1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992 Linus Torvalds
9 * Some corrections by tytso.
12 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
15 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
18 #include <linux/init.h>
19 #include <linux/export.h>
20 #include <linux/slab.h>
21 #include <linux/wordpart.h>
23 #include <linux/filelock.h>
24 #include <linux/namei.h>
25 #include <linux/pagemap.h>
26 #include <linux/sched/mm.h>
27 #include <linux/fsnotify.h>
28 #include <linux/personality.h>
29 #include <linux/security.h>
30 #include <linux/syscalls.h>
31 #include <linux/mount.h>
32 #include <linux/audit.h>
33 #include <linux/capability.h>
34 #include <linux/file.h>
35 #include <linux/fcntl.h>
36 #include <linux/device_cgroup.h>
37 #include <linux/fs_struct.h>
38 #include <linux/posix_acl.h>
39 #include <linux/hash.h>
40 #include <linux/bitops.h>
41 #include <linux/init_task.h>
42 #include <linux/uaccess.h>
47 /* [Feb-1997 T. Schoebel-Theuer]
48 * Fundamental changes in the pathname lookup mechanisms (namei)
49 * were necessary because of omirr. The reason is that omirr needs
50 * to know the _real_ pathname, not the user-supplied one, in case
51 * of symlinks (and also when transname replacements occur).
53 * The new code replaces the old recursive symlink resolution with
54 * an iterative one (in case of non-nested symlink chains). It does
55 * this with calls to <fs>_follow_link().
56 * As a side effect, dir_namei(), _namei() and follow_link() are now
57 * replaced with a single function lookup_dentry() that can handle all
58 * the special cases of the former code.
60 * With the new dcache, the pathname is stored at each inode, at least as
61 * long as the refcount of the inode is positive. As a side effect, the
62 * size of the dcache depends on the inode cache and thus is dynamic.
64 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
65 * resolution to correspond with current state of the code.
67 * Note that the symlink resolution is not *completely* iterative.
68 * There is still a significant amount of tail- and mid- recursion in
69 * the algorithm. Also, note that <fs>_readlink() is not used in
70 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
71 * may return different results than <fs>_follow_link(). Many virtual
72 * filesystems (including /proc) exhibit this behavior.
75 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
76 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
77 * and the name already exists in form of a symlink, try to create the new
78 * name indicated by the symlink. The old code always complained that the
79 * name already exists, due to not following the symlink even if its target
80 * is nonexistent. The new semantics affects also mknod() and link() when
81 * the name is a symlink pointing to a non-existent name.
83 * I don't know which semantics is the right one, since I have no access
84 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
85 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
86 * "old" one. Personally, I think the new semantics is much more logical.
87 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
88 * file does succeed in both HP-UX and SunOs, but not in Solaris
89 * and in the old Linux semantics.
92 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
93 * semantics. See the comments in "open_namei" and "do_link" below.
95 * [10-Sep-98 Alan Modra] Another symlink change.
98 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
99 * inside the path - always follow.
100 * in the last component in creation/removal/renaming - never follow.
101 * if LOOKUP_FOLLOW passed - follow.
102 * if the pathname has trailing slashes - follow.
103 * otherwise - don't follow.
104 * (applied in that order).
106 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
107 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
108 * During the 2.4 we need to fix the userland stuff depending on it -
109 * hopefully we will be able to get rid of that wart in 2.5. So far only
110 * XEmacs seems to be relying on it...
113 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
114 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
115 * any extra contention...
118 /* In order to reduce some races, while at the same time doing additional
119 * checking and hopefully speeding things up, we copy filenames to the
120 * kernel data space before using them..
122 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
123 * PATH_MAX includes the nul terminator --RR.
126 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
129 getname_flags(const char __user *filename, int flags, int *empty)
131 struct filename *result;
135 result = audit_reusename(filename);
139 result = __getname();
140 if (unlikely(!result))
141 return ERR_PTR(-ENOMEM);
144 * First, try to embed the struct filename inside the names_cache
147 kname = (char *)result->iname;
148 result->name = kname;
150 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
151 if (unlikely(len < 0)) {
157 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
158 * separate struct filename so we can dedicate the entire
159 * names_cache allocation for the pathname, and re-do the copy from
162 if (unlikely(len == EMBEDDED_NAME_MAX)) {
163 const size_t size = offsetof(struct filename, iname[1]);
164 kname = (char *)result;
167 * size is chosen that way we to guarantee that
168 * result->iname[0] is within the same object and that
169 * kname can't be equal to result->iname, no matter what.
171 result = kzalloc(size, GFP_KERNEL);
172 if (unlikely(!result)) {
174 return ERR_PTR(-ENOMEM);
176 result->name = kname;
177 len = strncpy_from_user(kname, filename, PATH_MAX);
178 if (unlikely(len < 0)) {
183 if (unlikely(len == PATH_MAX)) {
186 return ERR_PTR(-ENAMETOOLONG);
190 atomic_set(&result->refcnt, 1);
191 /* The empty path is special. */
192 if (unlikely(!len)) {
195 if (!(flags & LOOKUP_EMPTY)) {
197 return ERR_PTR(-ENOENT);
201 result->uptr = filename;
202 result->aname = NULL;
203 audit_getname(result);
208 getname_uflags(const char __user *filename, int uflags)
210 int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
212 return getname_flags(filename, flags, NULL);
216 getname(const char __user * filename)
218 return getname_flags(filename, 0, NULL);
222 getname_kernel(const char * filename)
224 struct filename *result;
225 int len = strlen(filename) + 1;
227 result = __getname();
228 if (unlikely(!result))
229 return ERR_PTR(-ENOMEM);
231 if (len <= EMBEDDED_NAME_MAX) {
232 result->name = (char *)result->iname;
233 } else if (len <= PATH_MAX) {
234 const size_t size = offsetof(struct filename, iname[1]);
235 struct filename *tmp;
237 tmp = kmalloc(size, GFP_KERNEL);
238 if (unlikely(!tmp)) {
240 return ERR_PTR(-ENOMEM);
242 tmp->name = (char *)result;
246 return ERR_PTR(-ENAMETOOLONG);
248 memcpy((char *)result->name, filename, len);
250 result->aname = NULL;
251 atomic_set(&result->refcnt, 1);
252 audit_getname(result);
256 EXPORT_SYMBOL(getname_kernel);
258 void putname(struct filename *name)
263 if (WARN_ON_ONCE(!atomic_read(&name->refcnt)))
266 if (!atomic_dec_and_test(&name->refcnt))
269 if (name->name != name->iname) {
270 __putname(name->name);
275 EXPORT_SYMBOL(putname);
278 * check_acl - perform ACL permission checking
279 * @idmap: idmap of the mount the inode was found from
280 * @inode: inode to check permissions on
281 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
283 * This function performs the ACL permission checking. Since this function
284 * retrieve POSIX acls it needs to know whether it is called from a blocking or
285 * non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
287 * If the inode has been found through an idmapped mount the idmap of
288 * the vfsmount must be passed through @idmap. This function will then take
289 * care to map the inode according to @idmap before checking permissions.
290 * On non-idmapped mounts or if permission checking is to be performed on the
291 * raw inode simply pass @nop_mnt_idmap.
293 static int check_acl(struct mnt_idmap *idmap,
294 struct inode *inode, int mask)
296 #ifdef CONFIG_FS_POSIX_ACL
297 struct posix_acl *acl;
299 if (mask & MAY_NOT_BLOCK) {
300 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
303 /* no ->get_inode_acl() calls in RCU mode... */
304 if (is_uncached_acl(acl))
306 return posix_acl_permission(idmap, inode, acl, mask);
309 acl = get_inode_acl(inode, ACL_TYPE_ACCESS);
313 int error = posix_acl_permission(idmap, inode, acl, mask);
314 posix_acl_release(acl);
323 * acl_permission_check - perform basic UNIX permission checking
324 * @idmap: idmap of the mount the inode was found from
325 * @inode: inode to check permissions on
326 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
328 * This function performs the basic UNIX permission checking. Since this
329 * function may retrieve POSIX acls it needs to know whether it is called from a
330 * blocking or non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
332 * If the inode has been found through an idmapped mount the idmap of
333 * the vfsmount must be passed through @idmap. This function will then take
334 * care to map the inode according to @idmap before checking permissions.
335 * On non-idmapped mounts or if permission checking is to be performed on the
336 * raw inode simply pass @nop_mnt_idmap.
338 static int acl_permission_check(struct mnt_idmap *idmap,
339 struct inode *inode, int mask)
341 unsigned int mode = inode->i_mode;
344 /* Are we the owner? If so, ACL's don't matter */
345 vfsuid = i_uid_into_vfsuid(idmap, inode);
346 if (likely(vfsuid_eq_kuid(vfsuid, current_fsuid()))) {
349 return (mask & ~mode) ? -EACCES : 0;
352 /* Do we have ACL's? */
353 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
354 int error = check_acl(idmap, inode, mask);
355 if (error != -EAGAIN)
359 /* Only RWX matters for group/other mode bits */
363 * Are the group permissions different from
364 * the other permissions in the bits we care
365 * about? Need to check group ownership if so.
367 if (mask & (mode ^ (mode >> 3))) {
368 vfsgid_t vfsgid = i_gid_into_vfsgid(idmap, inode);
369 if (vfsgid_in_group_p(vfsgid))
373 /* Bits in 'mode' clear that we require? */
374 return (mask & ~mode) ? -EACCES : 0;
378 * generic_permission - check for access rights on a Posix-like filesystem
379 * @idmap: idmap of the mount the inode was found from
380 * @inode: inode to check access rights for
381 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC,
382 * %MAY_NOT_BLOCK ...)
384 * Used to check for read/write/execute permissions on a file.
385 * We use "fsuid" for this, letting us set arbitrary permissions
386 * for filesystem access without changing the "normal" uids which
387 * are used for other things.
389 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
390 * request cannot be satisfied (eg. requires blocking or too much complexity).
391 * It would then be called again in ref-walk mode.
393 * If the inode has been found through an idmapped mount the idmap of
394 * the vfsmount must be passed through @idmap. This function will then take
395 * care to map the inode according to @idmap before checking permissions.
396 * On non-idmapped mounts or if permission checking is to be performed on the
397 * raw inode simply pass @nop_mnt_idmap.
399 int generic_permission(struct mnt_idmap *idmap, struct inode *inode,
405 * Do the basic permission checks.
407 ret = acl_permission_check(idmap, inode, mask);
411 if (S_ISDIR(inode->i_mode)) {
412 /* DACs are overridable for directories */
413 if (!(mask & MAY_WRITE))
414 if (capable_wrt_inode_uidgid(idmap, inode,
415 CAP_DAC_READ_SEARCH))
417 if (capable_wrt_inode_uidgid(idmap, inode,
424 * Searching includes executable on directories, else just read.
426 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
427 if (mask == MAY_READ)
428 if (capable_wrt_inode_uidgid(idmap, inode,
429 CAP_DAC_READ_SEARCH))
432 * Read/write DACs are always overridable.
433 * Executable DACs are overridable when there is
434 * at least one exec bit set.
436 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
437 if (capable_wrt_inode_uidgid(idmap, inode,
443 EXPORT_SYMBOL(generic_permission);
446 * do_inode_permission - UNIX permission checking
447 * @idmap: idmap of the mount the inode was found from
448 * @inode: inode to check permissions on
449 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
451 * We _really_ want to just do "generic_permission()" without
452 * even looking at the inode->i_op values. So we keep a cache
453 * flag in inode->i_opflags, that says "this has not special
454 * permission function, use the fast case".
456 static inline int do_inode_permission(struct mnt_idmap *idmap,
457 struct inode *inode, int mask)
459 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
460 if (likely(inode->i_op->permission))
461 return inode->i_op->permission(idmap, inode, mask);
463 /* This gets set once for the inode lifetime */
464 spin_lock(&inode->i_lock);
465 inode->i_opflags |= IOP_FASTPERM;
466 spin_unlock(&inode->i_lock);
468 return generic_permission(idmap, inode, mask);
472 * sb_permission - Check superblock-level permissions
473 * @sb: Superblock of inode to check permission on
474 * @inode: Inode to check permission on
475 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
477 * Separate out file-system wide checks from inode-specific permission checks.
479 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
481 if (unlikely(mask & MAY_WRITE)) {
482 umode_t mode = inode->i_mode;
484 /* Nobody gets write access to a read-only fs. */
485 if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
492 * inode_permission - Check for access rights to a given inode
493 * @idmap: idmap of the mount the inode was found from
494 * @inode: Inode to check permission on
495 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
497 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
498 * this, letting us set arbitrary permissions for filesystem access without
499 * changing the "normal" UIDs which are used for other things.
501 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
503 int inode_permission(struct mnt_idmap *idmap,
504 struct inode *inode, int mask)
508 retval = sb_permission(inode->i_sb, inode, mask);
512 if (unlikely(mask & MAY_WRITE)) {
514 * Nobody gets write access to an immutable file.
516 if (IS_IMMUTABLE(inode))
520 * Updating mtime will likely cause i_uid and i_gid to be
521 * written back improperly if their true value is unknown
524 if (HAS_UNMAPPED_ID(idmap, inode))
528 retval = do_inode_permission(idmap, inode, mask);
532 retval = devcgroup_inode_permission(inode, mask);
536 return security_inode_permission(inode, mask);
538 EXPORT_SYMBOL(inode_permission);
541 * path_get - get a reference to a path
542 * @path: path to get the reference to
544 * Given a path increment the reference count to the dentry and the vfsmount.
546 void path_get(const struct path *path)
551 EXPORT_SYMBOL(path_get);
554 * path_put - put a reference to a path
555 * @path: path to put the reference to
557 * Given a path decrement the reference count to the dentry and the vfsmount.
559 void path_put(const struct path *path)
564 EXPORT_SYMBOL(path_put);
566 #define EMBEDDED_LEVELS 2
571 struct inode *inode; /* path.dentry.d_inode */
572 unsigned int flags, state;
573 unsigned seq, next_seq, m_seq, r_seq;
576 int total_link_count;
579 struct delayed_call done;
582 } *stack, internal[EMBEDDED_LEVELS];
583 struct filename *name;
584 struct nameidata *saved;
589 } __randomize_layout;
591 #define ND_ROOT_PRESET 1
592 #define ND_ROOT_GRABBED 2
595 static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name)
597 struct nameidata *old = current->nameidata;
598 p->stack = p->internal;
603 p->path.dentry = NULL;
604 p->total_link_count = old ? old->total_link_count : 0;
606 current->nameidata = p;
609 static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name,
610 const struct path *root)
612 __set_nameidata(p, dfd, name);
614 if (unlikely(root)) {
615 p->state = ND_ROOT_PRESET;
620 static void restore_nameidata(void)
622 struct nameidata *now = current->nameidata, *old = now->saved;
624 current->nameidata = old;
626 old->total_link_count = now->total_link_count;
627 if (now->stack != now->internal)
631 static bool nd_alloc_stack(struct nameidata *nd)
635 p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved),
636 nd->flags & LOOKUP_RCU ? GFP_ATOMIC : GFP_KERNEL);
639 memcpy(p, nd->internal, sizeof(nd->internal));
645 * path_connected - Verify that a dentry is below mnt.mnt_root
646 * @mnt: The mountpoint to check.
647 * @dentry: The dentry to check.
649 * Rename can sometimes move a file or directory outside of a bind
650 * mount, path_connected allows those cases to be detected.
