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/kernel.h>
21 #include <linux/slab.h>
23 #include <linux/namei.h>
24 #include <linux/pagemap.h>
25 #include <linux/fsnotify.h>
26 #include <linux/personality.h>
27 #include <linux/security.h>
28 #include <linux/ima.h>
29 #include <linux/syscalls.h>
30 #include <linux/mount.h>
31 #include <linux/audit.h>
32 #include <linux/capability.h>
33 #include <linux/file.h>
34 #include <linux/fcntl.h>
35 #include <linux/device_cgroup.h>
36 #include <linux/fs_struct.h>
37 #include <linux/posix_acl.h>
38 #include <linux/hash.h>
39 #include <linux/bitops.h>
40 #include <linux/init_task.h>
41 #include <linux/uaccess.h>
46 /* [Feb-1997 T. Schoebel-Theuer]
47 * Fundamental changes in the pathname lookup mechanisms (namei)
48 * were necessary because of omirr. The reason is that omirr needs
49 * to know the _real_ pathname, not the user-supplied one, in case
50 * of symlinks (and also when transname replacements occur).
52 * The new code replaces the old recursive symlink resolution with
53 * an iterative one (in case of non-nested symlink chains). It does
54 * this with calls to <fs>_follow_link().
55 * As a side effect, dir_namei(), _namei() and follow_link() are now
56 * replaced with a single function lookup_dentry() that can handle all
57 * the special cases of the former code.
59 * With the new dcache, the pathname is stored at each inode, at least as
60 * long as the refcount of the inode is positive. As a side effect, the
61 * size of the dcache depends on the inode cache and thus is dynamic.
63 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
64 * resolution to correspond with current state of the code.
66 * Note that the symlink resolution is not *completely* iterative.
67 * There is still a significant amount of tail- and mid- recursion in
68 * the algorithm. Also, note that <fs>_readlink() is not used in
69 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
70 * may return different results than <fs>_follow_link(). Many virtual
71 * filesystems (including /proc) exhibit this behavior.
74 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
75 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
76 * and the name already exists in form of a symlink, try to create the new
77 * name indicated by the symlink. The old code always complained that the
78 * name already exists, due to not following the symlink even if its target
79 * is nonexistent. The new semantics affects also mknod() and link() when
80 * the name is a symlink pointing to a non-existent name.
82 * I don't know which semantics is the right one, since I have no access
83 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
84 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
85 * "old" one. Personally, I think the new semantics is much more logical.
86 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
87 * file does succeed in both HP-UX and SunOs, but not in Solaris
88 * and in the old Linux semantics.
91 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
92 * semantics. See the comments in "open_namei" and "do_link" below.
94 * [10-Sep-98 Alan Modra] Another symlink change.
97 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
98 * inside the path - always follow.
99 * in the last component in creation/removal/renaming - never follow.
100 * if LOOKUP_FOLLOW passed - follow.
101 * if the pathname has trailing slashes - follow.
102 * otherwise - don't follow.
103 * (applied in that order).
105 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
106 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
107 * During the 2.4 we need to fix the userland stuff depending on it -
108 * hopefully we will be able to get rid of that wart in 2.5. So far only
109 * XEmacs seems to be relying on it...
112 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
113 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
114 * any extra contention...
117 /* In order to reduce some races, while at the same time doing additional
118 * checking and hopefully speeding things up, we copy filenames to the
119 * kernel data space before using them..
121 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
122 * PATH_MAX includes the nul terminator --RR.
125 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
128 getname_flags(const char __user *filename, int flags, int *empty)
130 struct filename *result;
134 result = audit_reusename(filename);
138 result = __getname();
139 if (unlikely(!result))
140 return ERR_PTR(-ENOMEM);
143 * First, try to embed the struct filename inside the names_cache
146 kname = (char *)result->iname;
147 result->name = kname;
149 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
150 if (unlikely(len < 0)) {
156 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
157 * separate struct filename so we can dedicate the entire
158 * names_cache allocation for the pathname, and re-do the copy from
161 if (unlikely(len == EMBEDDED_NAME_MAX)) {
162 const size_t size = offsetof(struct filename, iname[1]);
163 kname = (char *)result;
166 * size is chosen that way we to guarantee that
167 * result->iname[0] is within the same object and that
168 * kname can't be equal to result->iname, no matter what.
170 result = kzalloc(size, GFP_KERNEL);
171 if (unlikely(!result)) {
173 return ERR_PTR(-ENOMEM);
175 result->name = kname;
176 len = strncpy_from_user(kname, filename, PATH_MAX);
177 if (unlikely(len < 0)) {
182 if (unlikely(len == PATH_MAX)) {
185 return ERR_PTR(-ENAMETOOLONG);
190 /* The empty path is special. */
191 if (unlikely(!len)) {
194 if (!(flags & LOOKUP_EMPTY)) {
196 return ERR_PTR(-ENOENT);
200 result->uptr = filename;
201 result->aname = NULL;
202 audit_getname(result);
207 getname(const char __user * filename)
209 return getname_flags(filename, 0, NULL);
213 getname_kernel(const char * filename)
215 struct filename *result;
216 int len = strlen(filename) + 1;
218 result = __getname();
219 if (unlikely(!result))
220 return ERR_PTR(-ENOMEM);
222 if (len <= EMBEDDED_NAME_MAX) {
223 result->name = (char *)result->iname;
224 } else if (len <= PATH_MAX) {
225 struct filename *tmp;
227 tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
228 if (unlikely(!tmp)) {
230 return ERR_PTR(-ENOMEM);
232 tmp->name = (char *)result;
236 return ERR_PTR(-ENAMETOOLONG);
238 memcpy((char *)result->name, filename, len);
240 result->aname = NULL;
242 audit_getname(result);
247 void putname(struct filename *name)
249 BUG_ON(name->refcnt <= 0);
251 if (--name->refcnt > 0)
254 if (name->name != name->iname) {
255 __putname(name->name);
261 static int check_acl(struct inode *inode, int mask)
263 #ifdef CONFIG_FS_POSIX_ACL
264 struct posix_acl *acl;
266 if (mask & MAY_NOT_BLOCK) {
267 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
270 /* no ->get_acl() calls in RCU mode... */
271 if (is_uncached_acl(acl))
273 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
276 acl = get_acl(inode, ACL_TYPE_ACCESS);
280 int error = posix_acl_permission(inode, acl, mask);
281 posix_acl_release(acl);
290 * This does the basic permission checking
292 static int acl_permission_check(struct inode *inode, int mask)
294 unsigned int mode = inode->i_mode;
296 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
299 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
300 int error = check_acl(inode, mask);
301 if (error != -EAGAIN)
305 if (in_group_p(inode->i_gid))
310 * If the DACs are ok we don't need any capability check.
312 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
318 * generic_permission - check for access rights on a Posix-like filesystem
319 * @inode: inode to check access rights for
320 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
322 * Used to check for read/write/execute permissions on a file.
323 * We use "fsuid" for this, letting us set arbitrary permissions
324 * for filesystem access without changing the "normal" uids which
325 * are used for other things.
327 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
328 * request cannot be satisfied (eg. requires blocking or too much complexity).
329 * It would then be called again in ref-walk mode.
331 int generic_permission(struct inode *inode, int mask)
336 * Do the basic permission checks.
338 ret = acl_permission_check(inode, mask);
342 if (S_ISDIR(inode->i_mode)) {
343 /* DACs are overridable for directories */
344 if (!(mask & MAY_WRITE))
345 if (capable_wrt_inode_uidgid(inode,
346 CAP_DAC_READ_SEARCH))
348 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
354 * Searching includes executable on directories, else just read.
356 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
357 if (mask == MAY_READ)
358 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
361 * Read/write DACs are always overridable.
362 * Executable DACs are overridable when there is
363 * at least one exec bit set.
365 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
366 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
371 EXPORT_SYMBOL(generic_permission);
374 * We _really_ want to just do "generic_permission()" without
375 * even looking at the inode->i_op values. So we keep a cache
376 * flag in inode->i_opflags, that says "this has not special
377 * permission function, use the fast case".
