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 <linux/bitops.h>
39 #include <asm/uaccess.h>
44 /* [Feb-1997 T. Schoebel-Theuer]
45 * Fundamental changes in the pathname lookup mechanisms (namei)
46 * were necessary because of omirr. The reason is that omirr needs
47 * to know the _real_ pathname, not the user-supplied one, in case
48 * of symlinks (and also when transname replacements occur).
50 * The new code replaces the old recursive symlink resolution with
51 * an iterative one (in case of non-nested symlink chains). It does
52 * this with calls to <fs>_follow_link().
53 * As a side effect, dir_namei(), _namei() and follow_link() are now
54 * replaced with a single function lookup_dentry() that can handle all
55 * the special cases of the former code.
57 * With the new dcache, the pathname is stored at each inode, at least as
58 * long as the refcount of the inode is positive. As a side effect, the
59 * size of the dcache depends on the inode cache and thus is dynamic.
61 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
62 * resolution to correspond with current state of the code.
64 * Note that the symlink resolution is not *completely* iterative.
65 * There is still a significant amount of tail- and mid- recursion in
66 * the algorithm. Also, note that <fs>_readlink() is not used in
67 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
68 * may return different results than <fs>_follow_link(). Many virtual
69 * filesystems (including /proc) exhibit this behavior.
72 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
73 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
74 * and the name already exists in form of a symlink, try to create the new
75 * name indicated by the symlink. The old code always complained that the
76 * name already exists, due to not following the symlink even if its target
77 * is nonexistent. The new semantics affects also mknod() and link() when
78 * the name is a symlink pointing to a non-existent name.
80 * I don't know which semantics is the right one, since I have no access
81 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
82 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
83 * "old" one. Personally, I think the new semantics is much more logical.
84 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
85 * file does succeed in both HP-UX and SunOs, but not in Solaris
86 * and in the old Linux semantics.
89 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
90 * semantics. See the comments in "open_namei" and "do_link" below.
92 * [10-Sep-98 Alan Modra] Another symlink change.
95 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
96 * inside the path - always follow.
97 * in the last component in creation/removal/renaming - never follow.
98 * if LOOKUP_FOLLOW passed - follow.
99 * if the pathname has trailing slashes - follow.
100 * otherwise - don't follow.
101 * (applied in that order).
103 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
104 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
105 * During the 2.4 we need to fix the userland stuff depending on it -
106 * hopefully we will be able to get rid of that wart in 2.5. So far only
107 * XEmacs seems to be relying on it...
110 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
111 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
112 * any extra contention...
115 /* In order to reduce some races, while at the same time doing additional
116 * checking and hopefully speeding things up, we copy filenames to the
117 * kernel data space before using them..
119 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
120 * PATH_MAX includes the nul terminator --RR.
123 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
126 getname_flags(const char __user
*filename
, int flags
, int *empty
)
128 struct filename
*result
;
132 result
= audit_reusename(filename
);
136 result
= __getname();
137 if (unlikely(!result
))
138 return ERR_PTR(-ENOMEM
);
141 * First, try to embed the struct filename inside the names_cache
144 kname
= (char *)result
->iname
;
145 result
->name
= kname
;
147 len
= strncpy_from_user(kname
, filename
, EMBEDDED_NAME_MAX
);
148 if (unlikely(len
< 0)) {
154 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
155 * separate struct filename so we can dedicate the entire
156 * names_cache allocation for the pathname, and re-do the copy from
159 if (unlikely(len
== EMBEDDED_NAME_MAX
)) {
160 const size_t size
= offsetof(struct filename
, iname
[1]);
161 kname
= (char *)result
;
164 * size is chosen that way we to guarantee that
165 * result->iname[0] is within the same object and that
166 * kname can't be equal to result->iname, no matter what.
168 result
= kzalloc(size
, GFP_KERNEL
);
169 if (unlikely(!result
)) {
171 return ERR_PTR(-ENOMEM
);
173 result
->name
= kname
;
174 len
= strncpy_from_user(kname
, filename
, PATH_MAX
);
175 if (unlikely(len
< 0)) {
180 if (unlikely(len
== PATH_MAX
)) {
183 return ERR_PTR(-ENAMETOOLONG
);
188 /* The empty path is special. */
189 if (unlikely(!len
)) {
192 if (!(flags
& LOOKUP_EMPTY
)) {
194 return ERR_PTR(-ENOENT
);
198 result
->uptr
= filename
;
199 result
->aname
= NULL
;
200 audit_getname(result
);
205 getname(const char __user
* filename
)
207 return getname_flags(filename
, 0, NULL
);
211 getname_kernel(const char * filename
)
213 struct filename
*result
;
214 int len
= strlen(filename
) + 1;
216 result
= __getname();
217 if (unlikely(!result
))
218 return ERR_PTR(-ENOMEM
);
220 if (len
<= EMBEDDED_NAME_MAX
) {
221 result
->name
= (char *)result
->iname
;
222 } else if (len
<= PATH_MAX
) {
223 struct filename
*tmp
;
225 tmp
= kmalloc(sizeof(*tmp
), GFP_KERNEL
);
226 if (unlikely(!tmp
)) {
228 return ERR_PTR(-ENOMEM
);
230 tmp
->name
= (char *)result
;
234 return ERR_PTR(-ENAMETOOLONG
);
236 memcpy((char *)result
->name
, filename
, len
);
238 result
->aname
= NULL
;
240 audit_getname(result
);
245 void putname(struct filename
*name
)
247 BUG_ON(name
->refcnt
<= 0);
249 if (--name
->refcnt
> 0)
252 if (name
->name
!= name
->iname
) {
253 __putname(name
->name
);
259 static int check_acl(struct inode
*inode
, int mask
)
261 #ifdef CONFIG_FS_POSIX_ACL
262 struct posix_acl
*acl
;
264 if (mask
& MAY_NOT_BLOCK
) {
265 acl
= get_cached_acl_rcu(inode
, ACL_TYPE_ACCESS
);
268 /* no ->get_acl() calls in RCU mode... */
269 if (is_uncached_acl(acl
))
271 return posix_acl_permission(inode
, acl
, mask
& ~MAY_NOT_BLOCK
);
274 acl
= get_acl(inode
, ACL_TYPE_ACCESS
);
278 int error
= posix_acl_permission(inode
, acl
, mask
);
279 posix_acl_release(acl
);
288 * This does the basic permission checking
290 static int acl_permission_check(struct inode
*inode
, int mask
)
292 unsigned int mode
= inode
->i_mode
;
294 if (likely(uid_eq(current_fsuid(), inode
->i_uid
)))
297 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
)) {
298 int error
= check_acl(inode
, mask
);
299 if (error
!= -EAGAIN
)
303 if (in_group_p(inode
->i_gid
))
308 * If the DACs are ok we don't need any capability check.
310 if ((mask
& ~mode
& (MAY_READ
| MAY_WRITE
| MAY_EXEC
)) == 0)
316 * generic_permission - check for access rights on a Posix-like filesystem
317 * @inode: inode to check access rights for
318 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
320 * Used to check for read/write/execute permissions on a file.
321 * We use "fsuid" for this, letting us set arbitrary permissions
322 * for filesystem access without changing the "normal" uids which
323 * are used for other things.
325 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
326 * request cannot be satisfied (eg. requires blocking or too much complexity).
327 * It would then be called again in ref-walk mode.
329 int generic_permission(struct inode
*inode
, int mask
)
334 * Do the basic permission checks.
336 ret
= acl_permission_check(inode
, mask
);
340 if (S_ISDIR(inode
->i_mode
)) {
341 /* DACs are overridable for directories */
342 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
344 if (!(mask
& MAY_WRITE
))
345 if (capable_wrt_inode_uidgid(inode
,
346 CAP_DAC_READ_SEARCH
))
351 * Read/write DACs are always overridable.
352 * Executable DACs are overridable when there is
353 * at least one exec bit set.
355 if (!(mask
& MAY_EXEC
) || (inode
->i_mode
& S_IXUGO
))
356 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
360 * Searching includes executable on directories, else just read.
362 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
363 if (mask
== MAY_READ
)
364 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_READ_SEARCH
))
369 EXPORT_SYMBOL(generic_permission
);
372 * We _really_ want to just do "generic_permission()" without
373 * even looking at the inode->i_op values. So we keep a cache
374 * flag in inode->i_opflags, that says "this has not special
375 * permission function, use the fast case".
377 static inline int do_inode_permission(struct inode
*inode
, int mask
)
379 if (unlikely(!(inode
->i_opflags
& IOP_FASTPERM
))) {
380 if (likely(inode
->i_op
->permission
))
381 return inode
->i_op
->permission(inode
, mask
);
383 /* This gets set once for the inode lifetime */
384 spin_lock(&inode
->i_lock
);
385 inode
->i_opflags
|= IOP_FASTPERM
;
386 spin_unlock(&inode
->i_lock
);
388 return generic_permission(inode
, mask
);
392 * __inode_permission - Check for access rights to a given inode
393 * @inode: Inode to check permission on
394 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
396 * Check for read/write/execute permissions on an inode.
398 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
400 * This does not check for a read-only file system. You probably want
401 * inode_permission().
403 int __inode_permission(struct inode
*inode
, int mask
)
407 if (unlikely(mask
& MAY_WRITE
)) {
409 * Nobody gets write access to an immutable file.
411 if (IS_IMMUTABLE(inode
))
415 retval
= do_inode_permission(inode
, mask
);
419 retval
= devcgroup_inode_permission(inode
, mask
);
423 return security_inode_permission(inode
, mask
);
425 EXPORT_SYMBOL(__inode_permission
);
428 * sb_permission - Check superblock-level permissions
429 * @sb: Superblock of inode to check permission on
430 * @inode: Inode to check permission on
431 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
433 * Separate out file-system wide checks from inode-specific permission checks.
435 static int sb_permission(struct super_block
*sb
, struct inode
*inode
, int mask
)
437 if (unlikely(mask
& MAY_WRITE
)) {
438 umode_t mode
= inode
->i_mode
;
440 /* Nobody gets write access to a read-only fs. */
441 if ((sb
->s_flags
& MS_RDONLY
) &&
442 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
449 * inode_permission - Check for access rights to a given inode
450 * @inode: Inode to check permission on
451 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
453 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
454 * this, letting us set arbitrary permissions for filesystem access without
455 * changing the "normal" UIDs which are used for other things.
457 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
459 int inode_permission(struct inode
*inode
, int mask
)
463 retval
= sb_permission(inode
->i_sb
, inode
, mask
);
466 return __inode_permission(inode
, mask
);
468 EXPORT_SYMBOL(inode_permission
);
471 * path_get - get a reference to a path
472 * @path: path to get the reference to
474 * Given a path increment the reference count to the dentry and the vfsmount.
476 void path_get(const struct path
*path
)
481 EXPORT_SYMBOL(path_get
);
484 * path_put - put a reference to a path
485 * @path: path to put the reference to
487 * Given a path decrement the reference count to the dentry and the vfsmount.
489 void path_put(const struct path
*path
)
494 EXPORT_SYMBOL(path_put
);
496 #define EMBEDDED_LEVELS 2
501 struct inode
*inode
; /* path.dentry.d_inode */
506 int total_link_count
;
509 struct delayed_call done
;
512 } *stack
, internal
[EMBEDDED_LEVELS
];
513 struct filename
*name
;
514 struct nameidata
*saved
;
515 struct inode
*link_inode
;
520 static void set_nameidata(struct nameidata
*p
, int dfd
, struct filename
*name
)
522 struct nameidata
*old
= current
->nameidata
;
523 p
->stack
= p
->internal
;
526 p
->total_link_count
= old
? old
->total_link_count
: 0;
528 current
->nameidata
= p
;
531 static void restore_nameidata(void)
533 struct nameidata
*now
= current
->nameidata
, *old
= now
->saved
;
535 current
->nameidata
= old
;
537 old
->total_link_count
= now
->total_link_count
;
538 if (now
->stack
!= now
->internal
)
542 static int __nd_alloc_stack(struct nameidata
*nd
)
546 if (nd
->flags
& LOOKUP_RCU
) {
547 p
= kmalloc(MAXSYMLINKS
* sizeof(struct saved
),
552 p
= kmalloc(MAXSYMLINKS
* sizeof(struct saved
),
557 memcpy(p
, nd
->internal
, sizeof(nd
->internal
));
563 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
564 * @path: nameidate to verify
566 * Rename can sometimes move a file or directory outside of a bind
567 * mount, path_connected allows those cases to be detected.
569 static bool path_connected(const struct path
*path
)
571 struct vfsmount
*mnt
= path
->mnt
;
573 /* Only bind mounts can have disconnected paths */
574 if (mnt
->mnt_root
== mnt
->mnt_sb
->s_root
)
577 return is_subdir(path
->dentry
, mnt
->mnt_root
);
580 static inline int nd_alloc_stack(struct nameidata
*nd
)
582 if (likely(nd
->depth
!= EMBEDDED_LEVELS
))
584 if (likely(nd
->stack
!= nd
->internal
))
586 return __nd_alloc_stack(nd
);
589 static void drop_links(struct nameidata
*nd
)
593 struct saved
*last
= nd
->stack
+ i
;
594 do_delayed_call(&last
->done
);
595 clear_delayed_call(&last
->done
);
599 static void terminate_walk(struct nameidata
*nd
)
602 if (!(nd
->flags
& LOOKUP_RCU
)) {
605 for (i
= 0; i
< nd
->depth
; i
++)
606 path_put(&nd
->stack
[i
].link
);
607 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
612 nd
->flags
&= ~LOOKUP_RCU
;
613 if (!(nd
->flags
& LOOKUP_ROOT
))
620 /* path_put is needed afterwards regardless of success or failure */
621 static bool legitimize_path(struct nameidata
*nd
,
622 struct path
*path
, unsigned seq
)
624 int res
= __legitimize_mnt(path
->mnt
, nd
->m_seq
);
631 if (unlikely(!lockref_get_not_dead(&path
->dentry
->d_lockref
))) {
635 return !read_seqcount_retry(&path
->dentry
->d_seq
, seq
);
638 static bool legitimize_links(struct nameidata
*nd
)
641 for (i
= 0; i
< nd
->depth
; i
++) {
642 struct saved
*last
= nd
->stack
+ i
;
643 if (unlikely(!legitimize_path(nd
, &last
->link
, last
->seq
))) {
653 * Path walking has 2 modes, rcu-walk and ref-walk (see
654 * Documentation/filesystems/path-lookup.txt). In situations when we can't
655 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
656 * normal reference counts on dentries and vfsmounts to transition to ref-walk
657 * mode. Refcounts are grabbed at the last known good point before rcu-walk
658 * got stuck, so ref-walk may continue from there. If this is not successful
659 * (eg. a seqcount has changed), then failure is returned and it's up to caller
660 * to restart the path walk from the beginning in ref-walk mode.
