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/module.h>
19 #include <linux/slab.h>
21 #include <linux/namei.h>
22 #include <linux/pagemap.h>
23 #include <linux/fsnotify.h>
24 #include <linux/personality.h>
25 #include <linux/security.h>
26 #include <linux/ima.h>
27 #include <linux/syscalls.h>
28 #include <linux/mount.h>
29 #include <linux/audit.h>
30 #include <linux/capability.h>
31 #include <linux/file.h>
32 #include <linux/fcntl.h>
33 #include <linux/device_cgroup.h>
34 #include <linux/fs_struct.h>
35 #include <asm/uaccess.h>
39 /* [Feb-1997 T. Schoebel-Theuer]
40 * Fundamental changes in the pathname lookup mechanisms (namei)
41 * were necessary because of omirr. The reason is that omirr needs
42 * to know the _real_ pathname, not the user-supplied one, in case
43 * of symlinks (and also when transname replacements occur).
45 * The new code replaces the old recursive symlink resolution with
46 * an iterative one (in case of non-nested symlink chains). It does
47 * this with calls to <fs>_follow_link().
48 * As a side effect, dir_namei(), _namei() and follow_link() are now
49 * replaced with a single function lookup_dentry() that can handle all
50 * the special cases of the former code.
52 * With the new dcache, the pathname is stored at each inode, at least as
53 * long as the refcount of the inode is positive. As a side effect, the
54 * size of the dcache depends on the inode cache and thus is dynamic.
56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57 * resolution to correspond with current state of the code.
59 * Note that the symlink resolution is not *completely* iterative.
60 * There is still a significant amount of tail- and mid- recursion in
61 * the algorithm. Also, note that <fs>_readlink() is not used in
62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63 * may return different results than <fs>_follow_link(). Many virtual
64 * filesystems (including /proc) exhibit this behavior.
67 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
69 * and the name already exists in form of a symlink, try to create the new
70 * name indicated by the symlink. The old code always complained that the
71 * name already exists, due to not following the symlink even if its target
72 * is nonexistent. The new semantics affects also mknod() and link() when
73 * the name is a symlink pointing to a non-existant name.
75 * I don't know which semantics is the right one, since I have no access
76 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78 * "old" one. Personally, I think the new semantics is much more logical.
79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
80 * file does succeed in both HP-UX and SunOs, but not in Solaris
81 * and in the old Linux semantics.
84 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85 * semantics. See the comments in "open_namei" and "do_link" below.
87 * [10-Sep-98 Alan Modra] Another symlink change.
90 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91 * inside the path - always follow.
92 * in the last component in creation/removal/renaming - never follow.
93 * if LOOKUP_FOLLOW passed - follow.
94 * if the pathname has trailing slashes - follow.
95 * otherwise - don't follow.
96 * (applied in that order).
98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100 * During the 2.4 we need to fix the userland stuff depending on it -
101 * hopefully we will be able to get rid of that wart in 2.5. So far only
102 * XEmacs seems to be relying on it...
105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
107 * any extra contention...
110 /* In order to reduce some races, while at the same time doing additional
111 * checking and hopefully speeding things up, we copy filenames to the
112 * kernel data space before using them..
114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115 * PATH_MAX includes the nul terminator --RR.
117 static int do_getname(const char __user
*filename
, char *page
)
120 unsigned long len
= PATH_MAX
;
122 if (!segment_eq(get_fs(), KERNEL_DS
)) {
123 if ((unsigned long) filename
>= TASK_SIZE
)
125 if (TASK_SIZE
- (unsigned long) filename
< PATH_MAX
)
126 len
= TASK_SIZE
- (unsigned long) filename
;
129 retval
= strncpy_from_user(page
, filename
, len
);
133 return -ENAMETOOLONG
;
139 static char *getname_flags(const char __user
* filename
, int flags
)
143 result
= ERR_PTR(-ENOMEM
);
146 int retval
= do_getname(filename
, tmp
);
150 if (retval
!= -ENOENT
|| !(flags
& LOOKUP_EMPTY
)) {
152 result
= ERR_PTR(retval
);
156 audit_getname(result
);
160 char *getname(const char __user
* filename
)
162 return getname_flags(filename
, 0);
165 #ifdef CONFIG_AUDITSYSCALL
166 void putname(const char *name
)
168 if (unlikely(!audit_dummy_context()))
173 EXPORT_SYMBOL(putname
);
177 * This does basic POSIX ACL permission checking
179 static int acl_permission_check(struct inode
*inode
, int mask
, unsigned int flags
,
180 int (*check_acl
)(struct inode
*inode
, int mask
, unsigned int flags
))
182 umode_t mode
= inode
->i_mode
;
184 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
186 if (current_fsuid() == inode
->i_uid
)
189 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
) && check_acl
) {
190 int error
= check_acl(inode
, mask
, flags
);
191 if (error
!= -EAGAIN
)
195 if (in_group_p(inode
->i_gid
))
200 * If the DACs are ok we don't need any capability check.
202 if ((mask
& ~mode
) == 0)
208 * generic_permission - check for access rights on a Posix-like filesystem
209 * @inode: inode to check access rights for
210 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
211 * @check_acl: optional callback to check for Posix ACLs
212 * @flags: IPERM_FLAG_ flags.
214 * Used to check for read/write/execute permissions on a file.
215 * We use "fsuid" for this, letting us set arbitrary permissions
216 * for filesystem access without changing the "normal" uids which
217 * are used for other things.
219 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
220 * request cannot be satisfied (eg. requires blocking or too much complexity).
221 * It would then be called again in ref-walk mode.
223 int generic_permission(struct inode
*inode
, int mask
, unsigned int flags
,
224 int (*check_acl
)(struct inode
*inode
, int mask
, unsigned int flags
))
229 * Do the basic POSIX ACL permission checks.
231 ret
= acl_permission_check(inode
, mask
, flags
, check_acl
);
236 * Read/write DACs are always overridable.
237 * Executable DACs are overridable if at least one exec bit is set.
239 if (!(mask
& MAY_EXEC
) || execute_ok(inode
))
240 if (capable(CAP_DAC_OVERRIDE
))
244 * Searching includes executable on directories, else just read.
246 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
247 if (mask
== MAY_READ
|| (S_ISDIR(inode
->i_mode
) && !(mask
& MAY_WRITE
)))
248 if (capable(CAP_DAC_READ_SEARCH
))
255 * inode_permission - check for access rights to a given inode
256 * @inode: inode to check permission on
257 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
259 * Used to check for read/write/execute permissions on an inode.
260 * We use "fsuid" for this, letting us set arbitrary permissions
261 * for filesystem access without changing the "normal" uids which
262 * are used for other things.
264 int inode_permission(struct inode
*inode
, int mask
)
268 if (mask
& MAY_WRITE
) {
269 umode_t mode
= inode
->i_mode
;
272 * Nobody gets write access to a read-only fs.
274 if (IS_RDONLY(inode
) &&
275 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
279 * Nobody gets write access to an immutable file.
281 if (IS_IMMUTABLE(inode
))
285 if (inode
->i_op
->permission
)
286 retval
= inode
->i_op
->permission(inode
, mask
, 0);
288 retval
= generic_permission(inode
, mask
, 0,
289 inode
->i_op
->check_acl
);
294 retval
= devcgroup_inode_permission(inode
, mask
);
298 return security_inode_permission(inode
, mask
);
302 * file_permission - check for additional access rights to a given file
303 * @file: file to check access rights for
304 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
306 * Used to check for read/write/execute permissions on an already opened
310 * Do not use this function in new code. All access checks should
311 * be done using inode_permission().
313 int file_permission(struct file
*file
, int mask
)
315 return inode_permission(file
->f_path
.dentry
->d_inode
, mask
);
319 * get_write_access() gets write permission for a file.
320 * put_write_access() releases this write permission.
321 * This is used for regular files.
322 * We cannot support write (and maybe mmap read-write shared) accesses and
323 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
324 * can have the following values:
325 * 0: no writers, no VM_DENYWRITE mappings
326 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
327 * > 0: (i_writecount) users are writing to the file.
329 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
330 * except for the cases where we don't hold i_writecount yet. Then we need to
331 * use {get,deny}_write_access() - these functions check the sign and refuse
332 * to do the change if sign is wrong. Exclusion between them is provided by
333 * the inode->i_lock spinlock.
336 int get_write_access(struct inode
* inode
)
338 spin_lock(&inode
->i_lock
);
339 if (atomic_read(&inode
->i_writecount
) < 0) {
340 spin_unlock(&inode
->i_lock
);
343 atomic_inc(&inode
->i_writecount
);
344 spin_unlock(&inode
->i_lock
);
349 int deny_write_access(struct file
* file
)
351 struct inode
*inode
= file
->f_path
.dentry
->d_inode
;
353 spin_lock(&inode
->i_lock
);
354 if (atomic_read(&inode
->i_writecount
) > 0) {
355 spin_unlock(&inode
->i_lock
);
358 atomic_dec(&inode
->i_writecount
);
359 spin_unlock(&inode
->i_lock
);
365 * path_get - get a reference to a path
366 * @path: path to get the reference to
368 * Given a path increment the reference count to the dentry and the vfsmount.
370 void path_get(struct path
*path
)
375 EXPORT_SYMBOL(path_get
);
378 * path_put - put a reference to a path
379 * @path: path to put the reference to
381 * Given a path decrement the reference count to the dentry and the vfsmount.
383 void path_put(struct path
*path
)
388 EXPORT_SYMBOL(path_put
);
391 * nameidata_drop_rcu - drop this nameidata out of rcu-walk
392 * @nd: nameidata pathwalk data to drop
393 * Returns: 0 on success, -ECHILD on failure
395 * Path walking has 2 modes, rcu-walk and ref-walk (see
396 * Documentation/filesystems/path-lookup.txt). __drop_rcu* functions attempt
397 * to drop out of rcu-walk mode and take normal reference counts on dentries
398 * and vfsmounts to transition to rcu-walk mode. __drop_rcu* functions take
399 * refcounts at the last known good point before rcu-walk got stuck, so
400 * ref-walk may continue from there. If this is not successful (eg. a seqcount
401 * has changed), then failure is returned and path walk restarts from the
402 * beginning in ref-walk mode.