652 static bool path_connected(struct vfsmount *mnt, struct dentry *dentry)
654 struct super_block *sb = mnt->mnt_sb;
656 /* Bind mounts can have disconnected paths */
657 if (mnt->mnt_root == sb->s_root)
660 return is_subdir(dentry, mnt->mnt_root);
663 static void drop_links(struct nameidata *nd)
667 struct saved *last = nd->stack + i;
668 do_delayed_call(&last->done);
669 clear_delayed_call(&last->done);
673 static void leave_rcu(struct nameidata *nd)
675 nd->flags &= ~LOOKUP_RCU;
676 nd->seq = nd->next_seq = 0;
680 static void terminate_walk(struct nameidata *nd)
683 if (!(nd->flags & LOOKUP_RCU)) {
686 for (i = 0; i < nd->depth; i++)
687 path_put(&nd->stack[i].link);
688 if (nd->state & ND_ROOT_GRABBED) {
690 nd->state &= ~ND_ROOT_GRABBED;
697 nd->path.dentry = NULL;
700 /* path_put is needed afterwards regardless of success or failure */
701 static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq)
703 int res = __legitimize_mnt(path->mnt, mseq);
710 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
714 return !read_seqcount_retry(&path->dentry->d_seq, seq);
717 static inline bool legitimize_path(struct nameidata *nd,
718 struct path *path, unsigned seq)
720 return __legitimize_path(path, seq, nd->m_seq);
723 static bool legitimize_links(struct nameidata *nd)
726 if (unlikely(nd->flags & LOOKUP_CACHED)) {
731 for (i = 0; i < nd->depth; i++) {
732 struct saved *last = nd->stack + i;
733 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
742 static bool legitimize_root(struct nameidata *nd)
744 /* Nothing to do if nd->root is zero or is managed by the VFS user. */
745 if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET))
747 nd->state |= ND_ROOT_GRABBED;
748 return legitimize_path(nd, &nd->root, nd->root_seq);
752 * Path walking has 2 modes, rcu-walk and ref-walk (see
753 * Documentation/filesystems/path-lookup.txt). In situations when we can't
754 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
755 * normal reference counts on dentries and vfsmounts to transition to ref-walk
756 * mode. Refcounts are grabbed at the last known good point before rcu-walk
757 * got stuck, so ref-walk may continue from there. If this is not successful
758 * (eg. a seqcount has changed), then failure is returned and it's up to caller
759 * to restart the path walk from the beginning in ref-walk mode.
763 * try_to_unlazy - try to switch to ref-walk mode.
764 * @nd: nameidata pathwalk data
765 * Returns: true on success, false on failure
767 * try_to_unlazy attempts to legitimize the current nd->path and nd->root
769 * Must be called from rcu-walk context.
770 * Nothing should touch nameidata between try_to_unlazy() failure and
773 static bool try_to_unlazy(struct nameidata *nd)
775 struct dentry *parent = nd->path.dentry;
777 BUG_ON(!(nd->flags & LOOKUP_RCU));
779 if (unlikely(!legitimize_links(nd)))
781 if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
783 if (unlikely(!legitimize_root(nd)))
786 BUG_ON(nd->inode != parent->d_inode);
791 nd->path.dentry = NULL;
798 * try_to_unlazy_next - try to switch to ref-walk mode.
799 * @nd: nameidata pathwalk data
800 * @dentry: next dentry to step into
801 * Returns: true on success, false on failure
803 * Similar to try_to_unlazy(), but here we have the next dentry already
804 * picked by rcu-walk and want to legitimize that in addition to the current
805 * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context.
806 * Nothing should touch nameidata between try_to_unlazy_next() failure and
809 static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry)
812 BUG_ON(!(nd->flags & LOOKUP_RCU));
814 if (unlikely(!legitimize_links(nd)))
816 res = __legitimize_mnt(nd->path.mnt, nd->m_seq);
822 if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
826 * We need to move both the parent and the dentry from the RCU domain
827 * to be properly refcounted. And the sequence number in the dentry
828 * validates *both* dentry counters, since we checked the sequence
829 * number of the parent after we got the child sequence number. So we
830 * know the parent must still be valid if the child sequence number is
832 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
834 if (read_seqcount_retry(&dentry->d_seq, nd->next_seq))
837 * Sequence counts matched. Now make sure that the root is
838 * still valid and get it if required.
840 if (unlikely(!legitimize_root(nd)))
848 nd->path.dentry = NULL;
858 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
860 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
861 return dentry->d_op->d_revalidate(dentry, flags);
867 * complete_walk - successful completion of path walk
868 * @nd: pointer nameidata
870 * If we had been in RCU mode, drop out of it and legitimize nd->path.
871 * Revalidate the final result, unless we'd already done that during
872 * the path walk or the filesystem doesn't ask for it. Return 0 on
873 * success, -error on failure. In case of failure caller does not
874 * need to drop nd->path.
876 static int complete_walk(struct nameidata *nd)
878 struct dentry *dentry = nd->path.dentry;
881 if (nd->flags & LOOKUP_RCU) {
883 * We don't want to zero nd->root for scoped-lookups or
884 * externally-managed nd->root.
886 if (!(nd->state & ND_ROOT_PRESET))
887 if (!(nd->flags & LOOKUP_IS_SCOPED))
889 nd->flags &= ~LOOKUP_CACHED;
890 if (!try_to_unlazy(nd))
894 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
896 * While the guarantee of LOOKUP_IS_SCOPED is (roughly) "don't
897 * ever step outside the root during lookup" and should already
898 * be guaranteed by the rest of namei, we want to avoid a namei
899 * BUG resulting in userspace being given a path that was not
900 * scoped within the root at some point during the lookup.
902 * So, do a final sanity-check to make sure that in the
903 * worst-case scenario (a complete bypass of LOOKUP_IS_SCOPED)
904 * we won't silently return an fd completely outside of the
905 * requested root to userspace.
907 * Userspace could move the path outside the root after this
908 * check, but as discussed elsewhere this is not a concern (the
909 * resolved file was inside the root at some point).
911 if (!path_is_under(&nd->path, &nd->root))
915 if (likely(!(nd->state & ND_JUMPED)))
918 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
921 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
931 static int set_root(struct nameidata *nd)
933 struct fs_struct *fs = current->fs;
936 * Jumping to the real root in a scoped-lookup is a BUG in namei, but we
937 * still have to ensure it doesn't happen because it will cause a breakout
940 if (WARN_ON(nd->flags & LOOKUP_IS_SCOPED))
941 return -ENOTRECOVERABLE;
943 if (nd->flags & LOOKUP_RCU) {
947 seq = read_seqcount_begin(&fs->seq);
949 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
950 } while (read_seqcount_retry(&fs->seq, seq));
952 get_fs_root(fs, &nd->root);
953 nd->state |= ND_ROOT_GRABBED;
958 static int nd_jump_root(struct nameidata *nd)
960 if (unlikely(nd->flags & LOOKUP_BENEATH))
962 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
963 /* Absolute path arguments to path_init() are allowed. */
964 if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt)
968 int error = set_root(nd);
972 if (nd->flags & LOOKUP_RCU) {
976 nd->inode = d->d_inode;
977 nd->seq = nd->root_seq;
978 if (read_seqcount_retry(&d->d_seq, nd->seq))
984 nd->inode = nd->path.dentry->d_inode;
986 nd->state |= ND_JUMPED;
991 * Helper to directly jump to a known parsed path from ->get_link,
992 * caller must have taken a reference to path beforehand.
994 int nd_jump_link(const struct path *path)
997 struct nameidata *nd = current->nameidata;
999 if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
1003 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
1004 if (nd->path.mnt != path->mnt)
1007 /* Not currently safe for scoped-lookups. */
1008 if (unlikely(nd->flags & LOOKUP_IS_SCOPED))
1011 path_put(&nd->path);
1013 nd->inode = nd->path.dentry->d_inode;
1014 nd->state |= ND_JUMPED;
1022 static inline void put_link(struct nameidata *nd)
1024 struct saved *last = nd->stack + --nd->depth;
1025 do_delayed_call(&last->done);
1026 if (!(nd->flags & LOOKUP_RCU))
1027 path_put(&last->link);
1030 static int sysctl_protected_symlinks __read_mostly;
1031 static int sysctl_protected_hardlinks __read_mostly;
1032 static int sysctl_protected_fifos __read_mostly;
1033 static int sysctl_protected_regular __read_mostly;
1035 #ifdef CONFIG_SYSCTL
1036 static struct ctl_table namei_sysctls[] = {
1038 .procname = "protected_symlinks",
1039 .data = &sysctl_protected_symlinks,
1040 .maxlen = sizeof(int),
1042 .proc_handler = proc_dointvec_minmax,
1043 .extra1 = SYSCTL_ZERO,
1044 .extra2 = SYSCTL_ONE,
1047 .procname = "protected_hardlinks",
1048 .data = &sysctl_protected_hardlinks,
1049 .maxlen = sizeof(int),
1051 .proc_handler = proc_dointvec_minmax,
1052 .extra1 = SYSCTL_ZERO,
1053 .extra2 = SYSCTL_ONE,
1056 .procname = "protected_fifos",
1057 .data = &sysctl_protected_fifos,
1058 .maxlen = sizeof(int),
1060 .proc_handler = proc_dointvec_minmax,
1061 .extra1 = SYSCTL_ZERO,
1062 .extra2 = SYSCTL_TWO,
1065 .procname = "protected_regular",
1066 .data = &sysctl_protected_regular,
1067 .maxlen = sizeof(int),
1069 .proc_handler = proc_dointvec_minmax,
1070 .extra1 = SYSCTL_ZERO,
1071 .extra2 = SYSCTL_TWO,
1075 static int __init init_fs_namei_sysctls(void)
1077 register_sysctl_init("fs", namei_sysctls);
1080 fs_initcall(init_fs_namei_sysctls);
1082 #endif /* CONFIG_SYSCTL */
1085 * may_follow_link - Check symlink following for unsafe situations
1086 * @nd: nameidata pathwalk data
1087 * @inode: Used for idmapping.
1089 * In the case of the sysctl_protected_symlinks sysctl being enabled,
1090 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
1091 * in a sticky world-writable directory. This is to protect privileged
1092 * processes from failing races against path names that may change out
1093 * from under them by way of other users creating malicious symlinks.
1094 * It will permit symlinks to be followed only when outside a sticky
1095 * world-writable directory, or when the uid of the symlink and follower
1096 * match, or when the directory owner matches the symlink's owner.
1098 * Returns 0 if following the symlink is allowed, -ve on error.
1100 static inline int may_follow_link(struct nameidata *nd, const struct inode *inode)
1102 struct mnt_idmap *idmap;
1105 if (!sysctl_protected_symlinks)
1108 idmap = mnt_idmap(nd->path.mnt);
1109 vfsuid = i_uid_into_vfsuid(idmap, inode);
1110 /* Allowed if owner and follower match. */
1111 if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
1114 /* Allowed if parent directory not sticky and world-writable. */
1115 if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
1118 /* Allowed if parent directory and link owner match. */
1119 if (vfsuid_valid(nd->dir_vfsuid) && vfsuid_eq(nd->dir_vfsuid, vfsuid))
1122 if (nd->flags & LOOKUP_RCU)
1125 audit_inode(nd->name, nd->stack[0].link.dentry, 0);
1126 audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link");
1131 * safe_hardlink_source - Check for safe hardlink conditions
1132 * @idmap: idmap of the mount the inode was found from
1133 * @inode: the source inode to hardlink from
1135 * Return false if at least one of the following conditions:
1136 * - inode is not a regular file
1138 * - inode is setgid and group-exec
1139 * - access failure for read and write
1141 * Otherwise returns true.
1143 static bool safe_hardlink_source(struct mnt_idmap *idmap,
1144 struct inode *inode)
1146 umode_t mode = inode->i_mode;
1148 /* Special files should not get pinned to the filesystem. */
1152 /* Setuid files should not get pinned to the filesystem. */
1156 /* Executable setgid files should not get pinned to the filesystem. */
1157 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
1160 /* Hardlinking to unreadable or unwritable sources is dangerous. */
1161 if (inode_permission(idmap, inode, MAY_READ | MAY_WRITE))
1168 * may_linkat - Check permissions for creating a hardlink
1169 * @idmap: idmap of the mount the inode was found from
1170 * @link: the source to hardlink from
1172 * Block hardlink when all of:
1173 * - sysctl_protected_hardlinks enabled
1174 * - fsuid does not match inode
1175 * - hardlink source is unsafe (see safe_hardlink_source() above)
1176 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
1178 * If the inode has been found through an idmapped mount the idmap of
1179 * the vfsmount must be passed through @idmap. This function will then take
1180 * care to map the inode according to @idmap before checking permissions.
1181 * On non-idmapped mounts or if permission checking is to be performed on the
1182 * raw inode simply pass @nop_mnt_idmap.
1184 * Returns 0 if successful, -ve on error.
1186 int may_linkat(struct mnt_idmap *idmap, const struct path *link)
1188 struct inode *inode = link->dentry->d_inode;
1190 /* Inode writeback is not safe when the uid or gid are invalid. */
1191 if (!vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) ||
1192 !vfsgid_valid(i_gid_into_vfsgid(idmap, inode)))
1195 if (!sysctl_protected_hardlinks)
1198 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
1199 * otherwise, it must be a safe source.
1201 if (safe_hardlink_source(idmap, inode) ||
1202 inode_owner_or_capable(idmap, inode))
1205 audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
1210 * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
1211 * should be allowed, or not, on files that already
1213 * @idmap: idmap of the mount the inode was found from
1214 * @nd: nameidata pathwalk data
1215 * @inode: the inode of the file to open
1217 * Block an O_CREAT open of a FIFO (or a regular file) when:
1218 * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
1219 * - the file already exists
1220 * - we are in a sticky directory
1221 * - we don't own the file
1222 * - the owner of the directory doesn't own the file
1223 * - the directory is world writable
1224 * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
1225 * the directory doesn't have to be world writable: being group writable will
1228 * If the inode has been found through an idmapped mount the idmap of
1229 * the vfsmount must be passed through @idmap. This function will then take
1230 * care to map the inode according to @idmap before checking permissions.
1231 * On non-idmapped mounts or if permission checking is to be performed on the
1232 * raw inode simply pass @nop_mnt_idmap.
1234 * Returns 0 if the open is allowed, -ve on error.
1236 static int may_create_in_sticky(struct mnt_idmap *idmap,
1237 struct nameidata *nd, struct inode *const inode)
1239 umode_t dir_mode = nd->dir_mode;
1240 vfsuid_t dir_vfsuid = nd->dir_vfsuid;
1242 if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
1243 (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
1244 likely(!(dir_mode & S_ISVTX)) ||
1245 vfsuid_eq(i_uid_into_vfsuid(idmap, inode), dir_vfsuid) ||
1246 vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
1249 if (likely(dir_mode & 0002) ||
1251 ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
1252 (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
1253 const char *operation = S_ISFIFO(inode->i_mode) ?
1254 "sticky_create_fifo" :
1255 "sticky_create_regular";
1256 audit_log_path_denied(AUDIT_ANOM_CREAT, operation);
1263 * follow_up - Find the mountpoint of path's vfsmount
1265 * Given a path, find the mountpoint of its source file system.
1266 * Replace @path with the path of the mountpoint in the parent mount.
1269 * Return 1 if we went up a level and 0 if we were already at the
1272 int follow_up(struct path *path)
1274 struct mount *mnt = real_mount(path->mnt);
1275 struct mount *parent;
1276 struct dentry *mountpoint;
1278 read_seqlock_excl(&mount_lock);
1279 parent = mnt->mnt_parent;
1280 if (parent == mnt) {
1281 read_sequnlock_excl(&mount_lock);
1284 mntget(&parent->mnt);
1285 mountpoint = dget(mnt->mnt_mountpoint);
1286 read_sequnlock_excl(&mount_lock);
1288 path->dentry = mountpoint;
1290 path->mnt = &parent->mnt;
1293 EXPORT_SYMBOL(follow_up);
1295 static bool choose_mountpoint_rcu(struct mount *m, const struct path *root,
1296 struct path *path, unsigned *seqp)
1298 while (mnt_has_parent(m)) {
1299 struct dentry *mountpoint = m->mnt_mountpoint;
1302 if (unlikely(root->dentry == mountpoint &&
1303 root->mnt == &m->mnt))
1305 if (mountpoint != m->mnt.mnt_root) {
1306 path->mnt = &m->mnt;
1307 path->dentry = mountpoint;
1308 *seqp = read_seqcount_begin(&mountpoint->d_seq);
1315 static bool choose_mountpoint(struct mount *m, const struct path *root,
1322 unsigned seq, mseq = read_seqbegin(&mount_lock);
1324 found = choose_mountpoint_rcu(m, root, path, &seq);
1325 if (unlikely(!found)) {
1326 if (!read_seqretry(&mount_lock, mseq))
1329 if (likely(__legitimize_path(path, seq, mseq)))
1341 * Perform an automount
1342 * - return -EISDIR to tell follow_managed() to stop and return the path we
1345 static int follow_automount(struct path *path, int *count, unsigned lookup_flags)
1347 struct dentry *dentry = path->dentry;
1349 /* We don't want to mount if someone's just doing a stat -
1350 * unless they're stat'ing a directory and appended a '/' to
1353 * We do, however, want to mount if someone wants to open or
1354 * create a file of any type under the mountpoint, wants to
1355 * traverse through the mountpoint or wants to open the
1356 * mounted directory. Also, autofs may mark negative dentries
1357 * as being automount points. These will need the attentions
1358 * of the daemon to instantiate them before they can be used.