379 static inline int do_inode_permission(struct inode *inode, int mask)
381 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
382 if (likely(inode->i_op->permission))
383 return inode->i_op->permission(inode, mask);
385 /* This gets set once for the inode lifetime */
386 spin_lock(&inode->i_lock);
387 inode->i_opflags |= IOP_FASTPERM;
388 spin_unlock(&inode->i_lock);
390 return generic_permission(inode, mask);
394 * sb_permission - Check superblock-level permissions
395 * @sb: Superblock of inode to check permission on
396 * @inode: Inode to check permission on
397 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
399 * Separate out file-system wide checks from inode-specific permission checks.
401 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
403 if (unlikely(mask & MAY_WRITE)) {
404 umode_t mode = inode->i_mode;
406 /* Nobody gets write access to a read-only fs. */
407 if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
414 * inode_permission - Check for access rights to a given inode
415 * @inode: Inode to check permission on
416 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
418 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
419 * this, letting us set arbitrary permissions for filesystem access without
420 * changing the "normal" UIDs which are used for other things.
422 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
424 int inode_permission(struct inode *inode, int mask)
428 retval = sb_permission(inode->i_sb, inode, mask);
432 if (unlikely(mask & MAY_WRITE)) {
434 * Nobody gets write access to an immutable file.
436 if (IS_IMMUTABLE(inode))
440 * Updating mtime will likely cause i_uid and i_gid to be
441 * written back improperly if their true value is unknown
444 if (HAS_UNMAPPED_ID(inode))
448 retval = do_inode_permission(inode, mask);
452 retval = devcgroup_inode_permission(inode, mask);
456 return security_inode_permission(inode, mask);
458 EXPORT_SYMBOL(inode_permission);
461 * path_get - get a reference to a path
462 * @path: path to get the reference to
464 * Given a path increment the reference count to the dentry and the vfsmount.
466 void path_get(const struct path *path)
471 EXPORT_SYMBOL(path_get);
474 * path_put - put a reference to a path
475 * @path: path to put the reference to
477 * Given a path decrement the reference count to the dentry and the vfsmount.
479 void path_put(const struct path *path)
484 EXPORT_SYMBOL(path_put);
486 #define EMBEDDED_LEVELS 2
491 struct inode *inode; /* path.dentry.d_inode */
496 int total_link_count;
499 struct delayed_call done;
502 } *stack, internal[EMBEDDED_LEVELS];
503 struct filename *name;
504 struct nameidata *saved;
505 struct inode *link_inode;
508 } __randomize_layout;
510 static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
512 struct nameidata *old = current->nameidata;
513 p->stack = p->internal;
516 p->total_link_count = old ? old->total_link_count : 0;
518 current->nameidata = p;
521 static void restore_nameidata(void)
523 struct nameidata *now = current->nameidata, *old = now->saved;
525 current->nameidata = old;
527 old->total_link_count = now->total_link_count;
528 if (now->stack != now->internal)
532 static int __nd_alloc_stack(struct nameidata *nd)
536 if (nd->flags & LOOKUP_RCU) {
537 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
542 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
547 memcpy(p, nd->internal, sizeof(nd->internal));
553 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
554 * @path: nameidate to verify
556 * Rename can sometimes move a file or directory outside of a bind
557 * mount, path_connected allows those cases to be detected.
559 static bool path_connected(const struct path *path)
561 struct vfsmount *mnt = path->mnt;
562 struct super_block *sb = mnt->mnt_sb;
564 /* Bind mounts and multi-root filesystems can have disconnected paths */
565 if (!(sb->s_iflags & SB_I_MULTIROOT) && (mnt->mnt_root == sb->s_root))
568 return is_subdir(path->dentry, mnt->mnt_root);
571 static inline int nd_alloc_stack(struct nameidata *nd)
573 if (likely(nd->depth != EMBEDDED_LEVELS))
575 if (likely(nd->stack != nd->internal))
577 return __nd_alloc_stack(nd);
580 static void drop_links(struct nameidata *nd)
584 struct saved *last = nd->stack + i;
585 do_delayed_call(&last->done);
586 clear_delayed_call(&last->done);
590 static void terminate_walk(struct nameidata *nd)
593 if (!(nd->flags & LOOKUP_RCU)) {
596 for (i = 0; i < nd->depth; i++)
597 path_put(&nd->stack[i].link);
598 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
603 nd->flags &= ~LOOKUP_RCU;
604 if (!(nd->flags & LOOKUP_ROOT))
611 /* path_put is needed afterwards regardless of success or failure */
612 static bool legitimize_path(struct nameidata *nd,
613 struct path *path, unsigned seq)
615 int res = __legitimize_mnt(path->mnt, nd->m_seq);
622 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
626 return !read_seqcount_retry(&path->dentry->d_seq, seq);
629 static bool legitimize_links(struct nameidata *nd)
632 for (i = 0; i < nd->depth; i++) {
633 struct saved *last = nd->stack + i;
634 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
644 * Path walking has 2 modes, rcu-walk and ref-walk (see
645 * Documentation/filesystems/path-lookup.txt). In situations when we can't
646 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
647 * normal reference counts on dentries and vfsmounts to transition to ref-walk
648 * mode. Refcounts are grabbed at the last known good point before rcu-walk
649 * got stuck, so ref-walk may continue from there. If this is not successful
650 * (eg. a seqcount has changed), then failure is returned and it's up to caller
651 * to restart the path walk from the beginning in ref-walk mode.
655 * unlazy_walk - try to switch to ref-walk mode.
656 * @nd: nameidata pathwalk data
657 * Returns: 0 on success, -ECHILD on failure
659 * unlazy_walk attempts to legitimize the current nd->path and nd->root
661 * Must be called from rcu-walk context.
662 * Nothing should touch nameidata between unlazy_walk() failure and
665 static int unlazy_walk(struct nameidata *nd)
667 struct dentry *parent = nd->path.dentry;
669 BUG_ON(!(nd->flags & LOOKUP_RCU));
671 nd->flags &= ~LOOKUP_RCU;
672 if (unlikely(!legitimize_links(nd)))
674 if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
676 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
677 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq)))
681 BUG_ON(nd->inode != parent->d_inode);
686 nd->path.dentry = NULL;
688 if (!(nd->flags & LOOKUP_ROOT))
696 * unlazy_child - try to switch to ref-walk mode.
697 * @nd: nameidata pathwalk data
698 * @dentry: child of nd->path.dentry
699 * @seq: seq number to check dentry against
700 * Returns: 0 on success, -ECHILD on failure
702 * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry
703 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
704 * @nd. Must be called from rcu-walk context.
705 * Nothing should touch nameidata between unlazy_child() failure and
708 static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned seq)
710 BUG_ON(!(nd->flags & LOOKUP_RCU));
712 nd->flags &= ~LOOKUP_RCU;
713 if (unlikely(!legitimize_links(nd)))
715 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
717 if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
721 * We need to move both the parent and the dentry from the RCU domain
722 * to be properly refcounted. And the sequence number in the dentry
723 * validates *both* dentry counters, since we checked the sequence
724 * number of the parent after we got the child sequence number. So we
725 * know the parent must still be valid if the child sequence number is
727 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
729 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) {
735 * Sequence counts matched. Now make sure that the root is
736 * still valid and get it if required.
738 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
739 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) {
752 nd->path.dentry = NULL;
756 if (!(nd->flags & LOOKUP_ROOT))
761 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
763 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
764 return dentry->d_op->d_revalidate(dentry, flags);
770 * complete_walk - successful completion of path walk
771 * @nd: pointer nameidata
773 * If we had been in RCU mode, drop out of it and legitimize nd->path.
774 * Revalidate the final result, unless we'd already done that during
775 * the path walk or the filesystem doesn't ask for it. Return 0 on
776 * success, -error on failure. In case of failure caller does not
777 * need to drop nd->path.
