOKUP_FOLLOW
)) {
3066 if (nd
->flags
& LOOKUP_RCU
) {
3067 if (unlikely(nd
->path
.mnt
!= path
.mnt
||
3068 unlazy_walk(nd
, path
.dentry
))) {
3073 BUG_ON(inode
!= path
.dentry
->d_inode
);
3078 if (unlikely(d_is_symlink(path
.dentry
)) && !(open_flag
& O_PATH
)) {
3079 path_to_nameidata(&path
, nd
);
3084 if ((nd
->flags
& LOOKUP_RCU
) || nd
->path
.mnt
!= path
.mnt
) {
3085 path_to_nameidata(&path
, nd
);
3087 save_parent
.dentry
= nd
->path
.dentry
;
3088 save_parent
.mnt
= mntget(path
.mnt
);
3089 nd
->path
.dentry
= path
.dentry
;
3093 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3095 error
= complete_walk(nd
);
3097 path_put(&save_parent
);
3100 audit_inode(name
, nd
->path
.dentry
, 0);
3102 if ((open_flag
& O_CREAT
) && d_is_dir(nd
->path
.dentry
))
3105 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_can_lookup(nd
->path
.dentry
))
3107 if (!d_is_reg(nd
->path
.dentry
))
3108 will_truncate
= false;
3110 if (will_truncate
) {
3111 error
= mnt_want_write(nd
->path
.mnt
);
3116 finish_open_created
:
3117 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3121 BUG_ON(*opened
& FILE_OPENED
); /* once it's opened, it's opened */
3122 error
= vfs_open(&nd
->path
, file
, current_cred());
3124 *opened
|= FILE_OPENED
;
3126 if (error
== -EOPENSTALE
)
3131 error
= open_check_o_direct(file
);
3134 error
= ima_file_check(file
, op
->acc_mode
, *opened
);
3138 if (will_truncate
) {
3139 error
= handle_truncate(file
);
3145 mnt_drop_write(nd
->path
.mnt
);
3146 path_put(&save_parent
);
3151 path_put_conditional(&path
, nd
);
3158 /* If no saved parent or already retried then can't retry */
3159 if (!save_parent
.dentry
|| retried
)
3162 BUG_ON(save_parent
.dentry
!= dir
);
3163 path_put(&nd
->path
);
3164 nd
->path
= save_parent
;
3165 nd
->inode
= dir
->d_inode
;
3166 save_parent
.mnt
= NULL
;
3167 save_parent
.dentry
= NULL
;
3169 mnt_drop_write(nd
->path
.mnt
);
3176 static int do_tmpfile(int dfd
, struct filename
*pathname
,
3177 struct nameidata
*nd
, int flags
,
3178 const struct open_flags
*op
,
3179 struct file
*file
, int *opened
)
3181 static const struct qstr name
= QSTR_INIT("/", 1);
3182 struct dentry
*dentry
, *child
;
3184 int error
= path_lookupat(dfd
, pathname
,
3185 flags
| LOOKUP_DIRECTORY
, nd
);
3186 if (unlikely(error
))
3188 error
= mnt_want_write(nd
->path
.mnt
);
3189 if (unlikely(error
))
3191 /* we want directory to be writable */
3192 error
= inode_permission(nd
->inode
, MAY_WRITE
| MAY_EXEC
);
3195 dentry
= nd
->path
.dentry
;
3196 dir
= dentry
->d_inode
;
3197 if (!dir
->i_op
->tmpfile
) {
3198 error
= -EOPNOTSUPP
;
3201 child
= d_alloc(dentry
, &name
);
3202 if (unlikely(!child
)) {
3206 nd
->flags
&= ~LOOKUP_DIRECTORY
;
3207 nd
->flags
|= op
->intent
;
3208 dput(nd
->path
.dentry
);
3209 nd
->path
.dentry
= child
;
3210 error
= dir
->i_op
->tmpfile(dir
, nd
->path
.dentry
, op
->mode
);
3213 audit_inode(pathname
, nd
->path
.dentry
, 0);
3214 /* Don't check for other permissions, the inode was just created */
3215 error
= may_open(&nd
->path
, MAY_OPEN
, op
->open_flag
);
3218 file
->f_path
.mnt
= nd
->path
.mnt
;
3219 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3222 error
= open_check_o_direct(file
);
3225 } else if (!(op
->open_flag
& O_EXCL
)) {
3226 struct inode
*inode
= file_inode(file
);
3227 spin_lock(&inode
->i_lock
);
3228 inode
->i_state
|= I_LINKABLE
;
3229 spin_unlock(&inode
->i_lock
);
3232 mnt_drop_write(nd
->path
.mnt
);
3234 path_put(&nd
->path
);
3238 static struct file