404 * nameidata_drop_rcu attempts to drop the current nd->path and nd->root into
405 * ref-walk. Must be called from rcu-walk context.
407 static int nameidata_drop_rcu(struct nameidata
*nd
)
409 struct fs_struct
*fs
= current
->fs
;
410 struct dentry
*dentry
= nd
->path
.dentry
;
413 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
414 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
416 spin_lock(&fs
->lock
);
417 if (nd
->root
.mnt
!= fs
->root
.mnt
||
418 nd
->root
.dentry
!= fs
->root
.dentry
)
421 spin_lock(&dentry
->d_lock
);
422 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
424 BUG_ON(nd
->inode
!= dentry
->d_inode
);
425 spin_unlock(&dentry
->d_lock
);
428 spin_unlock(&fs
->lock
);
430 mntget(nd
->path
.mnt
);
433 br_read_unlock(vfsmount_lock
);
434 nd
->flags
&= ~LOOKUP_RCU
;
437 spin_unlock(&dentry
->d_lock
);
440 spin_unlock(&fs
->lock
);
444 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
445 static inline int nameidata_drop_rcu_maybe(struct nameidata
*nd
)
447 if (nd
->flags
& LOOKUP_RCU
)
448 return nameidata_drop_rcu(nd
);
453 * nameidata_dentry_drop_rcu - drop nameidata and dentry out of rcu-walk
454 * @nd: nameidata pathwalk data to drop
455 * @dentry: dentry to drop
456 * Returns: 0 on success, -ECHILD on failure
458 * nameidata_dentry_drop_rcu attempts to drop the current nd->path and nd->root,
459 * and dentry into ref-walk. @dentry must be a path found by a do_lookup call on
460 * @nd. Must be called from rcu-walk context.
462 static int nameidata_dentry_drop_rcu(struct nameidata
*nd
, struct dentry
*dentry
)
464 struct fs_struct
*fs
= current
->fs
;
465 struct dentry
*parent
= nd
->path
.dentry
;
468 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
469 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
471 spin_lock(&fs
->lock
);
472 if (nd
->root
.mnt
!= fs
->root
.mnt
||
473 nd
->root
.dentry
!= fs
->root
.dentry
)
476 spin_lock(&parent
->d_lock
);
477 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
478 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
481 * If the sequence check on the child dentry passed, then the child has
482 * not been removed from its parent. This means the parent dentry must
483 * be valid and able to take a reference at this point.
485 BUG_ON(!IS_ROOT(dentry
) && dentry
->d_parent
!= parent
);
486 BUG_ON(!parent
->d_count
);
488 spin_unlock(&dentry
->d_lock
);
489 spin_unlock(&parent
->d_lock
);
492 spin_unlock(&fs
->lock
);
494 mntget(nd
->path
.mnt
);
497 br_read_unlock(vfsmount_lock
);
498 nd
->flags
&= ~LOOKUP_RCU
;
501 spin_unlock(&dentry
->d_lock
);
502 spin_unlock(&parent
->d_lock
);
505 spin_unlock(&fs
->lock
);
509 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
510 static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata
*nd
, struct dentry
*dentry
)
512 if (nd
->flags
& LOOKUP_RCU
) {
513 if (unlikely(nameidata_dentry_drop_rcu(nd
, dentry
))) {
514 nd
->flags
&= ~LOOKUP_RCU
;
515 if (!(nd
->flags
& LOOKUP_ROOT
))
518 br_read_unlock(vfsmount_lock
);
526 * nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
527 * @nd: nameidata pathwalk data to drop
528 * Returns: 0 on success, -ECHILD on failure
530 * nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
531 * nd->path should be the final element of the lookup, so nd->root is discarded.
532 * Must be called from rcu-walk context.
534 static int nameidata_drop_rcu_last(struct nameidata
*nd
)
536 struct dentry
*dentry
= nd
->path
.dentry
;
538 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
539 nd
->flags
&= ~LOOKUP_RCU
;
540 if (!(nd
->flags
& LOOKUP_ROOT
))
542 spin_lock(&dentry
->d_lock
);
543 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
545 BUG_ON(nd
->inode
!= dentry
->d_inode
);
546 spin_unlock(&dentry
->d_lock
);
548 mntget(nd
->path
.mnt
);
551 br_read_unlock(vfsmount_lock
);
556 spin_unlock(&dentry
->d_lock
);
558 br_read_unlock(vfsmount_lock
);
563 * release_open_intent - free up open intent resources
564 * @nd: pointer to nameidata
566 void release_open_intent(struct nameidata
*nd
)
568 struct file
*file
= nd
->intent
.open
.file
;
570 if (file
&& !IS_ERR(file
)) {
571 if (file
->f_path
.dentry
== NULL
)
578 static inline int d_revalidate(struct dentry
*dentry
, struct nameidata
*nd
)
580 return dentry
->d_op
->d_revalidate(dentry
, nd
);
583 static struct dentry
*
584 do_revalidate(struct dentry
*dentry
, struct nameidata
*nd
)
586 int status
= d_revalidate(dentry
, nd
);
587 if (unlikely(status
<= 0)) {
589 * The dentry failed validation.
590 * If d_revalidate returned 0 attempt to invalidate
591 * the dentry otherwise d_revalidate is asking us
592 * to return a fail status.
596 dentry
= ERR_PTR(status
);
597 } else if (!d_invalidate(dentry
)) {
606 * handle_reval_path - force revalidation of a dentry
608 * In some situations the path walking code will trust dentries without
609 * revalidating them. This causes problems for filesystems that depend on
610 * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
611 * (which indicates that it's possible for the dentry to go stale), force
612 * a d_revalidate call before proceeding.
614 * Returns 0 if the revalidation was successful. If the revalidation fails,
615 * either return the error returned by d_revalidate or -ESTALE if the
616 * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
617 * invalidate the dentry. It's up to the caller to handle putting references
618 * to the path if necessary.
620 static inline int handle_reval_path(struct nameidata
*nd
)
622 struct dentry
*dentry
= nd
->path
.dentry
;
625 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
628 if (likely(!(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)))
631 if (likely(!(dentry
->d_sb
->s_type
->fs_flags
& FS_REVAL_DOT
)))
634 /* Note: we do not d_invalidate() */
635 status
= d_revalidate(dentry
, nd
);
646 * Short-cut version of permission(), for calling on directories
647 * during pathname resolution. Combines parts of permission()
648 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
650 * If appropriate, check DAC only. If not appropriate, or
651 * short-cut DAC fails, then call ->permission() to do more
652 * complete permission check.
654 static inline int exec_permission(struct inode
*inode
, unsigned int flags
)
658 if (inode
->i_op
->permission
) {
659 ret
= inode
->i_op
->permission(inode
, MAY_EXEC
, flags
);
661 ret
= acl_permission_check(inode
, MAY_EXEC
, flags
,
662 inode
->i_op
->check_acl
);
669 if (capable(CAP_DAC_OVERRIDE
) || capable(CAP_DAC_READ_SEARCH
))
674 return security_inode_exec_permission(inode
, flags
);
677 static __always_inline
void set_root(struct nameidata
*nd
)
680 get_fs_root(current
->fs
, &nd
->root
);
683 static int link_path_walk(const char *, struct nameidata
*);
685 static __always_inline
void set_root_rcu(struct nameidata
*nd
)
688 struct fs_struct
*fs
= current
->fs
;
692 seq
= read_seqcount_begin(&fs
->seq
);
694 } while (read_seqcount_retry(&fs
->seq
, seq
));
698 static __always_inline
int __vfs_follow_link(struct nameidata
*nd
, const char *link
)
710 nd
->flags
|= LOOKUP_JUMPED
;
712 nd
->inode
= nd
->path
.dentry
->d_inode
;
714 ret
= link_path_walk(link
, nd
);
718 return PTR_ERR(link
);
721 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
724 if (path
->mnt
!= nd
->path
.mnt
)
728 static inline void path_to_nameidata(const struct path
*path
,
729 struct nameidata
*nd
)
731 if (!(nd
->flags
& LOOKUP_RCU
)) {
732 dput(nd
->path
.dentry
);
733 if (nd
->path
.mnt
!= path
->mnt
)
734 mntput(nd
->path
.mnt
);
736 nd
->path
.mnt
= path
->mnt
;
737 nd
->path
.dentry
= path
->dentry
;
740 static __always_inline
int
741 __do_follow_link(const struct path
*link
, struct nameidata
*nd
, void **p
)
744 struct dentry
*dentry
= link
->dentry
;
746 BUG_ON(nd
->flags
& LOOKUP_RCU
);
748 touch_atime(link
->mnt
, dentry
);
749 nd_set_link(nd
, NULL
);
751 if (link
->mnt
== nd
->path
.mnt
)
754 error
= security_inode_follow_link(link
->dentry
, nd
);
756 *p
= ERR_PTR(error
); /* no ->put_link(), please */
761 nd
->last_type
= LAST_BIND
;
762 *p
= dentry
->d_inode
->i_op
->follow_link(dentry
, nd
);
765 char *s
= nd_get_link(nd
);
768 error
= __vfs_follow_link(nd
, s
);
769 else if (nd
->last_type
== LAST_BIND
)
770 nd
->flags
|= LOOKUP_JUMPED
;
776 * This limits recursive symlink follows to 8, while
777 * limiting consecutive symlinks to 40.
779 * Without that kind of total limit, nasty chains of consecutive
780 * symlinks can cause almost arbitrarily long lookups.