1360 if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1361 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1365 if (count && (*count)++ >= MAXSYMLINKS)
1368 return finish_automount(dentry->d_op->d_automount(path), path);
1372 * mount traversal - out-of-line part. One note on ->d_flags accesses -
1373 * dentries are pinned but not locked here, so negative dentry can go
1374 * positive right under us. Use of smp_load_acquire() provides a barrier
1375 * sufficient for ->d_inode and ->d_flags consistency.
1377 static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped,
1378 int *count, unsigned lookup_flags)
1380 struct vfsmount *mnt = path->mnt;
1381 bool need_mntput = false;
1384 while (flags & DCACHE_MANAGED_DENTRY) {
1385 /* Allow the filesystem to manage the transit without i_mutex
1387 if (flags & DCACHE_MANAGE_TRANSIT) {
1388 ret = path->dentry->d_op->d_manage(path, false);
1389 flags = smp_load_acquire(&path->dentry->d_flags);
1394 if (flags & DCACHE_MOUNTED) { // something's mounted on it..
1395 struct vfsmount *mounted = lookup_mnt(path);
1396 if (mounted) { // ... in our namespace
1400 path->mnt = mounted;
1401 path->dentry = dget(mounted->mnt_root);
1402 // here we know it's positive
1403 flags = path->dentry->d_flags;
1409 if (!(flags & DCACHE_NEED_AUTOMOUNT))
1412 // uncovered automount point
1413 ret = follow_automount(path, count, lookup_flags);
1414 flags = smp_load_acquire(&path->dentry->d_flags);
1421 // possible if you race with several mount --move
1422 if (need_mntput && path->mnt == mnt)
1424 if (!ret && unlikely(d_flags_negative(flags)))
1426 *jumped = need_mntput;
1430 static inline int traverse_mounts(struct path *path, bool *jumped,
1431 int *count, unsigned lookup_flags)
1433 unsigned flags = smp_load_acquire(&path->dentry->d_flags);
1436 if (likely(!(flags & DCACHE_MANAGED_DENTRY))) {
1438 if (unlikely(d_flags_negative(flags)))
1442 return __traverse_mounts(path, flags, jumped, count, lookup_flags);
1445 int follow_down_one(struct path *path)
1447 struct vfsmount *mounted;
1449 mounted = lookup_mnt(path);
1453 path->mnt = mounted;
1454 path->dentry = dget(mounted->mnt_root);
1459 EXPORT_SYMBOL(follow_down_one);
1462 * Follow down to the covering mount currently visible to userspace. At each
1463 * point, the filesystem owning that dentry may be queried as to whether the
1464 * caller is permitted to proceed or not.
1466 int follow_down(struct path *path, unsigned int flags)
1468 struct vfsmount *mnt = path->mnt;
1470 int ret = traverse_mounts(path, &jumped, NULL, flags);
1472 if (path->mnt != mnt)
1476 EXPORT_SYMBOL(follow_down);
1479 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1480 * we meet a managed dentry that would need blocking.
1482 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path)
1484 struct dentry *dentry = path->dentry;
1485 unsigned int flags = dentry->d_flags;
1487 if (likely(!(flags & DCACHE_MANAGED_DENTRY)))
1490 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1495 * Don't forget we might have a non-mountpoint managed dentry
1496 * that wants to block transit.
1498 if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) {
1499 int res = dentry->d_op->d_manage(path, true);
1501 return res == -EISDIR;
1502 flags = dentry->d_flags;
1505 if (flags & DCACHE_MOUNTED) {
1506 struct mount *mounted = __lookup_mnt(path->mnt, dentry);
1508 path->mnt = &mounted->mnt;
1509 dentry = path->dentry = mounted->mnt.mnt_root;
1510 nd->state |= ND_JUMPED;
1511 nd->next_seq = read_seqcount_begin(&dentry->d_seq);
1512 flags = dentry->d_flags;
1513 // makes sure that non-RCU pathwalk could reach
1515 if (read_seqretry(&mount_lock, nd->m_seq))
1519 if (read_seqretry(&mount_lock, nd->m_seq))
1522 return !(flags & DCACHE_NEED_AUTOMOUNT);
1526 static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
1532 path->mnt = nd->path.mnt;
1533 path->dentry = dentry;
1534 if (nd->flags & LOOKUP_RCU) {
1535 unsigned int seq = nd->next_seq;
1536 if (likely(__follow_mount_rcu(nd, path)))
1538 // *path and nd->next_seq might've been clobbered
1539 path->mnt = nd->path.mnt;
1540 path->dentry = dentry;
1542 if (!try_to_unlazy_next(nd, dentry))
1545 ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags);
1547 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1550 nd->state |= ND_JUMPED;
1552 if (unlikely(ret)) {
1554 if (path->mnt != nd->path.mnt)
1561 * This looks up the name in dcache and possibly revalidates the found dentry.
1562 * NULL is returned if the dentry does not exist in the cache.
1564 static struct dentry *lookup_dcache(const struct qstr *name,
1568 struct dentry *dentry = d_lookup(dir, name);
1570 int error = d_revalidate(dentry, flags);
1571 if (unlikely(error <= 0)) {
1573 d_invalidate(dentry);
1575 return ERR_PTR(error);
1582 * Parent directory has inode locked exclusive. This is one
1583 * and only case when ->lookup() gets called on non in-lookup
1584 * dentries - as the matter of fact, this only gets called
1585 * when directory is guaranteed to have no in-lookup children
1588 struct dentry *lookup_one_qstr_excl(const struct qstr *name,
1589 struct dentry *base,
1592 struct dentry *dentry = lookup_dcache(name, base, flags);
1594 struct inode *dir = base->d_inode;
1599 /* Don't create child dentry for a dead directory. */
1600 if (unlikely(IS_DEADDIR(dir)))
1601 return ERR_PTR(-ENOENT);
1603 dentry = d_alloc(base, name);
1604 if (unlikely(!dentry))
1605 return ERR_PTR(-ENOMEM);
1607 old = dir->i_op->lookup(dir, dentry, flags);
1608 if (unlikely(old)) {
1614 EXPORT_SYMBOL(lookup_one_qstr_excl);
1616 static struct dentry *lookup_fast(struct nameidata *nd)
1618 struct dentry *dentry, *parent = nd->path.dentry;
1622 * Rename seqlock is not required here because in the off chance
1623 * of a false negative due to a concurrent rename, the caller is
1624 * going to fall back to non-racy lookup.
1626 if (nd->flags & LOOKUP_RCU) {
1627 dentry = __d_lookup_rcu(parent, &nd->last, &nd->next_seq);
1628 if (unlikely(!dentry)) {
1629 if (!try_to_unlazy(nd))
1630 return ERR_PTR(-ECHILD);
1635 * This sequence count validates that the parent had no
1636 * changes while we did the lookup of the dentry above.
1638 if (read_seqcount_retry(&parent->d_seq, nd->seq))
1639 return ERR_PTR(-ECHILD);
1641 status = d_revalidate(dentry, nd->flags);
1642 if (likely(status > 0))
1644 if (!try_to_unlazy_next(nd, dentry))
1645 return ERR_PTR(-ECHILD);
1646 if (status == -ECHILD)
1647 /* we'd been told to redo it in non-rcu mode */
1648 status = d_revalidate(dentry, nd->flags);
1650 dentry = __d_lookup(parent, &nd->last);
1651 if (unlikely(!dentry))
1653 status = d_revalidate(dentry, nd->flags);
1655 if (unlikely(status <= 0)) {
1657 d_invalidate(dentry);
1659 return ERR_PTR(status);
1664 /* Fast lookup failed, do it the slow way */
1665 static struct dentry *__lookup_slow(const struct qstr *name,
1669 struct dentry *dentry, *old;
1670 struct inode *inode = dir->d_inode;
1671 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1673 /* Don't go there if it's already dead */
1674 if (unlikely(IS_DEADDIR(inode)))
1675 return ERR_PTR(-ENOENT);
1677 dentry = d_alloc_parallel(dir, name, &wq);
1680 if (unlikely(!d_in_lookup(dentry))) {
1681 int error = d_revalidate(dentry, flags);
1682 if (unlikely(error <= 0)) {
1684 d_invalidate(dentry);
1689 dentry = ERR_PTR(error);
1692 old = inode->i_op->lookup(inode, dentry, flags);
1693 d_lookup_done(dentry);
1694 if (unlikely(old)) {
1702 static struct dentry *lookup_slow(const struct qstr *name,
1706 struct inode *inode = dir->d_inode;
1708 inode_lock_shared(inode);
1709 res = __lookup_slow(name, dir, flags);
1710 inode_unlock_shared(inode);
1714 static inline int may_lookup(struct mnt_idmap *idmap,
1715 struct nameidata *nd)
1717 if (nd->flags & LOOKUP_RCU) {
1718 int err = inode_permission(idmap, nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1719 if (!err) // success, keep going
1721 if (!try_to_unlazy(nd))
1722 return -ECHILD; // redo it all non-lazy
1723 if (err != -ECHILD) // hard error
1726 return inode_permission(idmap, nd->inode, MAY_EXEC);
1729 static int reserve_stack(struct nameidata *nd, struct path *link)
1731 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS))
1734 if (likely(nd->depth != EMBEDDED_LEVELS))
1736 if (likely(nd->stack != nd->internal))
1738 if (likely(nd_alloc_stack(nd)))
1741 if (nd->flags & LOOKUP_RCU) {
1742 // we need to grab link before we do unlazy. And we can't skip
1743 // unlazy even if we fail to grab the link - cleanup needs it
1744 bool grabbed_link = legitimize_path(nd, link, nd->next_seq);
1746 if (!try_to_unlazy(nd) || !grabbed_link)
1749 if (nd_alloc_stack(nd))
1755 enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4};
1757 static const char *pick_link(struct nameidata *nd, struct path *link,
1758 struct inode *inode, int flags)
1762 int error = reserve_stack(nd, link);
1764 if (unlikely(error)) {
1765 if (!(nd->flags & LOOKUP_RCU))
1767 return ERR_PTR(error);
1769 last = nd->stack + nd->depth++;
1771 clear_delayed_call(&last->done);
1772 last->seq = nd->next_seq;
1774 if (flags & WALK_TRAILING) {
1775 error = may_follow_link(nd, inode);
1776 if (unlikely(error))
1777 return ERR_PTR(error);
1780 if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS) ||
1781 unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW))
1782 return ERR_PTR(-ELOOP);
1784 if (!(nd->flags & LOOKUP_RCU)) {
1785 touch_atime(&last->link);
1787 } else if (atime_needs_update(&last->link, inode)) {
1788 if (!try_to_unlazy(nd))
1789 return ERR_PTR(-ECHILD);
1790 touch_atime(&last->link);
1793 error = security_inode_follow_link(link->dentry, inode,
1794 nd->flags & LOOKUP_RCU);
1795 if (unlikely(error))
1796 return ERR_PTR(error);
1798 res = READ_ONCE(inode->i_link);
1800 const char * (*get)(struct dentry *, struct inode *,
1801 struct delayed_call *);
1802 get = inode->i_op->get_link;
1803 if (nd->flags & LOOKUP_RCU) {
1804 res = get(NULL, inode, &last->done);
1805 if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
1806 res = get(link->dentry, inode, &last->done);
1808 res = get(link->dentry, inode, &last->done);
1816 error = nd_jump_root(nd);
1817 if (unlikely(error))
1818 return ERR_PTR(error);
1819 while (unlikely(*++res == '/'))
1824 all_done: // pure jump
1830 * Do we need to follow links? We _really_ want to be able
1831 * to do this check without having to look at inode->i_op,
1832 * so we keep a cache of "no, this doesn't need follow_link"
1833 * for the common case.
1835 * NOTE: dentry must be what nd->next_seq had been sampled from.
1837 static const char *step_into(struct nameidata *nd, int flags,
1838 struct dentry *dentry)
1841 struct inode *inode;
1842 int err = handle_mounts(nd, dentry, &path);
1845 return ERR_PTR(err);
1846 inode = path.dentry->d_inode;
1847 if (likely(!d_is_symlink(path.dentry)) ||
1848 ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) ||
1849 (flags & WALK_NOFOLLOW)) {
1850 /* not a symlink or should not follow */
1851 if (nd->flags & LOOKUP_RCU) {
1852 if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))
1853 return ERR_PTR(-ECHILD);
1854 if (unlikely(!inode))
1855 return ERR_PTR(-ENOENT);
1857 dput(nd->path.dentry);
1858 if (nd->path.mnt != path.mnt)
1859 mntput(nd->path.mnt);
1863 nd->seq = nd->next_seq;
1866 if (nd->flags & LOOKUP_RCU) {
1867 /* make sure that d_is_symlink above matches inode */
1868 if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))
1869 return ERR_PTR(-ECHILD);
1871 if (path.mnt == nd->path.mnt)
1874 return pick_link(nd, &path, inode, flags);
1877 static struct dentry *follow_dotdot_rcu(struct nameidata *nd)
1879 struct dentry *parent, *old;
1881 if (path_equal(&nd->path, &nd->root))
1883 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1886 if (!choose_mountpoint_rcu(real_mount(nd->path.mnt),
1887 &nd->root, &path, &seq))
1889 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1890 return ERR_PTR(-ECHILD);
1892 nd->inode = path.dentry->d_inode;
1894 // makes sure that non-RCU pathwalk could reach this state
1895 if (read_seqretry(&mount_lock, nd->m_seq))
1896 return ERR_PTR(-ECHILD);
1897 /* we know that mountpoint was pinned */
1899 old = nd->path.dentry;
1900 parent = old->d_parent;
1901 nd->next_seq = read_seqcount_begin(&parent->d_seq);
1902 // makes sure that non-RCU pathwalk could reach this state
1903 if (read_seqcount_retry(&old->d_seq, nd->seq))
1904 return ERR_PTR(-ECHILD);
1905 if (unlikely(!path_connected(nd->path.mnt, parent)))
1906 return ERR_PTR(-ECHILD);
1909 if (read_seqretry(&mount_lock, nd->m_seq))
1910 return ERR_PTR(-ECHILD);
1911 if (unlikely(nd->flags & LOOKUP_BENEATH))
1912 return ERR_PTR(-ECHILD);
1913 nd->next_seq = nd->seq;
1914 return nd->path.dentry;
1917 static struct dentry *follow_dotdot(struct nameidata *nd)
1919 struct dentry *parent;
1921 if (path_equal(&nd->path, &nd->root))
1923 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1926 if (!choose_mountpoint(real_mount(nd->path.mnt),
1929 path_put(&nd->path);
1931 nd->inode = path.dentry->d_inode;
1932 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1933 return ERR_PTR(-EXDEV);
1935 /* rare case of legitimate dget_parent()... */
1936 parent = dget_parent(nd->path.dentry);
1937 if (unlikely(!path_connected(nd->path.mnt, parent))) {
1939 return ERR_PTR(-ENOENT);
1944 if (unlikely(nd->flags & LOOKUP_BENEATH))
1945 return ERR_PTR(-EXDEV);
1946 return dget(nd->path.dentry);
1949 static const char *handle_dots(struct nameidata *nd, int type)
1951 if (type == LAST_DOTDOT) {
1952 const char *error = NULL;
1953 struct dentry *parent;
1955 if (!nd->root.mnt) {
1956 error = ERR_PTR(set_root(nd));
1960 if (nd->flags & LOOKUP_RCU)
1961 parent = follow_dotdot_rcu(nd);
1963 parent = follow_dotdot(nd);
1965 return ERR_CAST(parent);
1966 error = step_into(nd, WALK_NOFOLLOW, parent);
1967 if (unlikely(error))
1970 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
1972 * If there was a racing rename or mount along our
1973 * path, then we can't be sure that ".." hasn't jumped
1974 * above nd->root (and so userspace should retry or use
1978 if (__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq))
1979 return ERR_PTR(-EAGAIN);
1980 if (__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq))
1981 return ERR_PTR(-EAGAIN);
1987 static const char *walk_component(struct nameidata *nd, int flags)
1989 struct dentry *dentry;
1991 * "." and ".." are special - ".." especially so because it has
1992 * to be able to know about the current root directory and
1993 * parent relationships.