*path_openat(int dfd
, struct filename
*pathname
,
3239 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
3245 file
= get_empty_filp();
3249 file
->f_flags
= op
->open_flag
;
3251 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3252 error
= do_tmpfile(dfd
, pathname
, nd
, flags
, op
, file
, &opened
);
3256 error
= path_init(dfd
, pathname
, flags
, nd
);
3257 if (unlikely(error
))
3260 error
= do_last(nd
, file
, op
, &opened
, pathname
);
3261 while (unlikely(error
> 0)) { /* trailing symlink */
3262 struct path link
= nd
->link
;
3264 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3265 error
= trailing_symlink(&link
, nd
, &cookie
);
3266 if (unlikely(error
))
3268 error
= do_last(nd
, file
, op
, &opened
, pathname
);
3269 put_link(nd
, &link
, cookie
);
3274 if (!(opened
& FILE_OPENED
)) {
3278 if (unlikely(error
)) {
3279 if (error
== -EOPENSTALE
) {
3280 if (flags
& LOOKUP_RCU
)
3285 file
= ERR_PTR(error
);
3290 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3291 const struct open_flags
*op
)
3293 struct nameidata nd
;
3294 int flags
= op
->lookup_flags
;
3297 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
3298 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3299 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
3300 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3301 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
3305 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3306 const char *name
, const struct open_flags
*op
)
3308 struct nameidata nd
;
3310 struct filename
*filename
;
3311 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3314 nd
.root
.dentry
= dentry
;
3316 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3317 return ERR_PTR(-ELOOP
);
3319 filename
= getname_kernel(name
);
3320 if (unlikely(IS_ERR(filename
)))
3321 return ERR_CAST(filename
);
3323 file
= path_openat(-1, filename
, &nd
, op
, flags
| LOOKUP_RCU
);
3324 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3325 file
= path_openat(-1, filename
, &nd
, op
, flags
);
3326 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3327 file
= path_openat(-1, filename
, &nd
, op
, flags
| LOOKUP_REVAL
);
3332 static struct dentry
*filename_create(int dfd
, struct filename
*name
,
3333 struct path
*path
, unsigned int lookup_flags
)
3335 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3336 struct nameidata nd
;
3339 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3342 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3343 * other flags passed in are ignored!
3345 lookup_flags
&= LOOKUP_REVAL
;
3347 error
= filename_lookup(dfd
, name
, LOOKUP_PARENT
|lookup_flags
, &nd
);
3349 return ERR_PTR(error
);
3352 * Yucky last component or no last component at all?
3353 * (foo/., foo/.., /////)
3355 if (nd
.last_type
!= LAST_NORM
)
3357 nd
.flags
&= ~LOOKUP_PARENT
;
3358 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3360 /* don't fail immediately if it's r/o, at least try to report other errors */
3361 err2
= mnt_want_write(nd
.path
.mnt
);
3363 * Do the final lookup.
3365 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3366 dentry
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, nd
.flags
);
3371 if (d_is_positive(dentry
))
3375 * Special case - lookup gave negative, but... we had foo/bar/
3376 * From the vfs_mknod() POV we just have a negative dentry -
3377 * all is fine. Let's be bastards - you had / on the end, you've
3378 * been asking for (non-existent) directory. -ENOENT for you.