779 static int complete_walk(struct nameidata *nd)
781 struct dentry *dentry = nd->path.dentry;
784 if (nd->flags & LOOKUP_RCU) {
785 if (!(nd->flags & LOOKUP_ROOT))
787 if (unlikely(unlazy_walk(nd)))
791 if (likely(!(nd->flags & LOOKUP_JUMPED)))
794 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
797 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
807 static void set_root(struct nameidata *nd)
809 struct fs_struct *fs = current->fs;
811 if (nd->flags & LOOKUP_RCU) {
815 seq = read_seqcount_begin(&fs->seq);
817 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
818 } while (read_seqcount_retry(&fs->seq, seq));
820 get_fs_root(fs, &nd->root);
824 static void path_put_conditional(struct path *path, struct nameidata *nd)
827 if (path->mnt != nd->path.mnt)
831 static inline void path_to_nameidata(const struct path *path,
832 struct nameidata *nd)
834 if (!(nd->flags & LOOKUP_RCU)) {
835 dput(nd->path.dentry);
836 if (nd->path.mnt != path->mnt)
837 mntput(nd->path.mnt);
839 nd->path.mnt = path->mnt;
840 nd->path.dentry = path->dentry;
843 static int nd_jump_root(struct nameidata *nd)
845 if (nd->flags & LOOKUP_RCU) {
849 nd->inode = d->d_inode;
850 nd->seq = nd->root_seq;
851 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
857 nd->inode = nd->path.dentry->d_inode;
859 nd->flags |= LOOKUP_JUMPED;
864 * Helper to directly jump to a known parsed path from ->get_link,
865 * caller must have taken a reference to path beforehand.
867 void nd_jump_link(struct path *path)
869 struct nameidata *nd = current->nameidata;
873 nd->inode = nd->path.dentry->d_inode;
874 nd->flags |= LOOKUP_JUMPED;
877 static inline void put_link(struct nameidata *nd)
879 struct saved *last = nd->stack + --nd->depth;
880 do_delayed_call(&last->done);
881 if (!(nd->flags & LOOKUP_RCU))
882 path_put(&last->link);
885 int sysctl_protected_symlinks __read_mostly = 0;
886 int sysctl_protected_hardlinks __read_mostly = 0;
889 * may_follow_link - Check symlink following for unsafe situations
890 * @nd: nameidata pathwalk data
892 * In the case of the sysctl_protected_symlinks sysctl being enabled,
893 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
894 * in a sticky world-writable directory. This is to protect privileged
895 * processes from failing races against path names that may change out
896 * from under them by way of other users creating malicious symlinks.
897 * It will permit symlinks to be followed only when outside a sticky
898 * world-writable directory, or when the uid of the symlink and follower
899 * match, or when the directory owner matches the symlink's owner.
901 * Returns 0 if following the symlink is allowed, -ve on error.
903 static inline int may_follow_link(struct nameidata *nd)
905 const struct inode *inode;
906 const struct inode *parent;
909 if (!sysctl_protected_symlinks)
912 /* Allowed if owner and follower match. */
913 inode = nd->link_inode;
914 if (uid_eq(current_cred()->fsuid, inode->i_uid))
917 /* Allowed if parent directory not sticky and world-writable. */
919 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
922 /* Allowed if parent directory and link owner match. */
923 puid = parent->i_uid;
924 if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
927 if (nd->flags & LOOKUP_RCU)
930 audit_log_link_denied("follow_link", &nd->stack[0].link);
935 * safe_hardlink_source - Check for safe hardlink conditions
936 * @inode: the source inode to hardlink from
938 * Return false if at least one of the following conditions:
939 * - inode is not a regular file
941 * - inode is setgid and group-exec
942 * - access failure for read and write
944 * Otherwise returns true.
946 static bool safe_hardlink_source(struct inode *inode)
948 umode_t mode = inode->i_mode;
950 /* Special files should not get pinned to the filesystem. */
954 /* Setuid files should not get pinned to the filesystem. */
958 /* Executable setgid files should not get pinned to the filesystem. */
959 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
962 /* Hardlinking to unreadable or unwritable sources is dangerous. */
963 if (inode_permission(inode, MAY_READ | MAY_WRITE))
970 * may_linkat - Check permissions for creating a hardlink
971 * @link: the source to hardlink from
973 * Block hardlink when all of:
974 * - sysctl_protected_hardlinks enabled
975 * - fsuid does not match inode
976 * - hardlink source is unsafe (see safe_hardlink_source() above)
977 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
979 * Returns 0 if successful, -ve on error.
981 static int may_linkat(struct path *link)
985 if (!sysctl_protected_hardlinks)
988 inode = link->dentry->d_inode;
990 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
991 * otherwise, it must be a safe source.
993 if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
996 audit_log_link_denied("linkat", link);
1000 static __always_inline
1001 const char *get_link(struct nameidata *nd)
1003 struct saved *last = nd->stack + nd->depth - 1;
1004 struct dentry *dentry = last->link.dentry;
1005 struct inode *inode = nd->link_inode;
1009 if (!(nd->flags & LOOKUP_RCU)) {
1010 touch_atime(&last->link);
1012 } else if (atime_needs_update_rcu(&last->link, inode)) {
1013 if (unlikely(unlazy_walk(nd)))
1014 return ERR_PTR(-ECHILD);
1015 touch_atime(&last->link);
1018 error = security_inode_follow_link(dentry, inode,
1019 nd->flags & LOOKUP_RCU);
1020 if (unlikely(error))
1021 return ERR_PTR(error);
1023 nd->last_type = LAST_BIND;
1024 res = inode->i_link;
1026 const char * (*get)(struct dentry *, struct inode *,
1027 struct delayed_call *);
1028 get = inode->i_op->get_link;
1029 if (nd->flags & LOOKUP_RCU) {
1030 res = get(NULL, inode, &last->done);
1031 if (res == ERR_PTR(-ECHILD)) {
1032 if (unlikely(unlazy_walk(nd)))
1033 return ERR_PTR(-ECHILD);
1034 res = get(dentry, inode, &last->done);
1037 res = get(dentry, inode, &last->done);
1039 if (IS_ERR_OR_NULL(res))
1045 if (unlikely(nd_jump_root(nd)))
1046 return ERR_PTR(-ECHILD);
1047 while (unlikely(*++res == '/'))
1056 * follow_up - Find the mountpoint of path's vfsmount
1058 * Given a path, find the mountpoint of its source file system.
1059 * Replace @path with the path of the mountpoint in the parent mount.
1062 * Return 1 if we went up a level and 0 if we were already at the
1065 int follow_up(struct path *path)
1067 struct mount *mnt = real_mount(path->mnt);
1068 struct mount *parent;
1069 struct dentry *mountpoint;
1071 read_seqlock_excl(&mount_lock);
1072 parent = mnt->mnt_parent;
1073 if (parent == mnt) {
1074 read_sequnlock_excl(&mount_lock);
1077 mntget(&parent->mnt);
1078 mountpoint = dget(mnt->mnt_mountpoint);
1079 read_sequnlock_excl(&mount_lock);
1081 path->dentry = mountpoint;
1083 path->mnt = &parent->mnt;
1086 EXPORT_SYMBOL(follow_up);
1089 * Perform an automount
1090 * - return -EISDIR to tell follow_managed() to stop and return the path we
1093 static int follow_automount(struct path *path, struct nameidata *nd,
1096 struct vfsmount *mnt;
1099 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
1102 /* We don't want to mount if someone's just doing a stat -
1103 * unless they're stat'ing a directory and appended a '/' to
1106 * We do, however, want to mount if someone wants to open or
1107 * create a file of any type under the mountpoint, wants to
1108 * traverse through the mountpoint or wants to open the
1109 * mounted directory. Also, autofs may mark negative dentries
1110 * as being automount points. These will need the attentions
1111 * of the daemon to instantiate them before they can be used.
1113 if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1114 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1115 path->dentry->d_inode)
1118 nd->total_link_count++;
1119 if (nd->total_link_count >= 40)
1122 mnt = path->dentry->d_op->d_automount(path);
1125 * The filesystem is allowed to return -EISDIR here to indicate
1126 * it doesn't want to automount. For instance, autofs would do
1127 * this so that its userspace daemon can mount on this dentry.
1129 * However, we can only permit this if it's a terminal point in
1130 * the path being looked up; if it wasn't then the remainder of
1131 * the path is inaccessible and we should say so.