1995 if (unlikely(nd->last_type != LAST_NORM)) {
1996 if (!(flags & WALK_MORE) && nd->depth)
1998 return handle_dots(nd, nd->last_type);
2000 dentry = lookup_fast(nd);
2002 return ERR_CAST(dentry);
2003 if (unlikely(!dentry)) {
2004 dentry = lookup_slow(&nd->last, nd->path.dentry, nd->flags);
2006 return ERR_CAST(dentry);
2008 if (!(flags & WALK_MORE) && nd->depth)
2010 return step_into(nd, flags, dentry);
2014 * We can do the critical dentry name comparison and hashing
2015 * operations one word at a time, but we are limited to:
2017 * - Architectures with fast unaligned word accesses. We could
2018 * do a "get_unaligned()" if this helps and is sufficiently
2021 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
2022 * do not trap on the (extremely unlikely) case of a page
2023 * crossing operation.
2025 * - Furthermore, we need an efficient 64-bit compile for the
2026 * 64-bit case in order to generate the "number of bytes in
2027 * the final mask". Again, that could be replaced with a
2028 * efficient population count instruction or similar.
2030 #ifdef CONFIG_DCACHE_WORD_ACCESS
2032 #include <asm/word-at-a-time.h>
2036 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
2038 #elif defined(CONFIG_64BIT)
2040 * Register pressure in the mixing function is an issue, particularly
2041 * on 32-bit x86, but almost any function requires one state value and
2042 * one temporary. Instead, use a function designed for two state values
2043 * and no temporaries.
2045 * This function cannot create a collision in only two iterations, so
2046 * we have two iterations to achieve avalanche. In those two iterations,
2047 * we have six layers of mixing, which is enough to spread one bit's
2048 * influence out to 2^6 = 64 state bits.
2050 * Rotate constants are scored by considering either 64 one-bit input
2051 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
2052 * probability of that delta causing a change to each of the 128 output
2053 * bits, using a sample of random initial states.
2055 * The Shannon entropy of the computed probabilities is then summed
2056 * to produce a score. Ideally, any input change has a 50% chance of
2057 * toggling any given output bit.
2059 * Mixing scores (in bits) for (12,45):
2060 * Input delta: 1-bit 2-bit
2061 * 1 round: 713.3 42542.6
2062 * 2 rounds: 2753.7 140389.8
2063 * 3 rounds: 5954.1 233458.2
2064 * 4 rounds: 7862.6 256672.2
2065 * Perfect: 8192 258048
2066 * (64*128) (64*63/2 * 128)
2068 #define HASH_MIX(x, y, a) \
2070 y ^= x, x = rol64(x,12),\
2071 x += y, y = rol64(y,45),\
2075 * Fold two longs into one 32-bit hash value. This must be fast, but
2076 * latency isn't quite as critical, as there is a fair bit of additional
2077 * work done before the hash value is used.
2079 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2081 y ^= x * GOLDEN_RATIO_64;
2082 y *= GOLDEN_RATIO_64;
2086 #else /* 32-bit case */
2089 * Mixing scores (in bits) for (7,20):
2090 * Input delta: 1-bit 2-bit
2091 * 1 round: 330.3 9201.6
2092 * 2 rounds: 1246.4 25475.4
2093 * 3 rounds: 1907.1 31295.1
2094 * 4 rounds: 2042.3 31718.6
2095 * Perfect: 2048 31744
2096 * (32*64) (32*31/2 * 64)
2098 #define HASH_MIX(x, y, a) \
2100 y ^= x, x = rol32(x, 7),\
2101 x += y, y = rol32(y,20),\
2104 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2106 /* Use arch-optimized multiply if one exists */
2107 return __hash_32(y ^ __hash_32(x));
2113 * Return the hash of a string of known length. This is carfully
2114 * designed to match hash_name(), which is the more critical function.
2115 * In particular, we must end by hashing a final word containing 0..7
2116 * payload bytes, to match the way that hash_name() iterates until it
2117 * finds the delimiter after the name.
2119 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2121 unsigned long a, x = 0, y = (unsigned long)salt;
2126 a = load_unaligned_zeropad(name);
2127 if (len < sizeof(unsigned long))
2130 name += sizeof(unsigned long);
2131 len -= sizeof(unsigned long);
2133 x ^= a & bytemask_from_count(len);
2135 return fold_hash(x, y);
2137 EXPORT_SYMBOL(full_name_hash);
2139 /* Return the "hash_len" (hash and length) of a null-terminated string */
2140 u64 hashlen_string(const void *salt, const char *name)
2142 unsigned long a = 0, x = 0, y = (unsigned long)salt;
2143 unsigned long adata, mask, len;
2144 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2151 len += sizeof(unsigned long);
2153 a = load_unaligned_zeropad(name+len);
2154 } while (!has_zero(a, &adata, &constants));
2156 adata = prep_zero_mask(a, adata, &constants);
2157 mask = create_zero_mask(adata);
2158 x ^= a & zero_bytemask(mask);
2160 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2162 EXPORT_SYMBOL(hashlen_string);
2165 * Calculate the length and hash of the path component, and
2166 * return the "hash_len" as the result.
2168 static inline u64 hash_name(const void *salt, const char *name)
2170 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
2171 unsigned long adata, bdata, mask, len;
2172 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2179 len += sizeof(unsigned long);
2181 a = load_unaligned_zeropad(name+len);
2182 b = a ^ REPEAT_BYTE('/');
2183 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
2185 adata = prep_zero_mask(a, adata, &constants);
2186 bdata = prep_zero_mask(b, bdata, &constants);
2187 mask = create_zero_mask(adata | bdata);
2188 x ^= a & zero_bytemask(mask);
2190 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2193 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
2195 /* Return the hash of a string of known length */
2196 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2198 unsigned long hash = init_name_hash(salt);
2200 hash = partial_name_hash((unsigned char)*name++, hash);
2201 return end_name_hash(hash);
2203 EXPORT_SYMBOL(full_name_hash);
2205 /* Return the "hash_len" (hash and length) of a null-terminated string */
2206 u64 hashlen_string(const void *salt, const char *name)
2208 unsigned long hash = init_name_hash(salt);
2209 unsigned long len = 0, c;
2211 c = (unsigned char)*name;
2214 hash = partial_name_hash(c, hash);
2215 c = (unsigned char)name[len];
2217 return hashlen_create(end_name_hash(hash), len);
2219 EXPORT_SYMBOL(hashlen_string);
2222 * We know there's a real path component here of at least
2225 static inline u64 hash_name(const void *salt, const char *name)
2227 unsigned long hash = init_name_hash(salt);
2228 unsigned long len = 0, c;
2230 c = (unsigned char)*name;
2233 hash = partial_name_hash(c, hash);
2234 c = (unsigned char)name[len];
2235 } while (c && c != '/');
2236 return hashlen_create(end_name_hash(hash), len);
2243 * This is the basic name resolution function, turning a pathname into
2244 * the final dentry. We expect 'base' to be positive and a directory.
2246 * Returns 0 and nd will have valid dentry and mnt on success.
2247 * Returns error and drops reference to input namei data on failure.
2249 static int link_path_walk(const char *name, struct nameidata *nd)
2251 int depth = 0; // depth <= nd->depth
2254 nd->last_type = LAST_ROOT;
2255 nd->flags |= LOOKUP_PARENT;
2257 return PTR_ERR(name);
2261 nd->dir_mode = 0; // short-circuit the 'hardening' idiocy
2265 /* At this point we know we have a real path component. */
2267 struct mnt_idmap *idmap;
2272 idmap = mnt_idmap(nd->path.mnt);
2273 err = may_lookup(idmap, nd);
2277 hash_len = hash_name(nd->path.dentry, name);
2280 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2282 if (name[1] == '.') {
2284 nd->state |= ND_JUMPED;
2290 if (likely(type == LAST_NORM)) {
2291 struct dentry *parent = nd->path.dentry;
2292 nd->state &= ~ND_JUMPED;
2293 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2294 struct qstr this = { { .hash_len = hash_len }, .name = name };
2295 err = parent->d_op->d_hash(parent, &this);
2298 hash_len = this.hash_len;
2303 nd->last.hash_len = hash_len;
2304 nd->last.name = name;
2305 nd->last_type = type;
2307 name += hashlen_len(hash_len);
2311 * If it wasn't NUL, we know it was '/'. Skip that
2312 * slash, and continue until no more slashes.
2316 } while (unlikely(*name == '/'));
2317 if (unlikely(!*name)) {
2319 /* pathname or trailing symlink, done */
2321 nd->dir_vfsuid = i_uid_into_vfsuid(idmap, nd->inode);
2322 nd->dir_mode = nd->inode->i_mode;
2323 nd->flags &= ~LOOKUP_PARENT;
2326 /* last component of nested symlink */
2327 name = nd->stack[--depth].name;
2328 link = walk_component(nd, 0);
2330 /* not the last component */
2331 link = walk_component(nd, WALK_MORE);
2333 if (unlikely(link)) {
2335 return PTR_ERR(link);
2336 /* a symlink to follow */
2337 nd->stack[depth++].name = name;
2341 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2342 if (nd->flags & LOOKUP_RCU) {
2343 if (!try_to_unlazy(nd))
2351 /* must be paired with terminate_walk() */
2352 static const char *path_init(struct nameidata *nd, unsigned flags)
2355 const char *s = nd->name->name;
2357 /* LOOKUP_CACHED requires RCU, ask caller to retry */
2358 if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)
2359 return ERR_PTR(-EAGAIN);
2362 flags &= ~LOOKUP_RCU;
2363 if (flags & LOOKUP_RCU)
2366 nd->seq = nd->next_seq = 0;
2369 nd->state |= ND_JUMPED;
2371 nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount);
2372 nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount);
2375 if (nd->state & ND_ROOT_PRESET) {
2376 struct dentry *root = nd->root.dentry;
2377 struct inode *inode = root->d_inode;
2378 if (*s && unlikely(!d_can_lookup(root)))
2379 return ERR_PTR(-ENOTDIR);
2380 nd->path = nd->root;
2382 if (flags & LOOKUP_RCU) {
2383 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2384 nd->root_seq = nd->seq;
2386 path_get(&nd->path);
2391 nd->root.mnt = NULL;
2393 /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */
2394 if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) {
2395 error = nd_jump_root(nd);
2396 if (unlikely(error))
2397 return ERR_PTR(error);
2401 /* Relative pathname -- get the starting-point it is relative to. */
2402 if (nd->dfd == AT_FDCWD) {
2403 if (flags & LOOKUP_RCU) {
2404 struct fs_struct *fs = current->fs;
2408 seq = read_seqcount_begin(&fs->seq);
2410 nd->inode = nd->path.dentry->d_inode;
2411 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2412 } while (read_seqcount_retry(&fs->seq, seq));
2414 get_fs_pwd(current->fs, &nd->path);
2415 nd->inode = nd->path.dentry->d_inode;
2418 /* Caller must check execute permissions on the starting path component */
2419 struct fd f = fdget_raw(nd->dfd);
2420 struct dentry *dentry;
2423 return ERR_PTR(-EBADF);
2425 dentry = f.file->f_path.dentry;
2427 if (*s && unlikely(!d_can_lookup(dentry))) {
2429 return ERR_PTR(-ENOTDIR);
2432 nd->path = f.file->f_path;
2433 if (flags & LOOKUP_RCU) {
2434 nd->inode = nd->path.dentry->d_inode;
2435 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2437 path_get(&nd->path);
2438 nd->inode = nd->path.dentry->d_inode;
2443 /* For scoped-lookups we need to set the root to the dirfd as well. */
2444 if (flags & LOOKUP_IS_SCOPED) {
2445 nd->root = nd->path;
2446 if (flags & LOOKUP_RCU) {
2447 nd->root_seq = nd->seq;
2449 path_get(&nd->root);
2450 nd->state |= ND_ROOT_GRABBED;
2456 static inline const char *lookup_last(struct nameidata *nd)
2458 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2459 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2461 return walk_component(nd, WALK_TRAILING);
2464 static int handle_lookup_down(struct nameidata *nd)
2466 if (!(nd->flags & LOOKUP_RCU))
2467 dget(nd->path.dentry);
2468 nd->next_seq = nd->seq;
2469 return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry));
2472 /* Returns 0 and nd will be valid on success; Returns error, otherwise. */
2473 static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2475 const char *s = path_init(nd, flags);
2478 if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) {
2479 err = handle_lookup_down(nd);
2480 if (unlikely(err < 0))
2484 while (!(err = link_path_walk(s, nd)) &&
2485 (s = lookup_last(nd)) != NULL)
2487 if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
2488 err = handle_lookup_down(nd);
2489 nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please...
2492 err = complete_walk(nd);
2494 if (!err && nd->flags & LOOKUP_DIRECTORY)
2495 if (!d_can_lookup(nd->path.dentry))
2499 nd->path.mnt = NULL;
2500 nd->path.dentry = NULL;
2506 int filename_lookup(int dfd, struct filename *name, unsigned flags,
2507 struct path *path, struct path *root)
2510 struct nameidata nd;
2512 return PTR_ERR(name);
2513 set_nameidata(&nd, dfd, name, root);
2514 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2515 if (unlikely(retval == -ECHILD))
2516 retval = path_lookupat(&nd, flags, path);
2517 if (unlikely(retval == -ESTALE))
2518 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2520 if (likely(!retval))
2521 audit_inode(name, path->dentry,
2522 flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0);
2523 restore_nameidata();
2527 /* Returns 0 and nd will be valid on success; Returns error, otherwise. */
2528 static int path_parentat(struct nameidata *nd, unsigned flags,
2529 struct path *parent)
2531 const char *s = path_init(nd, flags);
2532 int err = link_path_walk(s, nd);
2534 err = complete_walk(nd);
2537 nd->path.mnt = NULL;
2538 nd->path.dentry = NULL;
2544 /* Note: this does not consume "name" */
2545 static int __filename_parentat(int dfd, struct filename *name,
2546 unsigned int flags, struct path *parent,
2547 struct qstr *last, int *type,
2548 const struct path *root)
2551 struct nameidata nd;
2554 return PTR_ERR(name);
2555 set_nameidata(&nd, dfd, name, root);
2556 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2557 if (unlikely(retval == -ECHILD))
2558 retval = path_parentat(&nd, flags, parent);
2559 if (unlikely(retval == -ESTALE))
2560 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2561 if (likely(!retval)) {
2563 *type = nd.last_type;
2564 audit_inode(name, parent->dentry, AUDIT_INODE_PARENT);
2566 restore_nameidata();
2570 static int filename_parentat(int dfd, struct filename *name,
2571 unsigned int flags, struct path *parent,
2572 struct qstr *last, int *type)
2574 return __filename_parentat(dfd, name, flags, parent, last, type, NULL);
2577 /* does lookup, returns the object with parent locked */
2578 static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct path *path)
2584 error = filename_parentat(dfd, name, 0, path, &last, &type);
2586 return ERR_PTR(error);
2587 if (unlikely(type != LAST_NORM)) {
2589 return ERR_PTR(-EINVAL);
2591 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2592 d = lookup_one_qstr_excl(&last, path->dentry, 0);
2594 inode_unlock(path->dentry->d_inode);
2600 struct dentry *kern_path_locked(const char *name, struct path *path)
2602 struct filename *filename = getname_kernel(name);
2603 struct dentry *res = __kern_path_locked(AT_FDCWD, filename, path);
2609 struct dentry *user_path_locked_at(int dfd, const char __user *name, struct path *path)
2611 struct filename *filename = getname(name);
2612 struct dentry *res = __kern_path_locked(dfd, filename, path);
2617 EXPORT_SYMBOL(user_path_locked_at);
2619 int kern_path(const char *name, unsigned int flags, struct path *path)
2621 struct filename *filename = getname_kernel(name);
2622 int ret = filename_lookup(AT_FDCWD, filename, flags, path, NULL);
2628 EXPORT_SYMBOL(kern_path);
2631 * vfs_path_parent_lookup - lookup a parent path relative to a dentry-vfsmount pair
2632 * @filename: filename structure
2633 * @flags: lookup flags
2634 * @parent: pointer to struct path to fill
2635 * @last: last component
2636 * @type: type of the last component
2637 * @root: pointer to struct path of the base directory
2639 int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
2640 struct path *parent, struct qstr *last, int *type,
2641 const struct path *root)
2643 return __filename_parentat(AT_FDCWD, filename, flags, parent, last,
2646 EXPORT_SYMBOL(vfs_path_parent_lookup);
2649 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2650 * @dentry: pointer to dentry of the base directory
2651 * @mnt: pointer to vfs mount of the base directory
2652 * @name: pointer to file name
2653 * @flags: lookup flags
2654 * @path: pointer to struct path to fill
2656 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2657 const char *name, unsigned int flags,
2660 struct filename *filename;
2661 struct path root = {.mnt = mnt, .dentry = dentry};
2664 filename = getname_kernel(name);
2665 /* the first argument of filename_lookup() is ignored with root */
2666 ret = filename_lookup(AT_FDCWD, filename, flags, path, &root);
2670 EXPORT_SYMBOL(vfs_path_lookup);
2672 static int lookup_one_common(struct mnt_idmap *idmap,
2673 const char *name, struct dentry *base, int len,
2678 this->hash = full_name_hash(base, name, len);
2682 if (is_dot_dotdot(name, len))
2686 unsigned int c = *(const unsigned char *)name++;
2687 if (c == '/' || c == '\0')
2691 * See if the low-level filesystem might want
2692 * to use its own hash..