3380 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
3384 if (unlikely(err2
)) {
3392 dentry
= ERR_PTR(error
);
3394 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3396 mnt_drop_write(nd
.path
.mnt
);
3402 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3403 struct path
*path
, unsigned int lookup_flags
)
3405 struct filename
*filename
= getname_kernel(pathname
);
3408 if (IS_ERR(filename
))
3409 return ERR_CAST(filename
);
3410 res
= filename_create(dfd
, filename
, path
, lookup_flags
);
3414 EXPORT_SYMBOL(kern_path_create
);
3416 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3419 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
3420 mnt_drop_write(path
->mnt
);
3423 EXPORT_SYMBOL(done_path_create
);
3425 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3426 struct path
*path
, unsigned int lookup_flags
)
3428 struct filename
*tmp
= getname(pathname
);
3431 return ERR_CAST(tmp
);
3432 res
= filename_create(dfd
, tmp
, path
, lookup_flags
);
3436 EXPORT_SYMBOL(user_path_create
);
3438 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3440 int error
= may_create(dir
, dentry
);
3445 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3448 if (!dir
->i_op
->mknod
)
3451 error
= devcgroup_inode_mknod(mode
, dev
);
3455 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3459 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3461 fsnotify_create(dir
, dentry
);
3464 EXPORT_SYMBOL(vfs_mknod
);
3466 static int may_mknod(umode_t mode
)
3468 switch (mode
& S_IFMT
) {
3474 case 0: /* zero mode translates to S_IFREG */
3483 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3486 struct dentry
*dentry
;
3489 unsigned int lookup_flags
= 0;
3491 error
= may_mknod(mode
);
3495 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3497 return PTR_ERR(dentry
);
3499 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3500 mode
&= ~current_umask();
3501 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3504 switch (mode
& S_IFMT
) {
3505 case 0: case S_IFREG
:
3506 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3508 case S_IFCHR
: case S_IFBLK
:
3509 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3510 new_decode_dev(dev
));
3512 case S_IFIFO
: case S_IFSOCK
:
3513 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3517 done_path_create(&path
, dentry
);
3518 if (retry_estale(error
, lookup_flags
)) {
3519 lookup_flags
|= LOOKUP_REVAL
;
3525 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3527 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3530 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3532 int error
= may_create(dir
, dentry
);
3533 unsigned max_links
= dir
->i_sb
->s_max_links
;
3538 if (!dir
->i_op
->mkdir
)
3541 mode
&= (S_IRWXUGO
|S_ISVTX
);
3542 error
= security_inode_mkdir(dir
, dentry
, mode
);
3546 if (max_links
&& dir
->i_nlink
>= max_links
)
3549 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3551 fsnotify_mkdir(dir
, dentry
);
3554 EXPORT_SYMBOL(vfs_mkdir
);
3556 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3558 struct dentry
*dentry
;
3561 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3564 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3566 return PTR_ERR(dentry
);
3568 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3569 mode
&= ~current_umask();
3570 error
= security_path_mkdir(&path
, dentry
, mode
);
3572 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3573 done_path_create(&path
, dentry
);
3574 if (retry_estale(error
, lookup_flags
)) {
3575 lookup_flags
|= LOOKUP_REVAL
;
3581 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3583 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3587 * The dentry_unhash() helper will try to drop the dentry early: we
3588 * should have a usage count of 1 if we're the only user of this
3589 * dentry, and if that is true (possibly after pruning the dcache),
3590 * then we drop the dentry now.
3592 * A low-level filesystem can, if it choses, legally
3595 * if (!d_unhashed(dentry))
3598 * if it cannot handle the case of removing a directory
3599 * that is still in use by something else..
3601 void dentry_unhash(struct dentry
*dentry
)
3603 shrink_dcache_parent(dentry
);
3604 spin_lock(&dentry
->d_lock
);
3605 if (dentry
->d_lockref
.count
== 1)
3607 spin_unlock(&dentry
->d_lock
);
3609 EXPORT_SYMBOL(dentry_unhash
);
3611 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3613 int error
= may_delete(dir
, dentry
, 1);
3618 if (!dir
->i_op
->rmdir
)
3622 mutex_lock(&dentry
->d_inode
->i_mutex
);
3625 if (is_local_mountpoint(dentry
))
3628 error
= security_inode_rmdir(dir
, dentry
);
3632 shrink_dcache_parent(dentry
);
3633 error
= dir
->i_op
->rmdir(dir
, dentry
);
3637 dentry
->d_inode
->i_flags
|= S_DEAD
;
3639 detach_mounts(dentry
);
3642 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3648 EXPORT_SYMBOL(vfs_rmdir
);
3650 static long do_rmdir(int dfd
, const char __user
*pathname
)
3653 struct filename
*name
;
3654 struct dentry
*dentry
;
3658 unsigned int lookup_flags
= 0;
3660 name
= user_path_parent(dfd
, pathname
,
3661 &path
, &last
, &type
, lookup_flags
);
3663 return PTR_ERR(name
);
3677 error
= mnt_want_write(path
.mnt
);
3681 mutex_lock_nested(&path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3682 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3683 error
= PTR_ERR(dentry
);
3686 if (!dentry
->d_inode
) {
3690 error
= security_path_rmdir(&path
, dentry
);
3693 error
= vfs_rmdir(path
.dentry
->d_inode
, dentry
);
3697 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
3698 mnt_drop_write(path
.mnt
);
3702 if (retry_estale(error
, lookup_flags
)) {
3703 lookup_flags
|= LOOKUP_REVAL
;
3709 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3711 return do_rmdir(AT_FDCWD
, pathname
);
3715 * vfs_unlink - unlink a filesystem object
3716 * @dir: parent directory
3718 * @delegated_inode: returns victim inode, if the inode is delegated.
