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.
121 void final_putname(struct filename
*name
)
123 if (name
->separate
) {
124 __putname(name
->name
);
131 #define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
133 static struct filename
*
134 getname_flags(const char __user
*filename
, int flags
, int *empty
)
136 struct filename
*result
, *err
;
141 result
= audit_reusename(filename
);
145 result
= __getname();
146 if (unlikely(!result
))
147 return ERR_PTR(-ENOMEM
);
150 * First, try to embed the struct filename inside the names_cache
153 kname
= (char *)result
+ sizeof(*result
);
154 result
->name
= kname
;
155 result
->separate
= false;
156 max
= EMBEDDED_NAME_MAX
;
159 len
= strncpy_from_user(kname
, filename
, max
);
160 if (unlikely(len
< 0)) {
166 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
167 * separate struct filename so we can dedicate the entire
168 * names_cache allocation for the pathname, and re-do the copy from
171 if (len
== EMBEDDED_NAME_MAX
&& max
== EMBEDDED_NAME_MAX
) {
172 kname
= (char *)result
;
174 result
= kzalloc(sizeof(*result
), GFP_KERNEL
);
176 err
= ERR_PTR(-ENOMEM
);
177 result
= (struct filename
*)kname
;
180 result
->name
= kname
;
181 result
->separate
= true;
186 /* The empty path is special. */
187 if (unlikely(!len
)) {
190 err
= ERR_PTR(-ENOENT
);
191 if (!(flags
& LOOKUP_EMPTY
))
195 err
= ERR_PTR(-ENAMETOOLONG
);
196 if (unlikely(len
>= PATH_MAX
))
199 result
->uptr
= filename
;
200 result
->aname
= NULL
;
201 audit_getname(result
);
205 final_putname(result
);
210 getname(const char __user
* filename
)
212 return getname_flags(filename
, 0, NULL
);
216 * The "getname_kernel()" interface doesn't do pathnames longer
217 * than EMBEDDED_NAME_MAX. Deal with it - you're a kernel user.
220 getname_kernel(const char * filename
)
222 struct filename
*result
;
226 len
= strlen(filename
);
227 if (len
>= EMBEDDED_NAME_MAX
)
228 return ERR_PTR(-ENAMETOOLONG
);
230 result
= __getname();
231 if (unlikely(!result
))
232 return ERR_PTR(-ENOMEM
);
234 kname
= (char *)result
+ sizeof(*result
);
235 result
->name
= kname
;
237 result
->aname
= NULL
;
238 result
->separate
= false;
240 strlcpy(kname
, filename
, EMBEDDED_NAME_MAX
);
244 #ifdef CONFIG_AUDITSYSCALL
245 void putname(struct filename
*name
)
247 if (unlikely(!audit_dummy_context()))
248 return audit_putname(name
);
253 static int check_acl(struct inode
*inode
, int mask
)
255 #ifdef CONFIG_FS_POSIX_ACL
256 struct posix_acl
*acl
;
258 if (mask
& MAY_NOT_BLOCK
) {
259 acl
= get_cached_acl_rcu(inode
, ACL_TYPE_ACCESS
);
262 /* no ->get_acl() calls in RCU mode... */
263 if (acl
== ACL_NOT_CACHED
)
265 return posix_acl_permission(inode
, acl
, mask
& ~MAY_NOT_BLOCK
);
268 acl
= get_acl(inode
, ACL_TYPE_ACCESS
);
272 int error
= posix_acl_permission(inode
, acl
, mask
);
273 posix_acl_release(acl
);
282 * This does the basic permission checking
284 static int acl_permission_check(struct inode
*inode
, int mask
)
286 unsigned int mode
= inode
->i_mode
;
288 if (likely(uid_eq(current_fsuid(), inode
->i_uid
)))
291 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
)) {
292 int error
= check_acl(inode
, mask
);
293 if (error
!= -EAGAIN
)
297 if (in_group_p(inode
->i_gid
))
302 * If the DACs are ok we don't need any capability check.
304 if ((mask
& ~mode
& (MAY_READ
| MAY_WRITE
| MAY_EXEC
)) == 0)
310 * generic_permission - check for access rights on a Posix-like filesystem
311 * @inode: inode to check access rights for
312 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
314 * Used to check for read/write/execute permissions on a file.
315 * We use "fsuid" for this, letting us set arbitrary permissions
316 * for filesystem access without changing the "normal" uids which
317 * are used for other things.
319 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
320 * request cannot be satisfied (eg. requires blocking or too much complexity).
321 * It would then be called again in ref-walk mode.
323 int generic_permission(struct inode
*inode
, int mask
)
328 * Do the basic permission checks.
330 ret
= acl_permission_check(inode
, mask
);
334 if (S_ISDIR(inode
->i_mode
)) {
335 /* DACs are overridable for directories */
336 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
338 if (!(mask
& MAY_WRITE
))
339 if (capable_wrt_inode_uidgid(inode
,
340 CAP_DAC_READ_SEARCH
))
345 * Read/write DACs are always overridable.
346 * Executable DACs are overridable when there is
347 * at least one exec bit set.
349 if (!(mask
& MAY_EXEC
) || (inode
->i_mode
& S_IXUGO
))
350 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
354 * Searching includes executable on directories, else just read.
356 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
357 if (mask
== MAY_READ
)
358 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_READ_SEARCH
))
363 EXPORT_SYMBOL(generic_permission
);
366 * We _really_ want to just do "generic_permission()" without
367 * even looking at the inode->i_op values. So we keep a cache
368 * flag in inode->i_opflags, that says "this has not special
369 * permission function, use the fast case".
371 static inline int do_inode_permission(struct inode
*inode
, int mask
)
373 if (unlikely(!(inode
->i_opflags
& IOP_FASTPERM
))) {
374 if (likely(inode
->i_op
->permission
))
375 return inode
->i_op
->permission(inode
, mask
);
377 /* This gets set once for the inode lifetime */
378 spin_lock(&inode
->i_lock
);
379 inode
->i_opflags
|= IOP_FASTPERM
;
380 spin_unlock(&inode
->i_lock
);
382 return generic_permission(inode
, mask
);
386 * __inode_permission - Check for access rights to a given inode
387 * @inode: Inode to check permission on
388 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
390 * Check for read/write/execute permissions on an inode.
392 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
394 * This does not check for a read-only file system. You probably want
395 * inode_permission().
397 int __inode_permission(struct inode
*inode
, int mask
)
401 if (unlikely(mask
& MAY_WRITE
)) {
403 * Nobody gets write access to an immutable file.
405 if (IS_IMMUTABLE(inode
))
409 retval
= do_inode_permission(inode
, mask
);
413 retval
= devcgroup_inode_permission(inode
, mask
);
417 return security_inode_permission(inode
, mask
);
421 * sb_permission - Check superblock-level permissions
422 * @sb: Superblock of inode to check permission on
423 * @inode: Inode to check permission on
424 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
426 * Separate out file-system wide checks from inode-specific permission checks.
428 static int sb_permission(struct super_block
*sb
, struct inode
*inode
, int mask
)
430 if (unlikely(mask
& MAY_WRITE
)) {
431 umode_t mode
= inode
->i_mode
;
433 /* Nobody gets write access to a read-only fs. */
434 if ((sb
->s_flags
& MS_RDONLY
) &&
435 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
442 * inode_permission - Check for access rights to a given inode
443 * @inode: Inode to check permission on
444 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
446 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
447 * this, letting us set arbitrary permissions for filesystem access without
448 * changing the "normal" UIDs which are used for other things.
450 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
452 int inode_permission(struct inode
*inode
, int mask
)
456 retval
= sb_permission(inode
->i_sb
, inode
, mask
);
459 return __inode_permission(inode
, mask
);
461 EXPORT_SYMBOL(inode_permission
);
464 * path_get - get a reference to a path
465 * @path: path to get the reference to
467 * Given a path increment the reference count to the dentry and the vfsmount.
469 void path_get(const struct path
*path
)
474 EXPORT_SYMBOL(path_get
);
477 * path_put - put a reference to a path
478 * @path: path to put the reference to
480 * Given a path decrement the reference count to the dentry and the vfsmount.
482 void path_put(const struct path
*path
)
487 EXPORT_SYMBOL(path_put
);
490 * Path walking has 2 modes, rcu-walk and ref-walk (see
491 * Documentation/filesystems/path-lookup.txt). In situations when we can't
492 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
493 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
494 * mode. Refcounts are grabbed at the last known good point before rcu-walk
495 * got stuck, so ref-walk may continue from there. If this is not successful
496 * (eg. a seqcount has changed), then failure is returned and it's up to caller
497 * to restart the path walk from the beginning in ref-walk mode.
501 * unlazy_walk - try to switch to ref-walk mode.
502 * @nd: nameidata pathwalk data
503 * @dentry: child of nd->path.dentry or NULL
504 * Returns: 0 on success, -ECHILD on failure
506 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
507 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
508 * @nd or NULL. Must be called from rcu-walk context.
510 static int unlazy_walk(struct nameidata
*nd
, struct dentry
*dentry
)
512 struct fs_struct
*fs
= current
->fs
;
513 struct dentry
*parent
= nd
->path
.dentry
;
515 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
518 * After legitimizing the bastards, terminate_walk()
519 * will do the right thing for non-RCU mode, and all our
520 * subsequent exit cases should rcu_read_unlock()
521 * before returning. Do vfsmount first; if dentry
522 * can't be legitimized, just set nd->path.dentry to NULL
523 * and rely on dput(NULL) being a no-op.
525 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
))
527 nd
->flags
&= ~LOOKUP_RCU
;
529 if (!lockref_get_not_dead(&parent
->d_lockref
)) {
530 nd
->path
.dentry
= NULL
;
535 * For a negative lookup, the lookup sequence point is the parents
536 * sequence point, and it only needs to revalidate the parent dentry.
538 * For a positive lookup, we need to move both the parent and the
539 * dentry from the RCU domain to be properly refcounted. And the
540 * sequence number in the dentry validates *both* dentry counters,
541 * since we checked the sequence number of the parent after we got
542 * the child sequence number. So we know the parent must still
543 * be valid if the child sequence number is still valid.
546 if (read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
548 BUG_ON(nd
->inode
!= parent
->d_inode
);
550 if (!lockref_get_not_dead(&dentry
->d_lockref
))
552 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
))
557 * Sequence counts matched. Now make sure that the root is
558 * still valid and get it if required.
560 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
561 spin_lock(&fs
->lock
);
562 if (nd
->root
.mnt
!= fs
->root
.mnt
|| nd
->root
.dentry
!= fs
->root
.dentry
)
563 goto unlock_and_drop_dentry
;
565 spin_unlock(&fs
->lock
);
571 unlock_and_drop_dentry
:
572 spin_unlock(&fs
->lock
);
580 if (!(nd
->flags
& LOOKUP_ROOT
))
585 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
587 return dentry
->d_op
->d_revalidate(dentry
, flags
);
591 * complete_walk - successful completion of path walk
592 * @nd: pointer nameidata
594 * If we had been in RCU mode, drop out of it and legitimize nd->path.
595 * Revalidate the final result, unless we'd already done that during
596 * the path walk or the filesystem doesn't ask for it. Return 0 on
597 * success, -error on failure. In case of failure caller does not
598 * need to drop nd->path.
600 static int complete_walk(struct nameidata
*nd
)
602 struct dentry
*dentry
= nd
->path
.dentry
;
605 if (nd
->flags
& LOOKUP_RCU
) {
606 nd
->flags
&= ~LOOKUP_RCU
;
607 if (!(nd
->flags
& LOOKUP_ROOT
))
610 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
)) {
614 if (unlikely(!lockref_get_not_dead(&dentry
->d_lockref
))) {
616 mntput(nd
->path
.mnt
);
619 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
)) {
622 mntput(nd
->path
.mnt
);
628 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
631 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
634 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
645 static __always_inline
void set_root(struct nameidata
*nd
)
647 get_fs_root(current
->fs
, &nd
->root
);
650 static int link_path_walk(const char *, struct nameidata
*);
652 static __always_inline
unsigned set_root_rcu(struct nameidata
*nd
)
654 struct fs_struct
*fs
= current
->fs
;
658 seq
= read_seqcount_begin(&fs
->seq
);
660 res
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
661 } while (read_seqcount_retry(&fs
->seq
, seq
));
665 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
668 if (path
->mnt
!= nd
->path
.mnt
)
672 static inline void path_to_nameidata(const struct path
*path
,
673 struct nameidata
*nd
)
675 if (!(nd
->flags
& LOOKUP_RCU
)) {
676 dput(nd
->path
.dentry
);
677 if (nd
->path
.mnt
!= path
->mnt
)
678 mntput(nd
->path
.mnt
);
680 nd
->path
.mnt
= path
->mnt
;
681 nd
->path
.dentry
= path
->dentry
;
685 * Helper to directly jump to a known parsed path from ->follow_link,
686 * caller must have taken a reference to path beforehand.