2694 if (base->d_flags & DCACHE_OP_HASH) {
2695 int err = base->d_op->d_hash(base, this);
2700 return inode_permission(idmap, base->d_inode, MAY_EXEC);
2704 * try_lookup_one_len - filesystem helper to lookup single pathname component
2705 * @name: pathname component to lookup
2706 * @base: base directory to lookup from
2707 * @len: maximum length @len should be interpreted to
2709 * Look up a dentry by name in the dcache, returning NULL if it does not
2710 * currently exist. The function does not try to create a dentry.
2712 * Note that this routine is purely a helper for filesystem usage and should
2713 * not be called by generic code.
2715 * The caller must hold base->i_mutex.
2717 struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len)
2722 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2724 err = lookup_one_common(&nop_mnt_idmap, name, base, len, &this);
2726 return ERR_PTR(err);
2728 return lookup_dcache(&this, base, 0);
2730 EXPORT_SYMBOL(try_lookup_one_len);
2733 * lookup_one_len - filesystem helper to lookup single pathname component
2734 * @name: pathname component to lookup
2735 * @base: base directory to lookup from
2736 * @len: maximum length @len should be interpreted to
2738 * Note that this routine is purely a helper for filesystem usage and should
2739 * not be called by generic code.
2741 * The caller must hold base->i_mutex.
2743 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2745 struct dentry *dentry;
2749 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2751 err = lookup_one_common(&nop_mnt_idmap, name, base, len, &this);
2753 return ERR_PTR(err);
2755 dentry = lookup_dcache(&this, base, 0);
2756 return dentry ? dentry : __lookup_slow(&this, base, 0);
2758 EXPORT_SYMBOL(lookup_one_len);
2761 * lookup_one - filesystem helper to lookup single pathname component
2762 * @idmap: idmap of the mount the lookup is performed from
2763 * @name: pathname component to lookup
2764 * @base: base directory to lookup from
2765 * @len: maximum length @len should be interpreted to
2767 * Note that this routine is purely a helper for filesystem usage and should
2768 * not be called by generic code.
2770 * The caller must hold base->i_mutex.
2772 struct dentry *lookup_one(struct mnt_idmap *idmap, const char *name,
2773 struct dentry *base, int len)
2775 struct dentry *dentry;
2779 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2781 err = lookup_one_common(idmap, name, base, len, &this);
2783 return ERR_PTR(err);
2785 dentry = lookup_dcache(&this, base, 0);
2786 return dentry ? dentry : __lookup_slow(&this, base, 0);
2788 EXPORT_SYMBOL(lookup_one);
2791 * lookup_one_unlocked - filesystem helper to lookup single pathname component
2792 * @idmap: idmap of the mount the lookup is performed from
2793 * @name: pathname component to lookup
2794 * @base: base directory to lookup from
2795 * @len: maximum length @len should be interpreted to
2797 * Note that this routine is purely a helper for filesystem usage and should
2798 * not be called by generic code.
2800 * Unlike lookup_one_len, it should be called without the parent
2801 * i_mutex held, and will take the i_mutex itself if necessary.
2803 struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
2804 const char *name, struct dentry *base,
2811 err = lookup_one_common(idmap, name, base, len, &this);
2813 return ERR_PTR(err);
2815 ret = lookup_dcache(&this, base, 0);
2817 ret = lookup_slow(&this, base, 0);
2820 EXPORT_SYMBOL(lookup_one_unlocked);
2823 * lookup_one_positive_unlocked - filesystem helper to lookup single
2824 * pathname component
2825 * @idmap: idmap of the mount the lookup is performed from
2826 * @name: pathname component to lookup
2827 * @base: base directory to lookup from
2828 * @len: maximum length @len should be interpreted to
2830 * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns
2831 * known positive or ERR_PTR(). This is what most of the users want.
2833 * Note that pinned negative with unlocked parent _can_ become positive at any
2834 * time, so callers of lookup_one_unlocked() need to be very careful; pinned
2835 * positives have >d_inode stable, so this one avoids such problems.
2837 * Note that this routine is purely a helper for filesystem usage and should
2838 * not be called by generic code.
2840 * The helper should be called without i_mutex held.
2842 struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
2844 struct dentry *base, int len)
2846 struct dentry *ret = lookup_one_unlocked(idmap, name, base, len);
2848 if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
2850 ret = ERR_PTR(-ENOENT);
2854 EXPORT_SYMBOL(lookup_one_positive_unlocked);
2857 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2858 * @name: pathname component to lookup
2859 * @base: base directory to lookup from
2860 * @len: maximum length @len should be interpreted to
2862 * Note that this routine is purely a helper for filesystem usage and should
2863 * not be called by generic code.
2865 * Unlike lookup_one_len, it should be called without the parent
2866 * i_mutex held, and will take the i_mutex itself if necessary.
2868 struct dentry *lookup_one_len_unlocked(const char *name,
2869 struct dentry *base, int len)
2871 return lookup_one_unlocked(&nop_mnt_idmap, name, base, len);
2873 EXPORT_SYMBOL(lookup_one_len_unlocked);
2876 * Like lookup_one_len_unlocked(), except that it yields ERR_PTR(-ENOENT)
2877 * on negatives. Returns known positive or ERR_PTR(); that's what
2878 * most of the users want. Note that pinned negative with unlocked parent
2879 * _can_ become positive at any time, so callers of lookup_one_len_unlocked()
2880 * need to be very careful; pinned positives have ->d_inode stable, so
2881 * this one avoids such problems.
2883 struct dentry *lookup_positive_unlocked(const char *name,
2884 struct dentry *base, int len)
2886 return lookup_one_positive_unlocked(&nop_mnt_idmap, name, base, len);
2888 EXPORT_SYMBOL(lookup_positive_unlocked);
2890 #ifdef CONFIG_UNIX98_PTYS
2891 int path_pts(struct path *path)
2893 /* Find something mounted on "pts" in the same directory as
2896 struct dentry *parent = dget_parent(path->dentry);
2897 struct dentry *child;
2898 struct qstr this = QSTR_INIT("pts", 3);
2900 if (unlikely(!path_connected(path->mnt, parent))) {
2905 path->dentry = parent;
2906 child = d_hash_and_lookup(parent, &this);
2907 if (IS_ERR_OR_NULL(child))
2910 path->dentry = child;
2912 follow_down(path, 0);
2917 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2918 struct path *path, int *empty)
2920 struct filename *filename = getname_flags(name, flags, empty);
2921 int ret = filename_lookup(dfd, filename, flags, path, NULL);
2926 EXPORT_SYMBOL(user_path_at_empty);
2928 int __check_sticky(struct mnt_idmap *idmap, struct inode *dir,
2929 struct inode *inode)
2931 kuid_t fsuid = current_fsuid();
2933 if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), fsuid))
2935 if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, dir), fsuid))
2937 return !capable_wrt_inode_uidgid(idmap, inode, CAP_FOWNER);
2939 EXPORT_SYMBOL(__check_sticky);
2942 * Check whether we can remove a link victim from directory dir, check
2943 * whether the type of victim is right.
2944 * 1. We can't do it if dir is read-only (done in permission())
2945 * 2. We should have write and exec permissions on dir
2946 * 3. We can't remove anything from append-only dir
2947 * 4. We can't do anything with immutable dir (done in permission())
2948 * 5. If the sticky bit on dir is set we should either
2949 * a. be owner of dir, or
2950 * b. be owner of victim, or
2951 * c. have CAP_FOWNER capability
2952 * 6. If the victim is append-only or immutable we can't do antyhing with
2953 * links pointing to it.
2954 * 7. If the victim has an unknown uid or gid we can't change the inode.
2955 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2956 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2957 * 10. We can't remove a root or mountpoint.
2958 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2959 * nfs_async_unlink().
2961 static int may_delete(struct mnt_idmap *idmap, struct inode *dir,
2962 struct dentry *victim, bool isdir)
2964 struct inode *inode = d_backing_inode(victim);
2967 if (d_is_negative(victim))
2971 BUG_ON(victim->d_parent->d_inode != dir);
2973 /* Inode writeback is not safe when the uid or gid are invalid. */
2974 if (!vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) ||
2975 !vfsgid_valid(i_gid_into_vfsgid(idmap, inode)))
2978 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2980 error = inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
2986 if (check_sticky(idmap, dir, inode) || IS_APPEND(inode) ||
2987 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) ||
2988 HAS_UNMAPPED_ID(idmap, inode))
2991 if (!d_is_dir(victim))
2993 if (IS_ROOT(victim))
2995 } else if (d_is_dir(victim))
2997 if (IS_DEADDIR(dir))
2999 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
3004 /* Check whether we can create an object with dentry child in directory
3006 * 1. We can't do it if child already exists (open has special treatment for
3007 * this case, but since we are inlined it's OK)
3008 * 2. We can't do it if dir is read-only (done in permission())
3009 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
3010 * 4. We should have write and exec permissions on dir
3011 * 5. We can't do it if dir is immutable (done in permission())
3013 static inline int may_create(struct mnt_idmap *idmap,
3014 struct inode *dir, struct dentry *child)
3016 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
3019 if (IS_DEADDIR(dir))
3021 if (!fsuidgid_has_mapping(dir->i_sb, idmap))
3024 return inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
3027 // p1 != p2, both are on the same filesystem, ->s_vfs_rename_mutex is held
3028 static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
3030 struct dentry *p = p1, *q = p2, *r;
3032 while ((r = p->d_parent) != p2 && r != p)
3035 // p is a child of p2 and an ancestor of p1 or p1 itself
3036 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
3037 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT2);
3040 // p is the root of connected component that contains p1
3041 // p2 does not occur on the path from p to p1
3042 while ((r = q->d_parent) != p1 && r != p && r != q)
3045 // q is a child of p1 and an ancestor of p2 or p2 itself
3046 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3047 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
3049 } else if (likely(r == p)) {
3050 // both p2 and p1 are descendents of p
3051 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3052 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
3054 } else { // no common ancestor at the time we'd been called
3055 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
3056 return ERR_PTR(-EXDEV);
3061 * p1 and p2 should be directories on the same fs.
3063 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
3066 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3070 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
3071 return lock_two_directories(p1, p2);
3073 EXPORT_SYMBOL(lock_rename);
3076 * c1 and p2 should be on the same fs.
3078 struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
3080 if (READ_ONCE(c1->d_parent) == p2) {
3082 * hopefully won't need to touch ->s_vfs_rename_mutex at all.
3084 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
3086 * now that p2 is locked, nobody can move in or out of it,
3087 * so the test below is safe.
3089 if (likely(c1->d_parent == p2))
3093 * c1 got moved out of p2 while we'd been taking locks;
3094 * unlock and fall back to slow case.
3096 inode_unlock(p2->d_inode);
3099 mutex_lock(&c1->d_sb->s_vfs_rename_mutex);
3101 * nobody can move out of any directories on this fs.
3103 if (likely(c1->d_parent != p2))
3104 return lock_two_directories(c1->d_parent, p2);
3107 * c1 got moved into p2 while we were taking locks;
3108 * we need p2 locked and ->s_vfs_rename_mutex unlocked,
3109 * for consistency with lock_rename().
3111 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
3112 mutex_unlock(&c1->d_sb->s_vfs_rename_mutex);
3115 EXPORT_SYMBOL(lock_rename_child);
3117 void unlock_rename(struct dentry *p1, struct dentry *p2)
3119 inode_unlock(p1->d_inode);
3121 inode_unlock(p2->d_inode);
3122 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
3125 EXPORT_SYMBOL(unlock_rename);
3128 * vfs_prepare_mode - prepare the mode to be used for a new inode
3129 * @idmap: idmap of the mount the inode was found from
3130 * @dir: parent directory of the new inode
3131 * @mode: mode of the new inode
3132 * @mask_perms: allowed permission by the vfs
3133 * @type: type of file to be created
3135 * This helper consolidates and enforces vfs restrictions on the @mode of a new
3136 * object to be created.
3138 * Umask stripping depends on whether the filesystem supports POSIX ACLs (see
3139 * the kernel documentation for mode_strip_umask()). Moving umask stripping
3140 * after setgid stripping allows the same ordering for both non-POSIX ACL and
3141 * POSIX ACL supporting filesystems.
3143 * Note that it's currently valid for @type to be 0 if a directory is created.
3144 * Filesystems raise that flag individually and we need to check whether each
3145 * filesystem can deal with receiving S_IFDIR from the vfs before we enforce a
3148 * Returns: mode to be passed to the filesystem
3150 static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
3151 const struct inode *dir, umode_t mode,
3152 umode_t mask_perms, umode_t type)
3154 mode = mode_strip_sgid(idmap, dir, mode);
3155 mode = mode_strip_umask(dir, mode);
3158 * Apply the vfs mandated allowed permission mask and set the type of
3159 * file to be created before we call into the filesystem.
3161 mode &= (mask_perms & ~S_IFMT);
3162 mode |= (type & S_IFMT);
3168 * vfs_create - create new file
3169 * @idmap: idmap of the mount the inode was found from
3170 * @dir: inode of @dentry
3171 * @dentry: pointer to dentry of the base directory
3172 * @mode: mode of the new file
3173 * @want_excl: whether the file must not yet exist
3175 * Create a new file.
3177 * If the inode has been found through an idmapped mount the idmap of
3178 * the vfsmount must be passed through @idmap. This function will then take
3179 * care to map the inode according to @idmap before checking permissions.
3180 * On non-idmapped mounts or if permission checking is to be performed on the
3181 * raw inode simply pass @nop_mnt_idmap.