782 static inline int do_follow_link(struct inode
*inode
, struct path
*path
, struct nameidata
*nd
)
787 /* We drop rcu-walk here */
788 if (nameidata_dentry_drop_rcu_maybe(nd
, path
->dentry
))
790 BUG_ON(inode
!= path
->dentry
->d_inode
);
792 if (current
->link_count
>= MAX_NESTED_LINKS
)
794 if (current
->total_link_count
>= 40)
796 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
798 current
->link_count
++;
799 current
->total_link_count
++;
801 err
= __do_follow_link(path
, nd
, &cookie
);
802 if (!IS_ERR(cookie
) && path
->dentry
->d_inode
->i_op
->put_link
)
803 path
->dentry
->d_inode
->i_op
->put_link(path
->dentry
, nd
, cookie
);
805 current
->link_count
--;
809 path_put_conditional(path
, nd
);
814 static int follow_up_rcu(struct path
*path
)
816 struct vfsmount
*parent
;
817 struct dentry
*mountpoint
;
819 parent
= path
->mnt
->mnt_parent
;
820 if (parent
== path
->mnt
)
822 mountpoint
= path
->mnt
->mnt_mountpoint
;
823 path
->dentry
= mountpoint
;
828 int follow_up(struct path
*path
)
830 struct vfsmount
*parent
;
831 struct dentry
*mountpoint
;
833 br_read_lock(vfsmount_lock
);
834 parent
= path
->mnt
->mnt_parent
;
835 if (parent
== path
->mnt
) {
836 br_read_unlock(vfsmount_lock
);
840 mountpoint
= dget(path
->mnt
->mnt_mountpoint
);
841 br_read_unlock(vfsmount_lock
);
843 path
->dentry
= mountpoint
;
850 * Perform an automount
851 * - return -EISDIR to tell follow_managed() to stop and return the path we
854 static int follow_automount(struct path
*path
, unsigned flags
,
857 struct vfsmount
*mnt
;
860 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
863 /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
864 * and this is the terminal part of the path.
866 if ((flags
& LOOKUP_NO_AUTOMOUNT
) && !(flags
& LOOKUP_CONTINUE
))
867 return -EISDIR
; /* we actually want to stop here */
869 /* We want to mount if someone is trying to open/create a file of any
870 * type under the mountpoint, wants to traverse through the mountpoint
871 * or wants to open the mounted directory.
873 * We don't want to mount if someone's just doing a stat and they've
874 * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
875 * appended a '/' to the name.
877 if (!(flags
& LOOKUP_FOLLOW
) &&
878 !(flags
& (LOOKUP_CONTINUE
| LOOKUP_DIRECTORY
|
879 LOOKUP_OPEN
| LOOKUP_CREATE
)))
882 current
->total_link_count
++;
883 if (current
->total_link_count
>= 40)
886 mnt
= path
->dentry
->d_op
->d_automount(path
);
889 * The filesystem is allowed to return -EISDIR here to indicate
890 * it doesn't want to automount. For instance, autofs would do
891 * this so that its userspace daemon can mount on this dentry.
893 * However, we can only permit this if it's a terminal point in
894 * the path being looked up; if it wasn't then the remainder of
895 * the path is inaccessible and we should say so.
897 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_CONTINUE
))
902 if (!mnt
) /* mount collision */
905 err
= finish_automount(mnt
, path
);
909 /* Someone else made a mount here whilst we were busy */
916 path
->dentry
= dget(mnt
->mnt_root
);
926 * Handle a dentry that is managed in some way.
927 * - Flagged for transit management (autofs)
928 * - Flagged as mountpoint
929 * - Flagged as automount point
931 * This may only be called in refwalk mode.
933 * Serialization is taken care of in namespace.c
935 static int follow_managed(struct path
*path
, unsigned flags
)
938 bool need_mntput
= false;
941 /* Given that we're not holding a lock here, we retain the value in a
942 * local variable for each dentry as we look at it so that we don't see
943 * the components of that value change under us */
944 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
945 managed
&= DCACHE_MANAGED_DENTRY
,
946 unlikely(managed
!= 0)) {
947 /* Allow the filesystem to manage the transit without i_mutex
949 if (managed
& DCACHE_MANAGE_TRANSIT
) {
950 BUG_ON(!path
->dentry
->d_op
);
951 BUG_ON(!path
->dentry
->d_op
->d_manage
);
952 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
,
955 return ret
== -EISDIR
? 0 : ret
;
958 /* Transit to a mounted filesystem. */
959 if (managed
& DCACHE_MOUNTED
) {
960 struct vfsmount
*mounted
= lookup_mnt(path
);
966 path
->dentry
= dget(mounted
->mnt_root
);
971 /* Something is mounted on this dentry in another
972 * namespace and/or whatever was mounted there in this
973 * namespace got unmounted before we managed to get the
977 /* Handle an automount point */
978 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
979 ret
= follow_automount(path
, flags
, &need_mntput
);
981 return ret
== -EISDIR
? 0 : ret
;
985 /* We didn't change the current path point */
991 int follow_down_one(struct path
*path
)
993 struct vfsmount
*mounted
;
995 mounted
= lookup_mnt(path
);
1000 path
->dentry
= dget(mounted
->mnt_root
);
1007 * Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
1008 * meet a managed dentry and we're not walking to "..". True is returned to
1009 * continue, false to abort.
1011 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1012 struct inode
**inode
, bool reverse_transit
)
1014 while (d_mountpoint(path
->dentry
)) {
1015 struct vfsmount
*mounted
;
1016 if (unlikely(path
->dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) &&
1018 path
->dentry
->d_op
->d_manage(path
->dentry
, false, true) < 0)
1020 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
, 1);
1023 path
->mnt
= mounted
;
1024 path
->dentry
= mounted
->mnt_root
;
1025 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1026 *inode
= path
->dentry
->d_inode
;
1029 if (unlikely(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
))
1030 return reverse_transit
;
1034 static int follow_dotdot_rcu(struct nameidata
*nd
)
1036 struct inode
*inode
= nd
->inode
;
1041 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1042 nd
->path
.mnt
== nd
->root
.mnt
) {
1045 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1046 struct dentry
*old
= nd
->path
.dentry
;
1047 struct dentry
*parent
= old
->d_parent
;
1050 seq
= read_seqcount_begin(&parent
->d_seq
);
1051 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1053 inode
= parent
->d_inode
;
1054 nd
->path
.dentry
= parent
;
1058 if (!follow_up_rcu(&nd
->path
))
1060 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1061 inode
= nd
->path
.dentry
->d_inode
;
1063 __follow_mount_rcu(nd
, &nd
->path
, &inode
, true);
1068 nd
->flags
&= ~LOOKUP_RCU
;
1069 if (!(nd
->flags
& LOOKUP_ROOT
))
1070 nd
->root
.mnt
= NULL
;
1072 br_read_unlock(vfsmount_lock
);
1077 * Follow down to the covering mount currently visible to userspace. At each
1078 * point, the filesystem owning that dentry may be queried as to whether the
1079 * caller is permitted to proceed or not.
1081 * Care must be taken as namespace_sem may be held (indicated by mounting_here
1084 int follow_down(struct path
*path
, bool mounting_here
)
1089 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1090 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1091 /* Allow the filesystem to manage the transit without i_mutex
1094 * We indicate to the filesystem if someone is trying to mount
1095 * something here. This gives autofs the chance to deny anyone
1096 * other than its daemon the right to mount on its
1099 * The filesystem may sleep at this point.
1101 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1102 BUG_ON(!path
->dentry
->d_op
);
1103 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1104 ret
= path
->dentry
->d_op
->d_manage(
1105 path
->dentry
, mounting_here
, false);
1107 return ret
== -EISDIR
? 0 : ret
;
1110 /* Transit to a mounted filesystem. */
1111 if (managed
& DCACHE_MOUNTED
) {
1112 struct vfsmount
*mounted
= lookup_mnt(path
);
1117 path
->mnt
= mounted
;
1118 path
->dentry
= dget(mounted
->mnt_root
);
1122 /* Don't handle automount points here */
1129 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1131 static void follow_mount(struct path
*path
)
1133 while (d_mountpoint(path
->dentry
)) {
1134 struct vfsmount
*mounted
= lookup_mnt(path
);
1139 path
->mnt
= mounted
;
1140 path
->dentry
= dget(mounted
->mnt_root
);
1144 static void follow_dotdot(struct nameidata
*nd
)
1149 struct dentry
*old
= nd
->path
.dentry
;
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 /* rare case of legitimate dget_parent()... */
1157 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1161 if (!follow_up(&nd
->path
))
1164 follow_mount(&nd
->path
);
1165 nd
->inode
= nd
->path
.dentry
->d_inode
;
1169 * Allocate a dentry with name and parent, and perform a parent
1170 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1171 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1172 * have verified that no child exists while under i_mutex.
1174 static struct dentry
*d_alloc_and_lookup(struct dentry
*parent
,
1175 struct qstr
*name
, struct nameidata
*nd
)
1177 struct inode
*inode
= parent
->d_inode
;
1178 struct dentry
*dentry
;
1181 /* Don't create child dentry for a dead directory. */
1182 if (unlikely(IS_DEADDIR(inode
)))
1183 return ERR_PTR(-ENOENT
);
1185 dentry
= d_alloc(parent
, name
);
1186 if (unlikely(!dentry
))
1187 return ERR_PTR(-ENOMEM
);
1189 old
= inode
->i_op
->lookup(inode
, dentry
, nd
);
1190 if (unlikely(old
)) {
1198 * It's more convoluted than I'd like it to be, but... it's still fairly
1199 * small and for now I'd prefer to have fast path as straight as possible.
1200 * It _is_ time-critical.
1202 static int do_lookup(struct nameidata
*nd
, struct qstr
*name
,
1203 struct path
*path
, struct inode
**inode
)
1205 struct vfsmount
*mnt
= nd
->path
.mnt
;
1206 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1212 * Rename seqlock is not required here because in the off chance
1213 * of a false negative due to a concurrent rename, we're going to
1214 * do the non-racy lookup, below.