1133 if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
1135 return PTR_ERR(mnt);
1138 if (!mnt) /* mount collision */
1141 if (!*need_mntput) {
1142 /* lock_mount() may release path->mnt on error */
1144 *need_mntput = true;
1146 err = finish_automount(mnt, path);
1150 /* Someone else made a mount here whilst we were busy */
1155 path->dentry = dget(mnt->mnt_root);
1164 * Handle a dentry that is managed in some way.
1165 * - Flagged for transit management (autofs)
1166 * - Flagged as mountpoint
1167 * - Flagged as automount point
1169 * This may only be called in refwalk mode.
1171 * Serialization is taken care of in namespace.c
1173 static int follow_managed(struct path *path, struct nameidata *nd)
1175 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1177 bool need_mntput = false;
1180 /* Given that we're not holding a lock here, we retain the value in a
1181 * local variable for each dentry as we look at it so that we don't see
1182 * the components of that value change under us */
1183 while (managed = READ_ONCE(path->dentry->d_flags),
1184 managed &= DCACHE_MANAGED_DENTRY,
1185 unlikely(managed != 0)) {
1186 /* Allow the filesystem to manage the transit without i_mutex
1188 if (managed & DCACHE_MANAGE_TRANSIT) {
1189 BUG_ON(!path->dentry->d_op);
1190 BUG_ON(!path->dentry->d_op->d_manage);
1191 ret = path->dentry->d_op->d_manage(path, false);
1196 /* Transit to a mounted filesystem. */
1197 if (managed & DCACHE_MOUNTED) {
1198 struct vfsmount *mounted = lookup_mnt(path);
1203 path->mnt = mounted;
1204 path->dentry = dget(mounted->mnt_root);
1209 /* Something is mounted on this dentry in another
1210 * namespace and/or whatever was mounted there in this
1211 * namespace got unmounted before lookup_mnt() could
1215 /* Handle an automount point */
1216 if (managed & DCACHE_NEED_AUTOMOUNT) {
1217 ret = follow_automount(path, nd, &need_mntput);
1223 /* We didn't change the current path point */
1227 if (need_mntput && path->mnt == mnt)
1229 if (ret == -EISDIR || !ret)
1232 nd->flags |= LOOKUP_JUMPED;
1233 if (unlikely(ret < 0))
1234 path_put_conditional(path, nd);
1238 int follow_down_one(struct path *path)
1240 struct vfsmount *mounted;
1242 mounted = lookup_mnt(path);
1246 path->mnt = mounted;
1247 path->dentry = dget(mounted->mnt_root);
1252 EXPORT_SYMBOL(follow_down_one);
1254 static inline int managed_dentry_rcu(const struct path *path)
1256 return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
1257 path->dentry->d_op->d_manage(path, true) : 0;
1261 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1262 * we meet a managed dentry that would need blocking.
1264 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1265 struct inode **inode, unsigned *seqp)
1268 struct mount *mounted;
1270 * Don't forget we might have a non-mountpoint managed dentry
1271 * that wants to block transit.
1273 switch (managed_dentry_rcu(path)) {
1283 if (!d_mountpoint(path->dentry))
1284 return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1286 mounted = __lookup_mnt(path->mnt, path->dentry);
1289 path->mnt = &mounted->mnt;
1290 path->dentry = mounted->mnt.mnt_root;
1291 nd->flags |= LOOKUP_JUMPED;
1292 *seqp = read_seqcount_begin(&path->dentry->d_seq);
1294 * Update the inode too. We don't need to re-check the
1295 * dentry sequence number here after this d_inode read,
1296 * because a mount-point is always pinned.
1298 *inode = path->dentry->d_inode;
1300 return !read_seqretry(&mount_lock, nd->m_seq) &&
1301 !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1304 static int follow_dotdot_rcu(struct nameidata *nd)
1306 struct inode *inode = nd->inode;
1309 if (path_equal(&nd->path, &nd->root))
1311 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1312 struct dentry *old = nd->path.dentry;
1313 struct dentry *parent = old->d_parent;
1316 inode = parent->d_inode;
1317 seq = read_seqcount_begin(&parent->d_seq);
1318 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
1320 nd->path.dentry = parent;
1322 if (unlikely(!path_connected(&nd->path)))
1326 struct mount *mnt = real_mount(nd->path.mnt);
1327 struct mount *mparent = mnt->mnt_parent;
1328 struct dentry *mountpoint = mnt->mnt_mountpoint;
1329 struct inode *inode2 = mountpoint->d_inode;
1330 unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
1331 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1333 if (&mparent->mnt == nd->path.mnt)
1335 /* we know that mountpoint was pinned */
1336 nd->path.dentry = mountpoint;
1337 nd->path.mnt = &mparent->mnt;
1342 while (unlikely(d_mountpoint(nd->path.dentry))) {
1343 struct mount *mounted;
1344 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
1345 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1349 nd->path.mnt = &mounted->mnt;
1350 nd->path.dentry = mounted->mnt.mnt_root;
1351 inode = nd->path.dentry->d_inode;
1352 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1359 * Follow down to the covering mount currently visible to userspace. At each
1360 * point, the filesystem owning that dentry may be queried as to whether the
1361 * caller is permitted to proceed or not.
1363 int follow_down(struct path *path)
1368 while (managed = READ_ONCE(path->dentry->d_flags),
1369 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1370 /* Allow the filesystem to manage the transit without i_mutex
1373 * We indicate to the filesystem if someone is trying to mount
1374 * something here. This gives autofs the chance to deny anyone
1375 * other than its daemon the right to mount on its
1378 * The filesystem may sleep at this point.
1380 if (managed & DCACHE_MANAGE_TRANSIT) {
1381 BUG_ON(!path->dentry->d_op);
1382 BUG_ON(!path->dentry->d_op->d_manage);
1383 ret = path->dentry->d_op->d_manage(path, false);
1385 return ret == -EISDIR ? 0 : ret;
1388 /* Transit to a mounted filesystem. */
1389 if (managed & DCACHE_MOUNTED) {
1390 struct vfsmount *mounted = lookup_mnt(path);
1395 path->mnt = mounted;
1396 path->dentry = dget(mounted->mnt_root);
1400 /* Don't handle automount points here */
1405 EXPORT_SYMBOL(follow_down);
1408 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1410 static void follow_mount(struct path *path)
1412 while (d_mountpoint(path->dentry)) {
1413 struct vfsmount *mounted = lookup_mnt(path);
1418 path->mnt = mounted;
1419 path->dentry = dget(mounted->mnt_root);
1423 static int path_parent_directory(struct path *path)
1425 struct dentry *old = path->dentry;
1426 /* rare case of legitimate dget_parent()... */
1427 path->dentry = dget_parent(path->dentry);
1429 if (unlikely(!path_connected(path)))
1434 static int follow_dotdot(struct nameidata *nd)
1437 if (nd->path.dentry == nd->root.dentry &&
1438 nd->path.mnt == nd->root.mnt) {
1441 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1442 int ret = path_parent_directory(&nd->path);
1447 if (!follow_up(&nd->path))
1450 follow_mount(&nd->path);
1451 nd->inode = nd->path.dentry->d_inode;
1456 * This looks up the name in dcache and possibly revalidates the found dentry.
1457 * NULL is returned if the dentry does not exist in the cache.
1459 static struct dentry *lookup_dcache(const struct qstr *name,
1463 struct dentry *dentry = d_lookup(dir, name);
1465 int error = d_revalidate(dentry, flags);
1466 if (unlikely(error <= 0)) {
1468 d_invalidate(dentry);
1470 return ERR_PTR(error);
1477 * Call i_op->lookup on the dentry. The dentry must be negative and
1480 * dir->d_inode->i_mutex must be held
1482 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1487 /* Don't create child dentry for a dead directory. */
1488 if (unlikely(IS_DEADDIR(dir))) {
1490 return ERR_PTR(-ENOENT);
1493 old = dir->i_op->lookup(dir, dentry, flags);
1494 if (unlikely(old)) {
1501 static struct dentry *__lookup_hash(const struct qstr *name,
1502 struct dentry *base, unsigned int flags)
1504 struct dentry *dentry = lookup_dcache(name, base, flags);
1509 dentry = d_alloc(base, name);
1510 if (unlikely(!dentry))
1511 return ERR_PTR(-ENOMEM);
1513 return lookup_real(base->d_inode, dentry, flags);
1516 static int lookup_fast(struct nameidata *nd,
1517 struct path *path, struct inode **inode,
1520 struct vfsmount *mnt = nd->path.mnt;
1521 struct dentry *dentry, *parent = nd->path.dentry;
1526 * Rename seqlock is not required here because in the off chance
1527 * of a false negative due to a concurrent rename, the caller is
1528 * going to fall back to non-racy lookup.