688 void nd_jump_link(struct nameidata
*nd
, struct path
*path
)
693 nd
->inode
= nd
->path
.dentry
->d_inode
;
694 nd
->flags
|= LOOKUP_JUMPED
;
697 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
699 struct inode
*inode
= link
->dentry
->d_inode
;
700 if (inode
->i_op
->put_link
)
701 inode
->i_op
->put_link(link
->dentry
, nd
, cookie
);
705 int sysctl_protected_symlinks __read_mostly
= 0;
706 int sysctl_protected_hardlinks __read_mostly
= 0;
709 * may_follow_link - Check symlink following for unsafe situations
710 * @link: The path of the symlink
711 * @nd: nameidata pathwalk data
713 * In the case of the sysctl_protected_symlinks sysctl being enabled,
714 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
715 * in a sticky world-writable directory. This is to protect privileged
716 * processes from failing races against path names that may change out
717 * from under them by way of other users creating malicious symlinks.
718 * It will permit symlinks to be followed only when outside a sticky
719 * world-writable directory, or when the uid of the symlink and follower
720 * match, or when the directory owner matches the symlink's owner.
722 * Returns 0 if following the symlink is allowed, -ve on error.
724 static inline int may_follow_link(struct path
*link
, struct nameidata
*nd
)
726 const struct inode
*inode
;
727 const struct inode
*parent
;
729 if (!sysctl_protected_symlinks
)
732 /* Allowed if owner and follower match. */
733 inode
= link
->dentry
->d_inode
;
734 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
737 /* Allowed if parent directory not sticky and world-writable. */
738 parent
= nd
->path
.dentry
->d_inode
;
739 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
742 /* Allowed if parent directory and link owner match. */
743 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
746 audit_log_link_denied("follow_link", link
);
747 path_put_conditional(link
, nd
);
753 * safe_hardlink_source - Check for safe hardlink conditions
754 * @inode: the source inode to hardlink from
756 * Return false if at least one of the following conditions:
757 * - inode is not a regular file
759 * - inode is setgid and group-exec
760 * - access failure for read and write
762 * Otherwise returns true.
764 static bool safe_hardlink_source(struct inode
*inode
)
766 umode_t mode
= inode
->i_mode
;
768 /* Special files should not get pinned to the filesystem. */
772 /* Setuid files should not get pinned to the filesystem. */
776 /* Executable setgid files should not get pinned to the filesystem. */
777 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
780 /* Hardlinking to unreadable or unwritable sources is dangerous. */
781 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
788 * may_linkat - Check permissions for creating a hardlink
789 * @link: the source to hardlink from
791 * Block hardlink when all of:
792 * - sysctl_protected_hardlinks enabled
793 * - fsuid does not match inode
794 * - hardlink source is unsafe (see safe_hardlink_source() above)
797 * Returns 0 if successful, -ve on error.
799 static int may_linkat(struct path
*link
)
801 const struct cred
*cred
;
804 if (!sysctl_protected_hardlinks
)
807 cred
= current_cred();
808 inode
= link
->dentry
->d_inode
;
810 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
811 * otherwise, it must be a safe source.
813 if (uid_eq(cred
->fsuid
, inode
->i_uid
) || safe_hardlink_source(inode
) ||
817 audit_log_link_denied("linkat", link
);
821 static __always_inline
int
822 follow_link(struct path
*link
, struct nameidata
*nd
, void **p
)
824 struct dentry
*dentry
= link
->dentry
;
828 BUG_ON(nd
->flags
& LOOKUP_RCU
);
830 if (link
->mnt
== nd
->path
.mnt
)
834 if (unlikely(current
->total_link_count
>= 40))
835 goto out_put_nd_path
;
838 current
->total_link_count
++;
841 nd_set_link(nd
, NULL
);
843 error
= security_inode_follow_link(link
->dentry
, nd
);
845 goto out_put_nd_path
;
847 nd
->last_type
= LAST_BIND
;
848 *p
= dentry
->d_inode
->i_op
->follow_link(dentry
, nd
);
851 goto out_put_nd_path
;
856 if (unlikely(IS_ERR(s
))) {
858 put_link(nd
, link
, *p
);
867 nd
->flags
|= LOOKUP_JUMPED
;
869 nd
->inode
= nd
->path
.dentry
->d_inode
;
870 error
= link_path_walk(s
, nd
);
872 put_link(nd
, link
, *p
);
884 static int follow_up_rcu(struct path
*path
)
886 struct mount
*mnt
= real_mount(path
->mnt
);
887 struct mount
*parent
;
888 struct dentry
*mountpoint
;
890 parent
= mnt
->mnt_parent
;
891 if (&parent
->mnt
== path
->mnt
)
893 mountpoint
= mnt
->mnt_mountpoint
;
894 path
->dentry
= mountpoint
;
895 path
->mnt
= &parent
->mnt
;
900 * follow_up - Find the mountpoint of path's vfsmount
902 * Given a path, find the mountpoint of its source file system.
903 * Replace @path with the path of the mountpoint in the parent mount.
906 * Return 1 if we went up a level and 0 if we were already at the
909 int follow_up(struct path
*path
)
911 struct mount
*mnt
= real_mount(path
->mnt
);
912 struct mount
*parent
;
913 struct dentry
*mountpoint
;
915 read_seqlock_excl(&mount_lock
);
916 parent
= mnt
->mnt_parent
;
918 read_sequnlock_excl(&mount_lock
);
921 mntget(&parent
->mnt
);
922 mountpoint
= dget(mnt
->mnt_mountpoint
);
923 read_sequnlock_excl(&mount_lock
);
925 path
->dentry
= mountpoint
;
927 path
->mnt
= &parent
->mnt
;
930 EXPORT_SYMBOL(follow_up
);
933 * Perform an automount
934 * - return -EISDIR to tell follow_managed() to stop and return the path we
937 static int follow_automount(struct path
*path
, unsigned flags
,
940 struct vfsmount
*mnt
;
943 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
946 /* We don't want to mount if someone's just doing a stat -
947 * unless they're stat'ing a directory and appended a '/' to
950 * We do, however, want to mount if someone wants to open or
951 * create a file of any type under the mountpoint, wants to
952 * traverse through the mountpoint or wants to open the
953 * mounted directory. Also, autofs may mark negative dentries
954 * as being automount points. These will need the attentions
955 * of the daemon to instantiate them before they can be used.
957 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
958 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
959 path
->dentry
->d_inode
)
962 current
->total_link_count
++;
963 if (current
->total_link_count
>= 40)
966 mnt
= path
->dentry
->d_op
->d_automount(path
);
969 * The filesystem is allowed to return -EISDIR here to indicate
970 * it doesn't want to automount. For instance, autofs would do
971 * this so that its userspace daemon can mount on this dentry.
973 * However, we can only permit this if it's a terminal point in
974 * the path being looked up; if it wasn't then the remainder of
975 * the path is inaccessible and we should say so.
977 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
982 if (!mnt
) /* mount collision */
986 /* lock_mount() may release path->mnt on error */
990 err
= finish_automount(mnt
, path
);
994 /* Someone else made a mount here whilst we were busy */
999 path
->dentry
= dget(mnt
->mnt_root
);
1008 * Handle a dentry that is managed in some way.
1009 * - Flagged for transit management (autofs)
1010 * - Flagged as mountpoint
1011 * - Flagged as automount point
1013 * This may only be called in refwalk mode.
1015 * Serialization is taken care of in namespace.c
1017 static int follow_managed(struct path
*path
, unsigned flags
)
1019 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1021 bool need_mntput
= false;
1024 /* Given that we're not holding a lock here, we retain the value in a
1025 * local variable for each dentry as we look at it so that we don't see
1026 * the components of that value change under us */
1027 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1028 managed
&= DCACHE_MANAGED_DENTRY
,
1029 unlikely(managed
!= 0)) {
1030 /* Allow the filesystem to manage the transit without i_mutex
1032 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1033 BUG_ON(!path
->dentry
->d_op
);
1034 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1035 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1040 /* Transit to a mounted filesystem. */
1041 if (managed
& DCACHE_MOUNTED
) {
1042 struct vfsmount
*mounted
= lookup_mnt(path
);
1047 path
->mnt
= mounted
;
1048 path
->dentry
= dget(mounted
->mnt_root
);
1053 /* Something is mounted on this dentry in another
1054 * namespace and/or whatever was mounted there in this
1055 * namespace got unmounted before lookup_mnt() could
1059 /* Handle an automount point */
1060 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1061 ret
= follow_automount(path
, flags
, &need_mntput
);
1067 /* We didn't change the current path point */
1071 if (need_mntput
&& path
->mnt
== mnt
)
1075 return ret
< 0 ? ret
: need_mntput
;
1078 int follow_down_one(struct path
*path
)
1080 struct vfsmount
*mounted
;
1082 mounted
= lookup_mnt(path
);
1086 path
->mnt
= mounted
;
1087 path
->dentry
= dget(mounted
->mnt_root
);
1092 EXPORT_SYMBOL(follow_down_one
);
1094 static inline int managed_dentry_rcu(struct dentry
*dentry
)
1096 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) ?
1097 dentry
->d_op
->d_manage(dentry
, true) : 0;
1101 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1102 * we meet a managed dentry that would need blocking.
1104 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1105 struct inode
**inode
)
1108 struct mount
*mounted
;
1110 * Don't forget we might have a non-mountpoint managed dentry
1111 * that wants to block transit.
1113 switch (managed_dentry_rcu(path
->dentry
)) {
1123 if (!d_mountpoint(path
->dentry
))
1124 return !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1126 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1129 path
->mnt
= &mounted
->mnt
;
1130 path
->dentry
= mounted
->mnt
.mnt_root
;
1131 nd
->flags
|= LOOKUP_JUMPED
;
1132 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1134 * Update the inode too. We don't need to re-check the
1135 * dentry sequence number here after this d_inode read,
1136 * because a mount-point is always pinned.
1138 *inode
= path
->dentry
->d_inode
;
1140 return !read_seqretry(&mount_lock
, nd
->m_seq
) &&
1141 !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1144 static int follow_dotdot_rcu(struct nameidata
*nd
)
1146 struct inode
*inode
= nd
->inode
;
1151 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1152 nd
->path
.mnt
== nd
->root
.mnt
) {
1155 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1156 struct dentry
*old
= nd
->path
.dentry
;
1157 struct dentry
*parent
= old
->d_parent
;
1160 inode
= parent
->d_inode
;
1161 seq
= read_seqcount_begin(&parent
->d_seq
);
1162 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1164 nd
->path
.dentry
= parent
;
1168 if (!follow_up_rcu(&nd
->path
))
1170 inode
= nd
->path
.dentry
->d_inode
;
1171 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1173 while (d_mountpoint(nd
->path
.dentry
)) {
1174 struct mount
*mounted
;
1175 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1178 nd
->path
.mnt
= &mounted
->mnt
;
1179 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1180 inode
= nd
->path
.dentry
->d_inode
;
1181 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1182 if (read_seqretry(&mount_lock
, nd
->m_seq
))
1189 nd
->flags
&= ~LOOKUP_RCU
;
1190 if (!(nd
->flags
& LOOKUP_ROOT
))
1191 nd
->root
.mnt
= NULL
;
1197 * Follow down to the covering mount currently visible to userspace. At each
1198 * point, the filesystem owning that dentry may be queried as to whether the
1199 * caller is permitted to proceed or not.
1201 int follow_down(struct path
*path
)
1206 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1207 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1208 /* Allow the filesystem to manage the transit without i_mutex
1211 * We indicate to the filesystem if someone is trying to mount
1212 * something here. This gives autofs the chance to deny anyone
1213 * other than its daemon the right to mount on its
1216 * The filesystem may sleep at this point.