3183 int vfs_create(struct mnt_idmap *idmap, struct inode *dir,
3184 struct dentry *dentry, umode_t mode, bool want_excl)
3188 error = may_create(idmap, dir, dentry);
3192 if (!dir->i_op->create)
3193 return -EACCES; /* shouldn't it be ENOSYS? */
3195 mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
3196 error = security_inode_create(dir, dentry, mode);
3199 error = dir->i_op->create(idmap, dir, dentry, mode, want_excl);
3201 fsnotify_create(dir, dentry);
3204 EXPORT_SYMBOL(vfs_create);
3206 int vfs_mkobj(struct dentry *dentry, umode_t mode,
3207 int (*f)(struct dentry *, umode_t, void *),
3210 struct inode *dir = dentry->d_parent->d_inode;
3211 int error = may_create(&nop_mnt_idmap, dir, dentry);
3217 error = security_inode_create(dir, dentry, mode);
3220 error = f(dentry, mode, arg);
3222 fsnotify_create(dir, dentry);
3225 EXPORT_SYMBOL(vfs_mkobj);
3227 bool may_open_dev(const struct path *path)
3229 return !(path->mnt->mnt_flags & MNT_NODEV) &&
3230 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
3233 static int may_open(struct mnt_idmap *idmap, const struct path *path,
3234 int acc_mode, int flag)
3236 struct dentry *dentry = path->dentry;
3237 struct inode *inode = dentry->d_inode;
3243 switch (inode->i_mode & S_IFMT) {
3247 if (acc_mode & MAY_WRITE)
3249 if (acc_mode & MAY_EXEC)
3254 if (!may_open_dev(path))
3259 if (acc_mode & MAY_EXEC)
3264 if ((acc_mode & MAY_EXEC) && path_noexec(path))
3269 error = inode_permission(idmap, inode, MAY_OPEN | acc_mode);
3274 * An append-only file must be opened in append mode for writing.
3276 if (IS_APPEND(inode)) {
3277 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
3283 /* O_NOATIME can only be set by the owner or superuser */
3284 if (flag & O_NOATIME && !inode_owner_or_capable(idmap, inode))
3290 static int handle_truncate(struct mnt_idmap *idmap, struct file *filp)
3292 const struct path *path = &filp->f_path;
3293 struct inode *inode = path->dentry->d_inode;
3294 int error = get_write_access(inode);
3298 error = security_file_truncate(filp);
3300 error = do_truncate(idmap, path->dentry, 0,
3301 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
3304 put_write_access(inode);
3308 static inline int open_to_namei_flags(int flag)
3310 if ((flag & O_ACCMODE) == 3)
3315 static int may_o_create(struct mnt_idmap *idmap,
3316 const struct path *dir, struct dentry *dentry,
3319 int error = security_path_mknod(dir, dentry, mode, 0);
3323 if (!fsuidgid_has_mapping(dir->dentry->d_sb, idmap))
3326 error = inode_permission(idmap, dir->dentry->d_inode,
3327 MAY_WRITE | MAY_EXEC);
3331 return security_inode_create(dir->dentry->d_inode, dentry, mode);
3335 * Attempt to atomically look up, create and open a file from a negative
3338 * Returns 0 if successful. The file will have been created and attached to
3339 * @file by the filesystem calling finish_open().
3341 * If the file was looked up only or didn't need creating, FMODE_OPENED won't
3342 * be set. The caller will need to perform the open themselves. @path will
3343 * have been updated to point to the new dentry. This may be negative.
3345 * Returns an error code otherwise.
3347 static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
3349 int open_flag, umode_t mode)
3351 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3352 struct inode *dir = nd->path.dentry->d_inode;
3355 if (nd->flags & LOOKUP_DIRECTORY)
3356 open_flag |= O_DIRECTORY;
3358 file->f_path.dentry = DENTRY_NOT_SET;
3359 file->f_path.mnt = nd->path.mnt;
3360 error = dir->i_op->atomic_open(dir, dentry, file,
3361 open_to_namei_flags(open_flag), mode);
3362 d_lookup_done(dentry);
3364 if (file->f_mode & FMODE_OPENED) {
3365 if (unlikely(dentry != file->f_path.dentry)) {
3367 dentry = dget(file->f_path.dentry);
3369 } else if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3372 if (file->f_path.dentry) {
3374 dentry = file->f_path.dentry;
3376 if (unlikely(d_is_negative(dentry)))
3382 dentry = ERR_PTR(error);
3388 * Look up and maybe create and open the last component.
3390 * Must be called with parent locked (exclusive in O_CREAT case).
3392 * Returns 0 on success, that is, if
3393 * the file was successfully atomically created (if necessary) and opened, or
3394 * the file was not completely opened at this time, though lookups and
3395 * creations were performed.
3396 * These case are distinguished by presence of FMODE_OPENED on file->f_mode.
3397 * In the latter case dentry returned in @path might be negative if O_CREAT
3398 * hadn't been specified.
3400 * An error code is returned on failure.
3402 static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
3403 const struct open_flags *op,
3406 struct mnt_idmap *idmap;
3407 struct dentry *dir = nd->path.dentry;
3408 struct inode *dir_inode = dir->d_inode;
3409 int open_flag = op->open_flag;
3410 struct dentry *dentry;
3411 int error, create_error = 0;
3412 umode_t mode = op->mode;
3413 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3415 if (unlikely(IS_DEADDIR(dir_inode)))
3416 return ERR_PTR(-ENOENT);
3418 file->f_mode &= ~FMODE_CREATED;
3419 dentry = d_lookup(dir, &nd->last);
3422 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3426 if (d_in_lookup(dentry))
3429 error = d_revalidate(dentry, nd->flags);
3430 if (likely(error > 0))
3434 d_invalidate(dentry);
3438 if (dentry->d_inode) {
3439 /* Cached positive dentry: will open in f_op->open */
3444 * Checking write permission is tricky, bacuse we don't know if we are
3445 * going to actually need it: O_CREAT opens should work as long as the
3446 * file exists. But checking existence breaks atomicity. The trick is
3447 * to check access and if not granted clear O_CREAT from the flags.
3449 * Another problem is returing the "right" error value (e.g. for an
3450 * O_EXCL open we want to return EEXIST not EROFS).
3452 if (unlikely(!got_write))
3453 open_flag &= ~O_TRUNC;
3454 idmap = mnt_idmap(nd->path.mnt);
3455 if (open_flag & O_CREAT) {
3456 if (open_flag & O_EXCL)
3457 open_flag &= ~O_TRUNC;
3458 mode = vfs_prepare_mode(idmap, dir->d_inode, mode, mode, mode);
3459 if (likely(got_write))
3460 create_error = may_o_create(idmap, &nd->path,
3463 create_error = -EROFS;
3466 open_flag &= ~O_CREAT;
3467 if (dir_inode->i_op->atomic_open) {
3468 dentry = atomic_open(nd, dentry, file, open_flag, mode);
3469 if (unlikely(create_error) && dentry == ERR_PTR(-ENOENT))
3470 dentry = ERR_PTR(create_error);
3474 if (d_in_lookup(dentry)) {
3475 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3477 d_lookup_done(dentry);
3478 if (unlikely(res)) {
3480 error = PTR_ERR(res);
3488 /* Negative dentry, just create the file */
3489 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3490 file->f_mode |= FMODE_CREATED;
3491 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3492 if (!dir_inode->i_op->create) {
3497 error = dir_inode->i_op->create(idmap, dir_inode, dentry,
3498 mode, open_flag & O_EXCL);
3502 if (unlikely(create_error) && !dentry->d_inode) {
3503 error = create_error;
3510 return ERR_PTR(error);
3513 static const char *open_last_lookups(struct nameidata *nd,
3514 struct file *file, const struct open_flags *op)
3516 struct dentry *dir = nd->path.dentry;
3517 int open_flag = op->open_flag;
3518 bool got_write = false;
3519 struct dentry *dentry;
3522 nd->flags |= op->intent;
3524 if (nd->last_type != LAST_NORM) {
3527 return handle_dots(nd, nd->last_type);
3530 if (!(open_flag & O_CREAT)) {
3531 if (nd->last.name[nd->last.len])
3532 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3533 /* we _can_ be in RCU mode here */
3534 dentry = lookup_fast(nd);
3536 return ERR_CAST(dentry);
3540 if (WARN_ON_ONCE(nd->flags & LOOKUP_RCU))
3541 return ERR_PTR(-ECHILD);
3543 /* create side of things */
3544 if (nd->flags & LOOKUP_RCU) {
3545 if (!try_to_unlazy(nd))
3546 return ERR_PTR(-ECHILD);
3548 audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
3549 /* trailing slashes? */
3550 if (unlikely(nd->last.name[nd->last.len]))
3551 return ERR_PTR(-EISDIR);
3554 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3555 got_write = !mnt_want_write(nd->path.mnt);
3557 * do _not_ fail yet - we might not need that or fail with
3558 * a different error; let lookup_open() decide; we'll be
3559 * dropping this one anyway.
3562 if (open_flag & O_CREAT)
3563 inode_lock(dir->d_inode);
3565 inode_lock_shared(dir->d_inode);
3566 dentry = lookup_open(nd, file, op, got_write);
3567 if (!IS_ERR(dentry) && (file->f_mode & FMODE_CREATED))
3568 fsnotify_create(dir->d_inode, dentry);
3569 if (open_flag & O_CREAT)
3570 inode_unlock(dir->d_inode);
3572 inode_unlock_shared(dir->d_inode);
3575 mnt_drop_write(nd->path.mnt);
3578 return ERR_CAST(dentry);
3580 if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) {
3581 dput(nd->path.dentry);
3582 nd->path.dentry = dentry;
3589 res = step_into(nd, WALK_TRAILING, dentry);
3591 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3596 * Handle the last step of open()
3598 static int do_open(struct nameidata *nd,
3599 struct file *file, const struct open_flags *op)
3601 struct mnt_idmap *idmap;
3602 int open_flag = op->open_flag;
3607 if (!(file->f_mode & (FMODE_OPENED | FMODE_CREATED))) {
3608 error = complete_walk(nd);
3612 if (!(file->f_mode & FMODE_CREATED))
3613 audit_inode(nd->name, nd->path.dentry, 0);
3614 idmap = mnt_idmap(nd->path.mnt);
3615 if (open_flag & O_CREAT) {
3616 if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED))
3618 if (d_is_dir(nd->path.dentry))
3620 error = may_create_in_sticky(idmap, nd,
3621 d_backing_inode(nd->path.dentry));
3622 if (unlikely(error))
3625 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3628 do_truncate = false;
3629 acc_mode = op->acc_mode;
3630 if (file->f_mode & FMODE_CREATED) {
3631 /* Don't check for write permission, don't truncate */
3632 open_flag &= ~O_TRUNC;
3634 } else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) {
3635 error = mnt_want_write(nd->path.mnt);
3640 error = may_open(idmap, &nd->path, acc_mode, open_flag);
3641 if (!error && !(file->f_mode & FMODE_OPENED))
3642 error = vfs_open(&nd->path, file);
3644 error = security_file_post_open(file, op->acc_mode);
3645 if (!error && do_truncate)
3646 error = handle_truncate(idmap, file);
3647 if (unlikely(error > 0)) {
3652 mnt_drop_write(nd->path.mnt);
3657 * vfs_tmpfile - create tmpfile
3658 * @idmap: idmap of the mount the inode was found from
3659 * @parentpath: pointer to the path of the base directory
3660 * @file: file descriptor of the new tmpfile
3661 * @mode: mode of the new tmpfile
3663 * Create a temporary file.
3665 * If the inode has been found through an idmapped mount the idmap of
3666 * the vfsmount must be passed through @idmap. This function will then take
3667 * care to map the inode according to @idmap before checking permissions.
3668 * On non-idmapped mounts or if permission checking is to be performed on the
3669 * raw inode simply pass @nop_mnt_idmap.
3671 static int vfs_tmpfile(struct mnt_idmap *idmap,
3672 const struct path *parentpath,
3673 struct file *file, umode_t mode)
3675 struct dentry *child;
3676 struct inode *dir = d_inode(parentpath->dentry);
3677 struct inode *inode;
3679 int open_flag = file->f_flags;
3681 /* we want directory to be writable */
3682 error = inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
3685 if (!dir->i_op->tmpfile)
3687 child = d_alloc(parentpath->dentry, &slash_name);
3688 if (unlikely(!child))
3690 file->f_path.mnt = parentpath->mnt;
3691 file->f_path.dentry = child;
3692 mode = vfs_prepare_mode(idmap, dir, mode, mode, mode);
3693 error = dir->i_op->tmpfile(idmap, dir, file, mode);
3697 /* Don't check for other permissions, the inode was just created */
3698 error = may_open(idmap, &file->f_path, 0, file->f_flags);
3701 inode = file_inode(file);
3702 if (!(open_flag & O_EXCL)) {
3703 spin_lock(&inode->i_lock);
3704 inode->i_state |= I_LINKABLE;
3705 spin_unlock(&inode->i_lock);
3707 security_inode_post_create_tmpfile(idmap, inode);
3712 * kernel_tmpfile_open - open a tmpfile for kernel internal use
3713 * @idmap: idmap of the mount the inode was found from
3714 * @parentpath: path of the base directory
3715 * @mode: mode of the new tmpfile
3717 * @cred: credentials for open
3719 * Create and open a temporary file. The file is not accounted in nr_files,
3720 * hence this is only for kernel internal use, and must not be installed into
3721 * file tables or such.
3723 struct file *kernel_tmpfile_open(struct mnt_idmap *idmap,
3724 const struct path *parentpath,
3725 umode_t mode, int open_flag,
3726 const struct cred *cred)
3731 file = alloc_empty_file_noaccount(open_flag, cred);
3735 error = vfs_tmpfile(idmap, parentpath, file, mode);
3738 file = ERR_PTR(error);
3742 EXPORT_SYMBOL(kernel_tmpfile_open);
3744 static int do_tmpfile(struct nameidata *nd, unsigned flags,
3745 const struct open_flags *op,
3749 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3751 if (unlikely(error))
3753 error = mnt_want_write(path.mnt);
3754 if (unlikely(error))
3756 error = vfs_tmpfile(mnt_idmap(path.mnt), &path, file, op->mode);
3759 audit_inode(nd->name, file->f_path.dentry, 0);
3761 mnt_drop_write(path.mnt);
3767 static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3770 int error = path_lookupat(nd, flags, &path);
3772 audit_inode(nd->name, path.dentry, 0);
3773 error = vfs_open(&path, file);
3779 static struct file *path_openat(struct nameidata *nd,
3780 const struct open_flags *op, unsigned flags)
3785 file = alloc_empty_file(op->open_flag, current_cred());
3789 if (unlikely(file->f_flags & __O_TMPFILE)) {
3790 error = do_tmpfile(nd, flags, op, file);
3791 } else if (unlikely(file->f_flags & O_PATH)) {
3792 error = do_o_path(nd, flags, file);
3794 const char *s = path_init(nd, flags);
3795 while (!(error = link_path_walk(s, nd)) &&
3796 (s = open_last_lookups(nd, file, op)) != NULL)
3799 error = do_open(nd, file, op);
3802 if (likely(!error)) {
3803 if (likely(file->f_mode & FMODE_OPENED))
3809 if (error == -EOPENSTALE) {
3810 if (flags & LOOKUP_RCU)
3815 return ERR_PTR(error);
3818 struct file *do_filp_open(int dfd, struct filename *pathname,
3819 const struct open_flags *op)
3821 struct nameidata nd;
3822 int flags = op->lookup_flags;
3825 set_nameidata(&nd, dfd, pathname, NULL);
3826 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3827 if (unlikely(filp == ERR_PTR(-ECHILD)))
3828 filp = path_openat(&nd, op, flags);
3829 if (unlikely(filp == ERR_PTR(-ESTALE)))
3830 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3831 restore_nameidata();
3835 struct file *do_file_open_root(const struct path *root,
3836 const char *name, const struct open_flags *op)
3838 struct nameidata nd;
3840 struct filename *filename;
3841 int flags = op->lookup_flags;
3843 if (d_is_symlink(root->dentry) && op->intent & LOOKUP_OPEN)
3844 return ERR_PTR(-ELOOP);
3846 filename = getname_kernel(name);
3847 if (IS_ERR(filename))
3848 return ERR_CAST(filename);
3850 set_nameidata(&nd, -1, filename, root);
3851 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3852 if (unlikely(file == ERR_PTR(-ECHILD)))
3853 file = path_openat(&nd, op, flags);
3854 if (unlikely(file == ERR_PTR(-ESTALE)))
3855 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3856 restore_nameidata();
3861 static struct dentry *filename_create(int dfd, struct filename *name,
3862 struct path *path, unsigned int lookup_flags)
3864 struct dentry *dentry = ERR_PTR(-EEXIST);
3866 bool want_dir = lookup_flags & LOOKUP_DIRECTORY;
3867 unsigned int reval_flag = lookup_flags & LOOKUP_REVAL;
3868 unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL;
3873 error = filename_parentat(dfd, name, reval_flag, path, &last, &type);
3875 return ERR_PTR(error);
3878 * Yucky last component or no last component at all?