664 * unlazy_walk - try to switch to ref-walk mode.
665 * @nd: nameidata pathwalk data
666 * @dentry: child of nd->path.dentry or NULL
667 * @seq: seq number to check dentry against
668 * Returns: 0 on success, -ECHILD on failure
670 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
671 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
672 * @nd or NULL. Must be called from rcu-walk context.
673 * Nothing should touch nameidata between unlazy_walk() failure and
676 static int unlazy_walk(struct nameidata
*nd
, struct dentry
*dentry
, unsigned seq
)
678 struct dentry
*parent
= nd
->path
.dentry
;
680 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
682 nd
->flags
&= ~LOOKUP_RCU
;
683 if (unlikely(!legitimize_links(nd
)))
685 if (unlikely(!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
)))
687 if (unlikely(!lockref_get_not_dead(&parent
->d_lockref
)))
691 * For a negative lookup, the lookup sequence point is the parents
692 * sequence point, and it only needs to revalidate the parent dentry.
694 * For a positive lookup, we need to move both the parent and the
695 * dentry from the RCU domain to be properly refcounted. And the
696 * sequence number in the dentry validates *both* dentry counters,
697 * since we checked the sequence number of the parent after we got
698 * the child sequence number. So we know the parent must still
699 * be valid if the child sequence number is still valid.
702 if (read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
704 BUG_ON(nd
->inode
!= parent
->d_inode
);
706 if (!lockref_get_not_dead(&dentry
->d_lockref
))
708 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
713 * Sequence counts matched. Now make sure that the root is
714 * still valid and get it if required.
716 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
717 if (unlikely(!legitimize_path(nd
, &nd
->root
, nd
->root_seq
))) {
734 nd
->path
.dentry
= NULL
;
738 if (!(nd
->flags
& LOOKUP_ROOT
))
743 static int unlazy_link(struct nameidata
*nd
, struct path
*link
, unsigned seq
)
745 if (unlikely(!legitimize_path(nd
, link
, seq
))) {
748 nd
->flags
&= ~LOOKUP_RCU
;
750 nd
->path
.dentry
= NULL
;
751 if (!(nd
->flags
& LOOKUP_ROOT
))
754 } else if (likely(unlazy_walk(nd
, NULL
, 0)) == 0) {
761 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
763 return dentry
->d_op
->d_revalidate(dentry
, flags
);
767 * complete_walk - successful completion of path walk
768 * @nd: pointer nameidata
770 * If we had been in RCU mode, drop out of it and legitimize nd->path.
771 * Revalidate the final result, unless we'd already done that during
772 * the path walk or the filesystem doesn't ask for it. Return 0 on
773 * success, -error on failure. In case of failure caller does not
774 * need to drop nd->path.
776 static int complete_walk(struct nameidata
*nd
)
778 struct dentry
*dentry
= nd
->path
.dentry
;
781 if (nd
->flags
& LOOKUP_RCU
) {
782 if (!(nd
->flags
& LOOKUP_ROOT
))
784 if (unlikely(unlazy_walk(nd
, NULL
, 0)))
788 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
791 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
794 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
804 static void set_root(struct nameidata
*nd
)
806 struct fs_struct
*fs
= current
->fs
;
808 if (nd
->flags
& LOOKUP_RCU
) {
812 seq
= read_seqcount_begin(&fs
->seq
);
814 nd
->root_seq
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
815 } while (read_seqcount_retry(&fs
->seq
, seq
));
817 get_fs_root(fs
, &nd
->root
);
821 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
824 if (path
->mnt
!= nd
->path
.mnt
)
828 static inline void path_to_nameidata(const struct path
*path
,
829 struct nameidata
*nd
)
831 if (!(nd
->flags
& LOOKUP_RCU
)) {
832 dput(nd
->path
.dentry
);
833 if (nd
->path
.mnt
!= path
->mnt
)
834 mntput(nd
->path
.mnt
);
836 nd
->path
.mnt
= path
->mnt
;
837 nd
->path
.dentry
= path
->dentry
;
840 static int nd_jump_root(struct nameidata
*nd
)
842 if (nd
->flags
& LOOKUP_RCU
) {
846 nd
->inode
= d
->d_inode
;
847 nd
->seq
= nd
->root_seq
;
848 if (unlikely(read_seqcount_retry(&d
->d_seq
, nd
->seq
)))
854 nd
->inode
= nd
->path
.dentry
->d_inode
;
856 nd
->flags
|= LOOKUP_JUMPED
;
861 * Helper to directly jump to a known parsed path from ->get_link,
862 * caller must have taken a reference to path beforehand.
864 void nd_jump_link(struct path
*path
)
866 struct nameidata
*nd
= current
->nameidata
;
870 nd
->inode
= nd
->path
.dentry
->d_inode
;
871 nd
->flags
|= LOOKUP_JUMPED
;
874 static inline void put_link(struct nameidata
*nd
)
876 struct saved
*last
= nd
->stack
+ --nd
->depth
;
877 do_delayed_call(&last
->done
);
878 if (!(nd
->flags
& LOOKUP_RCU
))
879 path_put(&last
->link
);
882 int sysctl_protected_symlinks __read_mostly
= 0;
883 int sysctl_protected_hardlinks __read_mostly
= 0;
886 * may_follow_link - Check symlink following for unsafe situations
887 * @nd: nameidata pathwalk data
889 * In the case of the sysctl_protected_symlinks sysctl being enabled,
890 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
891 * in a sticky world-writable directory. This is to protect privileged
892 * processes from failing races against path names that may change out
893 * from under them by way of other users creating malicious symlinks.
894 * It will permit symlinks to be followed only when outside a sticky
895 * world-writable directory, or when the uid of the symlink and follower
896 * match, or when the directory owner matches the symlink's owner.
898 * Returns 0 if following the symlink is allowed, -ve on error.
900 static inline int may_follow_link(struct nameidata
*nd
)
902 const struct inode
*inode
;
903 const struct inode
*parent
;
905 if (!sysctl_protected_symlinks
)
908 /* Allowed if owner and follower match. */
909 inode
= nd
->link_inode
;
910 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
913 /* Allowed if parent directory not sticky and world-writable. */
915 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
918 /* Allowed if parent directory and link owner match. */
919 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
922 if (nd
->flags
& LOOKUP_RCU
)
925 audit_log_link_denied("follow_link", &nd
->stack
[0].link
);
930 * safe_hardlink_source - Check for safe hardlink conditions
931 * @inode: the source inode to hardlink from
933 * Return false if at least one of the following conditions:
934 * - inode is not a regular file
936 * - inode is setgid and group-exec
937 * - access failure for read and write
939 * Otherwise returns true.
941 static bool safe_hardlink_source(struct inode
*inode
)
943 umode_t mode
= inode
->i_mode
;
945 /* Special files should not get pinned to the filesystem. */
949 /* Setuid files should not get pinned to the filesystem. */
953 /* Executable setgid files should not get pinned to the filesystem. */
954 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
957 /* Hardlinking to unreadable or unwritable sources is dangerous. */
958 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
965 * may_linkat - Check permissions for creating a hardlink
966 * @link: the source to hardlink from
968 * Block hardlink when all of:
969 * - sysctl_protected_hardlinks enabled
970 * - fsuid does not match inode
971 * - hardlink source is unsafe (see safe_hardlink_source() above)
972 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
974 * Returns 0 if successful, -ve on error.
976 static int may_linkat(struct path
*link
)
980 if (!sysctl_protected_hardlinks
)
983 inode
= link
->dentry
->d_inode
;
985 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
986 * otherwise, it must be a safe source.
988 if (inode_owner_or_capable(inode
) || safe_hardlink_source(inode
))
991 audit_log_link_denied("linkat", link
);
995 static __always_inline
996 const char *get_link(struct nameidata
*nd
)
998 struct saved
*last
= nd
->stack
+ nd
->depth
- 1;
999 struct dentry
*dentry
= last
->link
.dentry
;
1000 struct inode
*inode
= nd
->link_inode
;
1004 if (!(nd
->flags
& LOOKUP_RCU
)) {
1005 touch_atime(&last
->link
);
1007 } else if (atime_needs_update(&last
->link
, inode
)) {
1008 if (unlikely(unlazy_walk(nd
, NULL
, 0)))
1009 return ERR_PTR(-ECHILD
);
1010 touch_atime(&last
->link
);
1013 error
= security_inode_follow_link(dentry
, inode
,
1014 nd
->flags
& LOOKUP_RCU
);
1015 if (unlikely(error
))
1016 return ERR_PTR(error
);
1018 nd
->last_type
= LAST_BIND
;
1019 res
= inode
->i_link
;
1021 const char * (*get
)(struct dentry
*, struct inode
*,
1022 struct delayed_call
*);
1023 get
= inode
->i_op
->get_link
;
1024 if (nd
->flags
& LOOKUP_RCU
) {
1025 res
= get(NULL
, inode
, &last
->done
);
1026 if (res
== ERR_PTR(-ECHILD
)) {
1027 if (unlikely(unlazy_walk(nd
, NULL
, 0)))
1028 return ERR_PTR(-ECHILD
);
1029 res
= get(dentry
, inode
, &last
->done
);
1032 res
= get(dentry
, inode
, &last
->done
);
1034 if (IS_ERR_OR_NULL(res
))
1040 if (unlikely(nd_jump_root(nd
)))
1041 return ERR_PTR(-ECHILD
);
1042 while (unlikely(*++res
== '/'))
1051 * follow_up - Find the mountpoint of path's vfsmount
1053 * Given a path, find the mountpoint of its source file system.
1054 * Replace @path with the path of the mountpoint in the parent mount.
1057 * Return 1 if we went up a level and 0 if we were already at the
1060 int follow_up(struct path
*path
)
1062 struct mount
*mnt
= real_mount(path
->mnt
);
1063 struct mount
*parent
;
1064 struct dentry
*mountpoint
;
1066 read_seqlock_excl(&mount_lock
);
1067 parent
= mnt
->mnt_parent
;
1068 if (parent
== mnt
) {
1069 read_sequnlock_excl(&mount_lock
);
1072 mntget(&parent
->mnt
);
1073 mountpoint
= dget(mnt
->mnt_mountpoint
);
1074 read_sequnlock_excl(&mount_lock
);
1076 path
->dentry
= mountpoint
;
1078 path
->mnt
= &parent
->mnt
;
1081 EXPORT_SYMBOL(follow_up
);
1084 * Perform an automount
1085 * - return -EISDIR to tell follow_managed() to stop and return the path we
1088 static int follow_automount(struct path
*path
, struct nameidata
*nd
,
1091 struct vfsmount
*mnt
;
1094 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
1097 /* We don't want to mount if someone's just doing a stat -
1098 * unless they're stat'ing a directory and appended a '/' to
1101 * We do, however, want to mount if someone wants to open or
1102 * create a file of any type under the mountpoint, wants to
1103 * traverse through the mountpoint or wants to open the
1104 * mounted directory. Also, autofs may mark negative dentries
1105 * as being automount points. These will need the attentions
1106 * of the daemon to instantiate them before they can be used.
1108 if (!(nd
->flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
1109 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
1110 path
->dentry
->d_inode
)
1113 nd
->total_link_count
++;
1114 if (nd
->total_link_count
>= 40)
1117 mnt
= path
->dentry
->d_op
->d_automount(path
);
1120 * The filesystem is allowed to return -EISDIR here to indicate
1121 * it doesn't want to automount. For instance, autofs would do
1122 * this so that its userspace daemon can mount on this dentry.
1124 * However, we can only permit this if it's a terminal point in
1125 * the path being looked up; if it wasn't then the remainder of
1126 * the path is inaccessible and we should say so.
1128 if (PTR_ERR(mnt
) == -EISDIR
&& (nd
->flags
& LOOKUP_PARENT
))
1130 return PTR_ERR(mnt
);
1133 if (!mnt
) /* mount collision */
1136 if (!*need_mntput
) {
1137 /* lock_mount() may release path->mnt on error */
1139 *need_mntput
= true;
1141 err
= finish_automount(mnt
, path
);
1145 /* Someone else made a mount here whilst we were busy */
1150 path
->dentry
= dget(mnt
->mnt_root
);
1159 * Handle a dentry that is managed in some way.
1160 * - Flagged for transit management (autofs)
1161 * - Flagged as mountpoint
1162 * - Flagged as automount point
1164 * This may only be called in refwalk mode.