1218 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1219 BUG_ON(!path
->dentry
->d_op
);
1220 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1221 ret
= path
->dentry
->d_op
->d_manage(
1222 path
->dentry
, false);
1224 return ret
== -EISDIR
? 0 : ret
;
1227 /* Transit to a mounted filesystem. */
1228 if (managed
& DCACHE_MOUNTED
) {
1229 struct vfsmount
*mounted
= lookup_mnt(path
);
1234 path
->mnt
= mounted
;
1235 path
->dentry
= dget(mounted
->mnt_root
);
1239 /* Don't handle automount points here */
1244 EXPORT_SYMBOL(follow_down
);
1247 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1249 static void follow_mount(struct path
*path
)
1251 while (d_mountpoint(path
->dentry
)) {
1252 struct vfsmount
*mounted
= lookup_mnt(path
);
1257 path
->mnt
= mounted
;
1258 path
->dentry
= dget(mounted
->mnt_root
);
1262 static void follow_dotdot(struct nameidata
*nd
)
1268 struct dentry
*old
= nd
->path
.dentry
;
1270 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1271 nd
->path
.mnt
== nd
->root
.mnt
) {
1274 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1275 /* rare case of legitimate dget_parent()... */
1276 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1280 if (!follow_up(&nd
->path
))
1283 follow_mount(&nd
->path
);
1284 nd
->inode
= nd
->path
.dentry
->d_inode
;
1288 * This looks up the name in dcache, possibly revalidates the old dentry and
1289 * allocates a new one if not found or not valid. In the need_lookup argument
1290 * returns whether i_op->lookup is necessary.
1292 * dir->d_inode->i_mutex must be held
1294 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1295 unsigned int flags
, bool *need_lookup
)
1297 struct dentry
*dentry
;
1300 *need_lookup
= false;
1301 dentry
= d_lookup(dir
, name
);
1303 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1304 error
= d_revalidate(dentry
, flags
);
1305 if (unlikely(error
<= 0)) {
1308 return ERR_PTR(error
);
1309 } else if (!d_invalidate(dentry
)) {
1318 dentry
= d_alloc(dir
, name
);
1319 if (unlikely(!dentry
))
1320 return ERR_PTR(-ENOMEM
);
1322 *need_lookup
= true;
1328 * Call i_op->lookup on the dentry. The dentry must be negative and
1331 * dir->d_inode->i_mutex must be held
1333 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1338 /* Don't create child dentry for a dead directory. */
1339 if (unlikely(IS_DEADDIR(dir
))) {
1341 return ERR_PTR(-ENOENT
);
1344 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1345 if (unlikely(old
)) {
1352 static struct dentry
*__lookup_hash(struct qstr
*name
,
1353 struct dentry
*base
, unsigned int flags
)
1356 struct dentry
*dentry
;
1358 dentry
= lookup_dcache(name
, base
, flags
, &need_lookup
);
1362 return lookup_real(base
->d_inode
, dentry
, flags
);
1366 * It's more convoluted than I'd like it to be, but... it's still fairly
1367 * small and for now I'd prefer to have fast path as straight as possible.
1368 * It _is_ time-critical.
1370 static int lookup_fast(struct nameidata
*nd
,
1371 struct path
*path
, struct inode
**inode
)
1373 struct vfsmount
*mnt
= nd
->path
.mnt
;
1374 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1380 * Rename seqlock is not required here because in the off chance
1381 * of a false negative due to a concurrent rename, we're going to
1382 * do the non-racy lookup, below.
1384 if (nd
->flags
& LOOKUP_RCU
) {
1386 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1391 * This sequence count validates that the inode matches
1392 * the dentry name information from lookup.
1394 *inode
= dentry
->d_inode
;
1395 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
1399 * This sequence count validates that the parent had no
1400 * changes while we did the lookup of the dentry above.
1402 * The memory barrier in read_seqcount_begin of child is
1403 * enough, we can use __read_seqcount_retry here.
1405 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1409 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1410 status
= d_revalidate(dentry
, nd
->flags
);
1411 if (unlikely(status
<= 0)) {
1412 if (status
!= -ECHILD
)
1418 path
->dentry
= dentry
;
1419 if (likely(__follow_mount_rcu(nd
, path
, inode
)))
1422 if (unlazy_walk(nd
, dentry
))
1425 dentry
= __d_lookup(parent
, &nd
->last
);
1428 if (unlikely(!dentry
))
1431 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1432 status
= d_revalidate(dentry
, nd
->flags
);
1433 if (unlikely(status
<= 0)) {
1438 if (!d_invalidate(dentry
)) {
1445 path
->dentry
= dentry
;
1446 err
= follow_managed(path
, nd
->flags
);
1447 if (unlikely(err
< 0)) {
1448 path_put_conditional(path
, nd
);
1452 nd
->flags
|= LOOKUP_JUMPED
;
1453 *inode
= path
->dentry
->d_inode
;
1460 /* Fast lookup failed, do it the slow way */
1461 static int lookup_slow(struct nameidata
*nd
, struct path
*path
)
1463 struct dentry
*dentry
, *parent
;
1466 parent
= nd
->path
.dentry
;
1467 BUG_ON(nd
->inode
!= parent
->d_inode
);
1469 mutex_lock(&parent
->d_inode
->i_mutex
);
1470 dentry
= __lookup_hash(&nd
->last
, parent
, nd
->flags
);
1471 mutex_unlock(&parent
->d_inode
->i_mutex
);
1473 return PTR_ERR(dentry
);
1474 path
->mnt
= nd
->path
.mnt
;
1475 path
->dentry
= dentry
;
1476 err
= follow_managed(path
, nd
->flags
);
1477 if (unlikely(err
< 0)) {
1478 path_put_conditional(path
, nd
);
1482 nd
->flags
|= LOOKUP_JUMPED
;
1486 static inline int may_lookup(struct nameidata
*nd
)
1488 if (nd
->flags
& LOOKUP_RCU
) {
1489 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1492 if (unlazy_walk(nd
, NULL
))
1495 return inode_permission(nd
->inode
, MAY_EXEC
);
1498 static inline int handle_dots(struct nameidata
*nd
, int type
)
1500 if (type
== LAST_DOTDOT
) {
1501 if (nd
->flags
& LOOKUP_RCU
) {
1502 if (follow_dotdot_rcu(nd
))
1510 static void terminate_walk(struct nameidata
*nd
)
1512 if (!(nd
->flags
& LOOKUP_RCU
)) {
1513 path_put(&nd
->path
);
1515 nd
->flags
&= ~LOOKUP_RCU
;
1516 if (!(nd
->flags
& LOOKUP_ROOT
))
1517 nd
->root
.mnt
= NULL
;
1523 * Do we need to follow links? We _really_ want to be able
1524 * to do this check without having to look at inode->i_op,
1525 * so we keep a cache of "no, this doesn't need follow_link"
1526 * for the common case.
1528 static inline int should_follow_link(struct dentry
*dentry
, int follow
)
1530 return unlikely(d_is_symlink(dentry
)) ? follow
: 0;
1533 static inline int walk_component(struct nameidata
*nd
, struct path
*path
,
1536 struct inode
*inode
;
1539 * "." and ".." are special - ".." especially so because it has
1540 * to be able to know about the current root directory and
1541 * parent relationships.
1543 if (unlikely(nd
->last_type
!= LAST_NORM
))
1544 return handle_dots(nd
, nd
->last_type
);
1545 err
= lookup_fast(nd
, path
, &inode
);
1546 if (unlikely(err
)) {
1550 err
= lookup_slow(nd
, path
);
1554 inode
= path
->dentry
->d_inode
;
1557 if (!inode
|| d_is_negative(path
->dentry
))
1560 if (should_follow_link(path
->dentry
, follow
)) {
1561 if (nd
->flags
& LOOKUP_RCU
) {
1562 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
1567 BUG_ON(inode
!= path
->dentry
->d_inode
);
1570 path_to_nameidata(path
, nd
);
1575 path_to_nameidata(path
, nd
);
1582 * This limits recursive symlink follows to 8, while
1583 * limiting consecutive symlinks to 40.
1585 * Without that kind of total limit, nasty chains of consecutive
1586 * symlinks can cause almost arbitrarily long lookups.
1588 static inline int nested_symlink(struct path
*path
, struct nameidata
*nd
)
1592 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1593 path_put_conditional(path
, nd
);
1594 path_put(&nd
->path
);
1597 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1600 current
->link_count
++;
1603 struct path link
= *path
;
1606 res
= follow_link(&link
, nd
, &cookie
);
1609 res
= walk_component(nd
, path
, LOOKUP_FOLLOW
);
1610 put_link(nd
, &link
, cookie
);
1613 current
->link_count
--;
1619 * We can do the critical dentry name comparison and hashing
1620 * operations one word at a time, but we are limited to:
1622 * - Architectures with fast unaligned word accesses. We could
1623 * do a "get_unaligned()" if this helps and is sufficiently
1626 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1627 * do not trap on the (extremely unlikely) case of a page
1628 * crossing operation.
1630 * - Furthermore, we need an efficient 64-bit compile for the
1631 * 64-bit case in order to generate the "number of bytes in
1632 * the final mask". Again, that could be replaced with a
1633 * efficient population count instruction or similar.
1635 #ifdef CONFIG_DCACHE_WORD_ACCESS
1637 #include <asm/word-at-a-time.h>
1641 static inline unsigned int fold_hash(unsigned long hash
)
1643 return hash_64(hash
, 32);
1646 #else /* 32-bit case */
1648 #define fold_hash(x) (x)
1652 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1654 unsigned long a
, mask
;
1655 unsigned long hash
= 0;
1658 a
= load_unaligned_zeropad(name
);
1659 if (len
< sizeof(unsigned long))
1663 name
+= sizeof(unsigned long);
1664 len
-= sizeof(unsigned long);
1668 mask
= bytemask_from_count(len
);
1671 return fold_hash(hash
);
1673 EXPORT_SYMBOL(full_name_hash
);
1676 * Calculate the length and hash of the path component, and
1677 * return the "hash_len" as the result.
1679 static inline u64
hash_name(const char *name
)
1681 unsigned long a
, b
, adata
, bdata
, mask
, hash
, len
;
1682 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1685 len
= -sizeof(unsigned long);
1687 hash
= (hash
+ a
) * 9;
1688 len
+= sizeof(unsigned long);
1689 a
= load_unaligned_zeropad(name
+len
);
1690 b
= a
^ REPEAT_BYTE('/');
1691 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1693 adata
= prep_zero_mask(a
, adata
, &constants
);
1694 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1696 mask
= create_zero_mask(adata
| bdata
);
1698 hash
+= a
& zero_bytemask(mask
);
1699 len
+= find_zero(mask
);
1700 return hashlen_create(fold_hash(hash
), len
);
1705 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1707 unsigned long hash
= init_name_hash();
1709 hash
= partial_name_hash(*name
++, hash
);
1710 return end_name_hash(hash
);
1712 EXPORT_SYMBOL(full_name_hash
);
1715 * We know there's a real path component here of at least
1718 static inline u64
hash_name(const char *name
)
1720 unsigned long hash
= init_name_hash();
1721 unsigned long len
= 0, c
;
1723 c
= (unsigned char)*name
;
1726 hash
= partial_name_hash(c
, hash
);
1727 c
= (unsigned char)name
[len
];
1728 } while (c
&& c
!= '/');
1729 return hashlen_create(end_name_hash(hash
), len
);
1736 * This is the basic name resolution function, turning a pathname into
1737 * the final dentry. We expect 'base' to be positive and a directory.
1739 * Returns 0 and nd will have valid dentry and mnt on success.
1740 * Returns error and drops reference to input namei data on failure.
1742 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1752 /* At this point we know we have a real path component. */
1757 err
= may_lookup(nd
);
1761 hash_len
= hash_name(name
);
1764 if (name
[0] == '.') switch (hashlen_len(hash_len
)) {
1766 if (name
[1] == '.') {
1768 nd
->flags
|= LOOKUP_JUMPED
;
1774 if (likely(type
== LAST_NORM
)) {
1775 struct dentry
*parent
= nd
->path
.dentry
;
1776 nd
->flags
&= ~LOOKUP_JUMPED
;
1777 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1778 struct qstr
this = { { .hash_len
= hash_len
}, .name
= name
};
1779 err
= parent
->d_op
->d_hash(parent
, &this);
1782 hash_len
= this.hash_len
;
1787 nd
->last
.hash_len
= hash_len
;
1788 nd
->last
.name
= name
;
1789 nd
->last_type
= type
;
1791 name
+= hashlen_len(hash_len
);
1795 * If it wasn't NUL, we know it was '/'. Skip that
1796 * slash, and continue until no more slashes.