1216 if (nd
->flags
& LOOKUP_RCU
) {
1219 dentry
= __d_lookup_rcu(parent
, name
, &seq
, inode
);
1223 /* Memory barrier in read_seqcount_begin of child is enough */
1224 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1228 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1229 status
= d_revalidate(dentry
, nd
);
1230 if (unlikely(status
<= 0)) {
1231 if (status
!= -ECHILD
)
1237 path
->dentry
= dentry
;
1238 if (likely(__follow_mount_rcu(nd
, path
, inode
, false)))
1242 if (nameidata_dentry_drop_rcu(nd
, dentry
))
1245 if (nameidata_drop_rcu(nd
))
1249 dentry
= __d_lookup(parent
, name
);
1253 if (unlikely(!dentry
)) {
1254 struct inode
*dir
= parent
->d_inode
;
1255 BUG_ON(nd
->inode
!= dir
);
1257 mutex_lock(&dir
->i_mutex
);
1258 dentry
= d_lookup(parent
, name
);
1259 if (likely(!dentry
)) {
1260 dentry
= d_alloc_and_lookup(parent
, name
, nd
);
1261 if (IS_ERR(dentry
)) {
1262 mutex_unlock(&dir
->i_mutex
);
1263 return PTR_ERR(dentry
);
1269 mutex_unlock(&dir
->i_mutex
);
1271 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1272 status
= d_revalidate(dentry
, nd
);
1273 if (unlikely(status
<= 0)) {
1278 if (!d_invalidate(dentry
)) {
1287 path
->dentry
= dentry
;
1288 err
= follow_managed(path
, nd
->flags
);
1289 if (unlikely(err
< 0)) {
1290 path_put_conditional(path
, nd
);
1293 *inode
= path
->dentry
->d_inode
;
1297 static inline int may_lookup(struct nameidata
*nd
)
1299 if (nd
->flags
& LOOKUP_RCU
) {
1300 int err
= exec_permission(nd
->inode
, IPERM_FLAG_RCU
);
1303 if (nameidata_drop_rcu(nd
))
1306 return exec_permission(nd
->inode
, 0);
1309 static inline int handle_dots(struct nameidata
*nd
, int type
)
1311 if (type
== LAST_DOTDOT
) {
1312 if (nd
->flags
& LOOKUP_RCU
) {
1313 if (follow_dotdot_rcu(nd
))
1321 static void terminate_walk(struct nameidata
*nd
)
1323 if (!(nd
->flags
& LOOKUP_RCU
)) {
1324 path_put(&nd
->path
);
1326 nd
->flags
&= ~LOOKUP_RCU
;
1327 if (!(nd
->flags
& LOOKUP_ROOT
))
1328 nd
->root
.mnt
= NULL
;
1330 br_read_unlock(vfsmount_lock
);
1336 * This is the basic name resolution function, turning a pathname into
1337 * the final dentry. We expect 'base' to be positive and a directory.
1339 * Returns 0 and nd will have valid dentry and mnt on success.
1340 * Returns error and drops reference to input namei data on failure.
1342 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1346 unsigned int lookup_flags
= nd
->flags
;
1354 lookup_flags
= LOOKUP_FOLLOW
| (nd
->flags
& LOOKUP_CONTINUE
);
1356 /* At this point we know we have a real path component. */
1358 struct inode
*inode
;
1364 nd
->flags
|= LOOKUP_CONTINUE
;
1366 err
= may_lookup(nd
);
1371 c
= *(const unsigned char *)name
;
1373 hash
= init_name_hash();
1376 hash
= partial_name_hash(c
, hash
);
1377 c
= *(const unsigned char *)name
;
1378 } while (c
&& (c
!= '/'));
1379 this.len
= name
- (const char *) this.name
;
1380 this.hash
= end_name_hash(hash
);
1383 if (this.name
[0] == '.') switch (this.len
) {
1385 if (this.name
[1] == '.') {
1387 nd
->flags
|= LOOKUP_JUMPED
;
1393 if (likely(type
== LAST_NORM
)) {
1394 struct dentry
*parent
= nd
->path
.dentry
;
1395 nd
->flags
&= ~LOOKUP_JUMPED
;
1396 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1397 err
= parent
->d_op
->d_hash(parent
, nd
->inode
,
1404 /* remove trailing slashes? */
1406 goto last_component
;
1407 while (*++name
== '/');
1409 goto last_with_slashes
;
1412 * "." and ".." are special - ".." especially so because it has
1413 * to be able to know about the current root directory and
1414 * parent relationships.
1416 if (unlikely(type
!= LAST_NORM
)) {
1417 if (handle_dots(nd
, type
))
1422 /* This does the actual lookups.. */
1423 err
= do_lookup(nd
, &this, &next
, &inode
);
1427 if (inode
&& inode
->i_op
->follow_link
) {
1428 err
= do_follow_link(inode
, &next
, nd
);
1431 nd
->inode
= nd
->path
.dentry
->d_inode
;
1433 path_to_nameidata(&next
, nd
);
1440 if (!nd
->inode
->i_op
->lookup
)
1443 /* here ends the main loop */
1446 lookup_flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1448 /* Clear LOOKUP_CONTINUE iff it was previously unset */
1449 nd
->flags
&= lookup_flags
| ~LOOKUP_CONTINUE
;
1450 if (lookup_flags
& LOOKUP_PARENT
)
1452 if (unlikely(type
!= LAST_NORM
))
1453 return handle_dots(nd
, type
);
1454 err
= do_lookup(nd
, &this, &next
, &inode
);
1457 if (inode
&& unlikely(inode
->i_op
->follow_link
) &&
1458 (lookup_flags
& LOOKUP_FOLLOW
)) {
1459 err
= do_follow_link(inode
, &next
, nd
);
1462 nd
->inode
= nd
->path
.dentry
->d_inode
;
1464 path_to_nameidata(&next
, nd
);
1470 if (lookup_flags
& LOOKUP_DIRECTORY
) {
1472 if (!nd
->inode
->i_op
->lookup
)
1478 nd
->last_type
= type
;
1485 static int path_init(int dfd
, const char *name
, unsigned int flags
,
1486 struct nameidata
*nd
, struct file
**fp
)
1492 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1493 nd
->flags
= flags
| LOOKUP_JUMPED
;
1495 if (flags
& LOOKUP_ROOT
) {
1496 struct inode
*inode
= nd
->root
.dentry
->d_inode
;
1498 if (!inode
->i_op
->lookup
)
1500 retval
= inode_permission(inode
, MAY_EXEC
);
1504 nd
->path
= nd
->root
;
1506 if (flags
& LOOKUP_RCU
) {
1507 br_read_lock(vfsmount_lock
);
1509 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1511 path_get(&nd
->path
);
1516 nd
->root
.mnt
= NULL
;
1519 if (flags
& LOOKUP_RCU
) {
1520 br_read_lock(vfsmount_lock
);
1525 path_get(&nd
->root
);
1527 nd
->path
= nd
->root
;
1528 } else if (dfd
== AT_FDCWD
) {
1529 if (flags
& LOOKUP_RCU
) {
1530 struct fs_struct
*fs
= current
->fs
;
1533 br_read_lock(vfsmount_lock
);
1537 seq
= read_seqcount_begin(&fs
->seq
);
1539 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1540 } while (read_seqcount_retry(&fs
->seq
, seq
));
1542 get_fs_pwd(current
->fs
, &nd
->path
);
1545 struct dentry
*dentry
;
1547 file
= fget_raw_light(dfd
, &fput_needed
);
1552 dentry
= file
->f_path
.dentry
;
1556 if (!S_ISDIR(dentry
->d_inode
->i_mode
))
1559 retval
= file_permission(file
, MAY_EXEC
);
1564 nd
->path
= file
->f_path
;
1565 if (flags
& LOOKUP_RCU
) {
1568 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1569 br_read_lock(vfsmount_lock
);
1572 path_get(&file
->f_path
);
1573 fput_light(file
, fput_needed
);
1577 nd
->inode
= nd
->path
.dentry
->d_inode
;
1581 fput_light(file
, fput_needed
);
1586 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1587 static int path_lookupat(int dfd
, const char *name
,
1588 unsigned int flags
, struct nameidata
*nd
)
1590 struct file
*base
= NULL
;
1594 * Path walking is largely split up into 2 different synchronisation
1595 * schemes, rcu-walk and ref-walk (explained in
1596 * Documentation/filesystems/path-lookup.txt). These share much of the
1597 * path walk code, but some things particularly setup, cleanup, and
1598 * following mounts are sufficiently divergent that functions are
1599 * duplicated. Typically there is a function foo(), and its RCU
1600 * analogue, foo_rcu().
1602 * -ECHILD is the error number of choice (just to avoid clashes) that
1603 * is returned if some aspect of an rcu-walk fails. Such an error must
1604 * be handled by restarting a traditional ref-walk (which will always
1605 * be able to complete).
1607 retval
= path_init(dfd
, name
, flags
, nd
, &base
);
1609 if (unlikely(retval
))
1612 current
->total_link_count
= 0;
1613 retval
= link_path_walk(name
, nd
);
1615 if (nd
->flags
& LOOKUP_RCU
) {
1616 /* went all way through without dropping RCU */
1618 if (nameidata_drop_rcu_last(nd
))
1623 retval
= handle_reval_path(nd
);
1628 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1629 path_put(&nd
->root
);
1630 nd
->root
.mnt
= NULL
;
1635 static int do_path_lookup(int dfd
, const char *name
,
1636 unsigned int flags
, struct nameidata
*nd
)
1638 int retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_RCU
, nd
);
1639 if (unlikely(retval
== -ECHILD
))
1640 retval
= path_lookupat(dfd
, name
, flags
, nd
);
1641 if (unlikely(retval
== -ESTALE
))
1642 retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_REVAL
, nd
);
1644 if (likely(!retval
)) {
1645 if (unlikely(!audit_dummy_context())) {
1646 if (nd
->path
.dentry
&& nd
->inode
)
1647 audit_inode(name
, nd
->path
.dentry
);
1653 int kern_path_parent(const char *name
, struct nameidata
*nd
)
1655 return do_path_lookup(AT_FDCWD
, name
, LOOKUP_PARENT
, nd
);
1658 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
1660 struct nameidata nd
;
1661 int res
= do_path_lookup(AT_FDCWD
, name
, flags
, &nd
);
1668 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1669 * @dentry: pointer to dentry of the base directory
1670 * @mnt: pointer to vfs mount of the base directory
1671 * @name: pointer to file name
1672 * @flags: lookup flags
1673 * @nd: pointer to nameidata
1675 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
1676 const char *name
, unsigned int flags
,
1677 struct nameidata
*nd
)
1679 nd
->root
.dentry
= dentry
;
1681 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1682 return do_path_lookup(AT_FDCWD
, name
, flags
| LOOKUP_ROOT
, nd
);
1685 static struct dentry
*__lookup_hash(struct qstr
*name
,
1686 struct dentry
*base
, struct nameidata
*nd
)
1688 struct inode
*inode
= base
->d_inode
;
1689 struct dentry
*dentry
;
1692 err
= exec_permission(inode
, 0);
1694 return ERR_PTR(err
);
1697 * Don't bother with __d_lookup: callers are for creat as
1698 * well as unlink, so a lot of the time it would cost
1701 dentry
= d_lookup(base
, name
);
1703 if (dentry
&& (dentry
->d_flags
& DCACHE_OP_REVALIDATE
))
1704 dentry
= do_revalidate(dentry
, nd
);
1707 dentry
= d_alloc_and_lookup(base
, name
, nd
);
1713 * Restricted form of lookup. Doesn't follow links, single-component only,
1714 * needs parent already locked. Doesn't follow mounts.