1166 * Serialization is taken care of in namespace.c
1168 static int follow_managed(struct path
*path
, struct nameidata
*nd
)
1170 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1172 bool need_mntput
= false;
1175 /* Given that we're not holding a lock here, we retain the value in a
1176 * local variable for each dentry as we look at it so that we don't see
1177 * the components of that value change under us */
1178 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1179 managed
&= DCACHE_MANAGED_DENTRY
,
1180 unlikely(managed
!= 0)) {
1181 /* Allow the filesystem to manage the transit without i_mutex
1183 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1184 BUG_ON(!path
->dentry
->d_op
);
1185 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1186 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1191 /* Transit to a mounted filesystem. */
1192 if (managed
& DCACHE_MOUNTED
) {
1193 struct vfsmount
*mounted
= lookup_mnt(path
);
1198 path
->mnt
= mounted
;
1199 path
->dentry
= dget(mounted
->mnt_root
);
1204 /* Something is mounted on this dentry in another
1205 * namespace and/or whatever was mounted there in this
1206 * namespace got unmounted before lookup_mnt() could
1210 /* Handle an automount point */
1211 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1212 ret
= follow_automount(path
, nd
, &need_mntput
);
1218 /* We didn't change the current path point */
1222 if (need_mntput
&& path
->mnt
== mnt
)
1224 if (ret
== -EISDIR
|| !ret
)
1227 nd
->flags
|= LOOKUP_JUMPED
;
1228 if (unlikely(ret
< 0))
1229 path_put_conditional(path
, nd
);
1233 int follow_down_one(struct path
*path
)
1235 struct vfsmount
*mounted
;
1237 mounted
= lookup_mnt(path
);
1241 path
->mnt
= mounted
;
1242 path
->dentry
= dget(mounted
->mnt_root
);
1247 EXPORT_SYMBOL(follow_down_one
);
1249 static inline int managed_dentry_rcu(struct dentry
*dentry
)
1251 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) ?
1252 dentry
->d_op
->d_manage(dentry
, true) : 0;
1256 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1257 * we meet a managed dentry that would need blocking.
1259 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1260 struct inode
**inode
, unsigned *seqp
)
1263 struct mount
*mounted
;
1265 * Don't forget we might have a non-mountpoint managed dentry
1266 * that wants to block transit.
1268 switch (managed_dentry_rcu(path
->dentry
)) {
1278 if (!d_mountpoint(path
->dentry
))
1279 return !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1281 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1284 path
->mnt
= &mounted
->mnt
;
1285 path
->dentry
= mounted
->mnt
.mnt_root
;
1286 nd
->flags
|= LOOKUP_JUMPED
;
1287 *seqp
= read_seqcount_begin(&path
->dentry
->d_seq
);
1289 * Update the inode too. We don't need to re-check the
1290 * dentry sequence number here after this d_inode read,
1291 * because a mount-point is always pinned.
1293 *inode
= path
->dentry
->d_inode
;
1295 return !read_seqretry(&mount_lock
, nd
->m_seq
) &&
1296 !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1299 static int follow_dotdot_rcu(struct nameidata
*nd
)
1301 struct inode
*inode
= nd
->inode
;
1304 if (path_equal(&nd
->path
, &nd
->root
))
1306 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1307 struct dentry
*old
= nd
->path
.dentry
;
1308 struct dentry
*parent
= old
->d_parent
;
1311 inode
= parent
->d_inode
;
1312 seq
= read_seqcount_begin(&parent
->d_seq
);
1313 if (unlikely(read_seqcount_retry(&old
->d_seq
, nd
->seq
)))
1315 nd
->path
.dentry
= parent
;
1317 if (unlikely(!path_connected(&nd
->path
)))
1321 struct mount
*mnt
= real_mount(nd
->path
.mnt
);
1322 struct mount
*mparent
= mnt
->mnt_parent
;
1323 struct dentry
*mountpoint
= mnt
->mnt_mountpoint
;
1324 struct inode
*inode2
= mountpoint
->d_inode
;
1325 unsigned seq
= read_seqcount_begin(&mountpoint
->d_seq
);
1326 if (unlikely(read_seqretry(&mount_lock
, nd
->m_seq
)))
1328 if (&mparent
->mnt
== nd
->path
.mnt
)
1330 /* we know that mountpoint was pinned */
1331 nd
->path
.dentry
= mountpoint
;
1332 nd
->path
.mnt
= &mparent
->mnt
;
1337 while (unlikely(d_mountpoint(nd
->path
.dentry
))) {
1338 struct mount
*mounted
;
1339 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1340 if (unlikely(read_seqretry(&mount_lock
, nd
->m_seq
)))
1344 nd
->path
.mnt
= &mounted
->mnt
;
1345 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1346 inode
= nd
->path
.dentry
->d_inode
;
1347 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1354 * Follow down to the covering mount currently visible to userspace. At each
1355 * point, the filesystem owning that dentry may be queried as to whether the
1356 * caller is permitted to proceed or not.
1358 int follow_down(struct path
*path
)
1363 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1364 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1365 /* Allow the filesystem to manage the transit without i_mutex
1368 * We indicate to the filesystem if someone is trying to mount
1369 * something here. This gives autofs the chance to deny anyone
1370 * other than its daemon the right to mount on its
1373 * The filesystem may sleep at this point.
1375 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1376 BUG_ON(!path
->dentry
->d_op
);
1377 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1378 ret
= path
->dentry
->d_op
->d_manage(
1379 path
->dentry
, false);
1381 return ret
== -EISDIR
? 0 : ret
;
1384 /* Transit to a mounted filesystem. */
1385 if (managed
& DCACHE_MOUNTED
) {
1386 struct vfsmount
*mounted
= lookup_mnt(path
);
1391 path
->mnt
= mounted
;
1392 path
->dentry
= dget(mounted
->mnt_root
);
1396 /* Don't handle automount points here */
1401 EXPORT_SYMBOL(follow_down
);
1404 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1406 static void follow_mount(struct path
*path
)
1408 while (d_mountpoint(path
->dentry
)) {
1409 struct vfsmount
*mounted
= lookup_mnt(path
);
1414 path
->mnt
= mounted
;
1415 path
->dentry
= dget(mounted
->mnt_root
);
1419 static int path_parent_directory(struct path
*path
)
1421 struct dentry
*old
= path
->dentry
;
1422 /* rare case of legitimate dget_parent()... */
1423 path
->dentry
= dget_parent(path
->dentry
);
1425 if (unlikely(!path_connected(path
)))
1430 static int follow_dotdot(struct nameidata
*nd
)
1433 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1434 nd
->path
.mnt
== nd
->root
.mnt
) {
1437 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1438 int ret
= path_parent_directory(&nd
->path
);
1443 if (!follow_up(&nd
->path
))
1446 follow_mount(&nd
->path
);
1447 nd
->inode
= nd
->path
.dentry
->d_inode
;
1452 * This looks up the name in dcache and possibly revalidates the found dentry.
1453 * NULL is returned if the dentry does not exist in the cache.
1455 static struct dentry
*lookup_dcache(const struct qstr
*name
,
1459 struct dentry
*dentry
;
1462 dentry
= d_lookup(dir
, name
);
1464 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1465 error
= d_revalidate(dentry
, flags
);
1466 if (unlikely(error
<= 0)) {
1468 d_invalidate(dentry
);
1470 return ERR_PTR(error
);
1478 * Call i_op->lookup on the dentry. The dentry must be negative and
1481 * dir->d_inode->i_mutex must be held
1483 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1488 /* Don't create child dentry for a dead directory. */
1489 if (unlikely(IS_DEADDIR(dir
))) {
1491 return ERR_PTR(-ENOENT
);
1494 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1495 if (unlikely(old
)) {
1502 static struct dentry
*__lookup_hash(const struct qstr
*name
,
1503 struct dentry
*base
, unsigned int flags
)
1505 struct dentry
*dentry
= lookup_dcache(name
, base
, flags
);
1510 dentry
= d_alloc(base
, name
);
1511 if (unlikely(!dentry
))
1512 return ERR_PTR(-ENOMEM
);
1514 return lookup_real(base
->d_inode
, dentry
, flags
);
1517 static int lookup_fast(struct nameidata
*nd
,
1518 struct path
*path
, struct inode
**inode
,
1521 struct vfsmount
*mnt
= nd
->path
.mnt
;
1522 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1527 * Rename seqlock is not required here because in the off chance
1528 * of a false negative due to a concurrent rename, the caller is
1529 * going to fall back to non-racy lookup.
1531 if (nd
->flags
& LOOKUP_RCU
) {
1534 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1535 if (unlikely(!dentry
)) {
1536 if (unlazy_walk(nd
, NULL
, 0))
1542 * This sequence count validates that the inode matches
1543 * the dentry name information from lookup.
1545 *inode
= d_backing_inode(dentry
);
1546 negative
= d_is_negative(dentry
);
1547 if (unlikely(read_seqcount_retry(&dentry
->d_seq
, seq
)))
1551 * This sequence count validates that the parent had no
1552 * changes while we did the lookup of the dentry above.
1554 * The memory barrier in read_seqcount_begin of child is
1555 * enough, we can use __read_seqcount_retry here.
1557 if (unlikely(__read_seqcount_retry(&parent
->d_seq
, nd
->seq
)))
1561 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
))
1562 status
= d_revalidate(dentry
, nd
->flags
);
1563 if (unlikely(status
<= 0)) {
1564 if (unlazy_walk(nd
, dentry
, seq
))
1566 if (status
== -ECHILD
)
1567 status
= d_revalidate(dentry
, nd
->flags
);
1570 * Note: do negative dentry check after revalidation in
1571 * case that drops it.
1573 if (unlikely(negative
))
1576 path
->dentry
= dentry
;
1577 if (likely(__follow_mount_rcu(nd
, path
, inode
, seqp
)))
1579 if (unlazy_walk(nd
, dentry
, seq
))
1583 dentry
= __d_lookup(parent
, &nd
->last
);
1584 if (unlikely(!dentry
))
1586 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
))
1587 status
= d_revalidate(dentry
, nd
->flags
);
1589 if (unlikely(status
<= 0)) {
1591 d_invalidate(dentry
);
1595 if (unlikely(d_is_negative(dentry
))) {
1601 path
->dentry
= dentry
;
1602 err
= follow_managed(path
, nd
);
1603 if (likely(err
> 0))
1604 *inode
= d_backing_inode(path
->dentry
);
1608 /* Fast lookup failed, do it the slow way */
1609 static struct dentry
*lookup_slow(const struct qstr
*name
,
1613 struct dentry
*dentry
= ERR_PTR(-ENOENT
), *old
;
1614 struct inode
*inode
= dir
->d_inode
;
1615 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq
);
1617 inode_lock_shared(inode
);
1618 /* Don't go there if it's already dead */
1619 if (unlikely(IS_DEADDIR(inode
)))
1622 dentry
= d_alloc_parallel(dir
, name
, &wq
);
1625 if (unlikely(!d_in_lookup(dentry
))) {
1626 if ((dentry
->d_flags
& DCACHE_OP_REVALIDATE
) &&
1627 !(flags
& LOOKUP_NO_REVAL
)) {
1628 int error
= d_revalidate(dentry
, flags
);
1629 if (unlikely(error
<= 0)) {
1631 d_invalidate(dentry
);
1636 dentry
= ERR_PTR(error
);
1640 old
= inode
->i_op
->lookup(inode
, dentry
, flags
);
1641 d_lookup_done(dentry
);
1642 if (unlikely(old
)) {
1648 inode_unlock_shared(inode
);
1652 static inline int may_lookup(struct nameidata
*nd
)
1654 if (nd
->flags
& LOOKUP_RCU
) {
1655 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1658 if (unlazy_walk(nd
, NULL
, 0))
1661 return inode_permission(nd
->inode
, MAY_EXEC
);
1664 static inline int handle_dots(struct nameidata
*nd
, int type
)
1666 if (type
== LAST_DOTDOT
) {
1669 if (nd
->flags
& LOOKUP_RCU
) {
1670 return follow_dotdot_rcu(nd
);
1672 return follow_dotdot(nd
);
1677 static int pick_link(struct nameidata
*nd
, struct path
*link
,
1678 struct inode
*inode
, unsigned seq
)
1682 if (unlikely(nd
->total_link_count
++ >= MAXSYMLINKS
)) {
1683 path_to_nameidata(link
, nd
);
1686 if (!(nd
->flags
& LOOKUP_RCU
)) {
1687 if (link
->mnt
== nd
->path
.mnt
)
1690 error
= nd_alloc_stack(nd
);
1691 if (unlikely(error
)) {
1692 if (error
== -ECHILD
) {
1693 if (unlikely(unlazy_link(nd
, link
, seq
)))
1695 error
= nd_alloc_stack(nd
);
1703 last
= nd
->stack
+ nd
->depth
++;
1705 clear_delayed_call(&last
->done
);
1706 nd
->link_inode
= inode
;
1712 * Do we need to follow links? We _really_ want to be able
1713 * to do this check without having to look at inode->i_op,
1714 * so we keep a cache of "no, this doesn't need follow_link"
1715 * for the common case.
1717 static inline int should_follow_link(struct nameidata
*nd
, struct path
*link
,
1719 struct inode
*inode
, unsigned seq
)
1721 if (likely(!d_is_symlink(link
->dentry
)))
1725 /* make sure that d_is_symlink above matches inode */
1726 if (nd
->flags
& LOOKUP_RCU
) {
1727 if (read_seqcount_retry(&link
->dentry
->d_seq
, seq
))
1730 return pick_link(nd
, link
, inode
, seq
);
1733 enum {WALK_GET
= 1, WALK_PUT
= 2};
1735 static int walk_component(struct nameidata
*nd
, int flags
)
1738 struct inode
*inode
;
1742 * "." and ".." are special - ".." especially so because it has
1743 * to be able to know about the current root directory and
1744 * parent relationships.
1746 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
1747 err
= handle_dots(nd
, nd
->last_type
);
1748 if (flags
& WALK_PUT
)
1752 err
= lookup_fast(nd
, &path
, &inode
, &seq
);
1753 if (unlikely(err
<= 0)) {
1756 path
.dentry
= lookup_slow(&nd
->last
, nd
->path
.dentry
,
1758 if (IS_ERR(path
.dentry
))
1759 return PTR_ERR(path
.dentry
);
1761 path
.mnt
= nd
->path
.mnt
;
1762 err
= follow_managed(&path
, nd
);
1763 if (unlikely(err
< 0))
1766 if (unlikely(d_is_negative(path
.dentry
))) {
1767 path_to_nameidata(&path
, nd
);
1771 seq
= 0; /* we are already out of RCU mode */
1772 inode
= d_backing_inode(path
.dentry
);
1775 if (flags
& WALK_PUT
)
1777 err
= should_follow_link(nd
, &path
, flags
& WALK_GET
, inode
, seq
);
1780 path_to_nameidata(&path
, nd
);
1787 * We can do the critical dentry name comparison and hashing
1788 * operations one word at a time, but we are limited to:
1790 * - Architectures with fast unaligned word accesses. We could
1791 * do a "get_unaligned()" if this helps and is sufficiently
1794 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1795 * do not trap on the (extremely unlikely) case of a page
1796 * crossing operation.