1530 if (nd->flags & LOOKUP_RCU) {
1533 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1534 if (unlikely(!dentry)) {
1535 if (unlazy_walk(nd))
1541 * This sequence count validates that the inode matches
1542 * the dentry name information from lookup.
1544 *inode = d_backing_inode(dentry);
1545 negative = d_is_negative(dentry);
1546 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
1550 * This sequence count validates that the parent had no
1551 * changes while we did the lookup of the dentry above.
1553 * The memory barrier in read_seqcount_begin of child is
1554 * enough, we can use __read_seqcount_retry here.
1556 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
1560 status = d_revalidate(dentry, nd->flags);
1561 if (likely(status > 0)) {
1563 * Note: do negative dentry check after revalidation in
1564 * case that drops it.
1566 if (unlikely(negative))
1569 path->dentry = dentry;
1570 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
1573 if (unlazy_child(nd, dentry, seq))
1575 if (unlikely(status == -ECHILD))
1576 /* we'd been told to redo it in non-rcu mode */
1577 status = d_revalidate(dentry, nd->flags);
1579 dentry = __d_lookup(parent, &nd->last);
1580 if (unlikely(!dentry))
1582 status = d_revalidate(dentry, nd->flags);
1584 if (unlikely(status <= 0)) {
1586 d_invalidate(dentry);
1590 if (unlikely(d_is_negative(dentry))) {
1596 path->dentry = dentry;
1597 err = follow_managed(path, nd);
1598 if (likely(err > 0))
1599 *inode = d_backing_inode(path->dentry);
1603 /* Fast lookup failed, do it the slow way */
1604 static struct dentry *lookup_slow(const struct qstr *name,
1608 struct dentry *dentry = ERR_PTR(-ENOENT), *old;
1609 struct inode *inode = dir->d_inode;
1610 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1612 inode_lock_shared(inode);
1613 /* Don't go there if it's already dead */
1614 if (unlikely(IS_DEADDIR(inode)))
1617 dentry = d_alloc_parallel(dir, name, &wq);
1620 if (unlikely(!d_in_lookup(dentry))) {
1621 if (!(flags & LOOKUP_NO_REVAL)) {
1622 int error = d_revalidate(dentry, flags);
1623 if (unlikely(error <= 0)) {
1625 d_invalidate(dentry);
1630 dentry = ERR_PTR(error);
1634 old = inode->i_op->lookup(inode, dentry, flags);
1635 d_lookup_done(dentry);
1636 if (unlikely(old)) {
1642 inode_unlock_shared(inode);
1646 static inline int may_lookup(struct nameidata *nd)
1648 if (nd->flags & LOOKUP_RCU) {
1649 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1652 if (unlazy_walk(nd))
1655 return inode_permission(nd->inode, MAY_EXEC);
1658 static inline int handle_dots(struct nameidata *nd, int type)
1660 if (type == LAST_DOTDOT) {
1663 if (nd->flags & LOOKUP_RCU) {
1664 return follow_dotdot_rcu(nd);
1666 return follow_dotdot(nd);
1671 static int pick_link(struct nameidata *nd, struct path *link,
1672 struct inode *inode, unsigned seq)
1676 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) {
1677 path_to_nameidata(link, nd);
1680 if (!(nd->flags & LOOKUP_RCU)) {
1681 if (link->mnt == nd->path.mnt)
1684 error = nd_alloc_stack(nd);
1685 if (unlikely(error)) {
1686 if (error == -ECHILD) {
1687 if (unlikely(!legitimize_path(nd, link, seq))) {
1690 nd->flags &= ~LOOKUP_RCU;
1691 nd->path.mnt = NULL;
1692 nd->path.dentry = NULL;
1693 if (!(nd->flags & LOOKUP_ROOT))
1694 nd->root.mnt = NULL;
1696 } else if (likely(unlazy_walk(nd)) == 0)
1697 error = nd_alloc_stack(nd);
1705 last = nd->stack + nd->depth++;
1707 clear_delayed_call(&last->done);
1708 nd->link_inode = inode;
1713 enum {WALK_FOLLOW = 1, WALK_MORE = 2};
1716 * Do we need to follow links? We _really_ want to be able
1717 * to do this check without having to look at inode->i_op,
1718 * so we keep a cache of "no, this doesn't need follow_link"
1719 * for the common case.
1721 static inline int step_into(struct nameidata *nd, struct path *path,
1722 int flags, struct inode *inode, unsigned seq)
1724 if (!(flags & WALK_MORE) && nd->depth)
1726 if (likely(!d_is_symlink(path->dentry)) ||
1727 !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) {
1728 /* not a symlink or should not follow */
1729 path_to_nameidata(path, nd);
1734 /* make sure that d_is_symlink above matches inode */
1735 if (nd->flags & LOOKUP_RCU) {
1736 if (read_seqcount_retry(&path->dentry->d_seq, seq))
1739 return pick_link(nd, path, inode, seq);
1742 static int walk_component(struct nameidata *nd, int flags)
1745 struct inode *inode;
1749 * "." and ".." are special - ".." especially so because it has
1750 * to be able to know about the current root directory and
1751 * parent relationships.
1753 if (unlikely(nd->last_type != LAST_NORM)) {
1754 err = handle_dots(nd, nd->last_type);
1755 if (!(flags & WALK_MORE) && nd->depth)
1759 err = lookup_fast(nd, &path, &inode, &seq);
1760 if (unlikely(err <= 0)) {
1763 path.dentry = lookup_slow(&nd->last, nd->path.dentry,
1765 if (IS_ERR(path.dentry))
1766 return PTR_ERR(path.dentry);
1768 path.mnt = nd->path.mnt;
1769 err = follow_managed(&path, nd);
1770 if (unlikely(err < 0))
1773 if (unlikely(d_is_negative(path.dentry))) {
1774 path_to_nameidata(&path, nd);
1778 seq = 0; /* we are already out of RCU mode */
1779 inode = d_backing_inode(path.dentry);
1782 return step_into(nd, &path, flags, inode, seq);
1786 * We can do the critical dentry name comparison and hashing
1787 * operations one word at a time, but we are limited to:
1789 * - Architectures with fast unaligned word accesses. We could
1790 * do a "get_unaligned()" if this helps and is sufficiently
1793 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1794 * do not trap on the (extremely unlikely) case of a page
1795 * crossing operation.
1797 * - Furthermore, we need an efficient 64-bit compile for the
1798 * 64-bit case in order to generate the "number of bytes in
1799 * the final mask". Again, that could be replaced with a
1800 * efficient population count instruction or similar.
1802 #ifdef CONFIG_DCACHE_WORD_ACCESS
1804 #include <asm/word-at-a-time.h>
1808 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1810 #elif defined(CONFIG_64BIT)
1812 * Register pressure in the mixing function is an issue, particularly
1813 * on 32-bit x86, but almost any function requires one state value and
1814 * one temporary. Instead, use a function designed for two state values
1815 * and no temporaries.
1817 * This function cannot create a collision in only two iterations, so
1818 * we have two iterations to achieve avalanche. In those two iterations,
1819 * we have six layers of mixing, which is enough to spread one bit's
1820 * influence out to 2^6 = 64 state bits.
1822 * Rotate constants are scored by considering either 64 one-bit input
1823 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
1824 * probability of that delta causing a change to each of the 128 output
1825 * bits, using a sample of random initial states.
1827 * The Shannon entropy of the computed probabilities is then summed
1828 * to produce a score. Ideally, any input change has a 50% chance of
1829 * toggling any given output bit.