1717 static struct dentry
*lookup_hash(struct nameidata
*nd
)
1719 return __lookup_hash(&nd
->last
, nd
->path
.dentry
, nd
);
1723 * lookup_one_len - filesystem helper to lookup single pathname component
1724 * @name: pathname component to lookup
1725 * @base: base directory to lookup from
1726 * @len: maximum length @len should be interpreted to
1728 * Note that this routine is purely a helper for filesystem usage and should
1729 * not be called by generic code. Also note that by using this function the
1730 * nameidata argument is passed to the filesystem methods and a filesystem
1731 * using this helper needs to be prepared for that.
1733 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
1739 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
1744 return ERR_PTR(-EACCES
);
1746 hash
= init_name_hash();
1748 c
= *(const unsigned char *)name
++;
1749 if (c
== '/' || c
== '\0')
1750 return ERR_PTR(-EACCES
);
1751 hash
= partial_name_hash(c
, hash
);
1753 this.hash
= end_name_hash(hash
);
1755 * See if the low-level filesystem might want
1756 * to use its own hash..
1758 if (base
->d_flags
& DCACHE_OP_HASH
) {
1759 int err
= base
->d_op
->d_hash(base
, base
->d_inode
, &this);
1761 return ERR_PTR(err
);
1764 return __lookup_hash(&this, base
, NULL
);
1767 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
1770 struct nameidata nd
;
1771 char *tmp
= getname_flags(name
, flags
);
1772 int err
= PTR_ERR(tmp
);
1775 BUG_ON(flags
& LOOKUP_PARENT
);
1777 err
= do_path_lookup(dfd
, tmp
, flags
, &nd
);
1785 static int user_path_parent(int dfd
, const char __user
*path
,
1786 struct nameidata
*nd
, char **name
)
1788 char *s
= getname(path
);
1794 error
= do_path_lookup(dfd
, s
, LOOKUP_PARENT
, nd
);
1804 * It's inline, so penalty for filesystems that don't use sticky bit is
1807 static inline int check_sticky(struct inode
*dir
, struct inode
*inode
)
1809 uid_t fsuid
= current_fsuid();
1811 if (!(dir
->i_mode
& S_ISVTX
))
1813 if (inode
->i_uid
== fsuid
)
1815 if (dir
->i_uid
== fsuid
)
1817 return !capable(CAP_FOWNER
);
1821 * Check whether we can remove a link victim from directory dir, check
1822 * whether the type of victim is right.
1823 * 1. We can't do it if dir is read-only (done in permission())
1824 * 2. We should have write and exec permissions on dir
1825 * 3. We can't remove anything from append-only dir
1826 * 4. We can't do anything with immutable dir (done in permission())
1827 * 5. If the sticky bit on dir is set we should either
1828 * a. be owner of dir, or
1829 * b. be owner of victim, or
1830 * c. have CAP_FOWNER capability
1831 * 6. If the victim is append-only or immutable we can't do antyhing with
1832 * links pointing to it.
1833 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1834 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1835 * 9. We can't remove a root or mountpoint.
1836 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1837 * nfs_async_unlink().
1839 static int may_delete(struct inode
*dir
,struct dentry
*victim
,int isdir
)
1843 if (!victim
->d_inode
)
1846 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
1847 audit_inode_child(victim
, dir
);
1849 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
1854 if (check_sticky(dir
, victim
->d_inode
)||IS_APPEND(victim
->d_inode
)||
1855 IS_IMMUTABLE(victim
->d_inode
) || IS_SWAPFILE(victim
->d_inode
))
1858 if (!S_ISDIR(victim
->d_inode
->i_mode
))
1860 if (IS_ROOT(victim
))
1862 } else if (S_ISDIR(victim
->d_inode
->i_mode
))
1864 if (IS_DEADDIR(dir
))
1866 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
1871 /* Check whether we can create an object with dentry child in directory
1873 * 1. We can't do it if child already exists (open has special treatment for
1874 * this case, but since we are inlined it's OK)
1875 * 2. We can't do it if dir is read-only (done in permission())
1876 * 3. We should have write and exec permissions on dir
1877 * 4. We can't do it if dir is immutable (done in permission())
1879 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
1883 if (IS_DEADDIR(dir
))
1885 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
1889 * p1 and p2 should be directories on the same fs.
1891 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
1896 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1900 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
1902 p
= d_ancestor(p2
, p1
);
1904 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1905 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
1909 p
= d_ancestor(p1
, p2
);
1911 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1912 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
1916 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1917 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
1921 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
1923 mutex_unlock(&p1
->d_inode
->i_mutex
);
1925 mutex_unlock(&p2
->d_inode
->i_mutex
);
1926 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
1930 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, int mode
,
1931 struct nameidata
*nd
)
1933 int error
= may_create(dir
, dentry
);
1938 if (!dir
->i_op
->create
)
1939 return -EACCES
; /* shouldn't it be ENOSYS? */
1942 error
= security_inode_create(dir
, dentry
, mode
);
1945 error
= dir
->i_op
->create(dir
, dentry
, mode
, nd
);
1947 fsnotify_create(dir
, dentry
);
1951 static int may_open(struct path
*path
, int acc_mode
, int flag
)
1953 struct dentry
*dentry
= path
->dentry
;
1954 struct inode
*inode
= dentry
->d_inode
;
1960 switch (inode
->i_mode
& S_IFMT
) {
1964 if (acc_mode
& MAY_WRITE
)
1969 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
1978 error
= inode_permission(inode
, acc_mode
);
1983 * An append-only file must be opened in append mode for writing.
1985 if (IS_APPEND(inode
)) {
1986 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
1992 /* O_NOATIME can only be set by the owner or superuser */
1993 if (flag
& O_NOATIME
&& !is_owner_or_cap(inode
))
1997 * Ensure there are no outstanding leases on the file.
1999 return break_lease(inode
, flag
);
2002 static int handle_truncate(struct file
*filp
)
2004 struct path
*path
= &filp
->f_path
;
2005 struct inode
*inode
= path
->dentry
->d_inode
;
2006 int error
= get_write_access(inode
);
2010 * Refuse to truncate files with mandatory locks held on them.
2012 error
= locks_verify_locked(inode
);
2014 error
= security_path_truncate(path
);
2016 error
= do_truncate(path
->dentry
, 0,
2017 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2020 put_write_access(inode
);
2025 * Note that while the flag value (low two bits) for sys_open means:
2030 * it is changed into
2031 * 00 - no permissions needed
2032 * 01 - read-permission
2033 * 10 - write-permission
2035 * for the internal routines (ie open_namei()/follow_link() etc)
2036 * This is more logical, and also allows the 00 "no perm needed"
2037 * to be used for symlinks (where the permissions are checked
2041 static inline int open_to_namei_flags(int flag
)
2043 if ((flag
+1) & O_ACCMODE
)
2049 * Handle the last step of open()
2051 static struct file
*do_last(struct nameidata
*nd
, struct path
*path
,
2052 const struct open_flags
*op
, const char *pathname
)
2054 struct dentry
*dir
= nd
->path
.dentry
;
2055 struct dentry
*dentry
;
2056 int open_flag
= op
->open_flag
;
2057 int will_truncate
= open_flag
& O_TRUNC
;
2061 struct inode
*inode
;
2064 nd
->flags
&= ~LOOKUP_PARENT
;
2065 nd
->flags
|= op
->intent
;
2067 switch (nd
->last_type
) {
2070 error
= handle_dots(nd
, nd
->last_type
);
2072 return ERR_PTR(error
);
2075 if (nd
->flags
& LOOKUP_RCU
) {
2076 if (nameidata_drop_rcu_last(nd
))
2077 return ERR_PTR(-ECHILD
);
2079 error
= handle_reval_path(nd
);
2082 audit_inode(pathname
, nd
->path
.dentry
);
2083 if (open_flag
& O_CREAT
) {
2089 /* can't be RCU mode here */
2090 error
= handle_reval_path(nd
);
2093 audit_inode(pathname
, dir
);
2097 if (!(open_flag
& O_CREAT
)) {
2098 if (nd
->last
.name
[nd
->last
.len
])
2099 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2100 /* we _can_ be in RCU mode here */
2101 error
= do_lookup(nd
, &nd
->last
, path
, &inode
);
2104 return ERR_PTR(error
);
2107 path_to_nameidata(path
, nd
);
2109 return ERR_PTR(-ENOENT
);
2111 if (unlikely(inode
->i_op
->follow_link
)) {
2112 /* We drop rcu-walk here */
2113 if (nameidata_dentry_drop_rcu_maybe(nd
, path
->dentry
))
2114 return ERR_PTR(-ECHILD
);
2117 path_to_nameidata(path
, nd
);
2120 if (nd
->flags
& LOOKUP_RCU
) {
2121 if (nameidata_drop_rcu_last(nd
))
2122 return ERR_PTR(-ECHILD
);
2126 if (nd
->flags
& LOOKUP_DIRECTORY
) {
2127 if (!inode
->i_op
->lookup
)
2130 audit_inode(pathname
, nd
->path
.dentry
);
2134 /* create side of things */
2136 if (nd
->flags
& LOOKUP_RCU
) {
2137 if (nameidata_drop_rcu_last(nd
))
2138 return ERR_PTR(-ECHILD
);
2141 audit_inode(pathname
, dir
);
2143 /* trailing slashes? */
2144 if (nd
->last
.name
[nd
->last
.len
])
2147 mutex_lock(&dir
->d_inode
->i_mutex
);
2149 dentry
= lookup_hash(nd
);
2150 error
= PTR_ERR(dentry
);
2151 if (IS_ERR(dentry
)) {
2152 mutex_unlock(&dir
->d_inode
->i_mutex
);
2156 path
->dentry
= dentry
;
2157 path
->mnt
= nd
->path
.mnt
;
2159 /* Negative dentry, just create the file */
2160 if (!dentry
->d_inode
) {
2161 int mode
= op
->mode
;
2162 if (!IS_POSIXACL(dir
->d_inode
))
2163 mode
&= ~current_umask();
2165 * This write is needed to ensure that a
2166 * rw->ro transition does not occur between
2167 * the time when the file is created and when
2168 * a permanent write count is taken through
2169 * the 'struct file' in nameidata_to_filp().