1798 * - Furthermore, we need an efficient 64-bit compile for the
1799 * 64-bit case in order to generate the "number of bytes in
1800 * the final mask". Again, that could be replaced with a
1801 * efficient population count instruction or similar.
1803 #ifdef CONFIG_DCACHE_WORD_ACCESS
1805 #include <asm/word-at-a-time.h>
1809 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1811 #elif defined(CONFIG_64BIT)
1813 * Register pressure in the mixing function is an issue, particularly
1814 * on 32-bit x86, but almost any function requires one state value and
1815 * one temporary. Instead, use a function designed for two state values
1816 * and no temporaries.
1818 * This function cannot create a collision in only two iterations, so
1819 * we have two iterations to achieve avalanche. In those two iterations,
1820 * we have six layers of mixing, which is enough to spread one bit's
1821 * influence out to 2^6 = 64 state bits.
1823 * Rotate constants are scored by considering either 64 one-bit input
1824 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
1825 * probability of that delta causing a change to each of the 128 output
1826 * bits, using a sample of random initial states.
1828 * The Shannon entropy of the computed probabilities is then summed
1829 * to produce a score. Ideally, any input change has a 50% chance of
1830 * toggling any given output bit.
1832 * Mixing scores (in bits) for (12,45):
1833 * Input delta: 1-bit 2-bit
1834 * 1 round: 713.3 42542.6
1835 * 2 rounds: 2753.7 140389.8
1836 * 3 rounds: 5954.1 233458.2
1837 * 4 rounds: 7862.6 256672.2
1838 * Perfect: 8192 258048
1839 * (64*128) (64*63/2 * 128)
1841 #define HASH_MIX(x, y, a) \
1843 y ^= x, x = rol64(x,12),\
1844 x += y, y = rol64(y,45),\
1848 * Fold two longs into one 32-bit hash value. This must be fast, but
1849 * latency isn't quite as critical, as there is a fair bit of additional
1850 * work done before the hash value is used.
1852 static inline unsigned int fold_hash(unsigned long x
, unsigned long y
)
1854 y
^= x
* GOLDEN_RATIO_64
;
1855 y
*= GOLDEN_RATIO_64
;
1859 #else /* 32-bit case */
1862 * Mixing scores (in bits) for (7,20):
1863 * Input delta: 1-bit 2-bit
1864 * 1 round: 330.3 9201.6
1865 * 2 rounds: 1246.4 25475.4
1866 * 3 rounds: 1907.1 31295.1
1867 * 4 rounds: 2042.3 31718.6
1868 * Perfect: 2048 31744
1869 * (32*64) (32*31/2 * 64)
1871 #define HASH_MIX(x, y, a) \
1873 y ^= x, x = rol32(x, 7),\
1874 x += y, y = rol32(y,20),\
1877 static inline unsigned int fold_hash(unsigned long x
, unsigned long y
)
1879 /* Use arch-optimized multiply if one exists */
1880 return __hash_32(y
^ __hash_32(x
));
1886 * Return the hash of a string of known length. This is carfully
1887 * designed to match hash_name(), which is the more critical function.
1888 * In particular, we must end by hashing a final word containing 0..7
1889 * payload bytes, to match the way that hash_name() iterates until it
1890 * finds the delimiter after the name.
1892 unsigned int full_name_hash(const void *salt
, const char *name
, unsigned int len
)
1894 unsigned long a
, x
= 0, y
= (unsigned long)salt
;
1899 a
= load_unaligned_zeropad(name
);
1900 if (len
< sizeof(unsigned long))
1903 name
+= sizeof(unsigned long);
1904 len
-= sizeof(unsigned long);
1906 x
^= a
& bytemask_from_count(len
);
1908 return fold_hash(x
, y
);
1910 EXPORT_SYMBOL(full_name_hash
);
1912 /* Return the "hash_len" (hash and length) of a null-terminated string */
1913 u64
hashlen_string(const void *salt
, const char *name
)
1915 unsigned long a
= 0, x
= 0, y
= (unsigned long)salt
;
1916 unsigned long adata
, mask
, len
;
1917 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1924 len
+= sizeof(unsigned long);
1926 a
= load_unaligned_zeropad(name
+len
);
1927 } while (!has_zero(a
, &adata
, &constants
));
1929 adata
= prep_zero_mask(a
, adata
, &constants
);
1930 mask
= create_zero_mask(adata
);
1931 x
^= a
& zero_bytemask(mask
);
1933 return hashlen_create(fold_hash(x
, y
), len
+ find_zero(mask
));
1935 EXPORT_SYMBOL(hashlen_string
);
1938 * Calculate the length and hash of the path component, and
1939 * return the "hash_len" as the result.
1941 static inline u64
hash_name(const void *salt
, const char *name
)
1943 unsigned long a
= 0, b
, x
= 0, y
= (unsigned long)salt
;
1944 unsigned long adata
, bdata
, mask
, len
;
1945 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1952 len
+= sizeof(unsigned long);
1954 a
= load_unaligned_zeropad(name
+len
);
1955 b
= a
^ REPEAT_BYTE('/');
1956 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1958 adata
= prep_zero_mask(a
, adata
, &constants
);
1959 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1960 mask
= create_zero_mask(adata
| bdata
);
1961 x
^= a
& zero_bytemask(mask
);
1963 return hashlen_create(fold_hash(x
, y
), len
+ find_zero(mask
));
1966 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
1968 /* Return the hash of a string of known length */
1969 unsigned int full_name_hash(const void *salt
, const char *name
, unsigned int len
)
1971 unsigned long hash
= init_name_hash(salt
);
1973 hash
= partial_name_hash((unsigned char)*name
++, hash
);
1974 return end_name_hash(hash
);
1976 EXPORT_SYMBOL(full_name_hash
);
1978 /* Return the "hash_len" (hash and length) of a null-terminated string */
1979 u64
hashlen_string(const void *salt
, const char *name
)
1981 unsigned long hash
= init_name_hash(salt
);
1982 unsigned long len
= 0, c
;
1984 c
= (unsigned char)*name
;
1987 hash
= partial_name_hash(c
, hash
);
1988 c
= (unsigned char)name
[len
];
1990 return hashlen_create(end_name_hash(hash
), len
);
1992 EXPORT_SYMBOL(hashlen_string
);
1995 * We know there's a real path component here of at least
1998 static inline u64
hash_name(const void *salt
, const char *name
)
2000 unsigned long hash
= init_name_hash(salt
);
2001 unsigned long len
= 0, c
;
2003 c
= (unsigned char)*name
;
2006 hash
= partial_name_hash(c
, hash
);
2007 c
= (unsigned char)name
[len
];
2008 } while (c
&& c
!= '/');
2009 return hashlen_create(end_name_hash(hash
), len
);
2016 * This is the basic name resolution function, turning a pathname into
2017 * the final dentry. We expect 'base' to be positive and a directory.
2019 * Returns 0 and nd will have valid dentry and mnt on success.
2020 * Returns error and drops reference to input namei data on failure.
2022 static int link_path_walk(const char *name
, struct nameidata
*nd
)
2031 /* At this point we know we have a real path component. */
2036 err
= may_lookup(nd
);
2040 hash_len
= hash_name(nd
->path
.dentry
, name
);
2043 if (name
[0] == '.') switch (hashlen_len(hash_len
)) {
2045 if (name
[1] == '.') {
2047 nd
->flags
|= LOOKUP_JUMPED
;
2053 if (likely(type
== LAST_NORM
)) {
2054 struct dentry
*parent
= nd
->path
.dentry
;
2055 nd
->flags
&= ~LOOKUP_JUMPED
;
2056 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
2057 struct qstr
this = { { .hash_len
= hash_len
}, .name
= name
};
2058 err
= parent
->d_op
->d_hash(parent
, &this);
2061 hash_len
= this.hash_len
;
2066 nd
->last
.hash_len
= hash_len
;
2067 nd
->last
.name
= name
;
2068 nd
->last_type
= type
;
2070 name
+= hashlen_len(hash_len
);
2074 * If it wasn't NUL, we know it was '/'. Skip that
2075 * slash, and continue until no more slashes.
2079 } while (unlikely(*name
== '/'));
2080 if (unlikely(!*name
)) {
2082 /* pathname body, done */
2085 name
= nd
->stack
[nd
->depth
- 1].name
;
2086 /* trailing symlink, done */
2089 /* last component of nested symlink */
2090 err
= walk_component(nd
, WALK_GET
| WALK_PUT
);
2092 err
= walk_component(nd
, WALK_GET
);
2098 const char *s
= get_link(nd
);
2107 nd
->stack
[nd
->depth
- 1].name
= name
;
2112 if (unlikely(!d_can_lookup(nd
->path
.dentry
))) {
2113 if (nd
->flags
& LOOKUP_RCU
) {
2114 if (unlazy_walk(nd
, NULL
, 0))
2122 static const char *path_init(struct nameidata
*nd
, unsigned flags
)
2125 const char *s
= nd
->name
->name
;
2127 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
2128 nd
->flags
= flags
| LOOKUP_JUMPED
| LOOKUP_PARENT
;
2130 if (flags
& LOOKUP_ROOT
) {
2131 struct dentry
*root
= nd
->root
.dentry
;
2132 struct inode
*inode
= root
->d_inode
;
2134 if (!d_can_lookup(root
))
2135 return ERR_PTR(-ENOTDIR
);
2136 retval
= inode_permission(inode
, MAY_EXEC
);
2138 return ERR_PTR(retval
);
2140 nd
->path
= nd
->root
;
2142 if (flags
& LOOKUP_RCU
) {
2144 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2145 nd
->root_seq
= nd
->seq
;
2146 nd
->m_seq
= read_seqbegin(&mount_lock
);
2148 path_get(&nd
->path
);
2153 nd
->root
.mnt
= NULL
;
2154 nd
->path
.mnt
= NULL
;
2155 nd
->path
.dentry
= NULL
;
2157 nd
->m_seq
= read_seqbegin(&mount_lock
);
2159 if (flags
& LOOKUP_RCU
)
2162 if (likely(!nd_jump_root(nd
)))
2164 nd
->root
.mnt
= NULL
;
2166 return ERR_PTR(-ECHILD
);
2167 } else if (nd
->dfd
== AT_FDCWD
) {
2168 if (flags
& LOOKUP_RCU
) {
2169 struct fs_struct
*fs
= current
->fs
;
2175 seq
= read_seqcount_begin(&fs
->seq
);
2177 nd
->inode
= nd
->path
.dentry
->d_inode
;
2178 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2179 } while (read_seqcount_retry(&fs
->seq
, seq
));
2181 get_fs_pwd(current
->fs
, &nd
->path
);
2182 nd
->inode
= nd
->path
.dentry
->d_inode
;
2186 /* Caller must check execute permissions on the starting path component */
2187 struct fd f
= fdget_raw(nd
->dfd
);
2188 struct dentry
*dentry
;
2191 return ERR_PTR(-EBADF
);
2193 dentry
= f
.file
->f_path
.dentry
;
2196 if (!d_can_lookup(dentry
)) {
2198 return ERR_PTR(-ENOTDIR
);
2202 nd
->path
= f
.file
->f_path
;
2203 if (flags
& LOOKUP_RCU
) {
2205 nd
->inode
= nd
->path
.dentry
->d_inode
;
2206 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2208 path_get(&nd
->path
);
2209 nd
->inode
= nd
->path
.dentry
->d_inode
;
2216 static const char *trailing_symlink(struct nameidata
*nd
)
2219 int error
= may_follow_link(nd
);
2220 if (unlikely(error
))
2221 return ERR_PTR(error
);
2222 nd
->flags
|= LOOKUP_PARENT
;
2223 nd
->stack
[0].name
= NULL
;
2228 static inline int lookup_last(struct nameidata
*nd
)
2230 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
2231 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2233 nd
->flags
&= ~LOOKUP_PARENT
;
2234 return walk_component(nd
,
2235 nd
->flags
& LOOKUP_FOLLOW
2237 ? WALK_PUT
| WALK_GET
2242 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2243 static int path_lookupat(struct nameidata
*nd
, unsigned flags
, struct path
*path
)
2245 const char *s
= path_init(nd
, flags
);
2250 while (!(err
= link_path_walk(s
, nd
))
2251 && ((err
= lookup_last(nd
)) > 0)) {
2252 s
= trailing_symlink(nd
);
2259 err
= complete_walk(nd
);
2261 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
)
2262 if (!d_can_lookup(nd
->path
.dentry
))
2266 nd
->path
.mnt
= NULL
;
2267 nd
->path
.dentry
= NULL
;
2273 static int filename_lookup(int dfd
, struct filename
*name
, unsigned flags
,
2274 struct path
*path
, struct path
*root
)
2277 struct nameidata nd
;
2279 return PTR_ERR(name
);
2280 if (unlikely(root
)) {
2282 flags
|= LOOKUP_ROOT
;
2284 set_nameidata(&nd
, dfd
, name
);
2285 retval
= path_lookupat(&nd
, flags
| LOOKUP_RCU
, path
);
2286 if (unlikely(retval
== -ECHILD
))
2287 retval
= path_lookupat(&nd
, flags
, path
);
2288 if (unlikely(retval
== -ESTALE
))
2289 retval
= path_lookupat(&nd
, flags
| LOOKUP_REVAL
, path
);
2291 if (likely(!retval
))
2292 audit_inode(name
, path
->dentry
, flags
& LOOKUP_PARENT
);
2293 restore_nameidata();
2298 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2299 static int path_parentat(struct nameidata
*nd
, unsigned flags
,
2300 struct path
*parent
)
2302 const char *s
= path_init(nd
, flags
);
2306 err
= link_path_walk(s
, nd
);
2308 err
= complete_walk(nd
);
2311 nd
->path
.mnt
= NULL
;
2312 nd
->path
.dentry
= NULL
;
2318 static struct filename
*filename_parentat(int dfd
, struct filename
*name
,
2319 unsigned int flags
, struct path
*parent
,
2320 struct qstr
*last
, int *type
)
2323 struct nameidata nd
;
2327 set_nameidata(&nd
, dfd
, name
);
2328 retval
= path_parentat(&nd
, flags
| LOOKUP_RCU
, parent
);
2329 if (unlikely(retval
== -ECHILD
))
2330 retval
= path_parentat(&nd
, flags
, parent
);
2331 if (unlikely(retval
== -ESTALE
))
2332 retval
= path_parentat(&nd
, flags
| LOOKUP_REVAL
, parent
);
2333 if (likely(!retval
)) {
2335 *type
= nd
.last_type
;
2336 audit_inode(name
, parent
->dentry
, LOOKUP_PARENT
);
2339 name
= ERR_PTR(retval
);
2341 restore_nameidata();
2345 /* does lookup, returns the object with parent locked */
2346 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2348 struct filename
*filename
;
2353 filename
= filename_parentat(AT_FDCWD
, getname_kernel(name
), 0, path
,
2355 if (IS_ERR(filename
))
2356 return ERR_CAST(filename
);
2357 if (unlikely(type
!= LAST_NORM
)) {
2360 return ERR_PTR(-EINVAL
);
2362 inode_lock_nested(path
->dentry
->d_inode
, I_MUTEX_PARENT
);
2363 d
= __lookup_hash(&last
, path
->dentry
, 0);
2365 inode_unlock(path
->dentry
->d_inode
);
2372 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2374 return filename_lookup(AT_FDCWD
, getname_kernel(name
),
2377 EXPORT_SYMBOL(kern_path
);
2380 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2381 * @dentry: pointer to dentry of the base directory
2382 * @mnt: pointer to vfs mount of the base directory
2383 * @name: pointer to file name
2384 * @flags: lookup flags
2385 * @path: pointer to struct path to fill
2387 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2388 const char *name
, unsigned int flags
,
2391 struct path root
= {.mnt
= mnt
, .dentry
= dentry
};
2392 /* the first argument of filename_lookup() is ignored with root */
2393 return filename_lookup(AT_FDCWD
, getname_kernel(name
),
2394 flags
, path
, &root
);
2396 EXPORT_SYMBOL(vfs_path_lookup
);
2399 * lookup_one_len - filesystem helper to lookup single pathname component
2400 * @name: pathname component to lookup
2401 * @base: base directory to lookup from
2402 * @len: maximum length @len should be interpreted to
2404 * Note that this routine is purely a helper for filesystem usage and should
2405 * not be called by generic code.