1800 } while (unlikely(*name
== '/'));
1804 err
= walk_component(nd
, &next
, LOOKUP_FOLLOW
);
1809 err
= nested_symlink(&next
, nd
);
1813 if (!d_can_lookup(nd
->path
.dentry
)) {
1822 static int path_init(int dfd
, const char *name
, unsigned int flags
,
1823 struct nameidata
*nd
, struct file
**fp
)
1827 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1828 nd
->flags
= flags
| LOOKUP_JUMPED
;
1830 if (flags
& LOOKUP_ROOT
) {
1831 struct dentry
*root
= nd
->root
.dentry
;
1832 struct inode
*inode
= root
->d_inode
;
1834 if (!d_can_lookup(root
))
1836 retval
= inode_permission(inode
, MAY_EXEC
);
1840 nd
->path
= nd
->root
;
1842 if (flags
& LOOKUP_RCU
) {
1844 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1845 nd
->m_seq
= read_seqbegin(&mount_lock
);
1847 path_get(&nd
->path
);
1852 nd
->root
.mnt
= NULL
;
1854 nd
->m_seq
= read_seqbegin(&mount_lock
);
1856 if (flags
& LOOKUP_RCU
) {
1858 nd
->seq
= set_root_rcu(nd
);
1861 path_get(&nd
->root
);
1863 nd
->path
= nd
->root
;
1864 } else if (dfd
== AT_FDCWD
) {
1865 if (flags
& LOOKUP_RCU
) {
1866 struct fs_struct
*fs
= current
->fs
;
1872 seq
= read_seqcount_begin(&fs
->seq
);
1874 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1875 } while (read_seqcount_retry(&fs
->seq
, seq
));
1877 get_fs_pwd(current
->fs
, &nd
->path
);
1880 /* Caller must check execute permissions on the starting path component */
1881 struct fd f
= fdget_raw(dfd
);
1882 struct dentry
*dentry
;
1887 dentry
= f
.file
->f_path
.dentry
;
1890 if (!d_can_lookup(dentry
)) {
1896 nd
->path
= f
.file
->f_path
;
1897 if (flags
& LOOKUP_RCU
) {
1898 if (f
.flags
& FDPUT_FPUT
)
1900 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1903 path_get(&nd
->path
);
1908 nd
->inode
= nd
->path
.dentry
->d_inode
;
1909 if (!(flags
& LOOKUP_RCU
))
1911 if (likely(!read_seqcount_retry(&nd
->path
.dentry
->d_seq
, nd
->seq
)))
1913 if (!(nd
->flags
& LOOKUP_ROOT
))
1914 nd
->root
.mnt
= NULL
;
1919 static inline int lookup_last(struct nameidata
*nd
, struct path
*path
)
1921 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1922 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1924 nd
->flags
&= ~LOOKUP_PARENT
;
1925 return walk_component(nd
, path
, nd
->flags
& LOOKUP_FOLLOW
);
1928 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1929 static int path_lookupat(int dfd
, const char *name
,
1930 unsigned int flags
, struct nameidata
*nd
)
1932 struct file
*base
= NULL
;
1937 * Path walking is largely split up into 2 different synchronisation
1938 * schemes, rcu-walk and ref-walk (explained in
1939 * Documentation/filesystems/path-lookup.txt). These share much of the
1940 * path walk code, but some things particularly setup, cleanup, and
1941 * following mounts are sufficiently divergent that functions are
1942 * duplicated. Typically there is a function foo(), and its RCU
1943 * analogue, foo_rcu().
1945 * -ECHILD is the error number of choice (just to avoid clashes) that
1946 * is returned if some aspect of an rcu-walk fails. Such an error must
1947 * be handled by restarting a traditional ref-walk (which will always
1948 * be able to complete).
1950 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, nd
, &base
);
1955 current
->total_link_count
= 0;
1956 err
= link_path_walk(name
, nd
);
1958 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
1959 err
= lookup_last(nd
, &path
);
1962 struct path link
= path
;
1963 err
= may_follow_link(&link
, nd
);
1966 nd
->flags
|= LOOKUP_PARENT
;
1967 err
= follow_link(&link
, nd
, &cookie
);
1970 err
= lookup_last(nd
, &path
);
1971 put_link(nd
, &link
, cookie
);
1976 err
= complete_walk(nd
);
1978 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
1979 if (!d_can_lookup(nd
->path
.dentry
)) {
1980 path_put(&nd
->path
);
1988 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1989 path_put(&nd
->root
);
1990 nd
->root
.mnt
= NULL
;
1995 static int filename_lookup(int dfd
, struct filename
*name
,
1996 unsigned int flags
, struct nameidata
*nd
)
1998 int retval
= path_lookupat(dfd
, name
->name
, flags
| LOOKUP_RCU
, nd
);
1999 if (unlikely(retval
== -ECHILD
))
2000 retval
= path_lookupat(dfd
, name
->name
, flags
, nd
);
2001 if (unlikely(retval
== -ESTALE
))
2002 retval
= path_lookupat(dfd
, name
->name
,
2003 flags
| LOOKUP_REVAL
, nd
);
2005 if (likely(!retval
))
2006 audit_inode(name
, nd
->path
.dentry
, flags
& LOOKUP_PARENT
);
2010 static int do_path_lookup(int dfd
, const char *name
,
2011 unsigned int flags
, struct nameidata
*nd
)
2013 struct filename filename
= { .name
= name
};
2015 return filename_lookup(dfd
, &filename
, flags
, nd
);
2018 /* does lookup, returns the object with parent locked */
2019 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2021 struct nameidata nd
;
2023 int err
= do_path_lookup(AT_FDCWD
, name
, LOOKUP_PARENT
, &nd
);
2025 return ERR_PTR(err
);
2026 if (nd
.last_type
!= LAST_NORM
) {
2028 return ERR_PTR(-EINVAL
);
2030 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2031 d
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, 0);
2033 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2041 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2043 struct nameidata nd
;
2044 int res
= do_path_lookup(AT_FDCWD
, name
, flags
, &nd
);
2049 EXPORT_SYMBOL(kern_path
);
2052 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2053 * @dentry: pointer to dentry of the base directory
2054 * @mnt: pointer to vfs mount of the base directory
2055 * @name: pointer to file name
2056 * @flags: lookup flags
2057 * @path: pointer to struct path to fill
2059 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2060 const char *name
, unsigned int flags
,
2063 struct nameidata nd
;
2065 nd
.root
.dentry
= dentry
;
2067 BUG_ON(flags
& LOOKUP_PARENT
);
2068 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2069 err
= do_path_lookup(AT_FDCWD
, name
, flags
| LOOKUP_ROOT
, &nd
);
2074 EXPORT_SYMBOL(vfs_path_lookup
);
2077 * Restricted form of lookup. Doesn't follow links, single-component only,
2078 * needs parent already locked. Doesn't follow mounts.
2081 static struct dentry
*lookup_hash(struct nameidata
*nd
)
2083 return __lookup_hash(&nd
->last
, nd
->path
.dentry
, nd
->flags
);
2087 * lookup_one_len - filesystem helper to lookup single pathname component
2088 * @name: pathname component to lookup
2089 * @base: base directory to lookup from
2090 * @len: maximum length @len should be interpreted to
2092 * Note that this routine is purely a helper for filesystem usage and should
2093 * not be called by generic code. Also note that by using this function the
2094 * nameidata argument is passed to the filesystem methods and a filesystem
2095 * using this helper needs to be prepared for that.
2097 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2103 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
2107 this.hash
= full_name_hash(name
, len
);
2109 return ERR_PTR(-EACCES
);
2111 if (unlikely(name
[0] == '.')) {
2112 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2113 return ERR_PTR(-EACCES
);
2117 c
= *(const unsigned char *)name
++;
2118 if (c
== '/' || c
== '\0')
2119 return ERR_PTR(-EACCES
);
2122 * See if the low-level filesystem might want
2123 * to use its own hash..
2125 if (base
->d_flags
& DCACHE_OP_HASH
) {
2126 int err
= base
->d_op
->d_hash(base
, &this);
2128 return ERR_PTR(err
);
2131 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2133 return ERR_PTR(err
);
2135 return __lookup_hash(&this, base
, 0);
2137 EXPORT_SYMBOL(lookup_one_len
);
2139 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2140 struct path
*path
, int *empty
)
2142 struct nameidata nd
;
2143 struct filename
*tmp
= getname_flags(name
, flags
, empty
);
2144 int err
= PTR_ERR(tmp
);
2147 BUG_ON(flags
& LOOKUP_PARENT
);
2149 err
= filename_lookup(dfd
, tmp
, flags
, &nd
);
2157 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
2160 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
2162 EXPORT_SYMBOL(user_path_at
);
2165 * NB: most callers don't do anything directly with the reference to the
2166 * to struct filename, but the nd->last pointer points into the name string
2167 * allocated by getname. So we must hold the reference to it until all
2168 * path-walking is complete.
2170 static struct filename
*
2171 user_path_parent(int dfd
, const char __user
*path
, struct nameidata
*nd
,
2174 struct filename
*s
= getname(path
);
2177 /* only LOOKUP_REVAL is allowed in extra flags */
2178 flags
&= LOOKUP_REVAL
;
2183 error
= filename_lookup(dfd
, s
, flags
| LOOKUP_PARENT
, nd
);
2186 return ERR_PTR(error
);
2193 * mountpoint_last - look up last component for umount
2194 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2195 * @path: pointer to container for result
2197 * This is a special lookup_last function just for umount. In this case, we
2198 * need to resolve the path without doing any revalidation.
2200 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2201 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2202 * in almost all cases, this lookup will be served out of the dcache. The only
2203 * cases where it won't are if nd->last refers to a symlink or the path is
2204 * bogus and it doesn't exist.
2207 * -error: if there was an error during lookup. This includes -ENOENT if the
2208 * lookup found a negative dentry. The nd->path reference will also be
2211 * 0: if we successfully resolved nd->path and found it to not to be a
2212 * symlink that needs to be followed. "path" will also be populated.
2213 * The nd->path reference will also be put.
2215 * 1: if we successfully resolved nd->last and found it to be a symlink
2216 * that needs to be followed. "path" will be populated with the path
2217 * to the link, and nd->path will *not* be put.
2220 mountpoint_last(struct nameidata
*nd
, struct path
*path
)
2223 struct dentry
*dentry
;
2224 struct dentry
*dir
= nd
->path
.dentry
;
2226 /* If we're in rcuwalk, drop out of it to handle last component */
2227 if (nd
->flags
& LOOKUP_RCU
) {
2228 if (unlazy_walk(nd
, NULL
)) {
2234 nd
->flags
&= ~LOOKUP_PARENT
;
2236 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2237 error
= handle_dots(nd
, nd
->last_type
);
2240 dentry
= dget(nd
->path
.dentry
);
2244 mutex_lock(&dir
->d_inode
->i_mutex
);
2245 dentry
= d_lookup(dir
, &nd
->last
);
2248 * No cached dentry. Mounted dentries are pinned in the cache,
2249 * so that means that this dentry is probably a symlink or the
2250 * path doesn't actually point to a mounted dentry.
2252 dentry
= d_alloc(dir
, &nd
->last
);
2255 mutex_unlock(&dir
->d_inode
->i_mutex
);
2258 dentry
= lookup_real(dir
->d_inode
, dentry
, nd
->flags
);
2259 error
= PTR_ERR(dentry
);
2260 if (IS_ERR(dentry
)) {
2261 mutex_unlock(&dir
->d_inode
->i_mutex
);
2265 mutex_unlock(&dir
->d_inode
->i_mutex
);
2268 if (!dentry
->d_inode
|| d_is_negative(dentry
)) {
2273 path
->dentry
= dentry
;
2274 path
->mnt
= nd
->path
.mnt
;
2275 if (should_follow_link(dentry
, nd
->flags
& LOOKUP_FOLLOW
))
2286 * path_mountpoint - look up a path to be umounted
2287 * @dfd: directory file descriptor to start walk from
2288 * @name: full pathname to walk
2289 * @path: pointer to container for result
2290 * @flags: lookup flags
2292 * Look up the given name, but don't attempt to revalidate the last component.