1831 * Mixing scores (in bits) for (12,45):
1832 * Input delta: 1-bit 2-bit
1833 * 1 round: 713.3 42542.6
1834 * 2 rounds: 2753.7 140389.8
1835 * 3 rounds: 5954.1 233458.2
1836 * 4 rounds: 7862.6 256672.2
1837 * Perfect: 8192 258048
1838 * (64*128) (64*63/2 * 128)
1840 #define HASH_MIX(x, y, a) \
1842 y ^= x, x = rol64(x,12),\
1843 x += y, y = rol64(y,45),\
1847 * Fold two longs into one 32-bit hash value. This must be fast, but
1848 * latency isn't quite as critical, as there is a fair bit of additional
1849 * work done before the hash value is used.
1851 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1853 y ^= x * GOLDEN_RATIO_64;
1854 y *= GOLDEN_RATIO_64;
1858 #else /* 32-bit case */
1861 * Mixing scores (in bits) for (7,20):
1862 * Input delta: 1-bit 2-bit
1863 * 1 round: 330.3 9201.6
1864 * 2 rounds: 1246.4 25475.4
1865 * 3 rounds: 1907.1 31295.1
1866 * 4 rounds: 2042.3 31718.6
1867 * Perfect: 2048 31744
1868 * (32*64) (32*31/2 * 64)
1870 #define HASH_MIX(x, y, a) \
1872 y ^= x, x = rol32(x, 7),\
1873 x += y, y = rol32(y,20),\
1876 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1878 /* Use arch-optimized multiply if one exists */
1879 return __hash_32(y ^ __hash_32(x));
1885 * Return the hash of a string of known length. This is carfully
1886 * designed to match hash_name(), which is the more critical function.
1887 * In particular, we must end by hashing a final word containing 0..7
1888 * payload bytes, to match the way that hash_name() iterates until it
1889 * finds the delimiter after the name.
1891 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
1893 unsigned long a, x = 0, y = (unsigned long)salt;
1898 a = load_unaligned_zeropad(name);
1899 if (len < sizeof(unsigned long))
1902 name += sizeof(unsigned long);
1903 len -= sizeof(unsigned long);
1905 x ^= a & bytemask_from_count(len);
1907 return fold_hash(x, y);
1909 EXPORT_SYMBOL(full_name_hash);
1911 /* Return the "hash_len" (hash and length) of a null-terminated string */
1912 u64 hashlen_string(const void *salt, const char *name)
1914 unsigned long a = 0, x = 0, y = (unsigned long)salt;
1915 unsigned long adata, mask, len;
1916 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1923 len += sizeof(unsigned long);
1925 a = load_unaligned_zeropad(name+len);
1926 } while (!has_zero(a, &adata, &constants));
1928 adata = prep_zero_mask(a, adata, &constants);
1929 mask = create_zero_mask(adata);
1930 x ^= a & zero_bytemask(mask);
1932 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
1934 EXPORT_SYMBOL(hashlen_string);
1937 * Calculate the length and hash of the path component, and
1938 * return the "hash_len" as the result.
1940 static inline u64 hash_name(const void *salt, const char *name)
1942 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
1943 unsigned long adata, bdata, mask, len;
1944 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1951 len += sizeof(unsigned long);
1953 a = load_unaligned_zeropad(name+len);
1954 b = a ^ REPEAT_BYTE('/');
1955 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1957 adata = prep_zero_mask(a, adata, &constants);
1958 bdata = prep_zero_mask(b, bdata, &constants);
1959 mask = create_zero_mask(adata | bdata);
1960 x ^= a & zero_bytemask(mask);
1962 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
1965 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
1967 /* Return the hash of a string of known length */
1968 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
1970 unsigned long hash = init_name_hash(salt);
1972 hash = partial_name_hash((unsigned char)*name++, hash);
1973 return end_name_hash(hash);
1975 EXPORT_SYMBOL(full_name_hash);
1977 /* Return the "hash_len" (hash and length) of a null-terminated string */
1978 u64 hashlen_string(const void *salt, const char *name)
1980 unsigned long hash = init_name_hash(salt);
1981 unsigned long len = 0, c;
1983 c = (unsigned char)*name;
1986 hash = partial_name_hash(c, hash);
1987 c = (unsigned char)name[len];
1989 return hashlen_create(end_name_hash(hash), len);
1991 EXPORT_SYMBOL(hashlen_string);
1994 * We know there's a real path component here of at least
1997 static inline u64 hash_name(const void *salt, const char *name)
1999 unsigned long hash = init_name_hash(salt);
2000 unsigned long len = 0, c;
2002 c = (unsigned char)*name;
2005 hash = partial_name_hash(c, hash);
2006 c = (unsigned char)name[len];
2007 } while (c && c != '/');
2008 return hashlen_create(end_name_hash(hash), len);
2015 * This is the basic name resolution function, turning a pathname into
2016 * the final dentry. We expect 'base' to be positive and a directory.
2018 * Returns 0 and nd will have valid dentry and mnt on success.
2019 * Returns error and drops reference to input namei data on failure.
2021 static int link_path_walk(const char *name, struct nameidata *nd)
2030 /* At this point we know we have a real path component. */
2035 err = may_lookup(nd);
2039 hash_len = hash_name(nd->path.dentry, name);
2042 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2044 if (name[1] == '.') {
2046 nd->flags |= LOOKUP_JUMPED;
2052 if (likely(type == LAST_NORM)) {
2053 struct dentry *parent = nd->path.dentry;
2054 nd->flags &= ~LOOKUP_JUMPED;
2055 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2056 struct qstr this = { { .hash_len = hash_len }, .name = name };
2057 err = parent->d_op->d_hash(parent, &this);
2060 hash_len = this.hash_len;
2065 nd->last.hash_len = hash_len;
2066 nd->last.name = name;
2067 nd->last_type = type;
2069 name += hashlen_len(hash_len);
2073 * If it wasn't NUL, we know it was '/'. Skip that
2074 * slash, and continue until no more slashes.