2407 * The caller must hold base->i_mutex.
2409 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2415 WARN_ON_ONCE(!inode_is_locked(base
->d_inode
));
2419 this.hash
= full_name_hash(base
, name
, len
);
2421 return ERR_PTR(-EACCES
);
2423 if (unlikely(name
[0] == '.')) {
2424 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2425 return ERR_PTR(-EACCES
);
2429 c
= *(const unsigned char *)name
++;
2430 if (c
== '/' || c
== '\0')
2431 return ERR_PTR(-EACCES
);
2434 * See if the low-level filesystem might want
2435 * to use its own hash..
2437 if (base
->d_flags
& DCACHE_OP_HASH
) {
2438 int err
= base
->d_op
->d_hash(base
, &this);
2440 return ERR_PTR(err
);
2443 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2445 return ERR_PTR(err
);
2447 return __lookup_hash(&this, base
, 0);
2449 EXPORT_SYMBOL(lookup_one_len
);
2452 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2453 * @name: pathname component to lookup
2454 * @base: base directory to lookup from
2455 * @len: maximum length @len should be interpreted to
2457 * Note that this routine is purely a helper for filesystem usage and should
2458 * not be called by generic code.
2460 * Unlike lookup_one_len, it should be called without the parent
2461 * i_mutex held, and will take the i_mutex itself if necessary.
2463 struct dentry
*lookup_one_len_unlocked(const char *name
,
2464 struct dentry
*base
, int len
)
2473 this.hash
= full_name_hash(base
, name
, len
);
2475 return ERR_PTR(-EACCES
);
2477 if (unlikely(name
[0] == '.')) {
2478 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2479 return ERR_PTR(-EACCES
);
2483 c
= *(const unsigned char *)name
++;
2484 if (c
== '/' || c
== '\0')
2485 return ERR_PTR(-EACCES
);
2488 * See if the low-level filesystem might want
2489 * to use its own hash..
2491 if (base
->d_flags
& DCACHE_OP_HASH
) {
2492 int err
= base
->d_op
->d_hash(base
, &this);
2494 return ERR_PTR(err
);
2497 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2499 return ERR_PTR(err
);
2501 ret
= lookup_dcache(&this, base
, 0);
2503 ret
= lookup_slow(&this, base
, 0);
2506 EXPORT_SYMBOL(lookup_one_len_unlocked
);
2508 #ifdef CONFIG_UNIX98_PTYS
2509 int path_pts(struct path
*path
)
2511 /* Find something mounted on "pts" in the same directory as
2514 struct dentry
*child
, *parent
;
2518 ret
= path_parent_directory(path
);
2522 parent
= path
->dentry
;
2525 child
= d_hash_and_lookup(parent
, &this);
2529 path
->dentry
= child
;
2536 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2537 struct path
*path
, int *empty
)
2539 return filename_lookup(dfd
, getname_flags(name
, flags
, empty
),
2542 EXPORT_SYMBOL(user_path_at_empty
);
2545 * NB: most callers don't do anything directly with the reference to the
2546 * to struct filename, but the nd->last pointer points into the name string
2547 * allocated by getname. So we must hold the reference to it until all
2548 * path-walking is complete.
2550 static inline struct filename
*
2551 user_path_parent(int dfd
, const char __user
*path
,
2552 struct path
*parent
,
2557 /* only LOOKUP_REVAL is allowed in extra flags */
2558 return filename_parentat(dfd
, getname(path
), flags
& LOOKUP_REVAL
,
2559 parent
, last
, type
);
2563 * mountpoint_last - look up last component for umount
2564 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2565 * @path: pointer to container for result
2567 * This is a special lookup_last function just for umount. In this case, we
2568 * need to resolve the path without doing any revalidation.
2570 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2571 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2572 * in almost all cases, this lookup will be served out of the dcache. The only
2573 * cases where it won't are if nd->last refers to a symlink or the path is
2574 * bogus and it doesn't exist.
2577 * -error: if there was an error during lookup. This includes -ENOENT if the
2578 * lookup found a negative dentry. The nd->path reference will also be
2581 * 0: if we successfully resolved nd->path and found it to not to be a
2582 * symlink that needs to be followed. "path" will also be populated.
2583 * The nd->path reference will also be put.
2585 * 1: if we successfully resolved nd->last and found it to be a symlink
2586 * that needs to be followed. "path" will be populated with the path
2587 * to the link, and nd->path will *not* be put.
2590 mountpoint_last(struct nameidata
*nd
, struct path
*path
)
2593 struct dentry
*dentry
;
2594 struct dentry
*dir
= nd
->path
.dentry
;
2596 /* If we're in rcuwalk, drop out of it to handle last component */
2597 if (nd
->flags
& LOOKUP_RCU
) {
2598 if (unlazy_walk(nd
, NULL
, 0))
2602 nd
->flags
&= ~LOOKUP_PARENT
;
2604 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2605 error
= handle_dots(nd
, nd
->last_type
);
2608 dentry
= dget(nd
->path
.dentry
);
2610 dentry
= d_lookup(dir
, &nd
->last
);
2613 * No cached dentry. Mounted dentries are pinned in the
2614 * cache, so that means that this dentry is probably
2615 * a symlink or the path doesn't actually point
2616 * to a mounted dentry.
2618 dentry
= lookup_slow(&nd
->last
, dir
,
2619 nd
->flags
| LOOKUP_NO_REVAL
);
2621 return PTR_ERR(dentry
);
2624 if (d_is_negative(dentry
)) {
2630 path
->dentry
= dentry
;
2631 path
->mnt
= nd
->path
.mnt
;
2632 error
= should_follow_link(nd
, path
, nd
->flags
& LOOKUP_FOLLOW
,
2633 d_backing_inode(dentry
), 0);
2634 if (unlikely(error
))
2642 * path_mountpoint - look up a path to be umounted
2643 * @nd: lookup context
2644 * @flags: lookup flags
2645 * @path: pointer to container for result
2647 * Look up the given name, but don't attempt to revalidate the last component.
2648 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2651 path_mountpoint(struct nameidata
*nd
, unsigned flags
, struct path
*path
)
2653 const char *s
= path_init(nd
, flags
);
2657 while (!(err
= link_path_walk(s
, nd
)) &&
2658 (err
= mountpoint_last(nd
, path
)) > 0) {
2659 s
= trailing_symlink(nd
);
2670 filename_mountpoint(int dfd
, struct filename
*name
, struct path
*path
,
2673 struct nameidata nd
;
2676 return PTR_ERR(name
);
2677 set_nameidata(&nd
, dfd
, name
);
2678 error
= path_mountpoint(&nd
, flags
| LOOKUP_RCU
, path
);
2679 if (unlikely(error
== -ECHILD
))
2680 error
= path_mountpoint(&nd
, flags
, path
);
2681 if (unlikely(error
== -ESTALE
))
2682 error
= path_mountpoint(&nd
, flags
| LOOKUP_REVAL
, path
);
2684 audit_inode(name
, path
->dentry
, 0);
2685 restore_nameidata();
2691 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2692 * @dfd: directory file descriptor
2693 * @name: pathname from userland
2694 * @flags: lookup flags
2695 * @path: pointer to container to hold result
2697 * A umount is a special case for path walking. We're not actually interested
2698 * in the inode in this situation, and ESTALE errors can be a problem. We
2699 * simply want track down the dentry and vfsmount attached at the mountpoint
2700 * and avoid revalidating the last component.
2702 * Returns 0 and populates "path" on success.
2705 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2708 return filename_mountpoint(dfd
, getname(name
), path
, flags
);
2712 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2715 return filename_mountpoint(dfd
, getname_kernel(name
), path
, flags
);
2717 EXPORT_SYMBOL(kern_path_mountpoint
);
2719 int __check_sticky(struct inode
*dir
, struct inode
*inode
)
2721 kuid_t fsuid
= current_fsuid();
2723 if (uid_eq(inode
->i_uid
, fsuid
))
2725 if (uid_eq(dir
->i_uid
, fsuid
))
2727 return !capable_wrt_inode_uidgid(inode
, CAP_FOWNER
);
2729 EXPORT_SYMBOL(__check_sticky
);
2732 * Check whether we can remove a link victim from directory dir, check
2733 * whether the type of victim is right.
2734 * 1. We can't do it if dir is read-only (done in permission())
2735 * 2. We should have write and exec permissions on dir
2736 * 3. We can't remove anything from append-only dir
2737 * 4. We can't do anything with immutable dir (done in permission())
2738 * 5. If the sticky bit on dir is set we should either
2739 * a. be owner of dir, or
2740 * b. be owner of victim, or
2741 * c. have CAP_FOWNER capability
2742 * 6. If the victim is append-only or immutable we can't do antyhing with
2743 * links pointing to it.
2744 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2745 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2746 * 9. We can't remove a root or mountpoint.
2747 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2748 * nfs_async_unlink().
2750 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2752 struct inode
*inode
= d_backing_inode(victim
);
2755 if (d_is_negative(victim
))
2759 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2760 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2762 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2768 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2769 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
))
2772 if (!d_is_dir(victim
))
2774 if (IS_ROOT(victim
))
2776 } else if (d_is_dir(victim
))
2778 if (IS_DEADDIR(dir
))
2780 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2785 /* Check whether we can create an object with dentry child in directory
2787 * 1. We can't do it if child already exists (open has special treatment for
2788 * this case, but since we are inlined it's OK)
2789 * 2. We can't do it if dir is read-only (done in permission())
2790 * 3. We should have write and exec permissions on dir
2791 * 4. We can't do it if dir is immutable (done in permission())
2793 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2795 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2798 if (IS_DEADDIR(dir
))
2800 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2804 * p1 and p2 should be directories on the same fs.
2806 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2811 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2815 mutex_lock(&p1
->d_sb
->s_vfs_rename_mutex
);
2817 p
= d_ancestor(p2
, p1
);
2819 inode_lock_nested(p2
->d_inode
, I_MUTEX_PARENT
);
2820 inode_lock_nested(p1
->d_inode
, I_MUTEX_CHILD
);
2824 p
= d_ancestor(p1
, p2
);
2826 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2827 inode_lock_nested(p2
->d_inode
, I_MUTEX_CHILD
);
2831 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2832 inode_lock_nested(p2
->d_inode
, I_MUTEX_PARENT2
);
2835 EXPORT_SYMBOL(lock_rename
);
2837 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2839 inode_unlock(p1
->d_inode
);
2841 inode_unlock(p2
->d_inode
);
2842 mutex_unlock(&p1
->d_sb
->s_vfs_rename_mutex
);
2845 EXPORT_SYMBOL(unlock_rename
);
2847 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2850 int error
= may_create(dir
, dentry
);
2854 if (!dir
->i_op
->create
)
2855 return -EACCES
; /* shouldn't it be ENOSYS? */
2858 error
= security_inode_create(dir
, dentry
, mode
);
2861 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2863 fsnotify_create(dir
, dentry
);
2866 EXPORT_SYMBOL(vfs_create
);
2868 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2870 struct dentry
*dentry
= path
->dentry
;
2871 struct inode
*inode
= dentry
->d_inode
;
2877 switch (inode
->i_mode
& S_IFMT
) {
2881 if (acc_mode
& MAY_WRITE
)
2886 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2895 error
= inode_permission(inode
, MAY_OPEN
| acc_mode
);
2900 * An append-only file must be opened in append mode for writing.
2902 if (IS_APPEND(inode
)) {
2903 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2909 /* O_NOATIME can only be set by the owner or superuser */
2910 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2916 static int handle_truncate(struct file
*filp
)
2918 struct path
*path
= &filp
->f_path
;
2919 struct inode
*inode
= path
->dentry
->d_inode
;
2920 int error
= get_write_access(inode
);
2924 * Refuse to truncate files with mandatory locks held on them.