3720 * The caller must hold dir->i_mutex.
3722 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3723 * return a reference to the inode in delegated_inode. The caller
3724 * should then break the delegation on that inode and retry. Because
3725 * breaking a delegation may take a long time, the caller should drop
3726 * dir->i_mutex before doing so.
3728 * Alternatively, a caller may pass NULL for delegated_inode. This may
3729 * be appropriate for callers that expect the underlying filesystem not
3730 * to be NFS exported.
3732 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3734 struct inode
*target
= dentry
->d_inode
;
3735 int error
= may_delete(dir
, dentry
, 0);
3740 if (!dir
->i_op
->unlink
)
3743 mutex_lock(&target
->i_mutex
);
3744 if (is_local_mountpoint(dentry
))
3747 error
= security_inode_unlink(dir
, dentry
);
3749 error
= try_break_deleg(target
, delegated_inode
);
3752 error
= dir
->i_op
->unlink(dir
, dentry
);
3755 detach_mounts(dentry
);
3760 mutex_unlock(&target
->i_mutex
);
3762 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3763 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3764 fsnotify_link_count(target
);
3770 EXPORT_SYMBOL(vfs_unlink
);
3773 * Make sure that the actual truncation of the file will occur outside its
3774 * directory's i_mutex. Truncate can take a long time if there is a lot of
3775 * writeout happening, and we don't want to prevent access to the directory
3776 * while waiting on the I/O.
3778 static long do_unlinkat(int dfd
, const char __user
*pathname
)
3781 struct filename
*name
;
3782 struct dentry
*dentry
;
3786 struct inode
*inode
= NULL
;
3787 struct inode
*delegated_inode
= NULL
;
3788 unsigned int lookup_flags
= 0;
3790 name
= user_path_parent(dfd
, pathname
,
3791 &path
, &last
, &type
, lookup_flags
);
3793 return PTR_ERR(name
);
3796 if (type
!= LAST_NORM
)
3799 error
= mnt_want_write(path
.mnt
);
3803 mutex_lock_nested(&path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3804 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3805 error
= PTR_ERR(dentry
);
3806 if (!IS_ERR(dentry
)) {
3807 /* Why not before? Because we want correct error value */
3808 if (last
.name
[last
.len
])
3810 inode
= dentry
->d_inode
;
3811 if (d_is_negative(dentry
))
3814 error
= security_path_unlink(&path
, dentry
);
3817 error
= vfs_unlink(path
.dentry
->d_inode
, dentry
, &delegated_inode
);
3821 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
3823 iput(inode
); /* truncate the inode here */
3825 if (delegated_inode
) {
3826 error
= break_deleg_wait(&delegated_inode
);
3830 mnt_drop_write(path
.mnt
);
3834 if (retry_estale(error
, lookup_flags
)) {
3835 lookup_flags
|= LOOKUP_REVAL
;
3842 if (d_is_negative(dentry
))
3844 else if (d_is_dir(dentry
))
3851 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
3853 if ((flag
& ~AT_REMOVEDIR
) != 0)
3856 if (flag
& AT_REMOVEDIR
)
3857 return do_rmdir(dfd
, pathname
);
3859 return do_unlinkat(dfd
, pathname
);
3862 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
3864 return do_unlinkat(AT_FDCWD
, pathname
);
3867 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
3869 int error
= may_create(dir
, dentry
);
3874 if (!dir
->i_op
->symlink
)
3877 error
= security_inode_symlink(dir
, dentry
, oldname
);
3881 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
3883 fsnotify_create(dir
, dentry
);
3886 EXPORT_SYMBOL(vfs_symlink
);
3888 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
3889 int, newdfd
, const char __user
*, newname
)
3892 struct filename
*from
;
3893 struct dentry
*dentry
;
3895 unsigned int lookup_flags
= 0;
3897 from
= getname(oldname
);
3899 return PTR_ERR(from
);
3901 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
3902 error
= PTR_ERR(dentry
);
3906 error
= security_path_symlink(&path
, dentry
, from
->name
);
3908 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
3909 done_path_create(&path
, dentry
);
3910 if (retry_estale(error
, lookup_flags
)) {
3911 lookup_flags
|= LOOKUP_REVAL
;
3919 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
3921 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
3925 * vfs_link - create a new link
3926 * @old_dentry: object to be linked
3928 * @new_dentry: where to create the new link
3929 * @delegated_inode: returns inode needing a delegation break
3931 * The caller must hold dir->i_mutex
3933 * If vfs_link discovers a delegation on the to-be-linked file in need
3934 * of breaking, it will return -EWOULDBLOCK and return a reference to the
3935 * inode in delegated_inode. The caller should then break the delegation
3936 * and retry. Because breaking a delegation may take a long time, the
3937 * caller should drop the i_mutex before doing so.