2078 } while (unlikely(*name == '/'));
2079 if (unlikely(!*name)) {
2081 /* pathname body, done */
2084 name = nd->stack[nd->depth - 1].name;
2085 /* trailing symlink, done */
2088 /* last component of nested symlink */
2089 err = walk_component(nd, WALK_FOLLOW);
2091 /* not the last component */
2092 err = walk_component(nd, WALK_FOLLOW | WALK_MORE);
2098 const char *s = get_link(nd);
2107 nd->stack[nd->depth - 1].name = name;
2112 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2113 if (nd->flags & LOOKUP_RCU) {
2114 if (unlazy_walk(nd))
2122 static const char *path_init(struct nameidata *nd, unsigned flags)
2124 const char *s = nd->name->name;
2127 flags &= ~LOOKUP_RCU;
2129 nd->last_type = LAST_ROOT; /* if there are only slashes... */
2130 nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
2132 if (flags & LOOKUP_ROOT) {
2133 struct dentry *root = nd->root.dentry;
2134 struct inode *inode = root->d_inode;
2135 if (*s && unlikely(!d_can_lookup(root)))
2136 return ERR_PTR(-ENOTDIR);
2137 nd->path = nd->root;
2139 if (flags & LOOKUP_RCU) {
2141 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2142 nd->root_seq = nd->seq;
2143 nd->m_seq = read_seqbegin(&mount_lock);
2145 path_get(&nd->path);
2150 nd->root.mnt = NULL;
2151 nd->path.mnt = NULL;
2152 nd->path.dentry = NULL;
2154 nd->m_seq = read_seqbegin(&mount_lock);
2156 if (flags & LOOKUP_RCU)
2159 if (likely(!nd_jump_root(nd)))
2161 nd->root.mnt = NULL;
2163 return ERR_PTR(-ECHILD);
2164 } else if (nd->dfd == AT_FDCWD) {
2165 if (flags & LOOKUP_RCU) {
2166 struct fs_struct *fs = current->fs;
2172 seq = read_seqcount_begin(&fs->seq);
2174 nd->inode = nd->path.dentry->d_inode;
2175 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2176 } while (read_seqcount_retry(&fs->seq, seq));
2178 get_fs_pwd(current->fs, &nd->path);
2179 nd->inode = nd->path.dentry->d_inode;
2183 /* Caller must check execute permissions on the starting path component */
2184 struct fd f = fdget_raw(nd->dfd);
2185 struct dentry *dentry;
2188 return ERR_PTR(-EBADF);
2190 dentry = f.file->f_path.dentry;
2193 if (!d_can_lookup(dentry)) {
2195 return ERR_PTR(-ENOTDIR);
2199 nd->path = f.file->f_path;
2200 if (flags & LOOKUP_RCU) {
2202 nd->inode = nd->path.dentry->d_inode;
2203 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2205 path_get(&nd->path);
2206 nd->inode = nd->path.dentry->d_inode;
2213 static const char *trailing_symlink(struct nameidata *nd)
2216 int error = may_follow_link(nd);
2217 if (unlikely(error))
2218 return ERR_PTR(error);
2219 nd->flags |= LOOKUP_PARENT;
2220 nd->stack[0].name = NULL;
2225 static inline int lookup_last(struct nameidata *nd)
2227 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2228 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2230 nd->flags &= ~LOOKUP_PARENT;
2231 return walk_component(nd, 0);
2234 static int handle_lookup_down(struct nameidata *nd)
2236 struct path path = nd->path;
2237 struct inode *inode = nd->inode;
2238 unsigned seq = nd->seq;
2241 if (nd->flags & LOOKUP_RCU) {
2243 * don't bother with unlazy_walk on failure - we are
2244 * at the very beginning of walk, so we lose nothing
2245 * if we simply redo everything in non-RCU mode
2247 if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq)))
2251 err = follow_managed(&path, nd);
2252 if (unlikely(err < 0))
2254 inode = d_backing_inode(path.dentry);
2257 path_to_nameidata(&path, nd);
2263 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2264 static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2266 const char *s = path_init(nd, flags);
2272 if (unlikely(flags & LOOKUP_DOWN)) {
2273 err = handle_lookup_down(nd);
2274 if (unlikely(err < 0)) {
2280 while (!(err = link_path_walk(s, nd))
2281 && ((err = lookup_last(nd)) > 0)) {
2282 s = trailing_symlink(nd);
2289 err = complete_walk(nd);
2291 if (!err && nd->flags & LOOKUP_DIRECTORY)
2292 if (!d_can_lookup(nd->path.dentry))
2296 nd->path.mnt = NULL;
2297 nd->path.dentry = NULL;
2303 static int filename_lookup(int dfd, struct filename *name, unsigned flags,
2304 struct path *path, struct path *root)
2307 struct nameidata nd;
2309 return PTR_ERR(name);
2310 if (unlikely(root)) {
2312 flags |= LOOKUP_ROOT;
2314 set_nameidata(&nd, dfd, name);
2315 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2316 if (unlikely(retval == -ECHILD))
2317 retval = path_lookupat(&nd, flags, path);
2318 if (unlikely(retval == -ESTALE))
2319 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2321 if (likely(!retval))
2322 audit_inode(name, path->dentry, flags & LOOKUP_PARENT);
2323 restore_nameidata();
2328 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2329 static int path_parentat(struct nameidata *nd, unsigned flags,
2330 struct path *parent)
2332 const char *s = path_init(nd, flags);
2336 err = link_path_walk(s, nd);
2338 err = complete_walk(nd);
2341 nd->path.mnt = NULL;
2342 nd->path.dentry = NULL;
2348 static struct filename *filename_parentat(int dfd, struct filename *name,
2349 unsigned int flags, struct path *parent,
2350 struct qstr *last, int *type)
2353 struct nameidata nd;
2357 set_nameidata(&nd, dfd, name);
2358 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2359 if (unlikely(retval == -ECHILD))
2360 retval = path_parentat(&nd, flags, parent);
2361 if (unlikely(retval == -ESTALE))
2362 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2363 if (likely(!retval)) {
2365 *type = nd.last_type;
2366 audit_inode(name, parent->dentry, LOOKUP_PARENT);
2369 name = ERR_PTR(retval);
2371 restore_nameidata();
2375 /* does lookup, returns the object with parent locked */
2376 struct dentry *kern_path_locked(const char *name, struct path *path)
2378 struct filename *filename;
2383 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
2385 if (IS_ERR(filename))
2386 return ERR_CAST(filename);
2387 if (unlikely(type != LAST_NORM)) {
2390 return ERR_PTR(-EINVAL);
2392 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2393 d = __lookup_hash(&last, path->dentry, 0);
2395 inode_unlock(path->dentry->d_inode);
2402 int kern_path(const char *name, unsigned int flags, struct path *path)
2404 return filename_lookup(AT_FDCWD, getname_kernel(name),
2407 EXPORT_SYMBOL(kern_path);
2410 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2411 * @dentry: pointer to dentry of the base directory
2412 * @mnt: pointer to vfs mount of the base directory
2413 * @name: pointer to file name
2414 * @flags: lookup flags
2415 * @path: pointer to struct path to fill
2417 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2418 const char *name, unsigned int flags,
2421 struct path root = {.mnt = mnt, .dentry = dentry};
2422 /* the first argument of filename_lookup() is ignored with root */
2423 return filename_lookup(AT_FDCWD, getname_kernel(name),
2424 flags , path, &root);
2426 EXPORT_SYMBOL(vfs_path_lookup);
2429 * lookup_one_len - filesystem helper to lookup single pathname component
2430 * @name: pathname component to lookup
2431 * @base: base directory to lookup from
2432 * @len: maximum length @len should be interpreted to
2434 * Note that this routine is purely a helper for filesystem usage and should
2435 * not be called by generic code.
2437 * The caller must hold base->i_mutex.
2439 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2445 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2449 this.hash = full_name_hash(base, name, len);
2451 return ERR_PTR(-EACCES);
2453 if (unlikely(name[0] == '.')) {
2454 if (len < 2 || (len == 2 && name[1] == '.'))
2455 return ERR_PTR(-EACCES);
2459 c = *(const unsigned char *)name++;
2460 if (c == '/' || c == '\0')
2461 return ERR_PTR(-EACCES);
2464 * See if the low-level filesystem might want
2465 * to use its own hash..
2467 if (base->d_flags & DCACHE_OP_HASH) {
2468 int err = base->d_op->d_hash(base, &this);
2470 return ERR_PTR(err);
2473 err = inode_permission(base->d_inode, MAY_EXEC);
2475 return ERR_PTR(err);
2477 return __lookup_hash(&this, base, 0);
2479 EXPORT_SYMBOL(lookup_one_len);
2482 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2483 * @name: pathname component to lookup
2484 * @base: base directory to lookup from
2485 * @len: maximum length @len should be interpreted to
2487 * Note that this routine is purely a helper for filesystem usage and should
2488 * not be called by generic code.
2490 * Unlike lookup_one_len, it should be called without the parent
2491 * i_mutex held, and will take the i_mutex itself if necessary.
2493 struct dentry *lookup_one_len_unlocked(const char *name,
2494 struct dentry *base, int len)
2503 this.hash = full_name_hash(base, name, len);
2505 return ERR_PTR(-EACCES);
2507 if (unlikely(name[0] == '.')) {
2508 if (len < 2 || (len == 2 && name[1] == '.'))
2509 return ERR_PTR(-EACCES);
2513 c = *(const unsigned char *)name++;
2514 if (c == '/' || c == '\0')
2515 return ERR_PTR(-EACCES);
2518 * See if the low-level filesystem might want
2519 * to use its own hash..
2521 if (base->d_flags & DCACHE_OP_HASH) {
2522 int err = base->d_op->d_hash(base, &this);
2524 return ERR_PTR(err);
2527 err = inode_permission(base->d_inode, MAY_EXEC);
2529 return ERR_PTR(err);
2531 ret = lookup_dcache(&this, base, 0);
2533 ret = lookup_slow(&this, base, 0);
2536 EXPORT_SYMBOL(lookup_one_len_unlocked);
2538 #ifdef CONFIG_UNIX98_PTYS
2539 int path_pts(struct path *path)
2541 /* Find something mounted on "pts" in the same directory as
2544 struct dentry *child, *parent;
2548 ret = path_parent_directory(path);
2552 parent = path->dentry;
2555 child = d_hash_and_lookup(parent, &this);
2559 path->dentry = child;
2566 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2567 struct path *path, int *empty)
2569 return filename_lookup(dfd, getname_flags(name, flags, empty),
2572 EXPORT_SYMBOL(user_path_at_empty);
2575 * mountpoint_last - look up last component for umount
2576 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2578 * This is a special lookup_last function just for umount. In this case, we
2579 * need to resolve the path without doing any revalidation.