2293 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2296 path_mountpoint(int dfd
, const char *name
, struct path
*path
, unsigned int flags
)
2298 struct file
*base
= NULL
;
2299 struct nameidata nd
;
2302 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, &nd
, &base
);
2306 current
->total_link_count
= 0;
2307 err
= link_path_walk(name
, &nd
);
2311 err
= mountpoint_last(&nd
, path
);
2314 struct path link
= *path
;
2315 err
= may_follow_link(&link
, &nd
);
2318 nd
.flags
|= LOOKUP_PARENT
;
2319 err
= follow_link(&link
, &nd
, &cookie
);
2322 err
= mountpoint_last(&nd
, path
);
2323 put_link(&nd
, &link
, cookie
);
2329 if (nd
.root
.mnt
&& !(nd
.flags
& LOOKUP_ROOT
))
2336 filename_mountpoint(int dfd
, struct filename
*s
, struct path
*path
,
2339 int error
= path_mountpoint(dfd
, s
->name
, path
, flags
| LOOKUP_RCU
);
2340 if (unlikely(error
== -ECHILD
))
2341 error
= path_mountpoint(dfd
, s
->name
, path
, flags
);
2342 if (unlikely(error
== -ESTALE
))
2343 error
= path_mountpoint(dfd
, s
->name
, path
, flags
| LOOKUP_REVAL
);
2345 audit_inode(s
, path
->dentry
, 0);
2350 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2351 * @dfd: directory file descriptor
2352 * @name: pathname from userland
2353 * @flags: lookup flags
2354 * @path: pointer to container to hold result
2356 * A umount is a special case for path walking. We're not actually interested
2357 * in the inode in this situation, and ESTALE errors can be a problem. We
2358 * simply want track down the dentry and vfsmount attached at the mountpoint
2359 * and avoid revalidating the last component.
2361 * Returns 0 and populates "path" on success.
2364 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2367 struct filename
*s
= getname(name
);
2371 error
= filename_mountpoint(dfd
, s
, path
, flags
);
2377 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2380 struct filename s
= {.name
= name
};
2381 return filename_mountpoint(dfd
, &s
, path
, flags
);
2383 EXPORT_SYMBOL(kern_path_mountpoint
);
2386 * It's inline, so penalty for filesystems that don't use sticky bit is
2389 static inline int check_sticky(struct inode
*dir
, struct inode
*inode
)
2391 kuid_t fsuid
= current_fsuid();
2393 if (!(dir
->i_mode
& S_ISVTX
))
2395 if (uid_eq(inode
->i_uid
, fsuid
))
2397 if (uid_eq(dir
->i_uid
, fsuid
))
2399 return !capable_wrt_inode_uidgid(inode
, CAP_FOWNER
);
2403 * Check whether we can remove a link victim from directory dir, check
2404 * whether the type of victim is right.
2405 * 1. We can't do it if dir is read-only (done in permission())
2406 * 2. We should have write and exec permissions on dir
2407 * 3. We can't remove anything from append-only dir
2408 * 4. We can't do anything with immutable dir (done in permission())
2409 * 5. If the sticky bit on dir is set we should either
2410 * a. be owner of dir, or
2411 * b. be owner of victim, or
2412 * c. have CAP_FOWNER capability
2413 * 6. If the victim is append-only or immutable we can't do antyhing with
2414 * links pointing to it.
2415 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2416 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2417 * 9. We can't remove a root or mountpoint.
2418 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2419 * nfs_async_unlink().
2421 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2423 struct inode
*inode
= victim
->d_inode
;
2426 if (d_is_negative(victim
))
2430 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2431 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2433 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2439 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2440 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
))
2443 if (!d_is_dir(victim
))
2445 if (IS_ROOT(victim
))
2447 } else if (d_is_dir(victim
))
2449 if (IS_DEADDIR(dir
))
2451 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2456 /* Check whether we can create an object with dentry child in directory
2458 * 1. We can't do it if child already exists (open has special treatment for
2459 * this case, but since we are inlined it's OK)
2460 * 2. We can't do it if dir is read-only (done in permission())
2461 * 3. We should have write and exec permissions on dir
2462 * 4. We can't do it if dir is immutable (done in permission())
2464 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2466 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2469 if (IS_DEADDIR(dir
))
2471 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2475 * p1 and p2 should be directories on the same fs.
2477 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2482 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2486 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2488 p
= d_ancestor(p2
, p1
);
2490 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2491 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2495 p
= d_ancestor(p1
, p2
);
2497 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2498 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2502 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2503 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2506 EXPORT_SYMBOL(lock_rename
);
2508 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2510 mutex_unlock(&p1
->d_inode
->i_mutex
);
2512 mutex_unlock(&p2
->d_inode
->i_mutex
);
2513 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2516 EXPORT_SYMBOL(unlock_rename
);
2518 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2521 int error
= may_create(dir
, dentry
);
2525 if (!dir
->i_op
->create
)
2526 return -EACCES
; /* shouldn't it be ENOSYS? */
2529 error
= security_inode_create(dir
, dentry
, mode
);
2532 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2534 fsnotify_create(dir
, dentry
);
2537 EXPORT_SYMBOL(vfs_create
);
2539 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2541 struct dentry
*dentry
= path
->dentry
;
2542 struct inode
*inode
= dentry
->d_inode
;
2552 switch (inode
->i_mode
& S_IFMT
) {
2556 if (acc_mode
& MAY_WRITE
)
2561 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2570 error
= inode_permission(inode
, acc_mode
);
2575 * An append-only file must be opened in append mode for writing.
2577 if (IS_APPEND(inode
)) {
2578 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2584 /* O_NOATIME can only be set by the owner or superuser */
2585 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2591 static int handle_truncate(struct file
*filp
)
2593 struct path
*path
= &filp
->f_path
;
2594 struct inode
*inode
= path
->dentry
->d_inode
;
2595 int error
= get_write_access(inode
);
2599 * Refuse to truncate files with mandatory locks held on them.
2601 error
= locks_verify_locked(filp
);
2603 error
= security_path_truncate(path
);
2605 error
= do_truncate(path
->dentry
, 0,
2606 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2609 put_write_access(inode
);
2613 static inline int open_to_namei_flags(int flag
)
2615 if ((flag
& O_ACCMODE
) == 3)
2620 static int may_o_create(struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2622 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2626 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2630 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2634 * Attempt to atomically look up, create and open a file from a negative
2637 * Returns 0 if successful. The file will have been created and attached to
2638 * @file by the filesystem calling finish_open().
2640 * Returns 1 if the file was looked up only or didn't need creating. The
2641 * caller will need to perform the open themselves. @path will have been
2642 * updated to point to the new dentry. This may be negative.
2644 * Returns an error code otherwise.
2646 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2647 struct path
*path
, struct file
*file
,
2648 const struct open_flags
*op
,
2649 bool got_write
, bool need_lookup
,
2652 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2653 unsigned open_flag
= open_to_namei_flags(op
->open_flag
);
2657 int create_error
= 0;
2658 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2661 BUG_ON(dentry
->d_inode
);
2663 /* Don't create child dentry for a dead directory. */
2664 if (unlikely(IS_DEADDIR(dir
))) {
2670 if ((open_flag
& O_CREAT
) && !IS_POSIXACL(dir
))
2671 mode
&= ~current_umask();
2673 excl
= (open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
);
2675 open_flag
&= ~O_TRUNC
;
2678 * Checking write permission is tricky, bacuse we don't know if we are
2679 * going to actually need it: O_CREAT opens should work as long as the
2680 * file exists. But checking existence breaks atomicity. The trick is
2681 * to check access and if not granted clear O_CREAT from the flags.
2683 * Another problem is returing the "right" error value (e.g. for an
2684 * O_EXCL open we want to return EEXIST not EROFS).
2686 if (((open_flag
& (O_CREAT
| O_TRUNC
)) ||
2687 (open_flag
& O_ACCMODE
) != O_RDONLY
) && unlikely(!got_write
)) {
2688 if (!(open_flag
& O_CREAT
)) {
2690 * No O_CREATE -> atomicity not a requirement -> fall
2691 * back to lookup + open
2694 } else if (open_flag
& (O_EXCL
| O_TRUNC
)) {
2695 /* Fall back and fail with the right error */
2696 create_error
= -EROFS
;
2699 /* No side effects, safe to clear O_CREAT */
2700 create_error
= -EROFS
;
2701 open_flag
&= ~O_CREAT
;
2705 if (open_flag
& O_CREAT
) {
2706 error
= may_o_create(&nd
->path
, dentry
, mode
);
2708 create_error
= error
;
2709 if (open_flag
& O_EXCL
)
2711 open_flag
&= ~O_CREAT
;
2715 if (nd
->flags
& LOOKUP_DIRECTORY
)
2716 open_flag
|= O_DIRECTORY
;
2718 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2719 file
->f_path
.mnt
= nd
->path
.mnt
;
2720 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
, open_flag
, mode
,
2723 if (create_error
&& error
== -ENOENT
)
2724 error
= create_error
;
2728 if (error
) { /* returned 1, that is */
2729 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
2733 if (file
->f_path
.dentry
) {
2735 dentry
= file
->f_path
.dentry
;
2737 if (*opened
& FILE_CREATED
)
2738 fsnotify_create(dir
, dentry
);
2739 if (!dentry
->d_inode
) {
2740 WARN_ON(*opened
& FILE_CREATED
);
2742 error
= create_error
;
2746 if (excl
&& !(*opened
& FILE_CREATED
)) {
2755 * We didn't have the inode before the open, so check open permission
2758 acc_mode
= op
->acc_mode
;
2759 if (*opened
& FILE_CREATED
) {
2760 WARN_ON(!(open_flag
& O_CREAT
));
2761 fsnotify_create(dir
, dentry
);
2762 acc_mode
= MAY_OPEN
;
2764 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
2774 dentry
= lookup_real(dir
, dentry
, nd
->flags
);
2776 return PTR_ERR(dentry
);
2779 int open_flag
= op
->open_flag
;
2781 error
= create_error
;
2782 if ((open_flag
& O_EXCL
)) {
2783 if (!dentry
->d_inode
)
2785 } else if (!dentry
->d_inode
) {
2787 } else if ((open_flag
& O_TRUNC
) &&
2788 S_ISREG(dentry
->d_inode
->i_mode
)) {
2791 /* will fail later, go on to get the right error */
2795 path
->dentry
= dentry
;
2796 path
->mnt
= nd
->path
.mnt
;
2801 * Look up and maybe create and open the last component.
2803 * Must be called with i_mutex held on parent.
2805 * Returns 0 if the file was successfully atomically created (if necessary) and
2806 * opened. In this case the file will be returned attached to @file.
2808 * Returns 1 if the file was not completely opened at this time, though lookups
2809 * and creations will have been performed and the dentry returned in @path will
2810 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2811 * specified then a negative dentry may be returned.
2813 * An error code is returned otherwise.
2815 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2816 * cleared otherwise prior to returning.
2818 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
2820 const struct open_flags
*op
,
2821 bool got_write
, int *opened
)
2823 struct dentry
*dir
= nd
->path
.dentry
;
2824 struct inode
*dir_inode
= dir
->d_inode
;
2825 struct dentry
*dentry
;
2829 *opened
&= ~FILE_CREATED
;
2830 dentry
= lookup_dcache(&nd
->last
, dir
, nd
->flags
, &need_lookup
);
2832 return PTR_ERR(dentry
);
2834 /* Cached positive dentry: will open in f_op->open */
2835 if (!need_lookup
&& dentry
->d_inode
)
2838 if ((nd
->flags
& LOOKUP_OPEN
) && dir_inode
->i_op
->atomic_open
) {
2839 return atomic_open(nd
, dentry
, path
, file
, op
, got_write
,
2840 need_lookup
, opened
);
2844 BUG_ON(dentry
->d_inode
);
2846 dentry
= lookup_real(dir_inode
, dentry
, nd
->flags
);
2848 return PTR_ERR(dentry
);
2851 /* Negative dentry, just create the file */
2852 if (!dentry
->d_inode
&& (op
->open_flag
& O_CREAT
)) {
2853 umode_t mode
= op
->mode
;
2854 if (!IS_POSIXACL(dir
->d_inode
))
2855 mode
&= ~current_umask();
2857 * This write is needed to ensure that a
2858 * rw->ro transition does not occur between
2859 * the time when the file is created and when
2860 * a permanent write count is taken through
2861 * the 'struct file' in finish_open().