3939 * Alternatively, a caller may pass NULL for delegated_inode. This may
3940 * be appropriate for callers that expect the underlying filesystem not
3941 * to be NFS exported.
3943 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
3945 struct inode
*inode
= old_dentry
->d_inode
;
3946 unsigned max_links
= dir
->i_sb
->s_max_links
;
3952 error
= may_create(dir
, new_dentry
);
3956 if (dir
->i_sb
!= inode
->i_sb
)
3960 * A link to an append-only or immutable file cannot be created.
3962 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3964 if (!dir
->i_op
->link
)
3966 if (S_ISDIR(inode
->i_mode
))
3969 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3973 mutex_lock(&inode
->i_mutex
);
3974 /* Make sure we don't allow creating hardlink to an unlinked file */
3975 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
3977 else if (max_links
&& inode
->i_nlink
>= max_links
)
3980 error
= try_break_deleg(inode
, delegated_inode
);
3982 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3985 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
3986 spin_lock(&inode
->i_lock
);
3987 inode
->i_state
&= ~I_LINKABLE
;
3988 spin_unlock(&inode
->i_lock
);
3990 mutex_unlock(&inode
->i_mutex
);
3992 fsnotify_link(dir
, inode
, new_dentry
);
3995 EXPORT_SYMBOL(vfs_link
);
3998 * Hardlinks are often used in delicate situations. We avoid
3999 * security-related surprises by not following symlinks on the
4002 * We don't follow them on the oldname either to be compatible
4003 * with linux 2.0, and to avoid hard-linking to directories
4004 * and other special files. --ADM
4006 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
4007 int, newdfd
, const char __user
*, newname
, int, flags
)
4009 struct dentry
*new_dentry
;
4010 struct path old_path
, new_path
;
4011 struct inode
*delegated_inode
= NULL
;
4015 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
4018 * To use null names we require CAP_DAC_READ_SEARCH
4019 * This ensures that not everyone will be able to create
4020 * handlink using the passed filedescriptor.
4022 if (flags
& AT_EMPTY_PATH
) {
4023 if (!capable(CAP_DAC_READ_SEARCH
))
4028 if (flags
& AT_SYMLINK_FOLLOW
)
4029 how
|= LOOKUP_FOLLOW
;
4031 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
4035 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
4036 (how
& LOOKUP_REVAL
));
4037 error
= PTR_ERR(new_dentry
);
4038 if (IS_ERR(new_dentry
))
4042 if (old_path
.mnt
!= new_path
.mnt
)
4044 error
= may_linkat(&old_path
);
4045 if (unlikely(error
))
4047 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
4050 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
4052 done_path_create(&new_path
, new_dentry
);
4053 if (delegated_inode
) {
4054 error
= break_deleg_wait(&delegated_inode
);
4056 path_put(&old_path
);
4060 if (retry_estale(error
, how
)) {
4061 path_put(&old_path
);
4062 how
|= LOOKUP_REVAL
;
4066 path_put(&old_path
);
4071 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
4073 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4077 * vfs_rename - rename a filesystem object
4078 * @old_dir: parent of source
4079 * @old_dentry: source
4080 * @new_dir: parent of destination
4081 * @new_dentry: destination
4082 * @delegated_inode: returns an inode needing a delegation break
4083 * @flags: rename flags
4085 * The caller must hold multiple mutexes--see lock_rename()).