2926 error
= locks_verify_locked(filp
);
2928 error
= security_path_truncate(path
);
2930 error
= do_truncate(path
->dentry
, 0,
2931 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2934 put_write_access(inode
);
2938 static inline int open_to_namei_flags(int flag
)
2940 if ((flag
& O_ACCMODE
) == 3)
2945 static int may_o_create(const struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2947 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2951 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2955 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2959 * Attempt to atomically look up, create and open a file from a negative
2962 * Returns 0 if successful. The file will have been created and attached to
2963 * @file by the filesystem calling finish_open().
2965 * Returns 1 if the file was looked up only or didn't need creating. The
2966 * caller will need to perform the open themselves. @path will have been
2967 * updated to point to the new dentry. This may be negative.
2969 * Returns an error code otherwise.
2971 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2972 struct path
*path
, struct file
*file
,
2973 const struct open_flags
*op
,
2974 int open_flag
, umode_t mode
,
2977 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2978 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2981 if (!(~open_flag
& (O_EXCL
| O_CREAT
))) /* both O_EXCL and O_CREAT */
2982 open_flag
&= ~O_TRUNC
;
2984 if (nd
->flags
& LOOKUP_DIRECTORY
)
2985 open_flag
|= O_DIRECTORY
;
2987 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2988 file
->f_path
.mnt
= nd
->path
.mnt
;
2989 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
,
2990 open_to_namei_flags(open_flag
),
2992 d_lookup_done(dentry
);
2995 * We didn't have the inode before the open, so check open
2998 int acc_mode
= op
->acc_mode
;
2999 if (*opened
& FILE_CREATED
) {
3000 WARN_ON(!(open_flag
& O_CREAT
));
3001 fsnotify_create(dir
, dentry
);
3004 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
3005 if (WARN_ON(error
> 0))
3007 } else if (error
> 0) {
3008 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
3011 if (file
->f_path
.dentry
) {
3013 dentry
= file
->f_path
.dentry
;
3015 if (*opened
& FILE_CREATED
)
3016 fsnotify_create(dir
, dentry
);
3017 if (unlikely(d_is_negative(dentry
))) {
3020 path
->dentry
= dentry
;
3021 path
->mnt
= nd
->path
.mnt
;
3031 * Look up and maybe create and open the last component.
3033 * Must be called with i_mutex held on parent.
3035 * Returns 0 if the file was successfully atomically created (if necessary) and
3036 * opened. In this case the file will be returned attached to @file.
3038 * Returns 1 if the file was not completely opened at this time, though lookups
3039 * and creations will have been performed and the dentry returned in @path will
3040 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
3041 * specified then a negative dentry may be returned.
3043 * An error code is returned otherwise.
3045 * FILE_CREATE will be set in @*opened if the dentry was created and will be
3046 * cleared otherwise prior to returning.
3048 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
3050 const struct open_flags
*op
,
3051 bool got_write
, int *opened
)
3053 struct dentry
*dir
= nd
->path
.dentry
;
3054 struct inode
*dir_inode
= dir
->d_inode
;
3055 int open_flag
= op
->open_flag
;
3056 struct dentry
*dentry
;
3057 int error
, create_error
= 0;
3058 umode_t mode
= op
->mode
;
3059 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq
);
3061 if (unlikely(IS_DEADDIR(dir_inode
)))
3064 *opened
&= ~FILE_CREATED
;
3065 dentry
= d_lookup(dir
, &nd
->last
);
3068 dentry
= d_alloc_parallel(dir
, &nd
->last
, &wq
);
3070 return PTR_ERR(dentry
);
3072 if (d_in_lookup(dentry
))
3075 if (!(dentry
->d_flags
& DCACHE_OP_REVALIDATE
))
3078 error
= d_revalidate(dentry
, nd
->flags
);
3079 if (likely(error
> 0))
3083 d_invalidate(dentry
);
3087 if (dentry
->d_inode
) {
3088 /* Cached positive dentry: will open in f_op->open */
3093 * Checking write permission is tricky, bacuse we don't know if we are
3094 * going to actually need it: O_CREAT opens should work as long as the
3095 * file exists. But checking existence breaks atomicity. The trick is
3096 * to check access and if not granted clear O_CREAT from the flags.
3098 * Another problem is returing the "right" error value (e.g. for an
3099 * O_EXCL open we want to return EEXIST not EROFS).
3101 if (open_flag
& O_CREAT
) {
3102 if (!IS_POSIXACL(dir
->d_inode
))
3103 mode
&= ~current_umask();
3104 if (unlikely(!got_write
)) {
3105 create_error
= -EROFS
;
3106 open_flag
&= ~O_CREAT
;
3107 if (open_flag
& (O_EXCL
| O_TRUNC
))
3109 /* No side effects, safe to clear O_CREAT */
3111 create_error
= may_o_create(&nd
->path
, dentry
, mode
);
3113 open_flag
&= ~O_CREAT
;
3114 if (open_flag
& O_EXCL
)
3118 } else if ((open_flag
& (O_TRUNC
|O_WRONLY
|O_RDWR
)) &&
3119 unlikely(!got_write
)) {
3121 * No O_CREATE -> atomicity not a requirement -> fall
3122 * back to lookup + open
3127 if (dir_inode
->i_op
->atomic_open
) {
3128 error
= atomic_open(nd
, dentry
, path
, file
, op
, open_flag
,
3130 if (unlikely(error
== -ENOENT
) && create_error
)
3131 error
= create_error
;
3136 if (d_in_lookup(dentry
)) {
3137 struct dentry
*res
= dir_inode
->i_op
->lookup(dir_inode
, dentry
,
3139 d_lookup_done(dentry
);
3140 if (unlikely(res
)) {
3142 error
= PTR_ERR(res
);
3150 /* Negative dentry, just create the file */
3151 if (!dentry
->d_inode
&& (open_flag
& O_CREAT
)) {
3152 *opened
|= FILE_CREATED
;
3153 audit_inode_child(dir_inode
, dentry
, AUDIT_TYPE_CHILD_CREATE
);
3154 if (!dir_inode
->i_op
->create
) {
3158 error
= dir_inode
->i_op
->create(dir_inode
, dentry
, mode
,
3159 open_flag
& O_EXCL
);
3162 fsnotify_create(dir_inode
, dentry
);
3164 if (unlikely(create_error
) && !dentry
->d_inode
) {
3165 error
= create_error
;
3169 path
->dentry
= dentry
;
3170 path
->mnt
= nd
->path
.mnt
;
3179 * Handle the last step of open()
3181 static int do_last(struct nameidata
*nd
,
3182 struct file
*file
, const struct open_flags
*op
,
3185 struct dentry
*dir
= nd
->path
.dentry
;
3186 int open_flag
= op
->open_flag
;
3187 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
3188 bool got_write
= false;
3189 int acc_mode
= op
->acc_mode
;
3191 struct inode
*inode
;
3195 nd
->flags
&= ~LOOKUP_PARENT
;
3196 nd
->flags
|= op
->intent
;
3198 if (nd
->last_type
!= LAST_NORM
) {
3199 error
= handle_dots(nd
, nd
->last_type
);
3200 if (unlikely(error
))
3205 if (!(open_flag
& O_CREAT
)) {
3206 if (nd
->last
.name
[nd
->last
.len
])
3207 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
3208 /* we _can_ be in RCU mode here */
3209 error
= lookup_fast(nd
, &path
, &inode
, &seq
);
3210 if (likely(error
> 0))
3216 BUG_ON(nd
->inode
!= dir
->d_inode
);
3217 BUG_ON(nd
->flags
& LOOKUP_RCU
);
3219 /* create side of things */
3221 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3222 * has been cleared when we got to the last component we are
3225 error
= complete_walk(nd
);
3229 audit_inode(nd
->name
, dir
, LOOKUP_PARENT
);
3230 /* trailing slashes? */
3231 if (unlikely(nd
->last
.name
[nd
->last
.len
]))
3235 if (open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
3236 error
= mnt_want_write(nd
->path
.mnt
);
3240 * do _not_ fail yet - we might not need that or fail with
3241 * a different error; let lookup_open() decide; we'll be
3242 * dropping this one anyway.
3245 if (open_flag
& O_CREAT
)
3246 inode_lock(dir
->d_inode
);
3248 inode_lock_shared(dir
->d_inode
);
3249 error
= lookup_open(nd
, &path
, file
, op
, got_write
, opened
);
3250 if (open_flag
& O_CREAT
)
3251 inode_unlock(dir
->d_inode
);
3253 inode_unlock_shared(dir
->d_inode
);
3259 if ((*opened
& FILE_CREATED
) ||
3260 !S_ISREG(file_inode(file
)->i_mode
))
3261 will_truncate
= false;
3263 audit_inode(nd
->name
, file
->f_path
.dentry
, 0);
3267 if (*opened
& FILE_CREATED
) {
3268 /* Don't check for write permission, don't truncate */
3269 open_flag
&= ~O_TRUNC
;
3270 will_truncate
= false;
3272 path_to_nameidata(&path
, nd
);
3273 goto finish_open_created
;
3277 * If atomic_open() acquired write access it is dropped now due to
3278 * possible mount and symlink following (this might be optimized away if
3282 mnt_drop_write(nd
->path
.mnt
);
3286 error
= follow_managed(&path
, nd
);
3287 if (unlikely(error
< 0))
3290 if (unlikely(d_is_negative(path
.dentry
))) {
3291 path_to_nameidata(&path
, nd
);
3296 * create/update audit record if it already exists.
3298 audit_inode(nd
->name
, path
.dentry
, 0);
3300 if (unlikely((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))) {
3301 path_to_nameidata(&path
, nd
);
3305 seq
= 0; /* out of RCU mode, so the value doesn't matter */
3306 inode
= d_backing_inode(path
.dentry
);
3310 error
= should_follow_link(nd
, &path
, nd
->flags
& LOOKUP_FOLLOW
,
3312 if (unlikely(error
))
3315 path_to_nameidata(&path
, nd
);
3318 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3320 error
= complete_walk(nd
);
3323 audit_inode(nd
->name
, nd
->path
.dentry
, 0);
3325 if ((open_flag
& O_CREAT
) && d_is_dir(nd
->path
.dentry
))
3328 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_can_lookup(nd
->path
.dentry
))
3330 if (!d_is_reg(nd
->path
.dentry
))
3331 will_truncate
= false;
3333 if (will_truncate
) {
3334 error
= mnt_want_write(nd
->path
.mnt
);
3339 finish_open_created
:
3340 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3343 BUG_ON(*opened
& FILE_OPENED
); /* once it's opened, it's opened */
3344 error
= vfs_open(&nd
->path
, file
, current_cred());
3347 *opened
|= FILE_OPENED
;
3349 error
= open_check_o_direct(file
);
3351 error
= ima_file_check(file
, op
->acc_mode
, *opened
);
3352 if (!error
&& will_truncate
)
3353 error
= handle_truncate(file
);
3355 if (unlikely(error
) && (*opened
& FILE_OPENED
))
3357 if (unlikely(error
> 0)) {
3362 mnt_drop_write(nd
->path
.mnt
);
3366 static int do_tmpfile(struct nameidata
*nd
, unsigned flags
,
3367 const struct open_flags
*op
,
3368 struct file
*file
, int *opened
)
3370 static const struct qstr name
= QSTR_INIT("/", 1);
3371 struct dentry
*child
;
3374 int error
= path_lookupat(nd
, flags
| LOOKUP_DIRECTORY
, &path
);
3375 if (unlikely(error
))
3377 error
= mnt_want_write(path
.mnt
);
3378 if (unlikely(error
))
3380 dir
= path
.dentry
->d_inode
;
3381 /* we want directory to be writable */
3382 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
3385 if (!dir
->i_op
->tmpfile
) {
3386 error
= -EOPNOTSUPP
;
3389 child
= d_alloc(path
.dentry
, &name
);
3390 if (unlikely(!child
)) {
3395 path
.dentry
= child
;
3396 error
= dir
->i_op
->tmpfile(dir
, child
, op
->mode
);
3399 audit_inode(nd
->name
, child
, 0);
3400 /* Don't check for other permissions, the inode was just created */
3401 error
= may_open(&path
, 0, op
->open_flag
);
3404 file
->f_path
.mnt
= path
.mnt
;
3405 error
= finish_open(file
, child
, NULL
, opened
);
3408 error
= open_check_o_direct(file
);
3411 } else if (!(op
->open_flag
& O_EXCL
)) {
3412 struct inode
*inode
= file_inode(file
);
3413 spin_lock(&inode
->i_lock
);
3414 inode
->i_state
|= I_LINKABLE
;
3415 spin_unlock(&inode
->i_lock
);
3418 mnt_drop_write(path
.mnt
);
3424 static int do_o_path(struct nameidata
*nd
, unsigned flags
, struct file
*file
)
3427 int error
= path_lookupat(nd
, flags
, &path
);
3429 audit_inode(nd
->name
, path
.dentry
, 0);
3430 error
= vfs_open(&path
, file
, current_cred());
3436 static struct file
*path_openat(struct nameidata
*nd
,
3437 const struct open_flags
*op
, unsigned flags
)
3444 file
= get_empty_filp();
3448 file
->f_flags
= op
->open_flag
;
3450 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3451 error
= do_tmpfile(nd
, flags
, op
, file
, &opened
);
3455 if (unlikely(file
->f_flags
& O_PATH
)) {
3456 error
= do_o_path(nd
, flags
, file
);
3458 opened
|= FILE_OPENED
;
3462 s
= path_init(nd
, flags
);
3467 while (!(error
= link_path_walk(s
, nd
)) &&
3468 (error
= do_last(nd
, file
, op
, &opened
)) > 0) {
3469 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3470 s
= trailing_symlink(nd
);
3478 if (!(opened
& FILE_OPENED
)) {
3482 if (unlikely(error
)) {
3483 if (error
== -EOPENSTALE
) {
3484 if (flags
& LOOKUP_RCU
)
3489 file
= ERR_PTR(error
);
3494 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3495 const struct open_flags
*op
)
3497 struct nameidata nd
;
3498 int flags
= op
->lookup_flags
;
3501 set_nameidata(&nd
, dfd
, pathname
);
3502 filp
= path_openat(&nd
, op
, flags
| LOOKUP_RCU
);
3503 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3504 filp
= path_openat(&nd
, op
, flags
);
3505 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3506 filp
= path_openat(&nd
, op
, flags
| LOOKUP_REVAL
);
3507 restore_nameidata();
3511 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3512 const char *name
, const struct open_flags
*op
)
3514 struct nameidata nd
;
3516 struct filename
*filename
;
3517 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3520 nd
.root
.dentry
= dentry
;
3522 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3523 return ERR_PTR(-ELOOP
);
3525 filename
= getname_kernel(name
);
3526 if (IS_ERR(filename
))
3527 return ERR_CAST(filename
);
3529 set_nameidata(&nd
, -1, filename
);
3530 file
= path_openat(&nd
, op
, flags
| LOOKUP_RCU
);
3531 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3532 file
= path_openat(&nd
, op
, flags
);
3533 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3534 file
= path_openat(&nd
, op
, flags
| LOOKUP_REVAL
);
3535 restore_nameidata();
3540 static struct dentry
*filename_create(int dfd
, struct filename
*name
,
3541 struct path
*path
, unsigned int lookup_flags
)
3543 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3548 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3551 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3552 * other flags passed in are ignored!