2867 *opened
|= FILE_CREATED
;
2868 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2871 error
= vfs_create(dir
->d_inode
, dentry
, mode
,
2872 nd
->flags
& LOOKUP_EXCL
);
2877 path
->dentry
= dentry
;
2878 path
->mnt
= nd
->path
.mnt
;
2887 * Handle the last step of open()
2889 static int do_last(struct nameidata
*nd
, struct path
*path
,
2890 struct file
*file
, const struct open_flags
*op
,
2891 int *opened
, struct filename
*name
)
2893 struct dentry
*dir
= nd
->path
.dentry
;
2894 int open_flag
= op
->open_flag
;
2895 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
2896 bool got_write
= false;
2897 int acc_mode
= op
->acc_mode
;
2898 struct inode
*inode
;
2899 bool symlink_ok
= false;
2900 struct path save_parent
= { .dentry
= NULL
, .mnt
= NULL
};
2901 bool retried
= false;
2904 nd
->flags
&= ~LOOKUP_PARENT
;
2905 nd
->flags
|= op
->intent
;
2907 if (nd
->last_type
!= LAST_NORM
) {
2908 error
= handle_dots(nd
, nd
->last_type
);
2914 if (!(open_flag
& O_CREAT
)) {
2915 if (nd
->last
.name
[nd
->last
.len
])
2916 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2917 if (open_flag
& O_PATH
&& !(nd
->flags
& LOOKUP_FOLLOW
))
2919 /* we _can_ be in RCU mode here */
2920 error
= lookup_fast(nd
, path
, &inode
);
2927 BUG_ON(nd
->inode
!= dir
->d_inode
);
2929 /* create side of things */
2931 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2932 * has been cleared when we got to the last component we are
2935 error
= complete_walk(nd
);
2939 audit_inode(name
, dir
, LOOKUP_PARENT
);
2941 /* trailing slashes? */
2942 if (nd
->last
.name
[nd
->last
.len
])
2947 if (op
->open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
2948 error
= mnt_want_write(nd
->path
.mnt
);
2952 * do _not_ fail yet - we might not need that or fail with
2953 * a different error; let lookup_open() decide; we'll be
2954 * dropping this one anyway.
2957 mutex_lock(&dir
->d_inode
->i_mutex
);
2958 error
= lookup_open(nd
, path
, file
, op
, got_write
, opened
);
2959 mutex_unlock(&dir
->d_inode
->i_mutex
);
2965 if ((*opened
& FILE_CREATED
) ||
2966 !S_ISREG(file_inode(file
)->i_mode
))
2967 will_truncate
= false;
2969 audit_inode(name
, file
->f_path
.dentry
, 0);
2973 if (*opened
& FILE_CREATED
) {
2974 /* Don't check for write permission, don't truncate */
2975 open_flag
&= ~O_TRUNC
;
2976 will_truncate
= false;
2977 acc_mode
= MAY_OPEN
;
2978 path_to_nameidata(path
, nd
);
2979 goto finish_open_created
;
2983 * create/update audit record if it already exists.
2985 if (d_is_positive(path
->dentry
))
2986 audit_inode(name
, path
->dentry
, 0);
2989 * If atomic_open() acquired write access it is dropped now due to
2990 * possible mount and symlink following (this might be optimized away if
2994 mnt_drop_write(nd
->path
.mnt
);
2999 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))
3002 error
= follow_managed(path
, nd
->flags
);
3007 nd
->flags
|= LOOKUP_JUMPED
;
3009 BUG_ON(nd
->flags
& LOOKUP_RCU
);
3010 inode
= path
->dentry
->d_inode
;
3012 /* we _can_ be in RCU mode here */
3014 if (!inode
|| d_is_negative(path
->dentry
)) {
3015 path_to_nameidata(path
, nd
);
3019 if (should_follow_link(path
->dentry
, !symlink_ok
)) {
3020 if (nd
->flags
& LOOKUP_RCU
) {
3021 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
3026 BUG_ON(inode
!= path
->dentry
->d_inode
);
3030 if ((nd
->flags
& LOOKUP_RCU
) || nd
->path
.mnt
!= path
->mnt
) {
3031 path_to_nameidata(path
, nd
);
3033 save_parent
.dentry
= nd
->path
.dentry
;
3034 save_parent
.mnt
= mntget(path
->mnt
);
3035 nd
->path
.dentry
= path
->dentry
;
3039 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3041 error
= complete_walk(nd
);
3043 path_put(&save_parent
);
3046 audit_inode(name
, nd
->path
.dentry
, 0);
3048 if ((open_flag
& O_CREAT
) && d_is_dir(nd
->path
.dentry
))
3051 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_can_lookup(nd
->path
.dentry
))
3053 if (!S_ISREG(nd
->inode
->i_mode
))
3054 will_truncate
= false;
3056 if (will_truncate
) {
3057 error
= mnt_want_write(nd
->path
.mnt
);
3062 finish_open_created
:
3063 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3066 file
->f_path
.mnt
= nd
->path
.mnt
;
3067 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3069 if (error
== -EOPENSTALE
)
3074 error
= open_check_o_direct(file
);
3077 error
= ima_file_check(file
, op
->acc_mode
, *opened
);
3081 if (will_truncate
) {
3082 error
= handle_truncate(file
);
3088 mnt_drop_write(nd
->path
.mnt
);
3089 path_put(&save_parent
);
3094 path_put_conditional(path
, nd
);
3101 /* If no saved parent or already retried then can't retry */
3102 if (!save_parent
.dentry
|| retried
)
3105 BUG_ON(save_parent
.dentry
!= dir
);
3106 path_put(&nd
->path
);
3107 nd
->path
= save_parent
;
3108 nd
->inode
= dir
->d_inode
;
3109 save_parent
.mnt
= NULL
;
3110 save_parent
.dentry
= NULL
;
3112 mnt_drop_write(nd
->path
.mnt
);
3119 static int do_tmpfile(int dfd
, struct filename
*pathname
,
3120 struct nameidata
*nd
, int flags
,
3121 const struct open_flags
*op
,
3122 struct file
*file
, int *opened
)
3124 static const struct qstr name
= QSTR_INIT("/", 1);
3125 struct dentry
*dentry
, *child
;
3127 int error
= path_lookupat(dfd
, pathname
->name
,
3128 flags
| LOOKUP_DIRECTORY
, nd
);
3129 if (unlikely(error
))
3131 error
= mnt_want_write(nd
->path
.mnt
);
3132 if (unlikely(error
))
3134 /* we want directory to be writable */
3135 error
= inode_permission(nd
->inode
, MAY_WRITE
| MAY_EXEC
);
3138 dentry
= nd
->path
.dentry
;
3139 dir
= dentry
->d_inode
;
3140 if (!dir
->i_op
->tmpfile
) {
3141 error
= -EOPNOTSUPP
;
3144 child
= d_alloc(dentry
, &name
);
3145 if (unlikely(!child
)) {
3149 nd
->flags
&= ~LOOKUP_DIRECTORY
;
3150 nd
->flags
|= op
->intent
;
3151 dput(nd
->path
.dentry
);
3152 nd
->path
.dentry
= child
;
3153 error
= dir
->i_op
->tmpfile(dir
, nd
->path
.dentry
, op
->mode
);
3156 audit_inode(pathname
, nd
->path
.dentry
, 0);
3157 error
= may_open(&nd
->path
, op
->acc_mode
, op
->open_flag
);
3160 file
->f_path
.mnt
= nd
->path
.mnt
;
3161 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3164 error
= open_check_o_direct(file
);
3167 } else if (!(op
->open_flag
& O_EXCL
)) {
3168 struct inode
*inode
= file_inode(file
);
3169 spin_lock(&inode
->i_lock
);
3170 inode
->i_state
|= I_LINKABLE
;
3171 spin_unlock(&inode
->i_lock
);
3174 mnt_drop_write(nd
->path
.mnt
);
3176 path_put(&nd
->path
);
3180 static struct file
*path_openat(int dfd
, struct filename
*pathname
,
3181 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
3183 struct file
*base
= NULL
;
3189 file
= get_empty_filp();
3193 file
->f_flags
= op
->open_flag
;
3195 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3196 error
= do_tmpfile(dfd
, pathname
, nd
, flags
, op
, file
, &opened
);
3200 error
= path_init(dfd
, pathname
->name
, flags
| LOOKUP_PARENT
, nd
, &base
);
3201 if (unlikely(error
))
3204 current
->total_link_count
= 0;
3205 error
= link_path_walk(pathname
->name
, nd
);
3206 if (unlikely(error
))
3209 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3210 while (unlikely(error
> 0)) { /* trailing symlink */
3211 struct path link
= path
;
3213 if (!(nd
->flags
& LOOKUP_FOLLOW
)) {
3214 path_put_conditional(&path
, nd
);
3215 path_put(&nd
->path
);
3219 error
= may_follow_link(&link
, nd
);
3220 if (unlikely(error
))
3222 nd
->flags
|= LOOKUP_PARENT
;
3223 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3224 error
= follow_link(&link
, nd
, &cookie
);
3225 if (unlikely(error
))
3227 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3228 put_link(nd
, &link
, cookie
);
3231 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
))
3232 path_put(&nd
->root
);
3235 if (!(opened
& FILE_OPENED
)) {
3239 if (unlikely(error
)) {
3240 if (error
== -EOPENSTALE
) {
3241 if (flags
& LOOKUP_RCU
)
3246 file
= ERR_PTR(error
);
3251 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3252 const struct open_flags
*op
)
3254 struct nameidata nd
;
3255 int flags
= op
->lookup_flags
;
3258 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
3259 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3260 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
3261 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3262 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
3266 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3267 const char *name
, const struct open_flags
*op
)
3269 struct nameidata nd
;
3271 struct filename filename
= { .name
= name
};
3272 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3275 nd
.root
.dentry
= dentry
;
3277 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3278 return ERR_PTR(-ELOOP
);
3280 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_RCU
);
3281 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3282 file
= path_openat(-1, &filename
, &nd
, op
, flags
);
3283 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3284 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_REVAL
);
3288 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3289 struct path
*path
, unsigned int lookup_flags
)
3291 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3292 struct nameidata nd
;
3295 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3298 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3299 * other flags passed in are ignored!
3301 lookup_flags
&= LOOKUP_REVAL
;
3303 error
= do_path_lookup(dfd
, pathname
, LOOKUP_PARENT
|lookup_flags
, &nd
);
3305 return ERR_PTR(error
);
3308 * Yucky last component or no last component at all?
3309 * (foo/., foo/.., /////)
3311 if (nd
.last_type
!= LAST_NORM
)
3313 nd
.flags
&= ~LOOKUP_PARENT
;
3314 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3316 /* don't fail immediately if it's r/o, at least try to report other errors */
3317 err2
= mnt_want_write(nd
.path
.mnt
);
3319 * Do the final lookup.
3321 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3322 dentry
= lookup_hash(&nd
);
3327 if (d_is_positive(dentry
))
3331 * Special case - lookup gave negative, but... we had foo/bar/
3332 * From the vfs_mknod() POV we just have a negative dentry -
3333 * all is fine. Let's be bastards - you had / on the end, you've
3334 * been asking for (non-existent) directory. -ENOENT for you.