4087 * If vfs_rename discovers a delegation in need of breaking at either
4088 * the source or destination, it will return -EWOULDBLOCK and return a
4089 * reference to the inode in delegated_inode. The caller should then
4090 * break the delegation and retry. Because breaking a delegation may
4091 * take a long time, the caller should drop all locks before doing
4094 * Alternatively, a caller may pass NULL for delegated_inode. This may
4095 * be appropriate for callers that expect the underlying filesystem not
4096 * to be NFS exported.
4098 * The worst of all namespace operations - renaming directory. "Perverted"
4099 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4101 * a) we can get into loop creation.
4102 * b) race potential - two innocent renames can create a loop together.
4103 * That's where 4.4 screws up. Current fix: serialization on
4104 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4106 * c) we have to lock _four_ objects - parents and victim (if it exists),
4107 * and source (if it is not a directory).
4108 * And that - after we got ->i_mutex on parents (until then we don't know
4109 * whether the target exists). Solution: try to be smart with locking
4110 * order for inodes. We rely on the fact that tree topology may change
4111 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4112 * move will be locked. Thus we can rank directories by the tree
4113 * (ancestors first) and rank all non-directories after them.
4114 * That works since everybody except rename does "lock parent, lookup,
4115 * lock child" and rename is under ->s_vfs_rename_mutex.
4116 * HOWEVER, it relies on the assumption that any object with ->lookup()
4117 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4118 * we'd better make sure that there's no link(2) for them.
4119 * d) conversion from fhandle to dentry may come in the wrong moment - when
4120 * we are removing the target. Solution: we will have to grab ->i_mutex
4121 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4122 * ->i_mutex on parents, which works but leads to some truly excessive
4125 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4126 struct inode
*new_dir
, struct dentry
*new_dentry
,
4127 struct inode
**delegated_inode
, unsigned int flags
)
4130 bool is_dir
= d_is_dir(old_dentry
);
4131 const unsigned char *old_name
;
4132 struct inode
*source
= old_dentry
->d_inode
;
4133 struct inode
*target
= new_dentry
->d_inode
;
4134 bool new_is_dir
= false;
4135 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4137 if (source
== target
)
4140 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4145 error
= may_create(new_dir
, new_dentry
);
4147 new_is_dir
= d_is_dir(new_dentry
);
4149 if (!(flags
& RENAME_EXCHANGE
))
4150 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4152 error
= may_delete(new_dir
, new_dentry
, new_is_dir
);
4157 if (!old_dir
->i_op
->rename
&& !old_dir
->i_op
->rename2
)
4160 if (flags
&& !old_dir
->i_op
->rename2
)
4164 * If we are going to change the parent - check write permissions,
4165 * we'll need to flip '..'.
4167 if (new_dir
!= old_dir
) {
4169 error
= inode_permission(source
, MAY_WRITE
);
4173 if ((flags
& RENAME_EXCHANGE
) && new_is_dir
) {
4174 error
= inode_permission(target
, MAY_WRITE
);
4180 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
,
4185 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
4187 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4188 lock_two_nondirectories(source
, target
);
4190 mutex_lock(&target
->i_mutex
);
4193 if (is_local_mountpoint(old_dentry
) || is_local_mountpoint(new_dentry
))
4196 if (max_links
&& new_dir
!= old_dir
) {
4198 if (is_dir
&& !new_is_dir
&& new_dir
->i_nlink
>= max_links
)
4200 if ((flags
& RENAME_EXCHANGE
) && !is_dir
&& new_is_dir
&&
4201 old_dir
->i_nlink