3554 lookup_flags
&= LOOKUP_REVAL
;
3556 name
= filename_parentat(dfd
, name
, lookup_flags
, path
, &last
, &type
);
3558 return ERR_CAST(name
);
3561 * Yucky last component or no last component at all?
3562 * (foo/., foo/.., /////)
3564 if (unlikely(type
!= LAST_NORM
))
3567 /* don't fail immediately if it's r/o, at least try to report other errors */
3568 err2
= mnt_want_write(path
->mnt
);
3570 * Do the final lookup.
3572 lookup_flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3573 inode_lock_nested(path
->dentry
->d_inode
, I_MUTEX_PARENT
);
3574 dentry
= __lookup_hash(&last
, path
->dentry
, lookup_flags
);
3579 if (d_is_positive(dentry
))
3583 * Special case - lookup gave negative, but... we had foo/bar/
3584 * From the vfs_mknod() POV we just have a negative dentry -
3585 * all is fine. Let's be bastards - you had / on the end, you've
3586 * been asking for (non-existent) directory. -ENOENT for you.
3588 if (unlikely(!is_dir
&& last
.name
[last
.len
])) {
3592 if (unlikely(err2
)) {
3600 dentry
= ERR_PTR(error
);
3602 inode_unlock(path
->dentry
->d_inode
);
3604 mnt_drop_write(path
->mnt
);
3611 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3612 struct path
*path
, unsigned int lookup_flags
)
3614 return filename_create(dfd
, getname_kernel(pathname
),
3615 path
, lookup_flags
);
3617 EXPORT_SYMBOL(kern_path_create
);
3619 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3622 inode_unlock(path
->dentry
->d_inode
);
3623 mnt_drop_write(path
->mnt
);
3626 EXPORT_SYMBOL(done_path_create
);
3628 inline struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3629 struct path
*path
, unsigned int lookup_flags
)
3631 return filename_create(dfd
, getname(pathname
), path
, lookup_flags
);
3633 EXPORT_SYMBOL(user_path_create
);
3635 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3637 int error
= may_create(dir
, dentry
);
3642 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3645 if (!dir
->i_op
->mknod
)
3648 error
= devcgroup_inode_mknod(mode
, dev
);
3652 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3656 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3658 fsnotify_create(dir
, dentry
);
3661 EXPORT_SYMBOL(vfs_mknod
);
3663 static int may_mknod(umode_t mode
)
3665 switch (mode
& S_IFMT
) {
3671 case 0: /* zero mode translates to S_IFREG */
3680 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3683 struct dentry
*dentry
;
3686 unsigned int lookup_flags
= 0;
3688 error
= may_mknod(mode
);
3692 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3694 return PTR_ERR(dentry
);
3696 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3697 mode
&= ~current_umask();
3698 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3701 switch (mode
& S_IFMT
) {
3702 case 0: case S_IFREG
:
3703 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3705 ima_post_path_mknod(dentry
);
3707 case S_IFCHR
: case S_IFBLK
:
3708 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3709 new_decode_dev(dev
));
3711 case S_IFIFO
: case S_IFSOCK
:
3712 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3716 done_path_create(&path
, dentry
);
3717 if (retry_estale(error
, lookup_flags
)) {
3718 lookup_flags
|= LOOKUP_REVAL
;
3724 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3726 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3729 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3731 int error
= may_create(dir
, dentry
);
3732 unsigned max_links
= dir
->i_sb
->s_max_links
;
3737 if (!dir
->i_op
->mkdir
)
3740 mode
&= (S_IRWXUGO
|S_ISVTX
);
3741 error
= security_inode_mkdir(dir
, dentry
, mode
);
3745 if (max_links
&& dir
->i_nlink
>= max_links
)
3748 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3750 fsnotify_mkdir(dir
, dentry
);
3753 EXPORT_SYMBOL(vfs_mkdir
);
3755 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3757 struct dentry
*dentry
;
3760 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3763 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3765 return PTR_ERR(dentry
);
3767 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3768 mode
&= ~current_umask();
3769 error
= security_path_mkdir(&path
, dentry
, mode
);
3771 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3772 done_path_create(&path
, dentry
);
3773 if (retry_estale(error
, lookup_flags
)) {
3774 lookup_flags
|= LOOKUP_REVAL
;
3780 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3782 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3785 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3787 int error
= may_delete(dir
, dentry
, 1);
3792 if (!dir
->i_op
->rmdir
)
3796 inode_lock(dentry
->d_inode
);
3799 if (is_local_mountpoint(dentry
))
3802 error
= security_inode_rmdir(dir
, dentry
);
3806 shrink_dcache_parent(dentry
);
3807 error
= dir
->i_op
->rmdir(dir
, dentry
);
3811 dentry
->d_inode
->i_flags
|= S_DEAD
;
3813 detach_mounts(dentry
);
3816 inode_unlock(dentry
->d_inode
);
3822 EXPORT_SYMBOL(vfs_rmdir
);
3824 static long do_rmdir(int dfd
, const char __user
*pathname
)
3827 struct filename
*name
;
3828 struct dentry
*dentry
;
3832 unsigned int lookup_flags
= 0;
3834 name
= user_path_parent(dfd
, pathname
,
3835 &path
, &last
, &type
, lookup_flags
);
3837 return PTR_ERR(name
);
3851 error
= mnt_want_write(path
.mnt
);
3855 inode_lock_nested(path
.dentry
->d_inode
, I_MUTEX_PARENT
);
3856 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3857 error
= PTR_ERR(dentry
);
3860 if (!dentry
->d_inode
) {
3864 error
= security_path_rmdir(&path
, dentry
);
3867 error
= vfs_rmdir(path
.dentry
->d_inode
, dentry
);
3871 inode_unlock(path
.dentry
->d_inode
);
3872 mnt_drop_write(path
.mnt
);
3876 if (retry_estale(error
, lookup_flags
)) {
3877 lookup_flags
|= LOOKUP_REVAL
;
3883 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3885 return do_rmdir(AT_FDCWD
, pathname
);
3889 * vfs_unlink - unlink a filesystem object
3890 * @dir: parent directory
3892 * @delegated_inode: returns victim inode, if the inode is delegated.
3894 * The caller must hold dir->i_mutex.
3896 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3897 * return a reference to the inode in delegated_inode. The caller
3898 * should then break the delegation on that inode and retry. Because
3899 * breaking a delegation may take a long time, the caller should drop
3900 * dir->i_mutex before doing so.
3902 * Alternatively, a caller may pass NULL for delegated_inode. This may
3903 * be appropriate for callers that expect the underlying filesystem not
3904 * to be NFS exported.
3906 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3908 struct inode
*target
= dentry
->d_inode
;
3909 int error
= may_delete(dir
, dentry
, 0);
3914 if (!dir
->i_op
->unlink
)
3918 if (is_local_mountpoint(dentry
))
3921 error
= security_inode_unlink(dir
, dentry
);
3923 error
= try_break_deleg(target
, delegated_inode
);
3926 error
= dir
->i_op
->unlink(dir
, dentry
);
3929 detach_mounts(dentry
);
3934 inode_unlock(target
);
3936 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3937 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3938 fsnotify_link_count(target
);
3944 EXPORT_SYMBOL(vfs_unlink
);
3947 * Make sure that the actual truncation of the file will occur outside its
3948 * directory's i_mutex. Truncate can take a long time if there is a lot of
3949 * writeout happening, and we don't want to prevent access to the directory
3950 * while waiting on the I/O.
3952 static long do_unlinkat(int dfd
, const char __user
*pathname
)
3955 struct filename
*name
;
3956 struct dentry
*dentry
;
3960 struct inode
*inode
= NULL
;
3961 struct inode
*delegated_inode
= NULL
;
3962 unsigned int lookup_flags
= 0;
3964 name
= user_path_parent(dfd
, pathname
,
3965 &path
, &last
, &type
, lookup_flags
);
3967 return PTR_ERR(name
);
3970 if (type
!= LAST_NORM
)
3973 error
= mnt_want_write(path
.mnt
);
3977 inode_lock_nested(path
.dentry
->d_inode
, I_MUTEX_PARENT
);
3978 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3979 error
= PTR_ERR(dentry
);
3980 if (!IS_ERR(dentry
)) {
3981 /* Why not before? Because we want correct error value */
3982 if (last
.name
[last
.len
])
3984 inode
= dentry
->d_inode
;
3985 if (d_is_negative(dentry
))
3988 error
= security_path_unlink(&path
, dentry
);
3991 error
= vfs_unlink(path
.dentry
->d_inode
, dentry
, &delegated_inode
);
3995 inode_unlock(path
.dentry
->d_inode
);
3997 iput(inode
); /* truncate the inode here */
3999 if (delegated_inode
) {
4000 error
= break_deleg_wait(&delegated_inode
);
4004 mnt_drop_write(path
.mnt
);
4008 if (retry_estale(error
, lookup_flags
)) {
4009 lookup_flags
|= LOOKUP_REVAL
;
4016 if (d_is_negative(dentry
))
4018 else if (d_is_dir(dentry
))
4025 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
4027 if ((flag
& ~AT_REMOVEDIR
) != 0)
4030 if (flag
& AT_REMOVEDIR
)
4031 return do_rmdir(dfd
, pathname
);
4033 return do_unlinkat(dfd
, pathname
);
4036 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
4038 return do_unlinkat(AT_FDCWD
, pathname
);
4041 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
4043 int error
= may_create(dir
, dentry
);
4048 if (!dir
->i_op
->symlink
)
4051 error
= security_inode_symlink(dir
, dentry
, oldname
);
4055 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
4057 fsnotify_create(dir
, dentry
);
4060 EXPORT_SYMBOL(vfs_symlink
);
4062 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
4063 int, newdfd
, const char __user
*, newname
)
4066 struct filename
*from
;
4067 struct dentry
*dentry
;
4069 unsigned int lookup_flags
= 0;
4071 from
= getname(oldname
);
4073 return PTR_ERR(from
);
4075 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
4076 error
= PTR_ERR(dentry
);
4080 error
= security_path_symlink(&path
, dentry
, from
->name
);
4082 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
4083 done_path_create(&path
, dentry
);
4084 if (retry_estale(error
, lookup_flags
)) {
4085 lookup_flags
|= LOOKUP_REVAL
;
4093 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
4095 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
4099 * vfs_link - create a new link
4100 * @old_dentry: object to be linked
4102 * @new_dentry: where to create the new link
4103 * @delegated_inode: returns inode needing a delegation break
4105 * The caller must hold dir->i_mutex
4107 * If vfs_link discovers a delegation on the to-be-linked file in need
4108 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4109 * inode in delegated_inode. The caller should then break the delegation
4110 * and retry. Because breaking a delegation may take a long time, the
4111 * caller should drop the i_mutex before doing so.
4113 * Alternatively, a caller may pass NULL for delegated_inode. This may
4114 * be appropriate for callers that expect the underlying filesystem not
4115 * to be NFS exported.
4117 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
4119 struct inode
*inode
= old_dentry
->d_inode
;
4120 unsigned max_links
= dir
->i_sb
->s_max_links
;
4126 error
= may_create(dir
, new_dentry
);
4130 if (dir
->i_sb
!= inode
->i_sb
)
4134 * A link to an append-only or immutable file cannot be created.
4136 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
4138 if (!dir
->i_op
->link
)
4140 if (S_ISDIR(inode
->i_mode
))
4143 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
4148 /* Make sure we don't allow creating hardlink to an unlinked file */
4149 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
4151 else if (max_links
&& inode
->i_nlink
>= max_links
)
4154 error
= try_break_deleg(inode
, delegated_inode
);
4156 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
4159 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
4160 spin_lock(&inode
->i_lock
);
4161 inode
->i_state
&= ~I_LINKABLE
;
4162 spin_unlock(&inode
->i_lock
);
4164 inode_unlock(inode
);
4166 fsnotify_link(dir
, inode
, new_dentry
);
4169 EXPORT_SYMBOL(vfs_link
);
4172 * Hardlinks are often used in delicate situations. We avoid
4173 * security-related surprises by not following symlinks on the
4176 * We don't follow them on the oldname either to be compatible
4177 * with linux 2.0, and to avoid hard-linking to directories
4178 * and other special files. --ADM
4180 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
4181 int, newdfd
, const char __user
*, newname
, int, flags
)
4183 struct dentry
*new_dentry
;
4184 struct path old_path
, new_path
;
4185 struct inode
*delegated_inode
= NULL
;
4189 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
4192 * To use null names we require CAP_DAC_READ_SEARCH
4193 * This ensures that not everyone will be able to create
4194 * handlink using the passed filedescriptor.