3336 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
3340 if (unlikely(err2
)) {
3348 dentry
= ERR_PTR(error
);
3350 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3352 mnt_drop_write(nd
.path
.mnt
);
3357 EXPORT_SYMBOL(kern_path_create
);
3359 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3362 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
3363 mnt_drop_write(path
->mnt
);
3366 EXPORT_SYMBOL(done_path_create
);
3368 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3369 struct path
*path
, unsigned int lookup_flags
)
3371 struct filename
*tmp
= getname(pathname
);
3374 return ERR_CAST(tmp
);
3375 res
= kern_path_create(dfd
, tmp
->name
, path
, lookup_flags
);
3379 EXPORT_SYMBOL(user_path_create
);
3381 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3383 int error
= may_create(dir
, dentry
);
3388 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3391 if (!dir
->i_op
->mknod
)
3394 error
= devcgroup_inode_mknod(mode
, dev
);
3398 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3402 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3404 fsnotify_create(dir
, dentry
);
3407 EXPORT_SYMBOL(vfs_mknod
);
3409 static int may_mknod(umode_t mode
)
3411 switch (mode
& S_IFMT
) {
3417 case 0: /* zero mode translates to S_IFREG */
3426 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3429 struct dentry
*dentry
;
3432 unsigned int lookup_flags
= 0;
3434 error
= may_mknod(mode
);
3438 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3440 return PTR_ERR(dentry
);
3442 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3443 mode
&= ~current_umask();
3444 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3447 switch (mode
& S_IFMT
) {
3448 case 0: case S_IFREG
:
3449 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3451 case S_IFCHR
: case S_IFBLK
:
3452 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3453 new_decode_dev(dev
));
3455 case S_IFIFO
: case S_IFSOCK
:
3456 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3460 done_path_create(&path
, dentry
);
3461 if (retry_estale(error
, lookup_flags
)) {
3462 lookup_flags
|= LOOKUP_REVAL
;
3468 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3470 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3473 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3475 int error
= may_create(dir
, dentry
);
3476 unsigned max_links
= dir
->i_sb
->s_max_links
;
3481 if (!dir
->i_op
->mkdir
)
3484 mode
&= (S_IRWXUGO
|S_ISVTX
);
3485 error
= security_inode_mkdir(dir
, dentry
, mode
);
3489 if (max_links
&& dir
->i_nlink
>= max_links
)
3492 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3494 fsnotify_mkdir(dir
, dentry
);
3497 EXPORT_SYMBOL(vfs_mkdir
);
3499 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3501 struct dentry
*dentry
;
3504 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3507 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3509 return PTR_ERR(dentry
);
3511 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3512 mode
&= ~current_umask();
3513 error
= security_path_mkdir(&path
, dentry
, mode
);
3515 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3516 done_path_create(&path
, dentry
);
3517 if (retry_estale(error
, lookup_flags
)) {
3518 lookup_flags
|= LOOKUP_REVAL
;
3524 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3526 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3530 * The dentry_unhash() helper will try to drop the dentry early: we
3531 * should have a usage count of 1 if we're the only user of this
3532 * dentry, and if that is true (possibly after pruning the dcache),
3533 * then we drop the dentry now.
3535 * A low-level filesystem can, if it choses, legally
3538 * if (!d_unhashed(dentry))
3541 * if it cannot handle the case of removing a directory
3542 * that is still in use by something else..
3544 void dentry_unhash(struct dentry
*dentry
)
3546 shrink_dcache_parent(dentry
);
3547 spin_lock(&dentry
->d_lock
);
3548 if (dentry
->d_lockref
.count
== 1)
3550 spin_unlock(&dentry
->d_lock
);
3552 EXPORT_SYMBOL(dentry_unhash
);
3554 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3556 int error
= may_delete(dir
, dentry
, 1);
3561 if (!dir
->i_op
->rmdir
)
3565 mutex_lock(&dentry
->d_inode
->i_mutex
);
3568 if (d_mountpoint(dentry
))
3571 error
= security_inode_rmdir(dir
, dentry
);
3575 shrink_dcache_parent(dentry
);
3576 error
= dir
->i_op
->rmdir(dir
, dentry
);
3580 dentry
->d_inode
->i_flags
|= S_DEAD
;
3584 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3590 EXPORT_SYMBOL(vfs_rmdir
);
3592 static long do_rmdir(int dfd
, const char __user
*pathname
)
3595 struct filename
*name
;
3596 struct dentry
*dentry
;
3597 struct nameidata nd
;
3598 unsigned int lookup_flags
= 0;
3600 name
= user_path_parent(dfd
, pathname
, &nd
, lookup_flags
);
3602 return PTR_ERR(name
);
3604 switch(nd
.last_type
) {
3616 nd
.flags
&= ~LOOKUP_PARENT
;
3617 error
= mnt_want_write(nd
.path
.mnt
);
3621 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3622 dentry
= lookup_hash(&nd
);
3623 error
= PTR_ERR(dentry
);
3626 if (!dentry
->d_inode
) {
3630 error
= security_path_rmdir(&nd
.path
, dentry
);
3633 error
= vfs_rmdir(nd
.path
.dentry
->d_inode
, dentry
);
3637 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3638 mnt_drop_write(nd
.path
.mnt
);
3642 if (retry_estale(error
, lookup_flags
)) {
3643 lookup_flags
|= LOOKUP_REVAL
;
3649 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3651 return do_rmdir(AT_FDCWD
, pathname
);
3655 * vfs_unlink - unlink a filesystem object
3656 * @dir: parent directory
3658 * @delegated_inode: returns victim inode, if the inode is delegated.
3660 * The caller must hold dir->i_mutex.
3662 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3663 * return a reference to the inode in delegated_inode. The caller
3664 * should then break the delegation on that inode and retry. Because
3665 * breaking a delegation may take a long time, the caller should drop
3666 * dir->i_mutex before doing so.
3668 * Alternatively, a caller may pass NULL for delegated_inode. This may
3669 * be appropriate for callers that expect the underlying filesystem not
3670 * to be NFS exported.
3672 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3674 struct inode
*target
= dentry
->d_inode
;
3675 int error
= may_delete(dir
, dentry
, 0);
3680 if (!dir
->i_op
->unlink
)
3683 mutex_lock(&target
->i_mutex
);
3684 if (d_mountpoint(dentry
))
3687 error
= security_inode_unlink(dir
, dentry
);
3689 error
= try_break_deleg(target
, delegated_inode
);
3692 error
= dir
->i_op
->unlink(dir
, dentry
);
3698 mutex_unlock(&target
->i_mutex
);
3700 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3701 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3702 fsnotify_link_count(target
);
3708 EXPORT_SYMBOL(vfs_unlink
);
3711 * Make sure that the actual truncation of the file will occur outside its
3712 * directory's i_mutex. Truncate can take a long time if there is a lot of
3713 * writeout happening, and we don't want to prevent access to the directory
3714 * while waiting on the I/O.
3716 static long do_unlinkat(int dfd
, const char __user
*pathname
)
3719 struct filename
*name
;
3720 struct dentry
*dentry
;
3721 struct nameidata nd
;
3722 struct inode
*inode
= NULL
;
3723 struct inode
*delegated_inode
= NULL
;
3724 unsigned int lookup_flags
= 0;
3726 name
= user_path_parent(dfd
, pathname
, &nd
, lookup_flags
);
3728 return PTR_ERR(name
);
3731 if (nd
.last_type
!= LAST_NORM
)
3734 nd
.flags
&= ~LOOKUP_PARENT
;
3735 error
= mnt_want_write(nd
.path
.mnt
);
3739 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3740 dentry
= lookup_hash(&nd
);
3741 error
= PTR_ERR(dentry
);
3742 if (!IS_ERR(dentry
)) {
3743 /* Why not before? Because we want correct error value */
3744 if (nd
.last
.name
[nd
.last
.len
])
3746 inode
= dentry
->d_inode
;
3747 if (d_is_negative(dentry
))
3750 error
= security_path_unlink(&nd
.path
, dentry
);
3753 error
= vfs_unlink(nd
.path
.dentry
->d_inode
, dentry
, &delegated_inode
);
3757 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3759 iput(inode
); /* truncate the inode here */
3761 if (delegated_inode
) {
3762 error
= break_deleg_wait(&delegated_inode
);
3766 mnt_drop_write(nd
.path
.mnt
);
3770 if (retry_estale(error
, lookup_flags
)) {
3771 lookup_flags
|= LOOKUP_REVAL
;
3778 if (d_is_negative(dentry
))
3780 else if (d_is_dir(dentry
))
3787 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
3789 if ((flag
& ~AT_REMOVEDIR
) != 0)
3792 if (flag
& AT_REMOVEDIR
)
3793 return do_rmdir(dfd
, pathname
);
3795 return do_unlinkat(dfd
, pathname
);
3798 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
3800 return do_unlinkat(AT_FDCWD
, pathname
);
3803 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
3805 int error
= may_create(dir
, dentry
);
3810 if (!dir
->i_op
->symlink
)
3813 error
= security_inode_symlink(dir
, dentry
, oldname
);
3817 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
3819 fsnotify_create(dir
, dentry
);
3822 EXPORT_SYMBOL(vfs_symlink
);
3824 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
3825 int, newdfd
, const char __user
*, newname
)
3828 struct filename
*from
;
3829 struct dentry
*dentry
;
3831 unsigned int lookup_flags
= 0;
3833 from
= getname(oldname
);
3835 return PTR_ERR(from
);
3837 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
3838 error
= PTR_ERR(dentry
);
3842 error
= security_path_symlink(&path
, dentry
, from
->name
);
3844 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
3845 done_path_create(&path
, dentry
);
3846 if (retry_estale(error
, lookup_flags
)) {
3847 lookup_flags
|= LOOKUP_REVAL
;
3855 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
3857 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
3861 * vfs_link - create a new link
3862 * @old_dentry: object to be linked
3864 * @new_dentry: where to create the new link
3865 * @delegated_inode: returns inode needing a delegation break
3867 * The caller must hold dir->i_mutex
3869 * If vfs_link discovers a delegation on the to-be-linked file in need
3870 * of breaking, it will return -EWOULDBLOCK and return a reference to the
3871 * inode in delegated_inode. The caller should then break the delegation
3872 * and retry. Because breaking a delegation may take a long time, the
3873 * caller should drop the i_mutex before doing so.
3875 * Alternatively, a caller may pass NULL for delegated_inode. This may
3876 * be appropriate for callers that expect the underlying filesystem not
3877 * to be NFS exported.
3879 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
3881 struct inode
*inode
= old_dentry
->d_inode
;
3882 unsigned max_links
= dir
->i_sb
->s_max_links
;
3888 error
= may_create(dir
, new_dentry
);
3892 if (dir
->i_sb
!= inode
->i_sb
)
3896 * A link to an append-only or immutable file cannot be created.
3898 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3900 if (!dir
->i_op
->link
)
3902 if (S_ISDIR(inode
->i_mode
))
3905 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3909 mutex_lock(&inode
->i_mutex
);
3910 /* Make sure we don't allow creating hardlink to an unlinked file */
3911 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
3913 else if (max_links
&& inode
->i_nlink
>= max_links
)
3916 error
= try_break_deleg(inode
, delegated_inode
);
3918 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3921 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
3922 spin_lock(&inode
->i_lock
);
3923 inode
->i_state
&= ~I_LINKABLE
;
3924 spin_unlock(&inode
->i_lock
);
3926 mutex_unlock(&inode
->i_mutex
);
3928 fsnotify_link(dir
, inode
, new_dentry
);
3931 EXPORT_SYMBOL(vfs_link
);
3934 * Hardlinks are often used in delicate situations. We avoid
3935 * security-related surprises by not following symlinks on the
3938 * We don't follow them on the oldname either to be compatible
3939 * with linux 2.0, and to avoid hard-linking to directories
3940 * and other special files. --ADM
3942 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
3943 int, newdfd
, const char __user
*, newname
, int, flags
)
3945 struct dentry
*new_dentry
;
3946 struct path old_path
, new_path
;
3947 struct inode
*delegated_inode
= NULL
;
3951 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
3954 * To use null names we require CAP_DAC_READ_SEARCH
3955 * This ensures that not everyone will be able to create
3956 * handlink using the passed filedescriptor.
3958 if (flags
& AT_EMPTY_PATH
) {
3959 if (!capable(CAP_DAC_READ_SEARCH
))
3964 if (flags
& AT_SYMLINK_FOLLOW
)
3965 how
|= LOOKUP_FOLLOW
;
3967 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
3971 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
3972 (how
& LOOKUP_REVAL
));
3973 error
= PTR_ERR(new_dentry
);
3974 if (IS_ERR(new_dentry
))
3978 if (old_path
.mnt
!= new_path
.mnt
)
3980 error
= may_linkat(&old_path
);
3981 if (unlikely(error
))
3983 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
3986 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
3988 done_path_create(&new_path
, new_dentry
);
3989 if (delegated_inode
) {
3990 error
= break_deleg_wait(&delegated_inode
);
3992 path_put(&old_path
);
3996 if (retry_estale(error
, how
)) {
3997 path_put(&old_path
);
3998 how
|= LOOKUP_REVAL
;
4002 path_put(&old_path
);
4007 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
4009 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4013 * vfs_rename - rename a filesystem object
4014 * @old_dir: parent of source
4015 * @old_dentry: source
4016 * @new_dir: parent of destination
4017 * @new_dentry: destination
4018 * @delegated_inode: returns an inode needing a delegation break
4019 * @flags: rename flags
4021 * The caller must hold multiple mutexes--see lock_rename()).