>= max_links
)
4204 if (is_dir
&& !(flags
& RENAME_EXCHANGE
) && target
)
4205 shrink_dcache_parent(new_dentry
);
4207 error
= try_break_deleg(source
, delegated_inode
);
4211 if (target
&& !new_is_dir
) {
4212 error
= try_break_deleg(target
, delegated_inode
);
4216 if (!old_dir
->i_op
->rename2
) {
4217 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
,
4218 new_dir
, new_dentry
);
4220 WARN_ON(old_dir
->i_op
->rename
!= NULL
);
4221 error
= old_dir
->i_op
->rename2(old_dir
, old_dentry
,
4222 new_dir
, new_dentry
, flags
);
4227 if (!(flags
& RENAME_EXCHANGE
) && target
) {
4229 target
->i_flags
|= S_DEAD
;
4230 dont_mount(new_dentry
);
4231 detach_mounts(new_dentry
);
4233 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
)) {
4234 if (!(flags
& RENAME_EXCHANGE
))
4235 d_move(old_dentry
, new_dentry
);
4237 d_exchange(old_dentry
, new_dentry
);
4240 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4241 unlock_two_nondirectories(source
, target
);
4243 mutex_unlock(&target
->i_mutex
);
4246 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
4247 !(flags
& RENAME_EXCHANGE
) ? target
: NULL
, old_dentry
);
4248 if (flags
& RENAME_EXCHANGE
) {
4249 fsnotify_move(new_dir
, old_dir
, old_dentry
->d_name
.name
,
4250 new_is_dir
, NULL
, new_dentry
);
4253 fsnotify_oldname_free(old_name
);
4257 EXPORT_SYMBOL(vfs_rename
);
4259 SYSCALL_DEFINE5(renameat2
, int, olddfd
, const char __user
*, oldname
,
4260 int, newdfd
, const char __user
*, newname
, unsigned int, flags
)
4262 struct dentry
*old_dentry
, *new_dentry
;
4263 struct dentry
*trap
;
4264 struct path old_path
, new_path
;
4265 struct qstr old_last
, new_last
;
4266 int old_type
, new_type
;
4267 struct inode
*delegated_inode
= NULL
;
4268 struct filename
*from
;
4269 struct filename
*to
;
4270 unsigned int lookup_flags
= 0, target_flags
= LOOKUP_RENAME_TARGET
;
4271 bool should_retry
= false;
4274 if (flags
& ~(RENAME_NOREPLACE
| RENAME_EXCHANGE
| RENAME_WHITEOUT
))
4277 if ((flags
& (RENAME_NOREPLACE
| RENAME_WHITEOUT
)) &&
4278 (flags
& RENAME_EXCHANGE
))
4281 if ((flags
& RENAME_WHITEOUT
) && !capable(CAP_MKNOD
))
4284 if (flags
& RENAME_EXCHANGE
)
4288 from
= user_path_parent(olddfd
, oldname
,
4289 &old_path
, &old_last
, &old_type
, lookup_flags
);
4291 error
= PTR_ERR(from
);
4295 to
= user_path_parent(newdfd
, newname
,
4296 &new_path
, &new_last
, &new_type
, lookup_flags
);
4298 error
= PTR_ERR(to
);
4303 if (old_path
.mnt
!= new_path
.mnt
)
4307 if (old_type
!= LAST_NORM
)
4310 if (flags
& RENAME_NOREPLACE
)
4312 if (new_type
!= LAST_NORM
)
4315 error
= mnt_want_write(old_path
.mnt
);
4320 trap
= lock_rename(new_path
.dentry
, old_path
.dentry
);
4322 old_dentry
= __lookup_hash(&old_last
, old_path
.dentry
, lookup_flags
);
4323 error
= PTR_ERR(old_dentry
);
4324 if (IS_ERR(old_dentry
))
4326 /* source must exist */
4328 if (d_is_negative(old_dentry
))
4330 new_dentry
= __lookup_hash(&new_last
, new_path
.dentry
, lookup_flags
| target_flags
);
4331 error
= PTR_ERR(new_dentry
);
4332 if (IS_ERR(new_dentry
))
4335 if ((flags
& RENAME_NOREPLACE
) && d_is_positive(new_dentry
))
4337 if (flags
& RENAME_EXCHANGE
) {
4339 if (d_is_negative(new_dentry
))
4342 if (!d_is_dir(new_dentry
)) {
4344 if (new_last
.name
[new_last
.len
])
4348 /* unless the source is a directory trailing slashes give -ENOTDIR */
4349 if (!d_is_dir(old_dentry
)) {
4351 if (old_last
.name
[old_last
.len
])
4353 if (!(flags
& RENAME_EXCHANGE
) && new_last
.name
[new_last
.len
])
4356 /* source should not be ancestor of target */
4358 if (old_dentry
== trap
)
4360 /* target should not be an ancestor of source */
4361 if (!(flags
& RENAME_EXCHANGE
))
4363 if (new_dentry
== trap
)
4366 error
= security_path_rename(&old_path
, old_dentry
,
4367 &new_path
, new_dentry
, flags
);
4370 error