2171 error
= mnt_want_write(nd
->path
.mnt
);
2173 goto exit_mutex_unlock
;
2175 /* Don't check for write permission, don't truncate */
2176 open_flag
&= ~O_TRUNC
;
2179 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2181 goto exit_mutex_unlock
;
2182 error
= vfs_create(dir
->d_inode
, dentry
, mode
, nd
);
2184 goto exit_mutex_unlock
;
2185 mutex_unlock(&dir
->d_inode
->i_mutex
);
2186 dput(nd
->path
.dentry
);
2187 nd
->path
.dentry
= dentry
;
2192 * It already exists.
2194 mutex_unlock(&dir
->d_inode
->i_mutex
);
2195 audit_inode(pathname
, path
->dentry
);
2198 if (open_flag
& O_EXCL
)
2201 error
= follow_managed(path
, nd
->flags
);
2206 if (!path
->dentry
->d_inode
)
2209 if (path
->dentry
->d_inode
->i_op
->follow_link
)
2212 path_to_nameidata(path
, nd
);
2213 nd
->inode
= path
->dentry
->d_inode
;
2215 if (S_ISDIR(nd
->inode
->i_mode
))
2218 if (!S_ISREG(nd
->inode
->i_mode
))
2221 if (will_truncate
) {
2222 error
= mnt_want_write(nd
->path
.mnt
);
2228 error
= may_open(&nd
->path
, skip_perm
? 0 : op
->acc_mode
, open_flag
);
2231 filp
= nameidata_to_filp(nd
);
2232 if (!IS_ERR(filp
)) {
2233 error
= ima_file_check(filp
, op
->acc_mode
);
2236 filp
= ERR_PTR(error
);
2239 if (!IS_ERR(filp
)) {
2240 if (will_truncate
) {
2241 error
= handle_truncate(filp
);
2244 filp
= ERR_PTR(error
);
2250 mnt_drop_write(nd
->path
.mnt
);
2251 path_put(&nd
->path
);
2255 mutex_unlock(&dir
->d_inode
->i_mutex
);
2257 path_put_conditional(path
, nd
);
2259 filp
= ERR_PTR(error
);
2263 static struct file
*path_openat(int dfd
, const char *pathname
,
2264 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
2266 struct file
*base
= NULL
;
2272 filp
= get_empty_filp();
2274 return ERR_PTR(-ENFILE
);
2276 filp
->f_flags
= op
->open_flag
;
2277 nd
->intent
.open
.file
= filp
;
2278 nd
->intent
.open
.flags
= open_to_namei_flags(op
->open_flag
);
2279 nd
->intent
.open
.create_mode
= op
->mode
;
2281 error
= path_init(dfd
, pathname
, flags
| LOOKUP_PARENT
, nd
, &base
);
2282 if (unlikely(error
))
2285 current
->total_link_count
= 0;
2286 error
= link_path_walk(pathname
, nd
);
2287 if (unlikely(error
))
2290 filp
= do_last(nd
, &path
, op
, pathname
);
2291 while (unlikely(!filp
)) { /* trailing symlink */
2292 struct path link
= path
;
2293 struct inode
*linki
= link
.dentry
->d_inode
;
2295 if (!(nd
->flags
& LOOKUP_FOLLOW
) || count
++ == 32) {
2296 path_put_conditional(&path
, nd
);
2297 path_put(&nd
->path
);
2298 filp
= ERR_PTR(-ELOOP
);
2302 * This is subtle. Instead of calling do_follow_link() we do
2303 * the thing by hands. The reason is that this way we have zero
2304 * link_count and path_walk() (called from ->follow_link)
2305 * honoring LOOKUP_PARENT. After that we have the parent and
2306 * last component, i.e. we are in the same situation as after
2307 * the first path_walk(). Well, almost - if the last component
2308 * is normal we get its copy stored in nd->last.name and we will
2309 * have to putname() it when we are done. Procfs-like symlinks
2310 * just set LAST_BIND.
2312 nd
->flags
|= LOOKUP_PARENT
;
2313 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
2314 error
= __do_follow_link(&link
, nd
, &cookie
);
2315 if (unlikely(error
))
2316 filp
= ERR_PTR(error
);
2318 filp
= do_last(nd
, &path
, op
, pathname
);
2319 if (!IS_ERR(cookie
) && linki
->i_op
->put_link
)
2320 linki
->i_op
->put_link(link
.dentry
, nd
, cookie
);
2324 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
))
2325 path_put(&nd
->root
);
2328 release_open_intent(nd
);
2332 filp
= ERR_PTR(error
);
2336 struct file
*do_filp_open(int dfd
, const char *pathname
,
2337 const struct open_flags
*op
, int flags
)
2339 struct nameidata nd
;
2342 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
2343 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
2344 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
2345 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
2346 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
2350 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
2351 const char *name
, const struct open_flags
*op
, int flags
)
2353 struct nameidata nd
;
2357 nd
.root
.dentry
= dentry
;
2359 flags
|= LOOKUP_ROOT
;
2361 if (dentry
->d_inode
->i_op
->follow_link
)
2362 return ERR_PTR(-ELOOP
);
2364 file
= path_openat(-1, name
, &nd
, op
, flags
| LOOKUP_RCU
);
2365 if (unlikely(file
== ERR_PTR(-ECHILD
)))
2366 file
= path_openat(-1, name
, &nd
, op
, flags
);
2367 if (unlikely(file
== ERR_PTR(-ESTALE
)))
2368 file
= path_openat(-1, name
, &nd
, op
, flags
| LOOKUP_REVAL
);
2373 * lookup_create - lookup a dentry, creating it if it doesn't exist
2374 * @nd: nameidata info
2375 * @is_dir: directory flag
2377 * Simple function to lookup and return a dentry and create it
2378 * if it doesn't exist. Is SMP-safe.
2380 * Returns with nd->path.dentry->d_inode->i_mutex locked.
2382 struct dentry
*lookup_create(struct nameidata
*nd
, int is_dir
)
2384 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
2386 mutex_lock_nested(&nd
->path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2388 * Yucky last component or no last component at all?
2389 * (foo/., foo/.., /////)
2391 if (nd
->last_type
!= LAST_NORM
)
2393 nd
->flags
&= ~LOOKUP_PARENT
;
2394 nd
->flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
2395 nd
->intent
.open
.flags
= O_EXCL
;
2398 * Do the final lookup.
2400 dentry
= lookup_hash(nd
);
2404 if (dentry
->d_inode
)
2407 * Special case - lookup gave negative, but... we had foo/bar/
2408 * From the vfs_mknod() POV we just have a negative dentry -
2409 * all is fine. Let's be bastards - you had / on the end, you've
2410 * been asking for (non-existent) directory. -ENOENT for you.