4196 if (flags
& AT_EMPTY_PATH
) {
4197 if (!capable(CAP_DAC_READ_SEARCH
))
4202 if (flags
& AT_SYMLINK_FOLLOW
)
4203 how
|= LOOKUP_FOLLOW
;
4205 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
4209 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
4210 (how
& LOOKUP_REVAL
));
4211 error
= PTR_ERR(new_dentry
);
4212 if (IS_ERR(new_dentry
))
4216 if (old_path
.mnt
!= new_path
.mnt
)
4218 error
= may_linkat(&old_path
);
4219 if (unlikely(error
))
4221 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
4224 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
4226 done_path_create(&new_path
, new_dentry
);
4227 if (delegated_inode
) {
4228 error
= break_deleg_wait(&delegated_inode
);
4230 path_put(&old_path
);
4234 if (retry_estale(error
, how
)) {
4235 path_put(&old_path
);
4236 how
|= LOOKUP_REVAL
;
4240 path_put(&old_path
);
4245 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
4247 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4251 * vfs_rename - rename a filesystem object
4252 * @old_dir: parent of source
4253 * @old_dentry: source
4254 * @new_dir: parent of destination
4255 * @new_dentry: destination
4256 * @delegated_inode: returns an inode needing a delegation break
4257 * @flags: rename flags
4259 * The caller must hold multiple mutexes--see lock_rename()).
4261 * If vfs_rename discovers a delegation in need of breaking at either
4262 * the source or destination, it will return -EWOULDBLOCK and return a
4263 * reference to the inode in delegated_inode. The caller should then
4264 * break the delegation and retry. Because breaking a delegation may
4265 * take a long time, the caller should drop all locks before doing
4268 * Alternatively, a caller may pass NULL for delegated_inode. This may
4269 * be appropriate for callers that expect the underlying filesystem not
4270 * to be NFS exported.
4272 * The worst of all namespace operations - renaming directory. "Perverted"
4273 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4275 * a) we can get into loop creation.
4276 * b) race potential - two innocent renames can create a loop together.
4277 * That's where 4.4 screws up. Current fix: serialization on
4278 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4280 * c) we have to lock _four_ objects - parents and victim (if it exists),
4281 * and source (if it is not a directory).
4282 * And that - after we got ->i_mutex on parents (until then we don't know
4283 * whether the target exists). Solution: try to be smart with locking
4284 * order for inodes. We rely on the fact that tree topology may change
4285 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4286 * move will be locked. Thus we can rank directories by the tree
4287 * (ancestors first) and rank all non-directories after them.
4288 * That works since everybody except rename does "lock parent, lookup,
4289 * lock child" and rename is under ->s_vfs_rename_mutex.
4290 * HOWEVER, it relies on the assumption that any object with ->lookup()
4291 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4292 * we'd better make sure that there's no link(2) for them.
4293 * d) conversion from fhandle to dentry may come in the wrong moment - when
4294 * we are removing the target. Solution: we will have to grab ->i_mutex
4295 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4296 * ->i_mutex on parents, which works but leads to some truly excessive
4299 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4300 struct inode
*new_dir
, struct dentry
*new_dentry
,
4301 struct inode
**delegated_inode
, unsigned int flags
)
4304 bool is_dir
= d_is_dir(old_dentry
);
4305 const unsigned char *old_name
;
4306 struct inode
*source
= old_dentry
->d_inode
;
4307 struct inode
*target
= new_dentry
->d_inode
;
4308 bool new_is_dir
= false;
4309 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4312 * Check source == target.
4313 * On overlayfs need to look at underlying inodes.
4315 if (d_real_inode(old_dentry
) == d_real_inode(new_dentry
))
4318 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4323 error
= may_create(new_dir
, new_dentry
);
4325 new_is_dir
= d_is_dir(new_dentry
);
4327 if (!(flags
& RENAME_EXCHANGE
))
4328 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4330 error
= may_delete(new_dir
, new_dentry
, new_is_dir
);
4335 if (!old_dir
->i_op
->rename
&& !old_dir
->i_op
->rename2
)
4338 if (flags
&& !old_dir
->i_op
->rename2
)
4342 * If we are going to change the parent - check write permissions,
4343 * we'll need to flip '..'.
4345 if (new_dir
!= old_dir
) {
4347 error
= inode_permission(source
, MAY_WRITE
);
4351 if ((flags
& RENAME_EXCHANGE
) && new_is_dir
) {
4352 error
= inode_permission(target
, MAY_WRITE
);
4358 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
,
4363 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
4365 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4366 lock_two_nondirectories(source
, target
);
4371 if (is_local_mountpoint(old_dentry
) || is_local_mountpoint(new_dentry
))
4374 if (max_links
&& new_dir
!= old_dir
) {
4376 if (is_dir
&& !new_is_dir
&& new_dir
->i_nlink
>= max_links
)
4378 if ((flags
& RENAME_EXCHANGE
) && !is_dir
&& new_is_dir
&&
4379 old_dir
->i_nlink
>= max_links
)
4382 if (is_dir
&& !(flags
& RENAME_EXCHANGE
) && target
)
4383 shrink_dcache_parent(new_dentry
);
4385 error
= try_break_deleg(source
, delegated_inode
);
4389 if (target
&& !new_is_dir
) {
4390 error
= try_break_deleg(target
, delegated_inode
);
4394 if (!old_dir
->i_op
->rename2
) {
4395 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
,
4396 new_dir
, new_dentry
);
4398 WARN_ON(old_dir
->i_op
->rename
!= NULL
);
4399 error
= old_dir
->i_op
->rename2(old_dir
, old_dentry
,
4400 new_dir
, new_dentry
, flags
);
4405 if (!(flags
& RENAME_EXCHANGE
) && target
) {
4407 target
->i_flags
|= S_DEAD
;
4408 dont_mount(new_dentry
);
4409 detach_mounts(new_dentry
);
4411 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
)) {
4412 if (!(flags
& RENAME_EXCHANGE
))
4413 d_move(old_dentry
, new_dentry
);
4415 d_exchange(old_dentry
, new_dentry
);
4418 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4419 unlock_two_nondirectories(source
, target
);
4421 inode_unlock(target
);
4424 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
4425 !(flags
& RENAME_EXCHANGE
) ? target
: NULL
, old_dentry
);
4426 if (flags
& RENAME_EXCHANGE
) {
4427 fsnotify_move(new_dir
, old_dir
, old_dentry
->d_name
.name
,
4428 new_is_dir
, NULL
, new_dentry
);
4431 fsnotify_oldname_free(old_name
);
4435 EXPORT_SYMBOL(vfs_rename
);
4437 SYSCALL_DEFINE5(renameat2
, int, olddfd
, const char __user
*, oldname
,
4438 int, newdfd
, const char __user
*, newname
, unsigned int, flags
)
4440 struct dentry
*old_dentry
, *new_dentry
;
4441 struct dentry
*trap
;
4442 struct path old_path
, new_path
;
4443 struct qstr old_last
, new_last
;
4444 int old_type
, new_type
;
4445 struct inode
*delegated_inode
= NULL
;
4446 struct filename
*from
;
4447 struct filename
*to
;
4448 unsigned int lookup_flags
= 0, target_flags
= LOOKUP_RENAME_TARGET
;
4449 bool should_retry
= false;
4452 if (flags
& ~(RENAME_NOREPLACE
| RENAME_EXCHANGE
| RENAME_WHITEOUT
))
4455 if ((flags
& (RENAME_NOREPLACE
| RENAME_WHITEOUT
)) &&
4456 (flags
& RENAME_EXCHANGE
))
4459 if ((flags
& RENAME_WHITEOUT
) && !capable(CAP_MKNOD
))
4462 if (flags
& RENAME_EXCHANGE
)
4466 from
= user_path_parent(olddfd
, oldname
,
4467 &old_path
, &old_last
, &old_type
, lookup_flags
);
4469 error
= PTR_ERR(from
);
4473 to
= user_path_parent(newdfd
, newname
,
4474 &new_path
, &new_last
, &new_type
, lookup_flags
);
4476 error
= PTR_ERR(to
);
4481 if (old_path
.mnt
!= new_path
.mnt
)
4485 if (old_type
!= LAST_NORM
)
4488 if (flags
& RENAME_NOREPLACE
)
4490 if (new_type
!= LAST_NORM
)
4493 error
= mnt_want_write(old_path
.mnt
);
4498 trap
= lock_rename(new_path
.dentry
, old_path
.dentry
);
4500 old_dentry
= __lookup_hash(&old_last
, old_path
.dentry
, lookup_flags
);
4501 error
= PTR_ERR(old_dentry
);
4502 if (IS_ERR(old_dentry
))
4504 /* source must exist */
4506 if (d_is_negative(old_dentry
))
4508 new_dentry
= __lookup_hash(&new_last
, new_path
.dentry
, lookup_flags
| target_flags
);
4509 error
= PTR_ERR(new_dentry
);
4510 if (IS_ERR(new_dentry
))
4513 if ((flags
& RENAME_NOREPLACE
) && d_is_positive(new_dentry
))
4515 if (flags
& RENAME_EXCHANGE
) {
4517 if (d_is_negative(new_dentry
))
4520 if (!d_is_dir(new_dentry
)) {
4522 if (new_last
.name
[new_last
.len
])
4526 /* unless the source is a directory trailing slashes give -ENOTDIR */
4527 if (!d_is_dir(old_dentry
)) {
4529 if (old_last
.name
[old_last
.len
])
4531 if (!(flags
& RENAME_EXCHANGE
) && new_last
.name
[new_last
.len
])
4534 /* source should not be ancestor of target */
4536 if (old_dentry
== trap
)
4538 /* target should not be an ancestor of source */
4539 if (!(flags
& RENAME_EXCHANGE
))
4541 if (new_dentry
== trap
)
4544 error
= security_path_rename(&old_path
, old_dentry
,
4545 &new_path
, new_dentry
, flags
);
4548 error
= vfs_rename(old_path
.dentry
->d_inode
, old_dentry
,
4549 new_path
.dentry
->d_inode
, new_dentry
,
4550 &delegated_inode
, flags
);
4556 unlock_rename(new_path
.dentry
, old_path
.dentry
);
4557 if (delegated_inode
) {
4558 error
= break_deleg_wait(&delegated_inode
);
4562 mnt_drop_write(old_path
.mnt
);
4564 if (retry_estale(error
, lookup_flags
))
4565 should_retry
= true;
4566 path_put(&new_path
);
4569 path_put(&old_path
);
4572 should_retry
= false;
4573 lookup_flags
|= LOOKUP_REVAL
;
4580 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4581 int, newdfd
, const char __user
*, newname
)
4583 return sys_renameat2(olddfd
, oldname
, newdfd
, newname
, 0);
4586 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4588 return sys_renameat2(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4591 int vfs_whiteout(struct inode
*dir
, struct dentry
*dentry
)
4593 int error
= may_create(dir
, dentry
);
4597 if (!dir
->i_op
->mknod
)
4600 return dir
->i_op
->mknod(dir
, dentry
,
4601 S_IFCHR
| WHITEOUT_MODE
, WHITEOUT_DEV
);
4603 EXPORT_SYMBOL(vfs_whiteout
);
4605 int readlink_copy(char __user
*buffer
, int buflen
, const char *link
)
4607 int len
= PTR_ERR(link
);
4612 if (len
> (unsigned) buflen
)
4614 if (copy_to_user(buffer
, link
, len
))
4621 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4622 * have ->get_link() not calling nd_jump_link(). Using (or not using) it
4623 * for any given inode is up to filesystem.
4625 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4627 DEFINE_DELAYED_CALL(done
);
4628 struct inode
*inode
= d_inode(dentry
);
4629 const char *link
= inode
->i_link
;
4633 link
= inode
->i_op
->get_link(dentry
, inode
, &done
);
4635 return PTR_ERR(link
);
4637 res
= readlink_copy(buffer
, buflen
, link
);
4638 do_delayed_call(&done
);
4641 EXPORT_SYMBOL(generic_readlink
);
4643 /* get the link contents into pagecache */
4644 const char *page_get_link(struct dentry
*dentry
, struct inode
*inode
,
4645 struct delayed_call
*callback
)
4649 struct address_space
*mapping
= inode
->i_mapping
;
4652 page
= find_get_page(mapping
, 0);
4654 return ERR_PTR(-ECHILD
);
4655 if (!PageUptodate(page
)) {
4657 return ERR_PTR(-ECHILD
);
4660 page
= read_mapping_page(mapping
, 0, NULL
);
4664 set_delayed_call(callback
, page_put_link
, page
);
4665 BUG_ON(mapping_gfp_mask(mapping
) & __GFP_HIGHMEM
);
4666 kaddr
= page_address(page
);
4667 nd_terminate_link(kaddr
, inode
->i_size
, PAGE_SIZE
- 1);
4671 EXPORT_SYMBOL(page_get_link
);
4673 void page_put_link(void *arg
)
4677 EXPORT_SYMBOL(page_put_link
);
4679 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4681 DEFINE_DELAYED_CALL(done
);
4682 int res
= readlink_copy(buffer
, buflen
,
4683 page_get_link(dentry
, d_inode(dentry
),
4685 do_delayed_call(&done
);
4688 EXPORT_SYMBOL(page_readlink
);
4691 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4693 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4695 struct address_space
*mapping
= inode
->i_mapping
;
4699 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
4701 flags
|= AOP_FLAG_NOFS
;
4704 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4705 flags
, &page
, &fsdata
);
4709 memcpy(page_address(page
), symname
, len
-1);
4711 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4718 mark_inode_dirty(inode
);
4723 EXPORT_SYMBOL(__page_symlink
);
4725 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4727 return __page_symlink(inode
, symname
, len
,
4728 !mapping_gfp_constraint(inode
->i_mapping
, __GFP_FS
));
4730 EXPORT_SYMBOL(page_symlink
);
4732 const struct inode_operations page_symlink_inode_operations
= {
4733 .readlink
= generic_readlink
,
4734 .get_link
= page_get_link
,
4736 EXPORT_SYMBOL(page_symlink_inode_operations
);