= vfs_rename(old_path
.dentry
->d_inode
, old_dentry
,
4371 new_path
.dentry
->d_inode
, new_dentry
,
4372 &delegated_inode
, flags
);
4378 unlock_rename(new_path
.dentry
, old_path
.dentry
);
4379 if (delegated_inode
) {
4380 error
= break_deleg_wait(&delegated_inode
);
4384 mnt_drop_write(old_path
.mnt
);
4386 if (retry_estale(error
, lookup_flags
))
4387 should_retry
= true;
4388 path_put(&new_path
);
4391 path_put(&old_path
);
4394 should_retry
= false;
4395 lookup_flags
|= LOOKUP_REVAL
;
4402 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4403 int, newdfd
, const char __user
*, newname
)
4405 return sys_renameat2(olddfd
, oldname
, newdfd
, newname
, 0);
4408 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4410 return sys_renameat2(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4413 int vfs_whiteout(struct inode
*dir
, struct dentry
*dentry
)
4415 int error
= may_create(dir
, dentry
);
4419 if (!dir
->i_op
->mknod
)
4422 return dir
->i_op
->mknod(dir
, dentry
,
4423 S_IFCHR
| WHITEOUT_MODE
, WHITEOUT_DEV
);
4425 EXPORT_SYMBOL(vfs_whiteout
);
4427 int readlink_copy(char __user
*buffer
, int buflen
, const char *link
)
4429 int len
= PTR_ERR(link
);
4434 if (len
> (unsigned) buflen
)
4436 if (copy_to_user(buffer
, link
, len
))
4441 EXPORT_SYMBOL(readlink_copy
);
4444 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4445 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4446 * using) it for any given inode is up to filesystem.
4448 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4451 const char *link
= dentry
->d_inode
->i_link
;
4455 link
= dentry
->d_inode
->i_op
->follow_link(dentry
, &cookie
, NULL
);
4457 return PTR_ERR(link
);
4459 res
= readlink_copy(buffer
, buflen
, link
);
4460 if (cookie
&& dentry
->d_inode
->i_op
->put_link
)
4461 dentry
->d_inode
->i_op
->put_link(dentry
, cookie
);
4464 EXPORT_SYMBOL(generic_readlink
);
4466 /* get the link contents into pagecache */
4467 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
4471 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
4472 page
= read_mapping_page(mapping
, 0, NULL
);
4477 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
4481 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4483 struct page
*page
= NULL
;
4484 int res
= readlink_copy(buffer
, buflen
, page_getlink(dentry
, &page
));
4487 page_cache_release(page
);
4491 EXPORT_SYMBOL(page_readlink
);
4493 const char *page_follow_link_light(struct dentry
*dentry
, void **cookie
, struct nameidata
*nd
)
4495 struct page
*page
= NULL
;
4496 char *res
= page_getlink(dentry
, &page
);
4501 EXPORT_SYMBOL(page_follow_link_light
);
4503 void page_put_link(struct dentry
*dentry
, void *cookie
)
4505 struct page
*page
= cookie
;
4507 page_cache_release(page
);
4509 EXPORT_SYMBOL(page_put_link
);
4512 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4514 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4516 struct address_space
*mapping
= inode
->i_mapping
;
4521 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
4523 flags
|= AOP_FLAG_NOFS
;
4526 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4527 flags
, &page
, &fsdata
);
4531 kaddr
= kmap_atomic(page
);
4532 memcpy(kaddr
, symname
, len
-1);
4533 kunmap_atomic(kaddr
);
4535 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4542 mark_inode_dirty(inode
);
4547 EXPORT_SYMBOL(__page_symlink
);
4549 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4551 return __page_symlink(inode
, symname
, len
,
4552 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
4554 EXPORT_SYMBOL(page_symlink
);
4556 const struct inode_operations page_symlink_inode_operations
= {
4557 .readlink
= generic_readlink
,
4558 .follow_link
= page_follow_link_light
,
4559 .put_link
= page_put_link
,
4561 EXPORT_SYMBOL(page_symlink_inode_operations
);