3879 * (foo/., foo/.., /////)
3881 if (unlikely(type != LAST_NORM))
3884 /* don't fail immediately if it's r/o, at least try to report other errors */
3885 err2 = mnt_want_write(path->mnt);
3887 * Do the final lookup. Suppress 'create' if there is a trailing
3888 * '/', and a directory wasn't requested.
3890 if (last.name[last.len] && !want_dir)
3892 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3893 dentry = lookup_one_qstr_excl(&last, path->dentry,
3894 reval_flag | create_flags);
3899 if (d_is_positive(dentry))
3903 * Special case - lookup gave negative, but... we had foo/bar/
3904 * From the vfs_mknod() POV we just have a negative dentry -
3905 * all is fine. Let's be bastards - you had / on the end, you've
3906 * been asking for (non-existent) directory. -ENOENT for you.
3908 if (unlikely(!create_flags)) {
3912 if (unlikely(err2)) {
3919 dentry = ERR_PTR(error);
3921 inode_unlock(path->dentry->d_inode);
3923 mnt_drop_write(path->mnt);
3929 struct dentry *kern_path_create(int dfd, const char *pathname,
3930 struct path *path, unsigned int lookup_flags)
3932 struct filename *filename = getname_kernel(pathname);
3933 struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
3938 EXPORT_SYMBOL(kern_path_create);
3940 void done_path_create(struct path *path, struct dentry *dentry)
3943 inode_unlock(path->dentry->d_inode);
3944 mnt_drop_write(path->mnt);
3947 EXPORT_SYMBOL(done_path_create);
3949 inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3950 struct path *path, unsigned int lookup_flags)
3952 struct filename *filename = getname(pathname);
3953 struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
3958 EXPORT_SYMBOL(user_path_create);
3961 * vfs_mknod - create device node or file
3962 * @idmap: idmap of the mount the inode was found from
3963 * @dir: inode of @dentry
3964 * @dentry: pointer to dentry of the base directory
3965 * @mode: mode of the new device node or file
3966 * @dev: device number of device to create
3968 * Create a device node or file.
3970 * If the inode has been found through an idmapped mount the idmap of
3971 * the vfsmount must be passed through @idmap. This function will then take
3972 * care to map the inode according to @idmap before checking permissions.
3973 * On non-idmapped mounts or if permission checking is to be performed on the
3974 * raw inode simply pass @nop_mnt_idmap.
3976 int vfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
3977 struct dentry *dentry, umode_t mode, dev_t dev)
3979 bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV;
3980 int error = may_create(idmap, dir, dentry);
3985 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !is_whiteout &&
3986 !capable(CAP_MKNOD))
3989 if (!dir->i_op->mknod)
3992 mode = vfs_prepare_mode(idmap, dir, mode, mode, mode);
3993 error = devcgroup_inode_mknod(mode, dev);
3997 error = security_inode_mknod(dir, dentry, mode, dev);
4001 error = dir->i_op->mknod(idmap, dir, dentry, mode, dev);
4003 fsnotify_create(dir, dentry);
4006 EXPORT_SYMBOL(vfs_mknod);
4008 static int may_mknod(umode_t mode)
4010 switch (mode & S_IFMT) {
4016 case 0: /* zero mode translates to S_IFREG */
4025 static int do_mknodat(int dfd, struct filename *name, umode_t mode,
4028 struct mnt_idmap *idmap;
4029 struct dentry *dentry;
4032 unsigned int lookup_flags = 0;
4034 error = may_mknod(mode);
4038 dentry = filename_create(dfd, name, &path, lookup_flags);
4039 error = PTR_ERR(dentry);
4043 error = security_path_mknod(&path, dentry,
4044 mode_strip_umask(path.dentry->d_inode, mode), dev);
4048 idmap = mnt_idmap(path.mnt);
4049 switch (mode & S_IFMT) {
4050 case 0: case S_IFREG:
4051 error = vfs_create(idmap, path.dentry->d_inode,
4052 dentry, mode, true);
4054 security_path_post_mknod(idmap, dentry);
4056 case S_IFCHR: case S_IFBLK:
4057 error = vfs_mknod(idmap, path.dentry->d_inode,
4058 dentry, mode, new_decode_dev(dev));
4060 case S_IFIFO: case S_IFSOCK:
4061 error = vfs_mknod(idmap, path.dentry->d_inode,
4066 done_path_create(&path, dentry);
4067 if (retry_estale(error, lookup_flags)) {
4068 lookup_flags |= LOOKUP_REVAL;
4076 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
4079 return do_mknodat(dfd, getname(filename), mode, dev);
4082 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
4084 return do_mknodat(AT_FDCWD, getname(filename), mode, dev);
4088 * vfs_mkdir - create directory
4089 * @idmap: idmap of the mount the inode was found from
4090 * @dir: inode of @dentry
4091 * @dentry: pointer to dentry of the base directory
4092 * @mode: mode of the new directory
4094 * Create a directory.
4096 * If the inode has been found through an idmapped mount the idmap of
4097 * the vfsmount must be passed through @idmap. This function will then take
4098 * care to map the inode according to @idmap before checking permissions.
4099 * On non-idmapped mounts or if permission checking is to be performed on the
4100 * raw inode simply pass @nop_mnt_idmap.
4102 int vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
4103 struct dentry *dentry, umode_t mode)
4106 unsigned max_links = dir->i_sb->s_max_links;
4108 error = may_create(idmap, dir, dentry);
4112 if (!dir->i_op->mkdir)
4115 mode = vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO | S_ISVTX, 0);
4116 error = security_inode_mkdir(dir, dentry, mode);
4120 if (max_links && dir->i_nlink >= max_links)
4123 error = dir->i_op->mkdir(idmap, dir, dentry, mode);
4125 fsnotify_mkdir(dir, dentry);
4128 EXPORT_SYMBOL(vfs_mkdir);
4130 int do_mkdirat(int dfd, struct filename *name, umode_t mode)
4132 struct dentry *dentry;
4135 unsigned int lookup_flags = LOOKUP_DIRECTORY;
4138 dentry = filename_create(dfd, name, &path, lookup_flags);
4139 error = PTR_ERR(dentry);
4143 error = security_path_mkdir(&path, dentry,
4144 mode_strip_umask(path.dentry->d_inode, mode));
4146 error = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
4149 done_path_create(&path, dentry);
4150 if (retry_estale(error, lookup_flags)) {
4151 lookup_flags |= LOOKUP_REVAL;
4159 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
4161 return do_mkdirat(dfd, getname(pathname), mode);
4164 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
4166 return do_mkdirat(AT_FDCWD, getname(pathname), mode);
4170 * vfs_rmdir - remove directory
4171 * @idmap: idmap of the mount the inode was found from
4172 * @dir: inode of @dentry
4173 * @dentry: pointer to dentry of the base directory
4175 * Remove a directory.
4177 * If the inode has been found through an idmapped mount the idmap of
4178 * the vfsmount must be passed through @idmap. This function will then take
4179 * care to map the inode according to @idmap before checking permissions.
4180 * On non-idmapped mounts or if permission checking is to be performed on the
4181 * raw inode simply pass @nop_mnt_idmap.
4183 int vfs_rmdir(struct mnt_idmap *idmap, struct inode *dir,
4184 struct dentry *dentry)
4186 int error = may_delete(idmap, dir, dentry, 1);
4191 if (!dir->i_op->rmdir)
4195 inode_lock(dentry->d_inode);
4198 if (is_local_mountpoint(dentry) ||
4199 (dentry->d_inode->i_flags & S_KERNEL_FILE))
4202 error = security_inode_rmdir(dir, dentry);
4206 error = dir->i_op->rmdir(dir, dentry);
4210 shrink_dcache_parent(dentry);
4211 dentry->d_inode->i_flags |= S_DEAD;
4213 detach_mounts(dentry);
4216 inode_unlock(dentry->d_inode);
4219 d_delete_notify(dir, dentry);
4222 EXPORT_SYMBOL(vfs_rmdir);
4224 int do_rmdir(int dfd, struct filename *name)
4227 struct dentry *dentry;
4231 unsigned int lookup_flags = 0;
4233 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4249 error = mnt_want_write(path.mnt);
4253 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4254 dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
4255 error = PTR_ERR(dentry);
4258 if (!dentry->d_inode) {
4262 error = security_path_rmdir(&path, dentry);
4265 error = vfs_rmdir(mnt_idmap(path.mnt), path.dentry->d_inode, dentry);
4269 inode_unlock(path.dentry->d_inode);
4270 mnt_drop_write(path.mnt);
4273 if (retry_estale(error, lookup_flags)) {
4274 lookup_flags |= LOOKUP_REVAL;
4282 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
4284 return do_rmdir(AT_FDCWD, getname(pathname));
4288 * vfs_unlink - unlink a filesystem object
4289 * @idmap: idmap of the mount the inode was found from
4290 * @dir: parent directory
4292 * @delegated_inode: returns victim inode, if the inode is delegated.
4294 * The caller must hold dir->i_mutex.
4296 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
4297 * return a reference to the inode in delegated_inode. The caller
4298 * should then break the delegation on that inode and retry. Because
4299 * breaking a delegation may take a long time, the caller should drop
4300 * dir->i_mutex before doing so.
4302 * Alternatively, a caller may pass NULL for delegated_inode. This may
4303 * be appropriate for callers that expect the underlying filesystem not
4304 * to be NFS exported.
4306 * If the inode has been found through an idmapped mount the idmap of
4307 * the vfsmount must be passed through @idmap. This function will then take
4308 * care to map the inode according to @idmap before checking permissions.
4309 * On non-idmapped mounts or if permission checking is to be performed on the
4310 * raw inode simply pass @nop_mnt_idmap.
4312 int vfs_unlink(struct mnt_idmap *idmap, struct inode *dir,
4313 struct dentry *dentry, struct inode **delegated_inode)
4315 struct inode *target = dentry->d_inode;
4316 int error = may_delete(idmap, dir, dentry, 0);
4321 if (!dir->i_op->unlink)
4325 if (IS_SWAPFILE(target))
4327 else if (is_local_mountpoint(dentry))
4330 error = security_inode_unlink(dir, dentry);
4332 error = try_break_deleg(target, delegated_inode);
4335 error = dir->i_op->unlink(dir, dentry);
4338 detach_mounts(dentry);
4343 inode_unlock(target);
4345 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
4346 if (!error && dentry->d_flags & DCACHE_NFSFS_RENAMED) {
4347 fsnotify_unlink(dir, dentry);
4348 } else if (!error) {
4349 fsnotify_link_count(target);
4350 d_delete_notify(dir, dentry);
4355 EXPORT_SYMBOL(vfs_unlink);
4358 * Make sure that the actual truncation of the file will occur outside its
4359 * directory's i_mutex. Truncate can take a long time if there is a lot of
4360 * writeout happening, and we don't want to prevent access to the directory
4361 * while waiting on the I/O.
4363 int do_unlinkat(int dfd, struct filename *name)
4366 struct dentry *dentry;
4370 struct inode *inode = NULL;
4371 struct inode *delegated_inode = NULL;
4372 unsigned int lookup_flags = 0;
4374 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4379 if (type != LAST_NORM)
4382 error = mnt_want_write(path.mnt);
4386 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4387 dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
4388 error = PTR_ERR(dentry);
4389 if (!IS_ERR(dentry)) {
4391 /* Why not before? Because we want correct error value */
4392 if (last.name[last.len] || d_is_negative(dentry))
4394 inode = dentry->d_inode;
4396 error = security_path_unlink(&path, dentry);
4399 error = vfs_unlink(mnt_idmap(path.mnt), path.dentry->d_inode,
4400 dentry, &delegated_inode);
4404 inode_unlock(path.dentry->d_inode);
4406 iput(inode); /* truncate the inode here */
4408 if (delegated_inode) {
4409 error = break_deleg_wait(&delegated_inode);
4413 mnt_drop_write(path.mnt);
4416 if (retry_estale(error, lookup_flags)) {
4417 lookup_flags |= LOOKUP_REVAL;
4426 if (d_is_negative(dentry))
4428 else if (d_is_dir(dentry))
4435 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4437 if ((flag & ~AT_REMOVEDIR) != 0)
4440 if (flag & AT_REMOVEDIR)
4441 return do_rmdir(dfd, getname(pathname));
4442 return do_unlinkat(dfd, getname(pathname));
4445 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4447 return do_unlinkat(AT_FDCWD, getname(pathname));
4451 * vfs_symlink - create symlink
4452 * @idmap: idmap of the mount the inode was found from
4453 * @dir: inode of @dentry
4454 * @dentry: pointer to dentry of the base directory
4455 * @oldname: name of the file to link to
4459 * If the inode has been found through an idmapped mount the idmap of
4460 * the vfsmount must be passed through @idmap. This function will then take
4461 * care to map the inode according to @idmap before checking permissions.
4462 * On non-idmapped mounts or if permission checking is to be performed on the
4463 * raw inode simply pass @nop_mnt_idmap.
4465 int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
4466 struct dentry *dentry, const char *oldname)
4470 error = may_create(idmap, dir, dentry);
4474 if (!dir->i_op->symlink)
4477 error = security_inode_symlink(dir, dentry, oldname);
4481 error = dir->i_op->symlink(idmap, dir, dentry, oldname);
4483 fsnotify_create(dir, dentry);
4486 EXPORT_SYMBOL(vfs_symlink);
4488 int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
4491 struct dentry *dentry;
4493 unsigned int lookup_flags = 0;
4496 error = PTR_ERR(from);
4500 dentry = filename_create(newdfd, to, &path, lookup_flags);
4501 error = PTR_ERR(dentry);
4505 error = security_path_symlink(&path, dentry, from->name);
4507 error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
4508 dentry, from->name);
4509 done_path_create(&path, dentry);
4510 if (retry_estale(error, lookup_flags)) {
4511 lookup_flags |= LOOKUP_REVAL;
4520 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4521 int, newdfd, const char __user *, newname)
4523 return do_symlinkat(getname(oldname), newdfd, getname(newname));
4526 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4528 return do_symlinkat(getname(oldname), AT_FDCWD, getname(newname));
4532 * vfs_link - create a new link
4533 * @old_dentry: object to be linked
4534 * @idmap: idmap of the mount
4536 * @new_dentry: where to create the new link
4537 * @delegated_inode: returns inode needing a delegation break
4539 * The caller must hold dir->i_mutex
4541 * If vfs_link discovers a delegation on the to-be-linked file in need
4542 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4543 * inode in delegated_inode. The caller should then break the delegation
4544 * and retry. Because breaking a delegation may take a long time, the
4545 * caller should drop the i_mutex before doing so.
4547 * Alternatively, a caller may pass NULL for delegated_inode. This may
4548 * be appropriate for callers that expect the underlying filesystem not
4549 * to be NFS exported.
4551 * If the inode has been found through an idmapped mount the idmap of
4552 * the vfsmount must be passed through @idmap. This function will then take
4553 * care to map the inode according to @idmap before checking permissions.
4554 * On non-idmapped mounts or if permission checking is to be performed on the
4555 * raw inode simply pass @nop_mnt_idmap.
4557 int vfs_link(struct dentry *old_dentry, struct mnt_idmap *idmap,
4558 struct inode *dir, struct dentry *new_dentry,
4559 struct inode **delegated_inode)
4561 struct inode *inode = old_dentry->d_inode;
4562 unsigned max_links = dir->i_sb->s_max_links;
4568 error = may_create(idmap, dir, new_dentry);
4572 if (dir->i_sb != inode->i_sb)
4576 * A link to an append-only or immutable file cannot be created.