4023 * If vfs_rename discovers a delegation in need of breaking at either
4024 * the source or destination, it will return -EWOULDBLOCK and return a
4025 * reference to the inode in delegated_inode. The caller should then
4026 * break the delegation and retry. Because breaking a delegation may
4027 * take a long time, the caller should drop all locks before doing
4030 * Alternatively, a caller may pass NULL for delegated_inode. This may
4031 * be appropriate for callers that expect the underlying filesystem not
4032 * to be NFS exported.
4034 * The worst of all namespace operations - renaming directory. "Perverted"
4035 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4037 * a) we can get into loop creation.
4038 * b) race potential - two innocent renames can create a loop together.
4039 * That's where 4.4 screws up. Current fix: serialization on
4040 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4042 * c) we have to lock _four_ objects - parents and victim (if it exists),
4043 * and source (if it is not a directory).
4044 * And that - after we got ->i_mutex on parents (until then we don't know
4045 * whether the target exists). Solution: try to be smart with locking
4046 * order for inodes. We rely on the fact that tree topology may change
4047 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4048 * move will be locked. Thus we can rank directories by the tree
4049 * (ancestors first) and rank all non-directories after them.
4050 * That works since everybody except rename does "lock parent, lookup,
4051 * lock child" and rename is under ->s_vfs_rename_mutex.
4052 * HOWEVER, it relies on the assumption that any object with ->lookup()
4053 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4054 * we'd better make sure that there's no link(2) for them.
4055 * d) conversion from fhandle to dentry may come in the wrong moment - when
4056 * we are removing the target. Solution: we will have to grab ->i_mutex
4057 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4058 * ->i_mutex on parents, which works but leads to some truly excessive
4061 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4062 struct inode
*new_dir
, struct dentry
*new_dentry
,
4063 struct inode
**delegated_inode
, unsigned int flags
)
4066 bool is_dir
= d_is_dir(old_dentry
);
4067 const unsigned char *old_name
;
4068 struct inode
*source
= old_dentry
->d_inode
;
4069 struct inode
*target
= new_dentry
->d_inode
;
4070 bool new_is_dir
= false;
4071 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4073 if (source
== target
)
4076 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4081 error
= may_create(new_dir
, new_dentry
);
4083 new_is_dir
= d_is_dir(new_dentry
);
4085 if (!(flags
& RENAME_EXCHANGE
))
4086 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4088 error
= may_delete(new_dir
, new_dentry
, new_is_dir
);
4093 if (!old_dir
->i_op
->rename
&& !old_dir
->i_op
->rename2
)
4096 if (flags
&& !old_dir
->i_op
->rename2
)
4100 * If we are going to change the parent - check write permissions,
4101 * we'll need to flip '..'.
4103 if (new_dir
!= old_dir
) {
4105 error
= inode_permission(source
, MAY_WRITE
);
4109 if ((flags
& RENAME_EXCHANGE
) && new_is_dir
) {
4110 error
= inode_permission(target
, MAY_WRITE
);
4116 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
,
4121 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
4123 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4124 lock_two_nondirectories(source
, target
);
4126 mutex_lock(&target
->i_mutex
);
4129 if (d_mountpoint(old_dentry
) || d_mountpoint(new_dentry
))
4132 if (max_links
&& new_dir
!= old_dir
) {
4134 if (is_dir
&& !new_is_dir
&& new_dir
->i_nlink
>= max_links
)
4136 if ((flags
& RENAME_EXCHANGE
) && !is_dir
&& new_is_dir
&&
4137 old_dir
->i_nlink
>= max_links
)
4140 if (is_dir
&& !(flags
& RENAME_EXCHANGE
) && target
)
4141 shrink_dcache_parent(new_dentry
);
4143 error
= try_break_deleg(source
, delegated_inode
);
4147 if (target
&& !new_is_dir
) {
4148 error
= try_break_deleg(target
, delegated_inode
);
4152 if (!old_dir
->i_op
->rename2
) {
4153 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
,
4154 new_dir
, new_dentry
);
4156 WARN_ON(old_dir
->i_op
->rename
!= NULL
);
4157 error
= old_dir
->i_op
->rename2(old_dir
, old_dentry
,
4158 new_dir
, new_dentry
, flags
);
4163 if (!(flags
& RENAME_EXCHANGE
) && target
) {
4165 target
->i_flags
|= S_DEAD
;
4166 dont_mount(new_dentry
);
4168 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
)) {
4169 if (!(flags
& RENAME_EXCHANGE
))
4170 d_move(old_dentry
, new_dentry
);
4172 d_exchange(old_dentry
, new_dentry
);
4175 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4176 unlock_two_nondirectories(source
, target
);
4178 mutex_unlock(&target
->i_mutex
);
4181 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
4182 !(flags
& RENAME_EXCHANGE
) ? target
: NULL
, old_dentry
);
4183 if (flags
& RENAME_EXCHANGE
) {
4184 fsnotify_move(new_dir
, old_dir
, old_dentry
->d_name
.name
,
4185 new_is_dir
, NULL
, new_dentry
);
4188 fsnotify_oldname_free(old_name
);
4192 EXPORT_SYMBOL(vfs_rename
);
4194 SYSCALL_DEFINE5(renameat2
, int, olddfd
, const char __user
*, oldname
,
4195 int, newdfd
, const char __user
*, newname
, unsigned int, flags
)
4197 struct dentry
*old_dir
, *new_dir
;
4198 struct dentry
*old_dentry
, *new_dentry
;
4199 struct dentry
*trap
;
4200 struct nameidata oldnd
, newnd
;
4201 struct inode
*delegated_inode
= NULL
;
4202 struct filename
*from
;
4203 struct filename
*to
;
4204 unsigned int lookup_flags
= 0;
4205 bool should_retry
= false;
4208 if (flags
& ~(RENAME_NOREPLACE
| RENAME_EXCHANGE
))
4211 if ((flags
& RENAME_NOREPLACE
) && (flags
& RENAME_EXCHANGE
))
4215 from
= user_path_parent(olddfd
, oldname
, &oldnd
, lookup_flags
);
4217 error
= PTR_ERR(from
);
4221 to
= user_path_parent(newdfd
, newname
, &newnd
, lookup_flags
);
4223 error
= PTR_ERR(to
);
4228 if (oldnd
.path
.mnt
!= newnd
.path
.mnt
)
4231 old_dir
= oldnd
.path
.dentry
;
4233 if (oldnd
.last_type
!= LAST_NORM
)
4236 new_dir
= newnd
.path
.dentry
;
4237 if (flags
& RENAME_NOREPLACE
)
4239 if (newnd
.last_type
!= LAST_NORM
)
4242 error
= mnt_want_write(oldnd
.path
.mnt
);
4246 oldnd
.flags
&= ~LOOKUP_PARENT
;
4247 newnd
.flags
&= ~LOOKUP_PARENT
;
4248 if (!(flags
& RENAME_EXCHANGE
))
4249 newnd
.flags
|= LOOKUP_RENAME_TARGET
;
4252 trap
= lock_rename(new_dir
, old_dir
);
4254 old_dentry
= lookup_hash(&oldnd
);
4255 error
= PTR_ERR(old_dentry
);
4256 if (IS_ERR(old_dentry
))
4258 /* source must exist */
4260 if (d_is_negative(old_dentry
))
4262 new_dentry
= lookup_hash(&newnd
);
4263 error
= PTR_ERR(new_dentry
);
4264 if (IS_ERR(new_dentry
))
4267 if ((flags
& RENAME_NOREPLACE
) && d_is_positive(new_dentry
))
4269 if (flags
& RENAME_EXCHANGE
) {
4271 if (d_is_negative(new_dentry
))
4274 if (!d_is_dir(new_dentry
)) {
4276 if (newnd
.last
.name
[newnd
.last
.len
])
4280 /* unless the source is a directory trailing slashes give -ENOTDIR */
4281 if (!d_is_dir(old_dentry
)) {
4283 if (oldnd
.last
.name
[oldnd
.last
.len
])
4285 if (!(flags
& RENAME_EXCHANGE
) && newnd
.last
.name
[newnd
.last
.len
])
4288 /* source should not be ancestor of target */
4290 if (old_dentry
== trap
)
4292 /* target should not be an ancestor of source */
4293 if (!(flags
& RENAME_EXCHANGE
))
4295 if (new_dentry
== trap
)
4298 error
= security_path_rename(&oldnd
.path
, old_dentry
,
4299 &newnd
.path
, new_dentry
, flags
);
4302 error
= vfs_rename(old_dir
->d_inode
, old_dentry
,
4303 new_dir
->d_inode
, new_dentry
,
4304 &delegated_inode
, flags
);
4310 unlock_rename(new_dir
, old_dir
);
4311 if (delegated_inode
) {
4312 error
= break_deleg_wait(&delegated_inode
);
4316 mnt_drop_write(oldnd
.path
.mnt
);
4318 if (retry_estale(error
, lookup_flags
))
4319 should_retry
= true;
4320 path_put(&newnd
.path
);
4323 path_put(&oldnd
.path
);
4326 should_retry
= false;
4327 lookup_flags
|= LOOKUP_REVAL
;
4334 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4335 int, newdfd
, const char __user
*, newname
)
4337 return sys_renameat2(olddfd
, oldname
, newdfd
, newname
, 0);
4340 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4342 return sys_renameat2(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4345 int readlink_copy(char __user
*buffer
, int buflen
, const char *link
)
4347 int len
= PTR_ERR(link
);
4352 if (len
> (unsigned) buflen
)
4354 if (copy_to_user(buffer
, link
, len
))
4359 EXPORT_SYMBOL(readlink_copy
);
4362 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4363 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4364 * using) it for any given inode is up to filesystem.
4366 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4368 struct nameidata nd
;
4373 cookie
= dentry
->d_inode
->i_op
->follow_link(dentry
, &nd
);
4375 return PTR_ERR(cookie
);
4377 res
= readlink_copy(buffer
, buflen
, nd_get_link(&nd
));
4378 if (dentry
->d_inode
->i_op
->put_link
)
4379 dentry
->d_inode
->i_op
->put_link(dentry
, &nd
, cookie
);
4382 EXPORT_SYMBOL(generic_readlink
);
4384 /* get the link contents into pagecache */
4385 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
4389 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
4390 page
= read_mapping_page(mapping
, 0, NULL
);
4395 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
4399 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4401 struct page
*page
= NULL
;
4402 int res
= readlink_copy(buffer
, buflen
, page_getlink(dentry
, &page
));
4405 page_cache_release(page
);
4409 EXPORT_SYMBOL(page_readlink
);
4411 void *page_follow_link_light(struct dentry
*dentry
, struct nameidata
*nd
)
4413 struct page
*page
= NULL
;
4414 nd_set_link(nd
, page_getlink(dentry
, &page
));
4417 EXPORT_SYMBOL(page_follow_link_light
);
4419 void page_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
4421 struct page
*page
= cookie
;
4425 page_cache_release(page
);
4428 EXPORT_SYMBOL(page_put_link
);
4431 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4433 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4435 struct address_space
*mapping
= inode
->i_mapping
;
4440 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
4442 flags
|= AOP_FLAG_NOFS
;
4445 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4446 flags
, &page
, &fsdata
);
4450 kaddr
= kmap_atomic(page
);
4451 memcpy(kaddr
, symname
, len
-1);
4452 kunmap_atomic(kaddr
);
4454 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4461 mark_inode_dirty(inode
);
4466 EXPORT_SYMBOL(__page_symlink
);
4468 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4470 return __page_symlink(inode
, symname
, len
,
4471 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
4473 EXPORT_SYMBOL(page_symlink
);
4475 const struct inode_operations page_symlink_inode_operations
= {
4476 .readlink
= generic_readlink
,
4477 .follow_link
= page_follow_link_light
,
4478 .put_link
= page_put_link
,
4480 EXPORT_SYMBOL(page_symlink_inode_operations
);