2412 if (unlikely(!is_dir
&& nd
->last
.name
[nd
->last
.len
])) {
2414 dentry
= ERR_PTR(-ENOENT
);
2419 dentry
= ERR_PTR(-EEXIST
);
2423 EXPORT_SYMBOL_GPL(lookup_create
);
2425 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, int mode
, dev_t dev
)
2427 int error
= may_create(dir
, dentry
);
2432 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
2435 if (!dir
->i_op
->mknod
)
2438 error
= devcgroup_inode_mknod(mode
, dev
);
2442 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
2446 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
2448 fsnotify_create(dir
, dentry
);
2452 static int may_mknod(mode_t mode
)
2454 switch (mode
& S_IFMT
) {
2460 case 0: /* zero mode translates to S_IFREG */
2469 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, int, mode
,
2474 struct dentry
*dentry
;
2475 struct nameidata nd
;
2480 error
= user_path_parent(dfd
, filename
, &nd
, &tmp
);
2484 dentry
= lookup_create(&nd
, 0);
2485 if (IS_ERR(dentry
)) {
2486 error
= PTR_ERR(dentry
);
2489 if (!IS_POSIXACL(nd
.path
.dentry
->d_inode
))
2490 mode
&= ~current_umask();
2491 error
= may_mknod(mode
);
2494 error
= mnt_want_write(nd
.path
.mnt
);
2497 error
= security_path_mknod(&nd
.path
, dentry
, mode
, dev
);
2499 goto out_drop_write
;
2500 switch (mode
& S_IFMT
) {
2501 case 0: case S_IFREG
:
2502 error
= vfs_create(nd
.path
.dentry
->d_inode
,dentry
,mode
,&nd
);
2504 case S_IFCHR
: case S_IFBLK
:
2505 error
= vfs_mknod(nd
.path
.dentry
->d_inode
,dentry
,mode
,
2506 new_decode_dev(dev
));
2508 case S_IFIFO
: case S_IFSOCK
:
2509 error
= vfs_mknod(nd
.path
.dentry
->d_inode
,dentry
,mode
,0);
2513 mnt_drop_write(nd
.path
.mnt
);
2517 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2524 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, int, mode
, unsigned, dev
)
2526 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
2529 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, int mode
)
2531 int error
= may_create(dir
, dentry
);
2536 if (!dir
->i_op
->mkdir
)
2539 mode
&= (S_IRWXUGO
|S_ISVTX
);
2540 error
= security_inode_mkdir(dir
, dentry
, mode
);
2544 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
2546 fsnotify_mkdir(dir
, dentry
);
2550 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, int, mode
)
2554 struct dentry
*dentry
;
2555 struct nameidata nd
;
2557 error
= user_path_parent(dfd
, pathname
, &nd
, &tmp
);
2561 dentry
= lookup_create(&nd
, 1);
2562 error
= PTR_ERR(dentry
);
2566 if (!IS_POSIXACL(nd
.path
.dentry
->d_inode
))
2567 mode
&= ~current_umask();
2568 error
= mnt_want_write(nd
.path
.mnt
);
2571 error
= security_path_mkdir(&nd
.path
, dentry
, mode
);
2573 goto out_drop_write
;
2574 error
= vfs_mkdir(nd
.path
.dentry
->d_inode
, dentry
, mode
);
2576 mnt_drop_write(nd
.path
.mnt
);
2580 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2587 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, int, mode
)
2589 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
2593 * We try to drop the dentry early: we should have
2594 * a usage count of 2 if we're the only user of this
2595 * dentry, and if that is true (possibly after pruning
2596 * the dcache), then we drop the dentry now.
2598 * A low-level filesystem can, if it choses, legally
2601 * if (!d_unhashed(dentry))
2604 * if it cannot handle the case of removing a directory
2605 * that is still in use by something else..
2607 void dentry_unhash(struct dentry
*dentry
)
2610 shrink_dcache_parent(dentry
);
2611 spin_lock(&dentry
->d_lock
);
2612 if (dentry
->d_count
== 2)
2614 spin_unlock(&dentry
->d_lock
);
2617 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
2619 int error
= may_delete(dir
, dentry
, 1);
2624 if (!dir
->i_op
->rmdir
)
2627 mutex_lock(&dentry
->d_inode
->i_mutex
);
2628 dentry_unhash(dentry
);
2629 if (d_mountpoint(dentry
))
2632 error
= security_inode_rmdir(dir
, dentry
);
2634 error
= dir
->i_op
->rmdir(dir
, dentry
);
2636 dentry
->d_inode
->i_flags
|= S_DEAD
;
2641 mutex_unlock(&dentry
->d_inode
->i_mutex
);
2650 static long do_rmdir(int dfd
, const char __user
*pathname
)
2654 struct dentry
*dentry
;
2655 struct nameidata nd
;
2657 error
= user_path_parent(dfd
, pathname
, &nd
, &name
);
2661 switch(nd
.last_type
) {
2673 nd
.flags
&= ~LOOKUP_PARENT
;
2675 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2676 dentry
= lookup_hash(&nd
);
2677 error
= PTR_ERR(dentry
);
2680 error
= mnt_want_write(nd
.path
.mnt
);
2683 error
= security_path_rmdir(&nd
.path
, dentry
);
2686 error
= vfs_rmdir(nd
.path
.dentry
->d_inode
, dentry
);
2688 mnt_drop_write(nd
.path
.mnt
);
2692 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2699 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
2701 return do_rmdir(AT_FDCWD
, pathname
);
2704 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
)
2706 int error
= may_delete(dir
, dentry
, 0);
2711 if (!dir
->i_op
->unlink
)
2714 mutex_lock(&dentry
->d_inode
->i_mutex
);
2715 if (d_mountpoint(dentry
))
2718 error
= security_inode_unlink(dir
, dentry
);
2720 error
= dir
->i_op
->unlink(dir
, dentry
);
2725 mutex_unlock(&dentry
->d_inode
->i_mutex
);
2727 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2728 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
2729 fsnotify_link_count(dentry
->d_inode
);
2737 * Make sure that the actual truncation of the file will occur outside its
2738 * directory's i_mutex. Truncate can take a long time if there is a lot of
2739 * writeout happening, and we don't want to prevent access to the directory
2740 * while waiting on the I/O.
2742 static long do_unlinkat(int dfd
, const char __user
*pathname
)
2746 struct dentry
*dentry
;
2747 struct nameidata nd
;
2748 struct inode
*inode
= NULL
;
2750 error
= user_path_parent(dfd
, pathname
, &nd
, &name
);
2755 if (nd
.last_type
!= LAST_NORM
)
2758 nd
.flags
&= ~LOOKUP_PARENT
;
2760 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2761 dentry
= lookup_hash(&nd
);
2762 error
= PTR_ERR(dentry
);
2763 if (!IS_ERR(dentry
)) {
2764 /* Why not before? Because we want correct error value */
2765 if (nd
.last
.name
[nd
.last
.len
])
2767 inode
= dentry
->d_inode
;
2770 error
= mnt_want_write(nd
.path
.mnt
);
2773 error
= security_path_unlink(&nd
.path
, dentry
);
2776 error
= vfs_unlink(nd
.path
.dentry
->d_inode
, dentry
);
2778 mnt_drop_write(nd
.path
.mnt
);
2782 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2784 iput(inode
); /* truncate the inode here */
2791 error
= !dentry
->d_inode
? -ENOENT
:
2792 S_ISDIR(dentry
->d_inode
->i_mode
) ? -EISDIR
: -ENOTDIR
;
2796 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
2798 if ((flag
& ~AT_REMOVEDIR
) != 0)
2801 if (flag
& AT_REMOVEDIR
)
2802 return do_rmdir(dfd
, pathname
);
2804 return do_unlinkat(dfd
, pathname
);
2807 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
2809 return do_unlinkat(AT_FDCWD
, pathname
);
2812 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
2814 int error
= may_create(dir
, dentry
);
2819 if (!dir
->i_op
->symlink
)
2822 error
= security_inode_symlink(dir
, dentry
, oldname
);
2826 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
2828 fsnotify_create(dir
, dentry
);
2832 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
2833 int, newdfd
, const char __user
*, newname
)
2838 struct dentry
*dentry
;
2839 struct nameidata nd
;
2841 from
= getname(oldname
);
2843 return PTR_ERR(from
);
2845 error
= user_path_parent(newdfd
, newname
, &nd
, &to
);
2849 dentry
= lookup_create(&nd
, 0);
2850 error
= PTR_ERR(dentry
);
2854 error
= mnt_want_write(nd
.path
.mnt
);
2857 error
= security_path_symlink(&nd
.path
, dentry
, from
);
2859 goto out_drop_write
;
2860 error
= vfs_symlink(nd
.path
.dentry
->d_inode
, dentry
, from
);
2862 mnt_drop_write(nd
.path
.mnt
);
2866 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2874 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
2876 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
2879 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
)
2881 struct inode
*inode
= old_dentry
->d_inode
;
2887 error
= may_create(dir
, new_dentry
);
2891 if (dir
->i_sb
!= inode
->i_sb
)
2895 * A link to an append-only or immutable file cannot be created.
2897 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
2899 if (!dir
->i_op
->link
)
2901 if (S_ISDIR(inode
->i_mode
))
2904 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
2908 mutex_lock(&inode
->i_mutex
);
2909 /* Make sure we don't allow creating hardlink to an unlinked file */
2910 if (inode
->i_nlink
== 0)
2913 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
2914 mutex_unlock(&inode
->i_mutex
);
2916 fsnotify_link(dir
, inode
, new_dentry
);
2921 * Hardlinks are often used in delicate situations. We avoid
2922 * security-related surprises by not following symlinks on the
2925 * We don't follow them on the oldname either to be compatible
2926 * with linux 2.0, and to avoid hard-linking to directories
2927 * and other special files. --ADM
2929 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
2930 int, newdfd
, const char __user
*, newname
, int, flags
)
2932 struct dentry
*new_dentry
;
2933 struct nameidata nd
;
2934 struct path old_path
;
2938 if ((flags
& ~AT_SYMLINK_FOLLOW
) != 0)
2941 error
= user_path_at(olddfd
, oldname
,
2942 flags
& AT_SYMLINK_FOLLOW
? LOOKUP_FOLLOW
: 0,
2947 error
= user_path_parent(newdfd
, newname
, &nd
, &to
);
2951 if (old_path
.mnt
!= nd
.path
.mnt
)
2953 new_dentry
= lookup_create(&nd
, 0);
2954 error
= PTR_ERR(new_dentry
);
2955 if (IS_ERR(new_dentry
))
2957 error
= mnt_want_write(nd
.path
.mnt
);
2960 error
= security_path_link(old_path
.dentry
, &nd
.path
, new_dentry
);
2962 goto out_drop_write
;
2963 error
= vfs_link(old_path
.dentry
, nd
.path
.dentry
->d_inode
, new_dentry
);
2965 mnt_drop_write(nd
.path
.mnt
);
2969 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2974 path_put(&old_path
);
2979 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
2981 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
2985 * The worst of all namespace operations - renaming directory. "Perverted"
2986 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2988 * a) we can get into loop creation. Check is done in is_subdir().
2989 * b) race potential - two innocent renames can create a loop together.
2990 * That's where 4.4 screws up. Current fix: serialization on
2991 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
2993 * c) we have to lock _three_ objects - parents and victim (if it exists).
2994 * And that - after we got ->i_mutex on parents (until then we don't know
2995 * whether the target exists). Solution: try to be smart with locking
2996 * order for inodes. We rely on the fact that tree topology may change
2997 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
2998 * move will be locked. Thus we can rank directories by the tree
2999 * (ancestors first) and rank all non-directories after them.