4578 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4581 * Updating the link count will likely cause i_uid and i_gid to
4582 * be writen back improperly if their true value is unknown to
4585 if (HAS_UNMAPPED_ID(idmap, inode))
4587 if (!dir->i_op->link)
4589 if (S_ISDIR(inode->i_mode))
4592 error = security_inode_link(old_dentry, dir, new_dentry);
4597 /* Make sure we don't allow creating hardlink to an unlinked file */
4598 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4600 else if (max_links && inode->i_nlink >= max_links)
4603 error = try_break_deleg(inode, delegated_inode);
4605 error = dir->i_op->link(old_dentry, dir, new_dentry);
4608 if (!error && (inode->i_state & I_LINKABLE)) {
4609 spin_lock(&inode->i_lock);
4610 inode->i_state &= ~I_LINKABLE;
4611 spin_unlock(&inode->i_lock);
4613 inode_unlock(inode);
4615 fsnotify_link(dir, inode, new_dentry);
4618 EXPORT_SYMBOL(vfs_link);
4621 * Hardlinks are often used in delicate situations. We avoid
4622 * security-related surprises by not following symlinks on the
4625 * We don't follow them on the oldname either to be compatible
4626 * with linux 2.0, and to avoid hard-linking to directories
4627 * and other special files. --ADM
4629 int do_linkat(int olddfd, struct filename *old, int newdfd,
4630 struct filename *new, int flags)
4632 struct mnt_idmap *idmap;
4633 struct dentry *new_dentry;
4634 struct path old_path, new_path;
4635 struct inode *delegated_inode = NULL;
4639 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) {
4644 * To use null names we require CAP_DAC_READ_SEARCH
4645 * This ensures that not everyone will be able to create
4646 * handlink using the passed filedescriptor.
4648 if (flags & AT_EMPTY_PATH && !capable(CAP_DAC_READ_SEARCH)) {
4653 if (flags & AT_SYMLINK_FOLLOW)
4654 how |= LOOKUP_FOLLOW;
4656 error = filename_lookup(olddfd, old, how, &old_path, NULL);
4660 new_dentry = filename_create(newdfd, new, &new_path,
4661 (how & LOOKUP_REVAL));
4662 error = PTR_ERR(new_dentry);
4663 if (IS_ERR(new_dentry))
4667 if (old_path.mnt != new_path.mnt)
4669 idmap = mnt_idmap(new_path.mnt);
4670 error = may_linkat(idmap, &old_path);
4671 if (unlikely(error))
4673 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4676 error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode,
4677 new_dentry, &delegated_inode);
4679 done_path_create(&new_path, new_dentry);
4680 if (delegated_inode) {
4681 error = break_deleg_wait(&delegated_inode);
4683 path_put(&old_path);
4687 if (retry_estale(error, how)) {
4688 path_put(&old_path);
4689 how |= LOOKUP_REVAL;
4693 path_put(&old_path);
4701 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4702 int, newdfd, const char __user *, newname, int, flags)
4704 return do_linkat(olddfd, getname_uflags(oldname, flags),
4705 newdfd, getname(newname), flags);
4708 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4710 return do_linkat(AT_FDCWD, getname(oldname), AT_FDCWD, getname(newname), 0);
4714 * vfs_rename - rename a filesystem object
4715 * @rd: pointer to &struct renamedata info
4717 * The caller must hold multiple mutexes--see lock_rename()).
4719 * If vfs_rename discovers a delegation in need of breaking at either
4720 * the source or destination, it will return -EWOULDBLOCK and return a
4721 * reference to the inode in delegated_inode. The caller should then
4722 * break the delegation and retry. Because breaking a delegation may
4723 * take a long time, the caller should drop all locks before doing
4726 * Alternatively, a caller may pass NULL for delegated_inode. This may
4727 * be appropriate for callers that expect the underlying filesystem not
4728 * to be NFS exported.
4730 * The worst of all namespace operations - renaming directory. "Perverted"
4731 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4734 * a) we can get into loop creation.
4735 * b) race potential - two innocent renames can create a loop together.
4736 * That's where 4.4BSD screws up. Current fix: serialization on
4737 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4739 * c) we may have to lock up to _four_ objects - parents and victim (if it exists),
4740 * and source (if it's a non-directory or a subdirectory that moves to
4741 * different parent).
4742 * And that - after we got ->i_mutex on parents (until then we don't know
4743 * whether the target exists). Solution: try to be smart with locking
4744 * order for inodes. We rely on the fact that tree topology may change
4745 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4746 * move will be locked. Thus we can rank directories by the tree
4747 * (ancestors first) and rank all non-directories after them.
4748 * That works since everybody except rename does "lock parent, lookup,
4749 * lock child" and rename is under ->s_vfs_rename_mutex.
4750 * HOWEVER, it relies on the assumption that any object with ->lookup()
4751 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4752 * we'd better make sure that there's no link(2) for them.
4753 * d) conversion from fhandle to dentry may come in the wrong moment - when
4754 * we are removing the target. Solution: we will have to grab ->i_mutex
4755 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4756 * ->i_mutex on parents, which works but leads to some truly excessive
4759 int vfs_rename(struct renamedata *rd)
4762 struct inode *old_dir = rd->old_dir, *new_dir = rd->new_dir;
4763 struct dentry *old_dentry = rd->old_dentry;
4764 struct dentry *new_dentry = rd->new_dentry;
4765 struct inode **delegated_inode = rd->delegated_inode;
4766 unsigned int flags = rd->flags;
4767 bool is_dir = d_is_dir(old_dentry);
4768 struct inode *source = old_dentry->d_inode;
4769 struct inode *target = new_dentry->d_inode;
4770 bool new_is_dir = false;
4771 unsigned max_links = new_dir->i_sb->s_max_links;
4772 struct name_snapshot old_name;
4773 bool lock_old_subdir, lock_new_subdir;
4775 if (source == target)
4778 error = may_delete(rd->old_mnt_idmap, old_dir, old_dentry, is_dir);
4783 error = may_create(rd->new_mnt_idmap, new_dir, new_dentry);
4785 new_is_dir = d_is_dir(new_dentry);
4787 if (!(flags & RENAME_EXCHANGE))
4788 error = may_delete(rd->new_mnt_idmap, new_dir,
4789 new_dentry, is_dir);
4791 error = may_delete(rd->new_mnt_idmap, new_dir,
4792 new_dentry, new_is_dir);
4797 if (!old_dir->i_op->rename)
4801 * If we are going to change the parent - check write permissions,
4802 * we'll need to flip '..'.
4804 if (new_dir != old_dir) {
4806 error = inode_permission(rd->old_mnt_idmap, source,
4811 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4812 error = inode_permission(rd->new_mnt_idmap, target,
4819 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4824 take_dentry_name_snapshot(&old_name, old_dentry);
4828 * The source subdirectory needs to be locked on cross-directory
4829 * rename or cross-directory exchange since its parent changes.
4830 * The target subdirectory needs to be locked on cross-directory
4831 * exchange due to parent change and on any rename due to becoming
4833 * Non-directories need locking in all cases (for NFS reasons);
4834 * they get locked after any subdirectories (in inode address order).
4836 * NOTE: WE ONLY LOCK UNRELATED DIRECTORIES IN CROSS-DIRECTORY CASE.
4837 * NEVER, EVER DO THAT WITHOUT ->s_vfs_rename_mutex.
4839 lock_old_subdir = new_dir != old_dir;
4840 lock_new_subdir = new_dir != old_dir || !(flags & RENAME_EXCHANGE);
4842 if (lock_old_subdir)
4843 inode_lock_nested(source, I_MUTEX_CHILD);
4844 if (target && (!new_is_dir || lock_new_subdir))
4846 } else if (new_is_dir) {
4847 if (lock_new_subdir)
4848 inode_lock_nested(target, I_MUTEX_CHILD);
4851 lock_two_nondirectories(source, target);
4855 if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target)))
4859 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4862 if (max_links && new_dir != old_dir) {
4864 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4866 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4867 old_dir->i_nlink >= max_links)
4871 error = try_break_deleg(source, delegated_inode);
4875 if (target && !new_is_dir) {
4876 error = try_break_deleg(target, delegated_inode);
4880 error = old_dir->i_op->rename(rd->new_mnt_idmap, old_dir, old_dentry,
4881 new_dir, new_dentry, flags);
4885 if (!(flags & RENAME_EXCHANGE) && target) {
4887 shrink_dcache_parent(new_dentry);
4888 target->i_flags |= S_DEAD;
4890 dont_mount(new_dentry);
4891 detach_mounts(new_dentry);
4893 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4894 if (!(flags & RENAME_EXCHANGE))
4895 d_move(old_dentry, new_dentry);
4897 d_exchange(old_dentry, new_dentry);
4900 if (!is_dir || lock_old_subdir)
4901 inode_unlock(source);
4902 if (target && (!new_is_dir || lock_new_subdir))
4903 inode_unlock(target);
4906 fsnotify_move(old_dir, new_dir, &old_name.name, is_dir,
4907 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4908 if (flags & RENAME_EXCHANGE) {
4909 fsnotify_move(new_dir, old_dir, &old_dentry->d_name,
4910 new_is_dir, NULL, new_dentry);
4913 release_dentry_name_snapshot(&old_name);
4917 EXPORT_SYMBOL(vfs_rename);
4919 int do_renameat2(int olddfd, struct filename *from, int newdfd,
4920 struct filename *to, unsigned int flags)
4922 struct renamedata rd;
4923 struct dentry *old_dentry, *new_dentry;
4924 struct dentry *trap;
4925 struct path old_path, new_path;
4926 struct qstr old_last, new_last;
4927 int old_type, new_type;
4928 struct inode *delegated_inode = NULL;
4929 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4930 bool should_retry = false;
4931 int error = -EINVAL;
4933 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4936 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4937 (flags & RENAME_EXCHANGE))
4940 if (flags & RENAME_EXCHANGE)
4944 error = filename_parentat(olddfd, from, lookup_flags, &old_path,
4945 &old_last, &old_type);
4949 error = filename_parentat(newdfd, to, lookup_flags, &new_path, &new_last,
4955 if (old_path.mnt != new_path.mnt)
4959 if (old_type != LAST_NORM)
4962 if (flags & RENAME_NOREPLACE)
4964 if (new_type != LAST_NORM)
4967 error = mnt_want_write(old_path.mnt);
4972 trap = lock_rename(new_path.dentry, old_path.dentry);
4974 error = PTR_ERR(trap);
4975 goto exit_lock_rename;
4978 old_dentry = lookup_one_qstr_excl(&old_last, old_path.dentry,
4980 error = PTR_ERR(old_dentry);
4981 if (IS_ERR(old_dentry))
4983 /* source must exist */
4985 if (d_is_negative(old_dentry))
4987 new_dentry = lookup_one_qstr_excl(&new_last, new_path.dentry,
4988 lookup_flags | target_flags);
4989 error = PTR_ERR(new_dentry);
4990 if (IS_ERR(new_dentry))
4993 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4995 if (flags & RENAME_EXCHANGE) {
4997 if (d_is_negative(new_dentry))
5000 if (!d_is_dir(new_dentry)) {
5002 if (new_last.name[new_last.len])
5006 /* unless the source is a directory trailing slashes give -ENOTDIR */
5007 if (!d_is_dir(old_dentry)) {
5009 if (old_last.name[old_last.len])
5011 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
5014 /* source should not be ancestor of target */
5016 if (old_dentry == trap)
5018 /* target should not be an ancestor of source */
5019 if (!(flags & RENAME_EXCHANGE))
5021 if (new_dentry == trap)
5024 error = security_path_rename(&old_path, old_dentry,
5025 &new_path, new_dentry, flags);
5029 rd.old_dir = old_path.dentry->d_inode;
5030 rd.old_dentry = old_dentry;
5031 rd.old_mnt_idmap = mnt_idmap(old_path.mnt);
5032 rd.new_dir = new_path.dentry->d_inode;
5033 rd.new_dentry = new_dentry;
5034 rd.new_mnt_idmap = mnt_idmap(new_path.mnt);
5035 rd.delegated_inode = &delegated_inode;
5037 error = vfs_rename(&rd);
5043 unlock_rename(new_path.dentry, old_path.dentry);
5045 if (delegated_inode) {
5046 error = break_deleg_wait(&delegated_inode);
5050 mnt_drop_write(old_path.mnt);
5052 if (retry_estale(error, lookup_flags))
5053 should_retry = true;
5054 path_put(&new_path);
5056 path_put(&old_path);
5058 should_retry = false;
5059 lookup_flags |= LOOKUP_REVAL;
5068 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
5069 int, newdfd, const char __user *, newname, unsigned int, flags)
5071 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
5075 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
5076 int, newdfd, const char __user *, newname)
5078 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
5082 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
5084 return do_renameat2(AT_FDCWD, getname(oldname), AT_FDCWD,
5085 getname(newname), 0);
5088 int readlink_copy(char __user *buffer, int buflen, const char *link)
5090 int len = PTR_ERR(link);
5095 if (len > (unsigned) buflen)
5097 if (copy_to_user(buffer, link, len))
5104 * vfs_readlink - copy symlink body into userspace buffer
5105 * @dentry: dentry on which to get symbolic link
5106 * @buffer: user memory pointer
5107 * @buflen: size of buffer
5109 * Does not touch atime. That's up to the caller if necessary
5111 * Does not call security hook.
5113 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
5115 struct inode *inode = d_inode(dentry);
5116 DEFINE_DELAYED_CALL(done);
5120 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
5121 if (unlikely(inode->i_op->readlink))
5122 return inode->i_op->readlink(dentry, buffer, buflen);
5124 if (!d_is_symlink(dentry))
5127 spin_lock(&inode->i_lock);
5128 inode->i_opflags |= IOP_DEFAULT_READLINK;
5129 spin_unlock(&inode->i_lock);
5132 link = READ_ONCE(inode->i_link);
5134 link = inode->i_op->get_link(dentry, inode, &done);
5136 return PTR_ERR(link);
5138 res = readlink_copy(buffer, buflen, link);
5139 do_delayed_call(&done);
5142 EXPORT_SYMBOL(vfs_readlink);
5145 * vfs_get_link - get symlink body
5146 * @dentry: dentry on which to get symbolic link
5147 * @done: caller needs to free returned data with this
5149 * Calls security hook and i_op->get_link() on the supplied inode.
5151 * It does not touch atime. That's up to the caller if necessary.
5153 * Does not work on "special" symlinks like /proc/$$/fd/N
5155 const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
5157 const char *res = ERR_PTR(-EINVAL);
5158 struct inode *inode = d_inode(dentry);
5160 if (d_is_symlink(dentry)) {
5161 res = ERR_PTR(security_inode_readlink(dentry));
5163 res = inode->i_op->get_link(dentry, inode, done);
5167 EXPORT_SYMBOL(vfs_get_link);
5169 /* get the link contents into pagecache */
5170 const char *page_get_link(struct dentry *dentry, struct inode *inode,
5171 struct delayed_call *callback)
5175 struct address_space *mapping = inode->i_mapping;
5178 page = find_get_page(mapping, 0);
5180 return ERR_PTR(-ECHILD);
5181 if (!PageUptodate(page)) {
5183 return ERR_PTR(-ECHILD);
5186 page = read_mapping_page(mapping, 0, NULL);
5190 set_delayed_call(callback, page_put_link, page);
5191 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
5192 kaddr = page_address(page);
5193 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
5197 EXPORT_SYMBOL(page_get_link);
5199 void page_put_link(void *arg)
5203 EXPORT_SYMBOL(page_put_link);
5205 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
5207 DEFINE_DELAYED_CALL(done);
5208 int res = readlink_copy(buffer, buflen,
5209 page_get_link(dentry, d_inode(dentry),
5211 do_delayed_call(&done);
5214 EXPORT_SYMBOL(page_readlink);
5216 int page_symlink(struct inode *inode, const char *symname, int len)
5218 struct address_space *mapping = inode->i_mapping;
5219 const struct address_space_operations *aops = mapping->a_ops;
5220 bool nofs = !mapping_gfp_constraint(mapping, __GFP_FS);
5222 void *fsdata = NULL;
5228 flags = memalloc_nofs_save();
5229 err = aops->write_begin(NULL, mapping, 0, len-1, &page, &fsdata);
5231 memalloc_nofs_restore(flags);
5235 memcpy(page_address(page), symname, len-1);
5237 err = aops->write_end(NULL, mapping, 0, len-1, len-1,
5244 mark_inode_dirty(inode);
5249 EXPORT_SYMBOL(page_symlink);
5251 const struct inode_operations page_symlink_inode_operations = {
5252 .get_link = page_get_link,
5254 EXPORT_SYMBOL(page_symlink_inode_operations);