3000 * That works since everybody except rename does "lock parent, lookup,
3001 * lock child" and rename is under ->s_vfs_rename_mutex.
3002 * HOWEVER, it relies on the assumption that any object with ->lookup()
3003 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3004 * we'd better make sure that there's no link(2) for them.
3005 * d) some filesystems don't support opened-but-unlinked directories,
3006 * either because of layout or because they are not ready to deal with
3007 * all cases correctly. The latter will be fixed (taking this sort of
3008 * stuff into VFS), but the former is not going away. Solution: the same
3009 * trick as in rmdir().
3010 * e) conversion from fhandle to dentry may come in the wrong moment - when
3011 * we are removing the target. Solution: we will have to grab ->i_mutex
3012 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3013 * ->i_mutex on parents, which works but leads to some truly excessive
3016 static int vfs_rename_dir(struct inode
*old_dir
, struct dentry
*old_dentry
,
3017 struct inode
*new_dir
, struct dentry
*new_dentry
)
3020 struct inode
*target
;
3023 * If we are going to change the parent - check write permissions,
3024 * we'll need to flip '..'.
3026 if (new_dir
!= old_dir
) {
3027 error
= inode_permission(old_dentry
->d_inode
, MAY_WRITE
);
3032 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3036 target
= new_dentry
->d_inode
;
3038 mutex_lock(&target
->i_mutex
);
3039 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
3043 dentry_unhash(new_dentry
);
3044 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3048 target
->i_flags
|= S_DEAD
;
3049 dont_mount(new_dentry
);
3051 mutex_unlock(&target
->i_mutex
);
3052 if (d_unhashed(new_dentry
))
3053 d_rehash(new_dentry
);
3057 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3058 d_move(old_dentry
,new_dentry
);
3062 static int vfs_rename_other(struct inode
*old_dir
, struct dentry
*old_dentry
,
3063 struct inode
*new_dir
, struct dentry
*new_dentry
)
3065 struct inode
*target
;
3068 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3073 target
= new_dentry
->d_inode
;
3075 mutex_lock(&target
->i_mutex
);
3076 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
3079 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3082 dont_mount(new_dentry
);
3083 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3084 d_move(old_dentry
, new_dentry
);
3087 mutex_unlock(&target
->i_mutex
);
3092 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
3093 struct inode
*new_dir
, struct dentry
*new_dentry
)
3096 int is_dir
= S_ISDIR(old_dentry
->d_inode
->i_mode
);
3097 const unsigned char *old_name
;
3099 if (old_dentry
->d_inode
== new_dentry
->d_inode
)
3102 error
= may_delete(old_dir
, old_dentry
, is_dir
);
3106 if (!new_dentry
->d_inode
)
3107 error
= may_create(new_dir
, new_dentry
);
3109 error
= may_delete(new_dir
, new_dentry
, is_dir
);
3113 if (!old_dir
->i_op
->rename
)
3116 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
3119 error
= vfs_rename_dir(old_dir
,old_dentry
,new_dir
,new_dentry
);
3121 error
= vfs_rename_other(old_dir
,old_dentry
,new_dir
,new_dentry
);
3123 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
3124 new_dentry
->d_inode
, old_dentry
);
3125 fsnotify_oldname_free(old_name
);
3130 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
3131 int, newdfd
, const char __user
*, newname
)
3133 struct dentry
*old_dir
, *new_dir
;
3134 struct dentry
*old_dentry
, *new_dentry
;
3135 struct dentry
*trap
;
3136 struct nameidata oldnd
, newnd
;
3141 error
= user_path_parent(olddfd
, oldname
, &oldnd
, &from
);
3145 error
= user_path_parent(newdfd
, newname
, &newnd
, &to
);
3150 if (oldnd
.path
.mnt
!= newnd
.path
.mnt
)
3153 old_dir
= oldnd
.path
.dentry
;
3155 if (oldnd
.last_type
!= LAST_NORM
)
3158 new_dir
= newnd
.path
.dentry
;
3159 if (newnd
.last_type
!= LAST_NORM
)
3162 oldnd
.flags
&= ~LOOKUP_PARENT
;
3163 newnd
.flags
&= ~LOOKUP_PARENT
;
3164 newnd
.flags
|= LOOKUP_RENAME_TARGET
;
3166 trap
= lock_rename(new_dir
, old_dir
);
3168 old_dentry
= lookup_hash(&oldnd
);
3169 error
= PTR_ERR(old_dentry
);
3170 if (IS_ERR(old_dentry
))
3172 /* source must exist */
3174 if (!old_dentry
->d_inode
)
3176 /* unless the source is a directory trailing slashes give -ENOTDIR */
3177 if (!S_ISDIR(old_dentry
->d_inode
->i_mode
)) {
3179 if (oldnd
.last
.name
[oldnd
.last
.len
])
3181 if (newnd
.last
.name
[newnd
.last
.len
])
3184 /* source should not be ancestor of target */
3186 if (old_dentry
== trap
)
3188 new_dentry
= lookup_hash(&newnd
);
3189 error
= PTR_ERR(new_dentry
);
3190 if (IS_ERR(new_dentry
))
3192 /* target should not be an ancestor of source */
3194 if (new_dentry
== trap
)
3197 error
= mnt_want_write(oldnd
.path
.mnt
);
3200 error
= security_path_rename(&oldnd
.path
, old_dentry
,
3201 &newnd
.path
, new_dentry
);
3204 error
= vfs_rename(old_dir
->d_inode
, old_dentry
,
3205 new_dir
->d_inode
, new_dentry
);
3207 mnt_drop_write(oldnd
.path
.mnt
);
3213 unlock_rename(new_dir
, old_dir
);
3215 path_put(&newnd
.path
);
3218 path_put(&oldnd
.path
);
3224 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
3226 return sys_renameat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
);
3229 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
, const char *link
)
3233 len
= PTR_ERR(link
);
3238 if (len
> (unsigned) buflen
)
3240 if (copy_to_user(buffer
, link
, len
))
3247 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3248 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3249 * using) it for any given inode is up to filesystem.
3251 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3253 struct nameidata nd
;
3258 cookie
= dentry
->d_inode
->i_op
->follow_link(dentry
, &nd
);
3260 return PTR_ERR(cookie
);
3262 res
= vfs_readlink(dentry
, buffer
, buflen
, nd_get_link(&nd
));
3263 if (dentry
->d_inode
->i_op
->put_link
)
3264 dentry
->d_inode
->i_op
->put_link(dentry
, &nd
, cookie
);
3268 int vfs_follow_link(struct nameidata
*nd
, const char *link
)
3270 return __vfs_follow_link(nd
, link
);
3273 /* get the link contents into pagecache */
3274 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
3278 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
3279 page
= read_mapping_page(mapping
, 0, NULL
);
3284 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
3288 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3290 struct page
*page
= NULL
;
3291 char *s
= page_getlink(dentry
, &page
);
3292 int res
= vfs_readlink(dentry
,buffer
,buflen
,s
);
3295 page_cache_release(page
);
3300 void *page_follow_link_light(struct dentry
*dentry
, struct nameidata
*nd
)
3302 struct page
*page
= NULL
;
3303 nd_set_link(nd
, page_getlink(dentry
, &page
));
3307 void page_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
3309 struct page
*page
= cookie
;
3313 page_cache_release(page
);
3318 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3320 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
3322 struct address_space
*mapping
= inode
->i_mapping
;
3327 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
3329 flags
|= AOP_FLAG_NOFS
;
3332 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
3333 flags
, &page
, &fsdata
);
3337 kaddr
= kmap_atomic(page
, KM_USER0
);
3338 memcpy(kaddr
, symname
, len
-1);
3339 kunmap_atomic(kaddr
, KM_USER0
);
3341 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
3348 mark_inode_dirty(inode
);
3354 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
3356 return __page_symlink(inode
, symname
, len
,
3357 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
3360 const struct inode_operations page_symlink_inode_operations
= {
3361 .readlink
= generic_readlink
,
3362 .follow_link
= page_follow_link_light
,
3363 .put_link
= page_put_link
,
3366 EXPORT_SYMBOL(user_path_at
);
3367 EXPORT_SYMBOL(follow_down_one
);
3368 EXPORT_SYMBOL(follow_down
);
3369 EXPORT_SYMBOL(follow_up
);
3370 EXPORT_SYMBOL(get_write_access
); /* binfmt_aout */
3371 EXPORT_SYMBOL(getname
);
3372 EXPORT_SYMBOL(lock_rename
);
3373 EXPORT_SYMBOL(lookup_one_len
);
3374 EXPORT_SYMBOL(page_follow_link_light
);
3375 EXPORT_SYMBOL(page_put_link
);
3376 EXPORT_SYMBOL(page_readlink
);
3377 EXPORT_SYMBOL(__page_symlink
);
3378 EXPORT_SYMBOL(page_symlink
);
3379 EXPORT_SYMBOL(page_symlink_inode_operations
);
3380 EXPORT_SYMBOL(kern_path_parent
);
3381 EXPORT_SYMBOL(kern_path
);
3382 EXPORT_SYMBOL(vfs_path_lookup
);
3383 EXPORT_SYMBOL(inode_permission
);
3384 EXPORT_SYMBOL(file_permission
);
3385 EXPORT_SYMBOL(unlock_rename
);
3386 EXPORT_SYMBOL(vfs_create
);
3387 EXPORT_SYMBOL(vfs_follow_link
);
3388 EXPORT_SYMBOL(vfs_link
);
3389 EXPORT_SYMBOL(vfs_mkdir
);
3390 EXPORT_SYMBOL(vfs_mknod
);
3391 EXPORT_SYMBOL(generic_permission
);
3392 EXPORT_SYMBOL(vfs_readlink
);
3393 EXPORT_SYMBOL(vfs_rename
);
3394 EXPORT_SYMBOL(vfs_rmdir
);
3395 EXPORT_SYMBOL(vfs_symlink
);
3396 EXPORT_SYMBOL(vfs_unlink
);
3397 EXPORT_SYMBOL(dentry_unhash
);
3398 EXPORT_SYMBOL(generic_readlink
);