2581 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2582 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2583 * in almost all cases, this lookup will be served out of the dcache. The only
2584 * cases where it won't are if nd->last refers to a symlink or the path is
2585 * bogus and it doesn't exist.
2588 * -error: if there was an error during lookup. This includes -ENOENT if the
2589 * lookup found a negative dentry.
2591 * 0: if we successfully resolved nd->last and found it to not to be a
2592 * symlink that needs to be followed.
2594 * 1: if we successfully resolved nd->last and found it to be a symlink
2595 * that needs to be followed.
2598 mountpoint_last(struct nameidata *nd)
2601 struct dentry *dir = nd->path.dentry;
2604 /* If we're in rcuwalk, drop out of it to handle last component */
2605 if (nd->flags & LOOKUP_RCU) {
2606 if (unlazy_walk(nd))
2610 nd->flags &= ~LOOKUP_PARENT;
2612 if (unlikely(nd->last_type != LAST_NORM)) {
2613 error = handle_dots(nd, nd->last_type);
2616 path.dentry = dget(nd->path.dentry);
2618 path.dentry = d_lookup(dir, &nd->last);
2621 * No cached dentry. Mounted dentries are pinned in the
2622 * cache, so that means that this dentry is probably
2623 * a symlink or the path doesn't actually point
2624 * to a mounted dentry.
2626 path.dentry = lookup_slow(&nd->last, dir,
2627 nd->flags | LOOKUP_NO_REVAL);
2628 if (IS_ERR(path.dentry))
2629 return PTR_ERR(path.dentry);
2632 if (d_is_negative(path.dentry)) {
2636 path.mnt = nd->path.mnt;
2637 return step_into(nd, &path, 0, d_backing_inode(path.dentry), 0);
2641 * path_mountpoint - look up a path to be umounted
2642 * @nd: lookup context
2643 * @flags: lookup flags
2644 * @path: pointer to container for result
2646 * Look up the given name, but don't attempt to revalidate the last component.
2647 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2650 path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path)
2652 const char *s = path_init(nd, flags);
2656 while (!(err = link_path_walk(s, nd)) &&
2657 (err = mountpoint_last(nd)) > 0) {
2658 s = trailing_symlink(nd);
2666 nd->path.mnt = NULL;
2667 nd->path.dentry = NULL;
2675 filename_mountpoint(int dfd, struct filename *name, struct path *path,
2678 struct nameidata nd;
2681 return PTR_ERR(name);
2682 set_nameidata(&nd, dfd, name);
2683 error = path_mountpoint(&nd, flags | LOOKUP_RCU, path);
2684 if (unlikely(error == -ECHILD))
2685 error = path_mountpoint(&nd, flags, path);
2686 if (unlikely(error == -ESTALE))
2687 error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
2689 audit_inode(name, path->dentry, 0);
2690 restore_nameidata();
2696 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2697 * @dfd: directory file descriptor
2698 * @name: pathname from userland
2699 * @flags: lookup flags
2700 * @path: pointer to container to hold result
2702 * A umount is a special case for path walking. We're not actually interested
2703 * in the inode in this situation, and ESTALE errors can be a problem. We
2704 * simply want track down the dentry and vfsmount attached at the mountpoint
2705 * and avoid revalidating the last component.
2707 * Returns 0 and populates "path" on success.
2710 user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
2713 return filename_mountpoint(dfd, getname(name), path, flags);
2717 kern_path_mountpoint(int dfd, const char *name, struct path *path,
2720 return filename_mountpoint(dfd, getname_kernel(name), path, flags);
2722 EXPORT_SYMBOL(kern_path_mountpoint);
2724 int __check_sticky(struct inode *dir, struct inode *inode)
2726 kuid_t fsuid = current_fsuid();
2728 if (uid_eq(inode->i_uid, fsuid))
2730 if (uid_eq(dir->i_uid, fsuid))
2732 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
2734 EXPORT_SYMBOL(__check_sticky);
2737 * Check whether we can remove a link victim from directory dir, check
2738 * whether the type of victim is right.
2739 * 1. We can't do it if dir is read-only (done in permission())
2740 * 2. We should have write and exec permissions on dir
2741 * 3. We can't remove anything from append-only dir
2742 * 4. We can't do anything with immutable dir (done in permission())
2743 * 5. If the sticky bit on dir is set we should either
2744 * a. be owner of dir, or
2745 * b. be owner of victim, or
2746 * c. have CAP_FOWNER capability
2747 * 6. If the victim is append-only or immutable we can't do antyhing with
2748 * links pointing to it.
2749 * 7. If the victim has an unknown uid or gid we can't change the inode.
2750 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2751 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2752 * 10. We can't remove a root or mountpoint.
2753 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2754 * nfs_async_unlink().
2756 static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
2758 struct inode *inode = d_backing_inode(victim);
2761 if (d_is_negative(victim))
2765 BUG_ON(victim->d_parent->d_inode != dir);
2766 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2768 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2774 if (check_sticky(dir, inode) || IS_APPEND(inode) ||
2775 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
2778 if (!d_is_dir(victim))
2780 if (IS_ROOT(victim))
2782 } else if (d_is_dir(victim))
2784 if (IS_DEADDIR(dir))
2786 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2791 /* Check whether we can create an object with dentry child in directory
2793 * 1. We can't do it if child already exists (open has special treatment for
2794 * this case, but since we are inlined it's OK)
2795 * 2. We can't do it if dir is read-only (done in permission())
2796 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2797 * 4. We should have write and exec permissions on dir
2798 * 5. We can't do it if dir is immutable (done in permission())
2800 static inline int may_create(struct inode *dir, struct dentry *child)
2802 struct user_namespace *s_user_ns;
2803 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2806 if (IS_DEADDIR(dir))
2808 s_user_ns = dir->i_sb->s_user_ns;
2809 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
2810 !kgid_has_mapping(s_user_ns, current_fsgid()))
2812 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2816 * p1 and p2 should be directories on the same fs.
2818 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2823 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2827 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
2829 p = d_ancestor(p2, p1);
2831 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2832 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
2836 p = d_ancestor(p1, p2);
2838 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2839 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
2843 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2844 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
2847 EXPORT_SYMBOL(lock_rename);
2849 void unlock_rename(struct dentry *p1, struct dentry *p2)
2851 inode_unlock(p1->d_inode);
2853 inode_unlock(p2->d_inode);
2854 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
2857 EXPORT_SYMBOL(unlock_rename);
2859 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2862 int error = may_create(dir, dentry);
2866 if (!dir->i_op->create)
2867 return -EACCES; /* shouldn't it be ENOSYS? */
2870 error = security_inode_create(dir, dentry, mode);
2873 error = dir->i_op->create(dir, dentry, mode, want_excl);
2875 fsnotify_create(dir, dentry);
2878 EXPORT_SYMBOL(vfs_create);
2880 int vfs_mkobj(struct dentry *dentry, umode_t mode,
2881 int (*f)(struct dentry *, umode_t, void *),
2884 struct inode *dir = dentry->d_parent->d_inode;
2885 int error = may_create(dir, dentry);
2891 error = security_inode_create(dir, dentry, mode);
2894 error = f(dentry, mode, arg);
2896 fsnotify_create(dir, dentry);
2899 EXPORT_SYMBOL(vfs_mkobj);
2901 bool may_open_dev(const struct path *path)
2903 return !(path->mnt->mnt_flags & MNT_NODEV) &&
2904 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
2907 static int may_open(const struct path *path, int acc_mode, int flag)
2909 struct dentry *dentry = path->dentry;
2910 struct inode *inode = dentry->d_inode;
2916 switch (inode->i_mode & S_IFMT) {
2920 if (acc_mode & MAY_WRITE)
2925 if (!may_open_dev(path))
2934 error = inode_permission(inode, MAY_OPEN | acc_mode);
2939 * An append-only file must be opened in append mode for writing.
2941 if (IS_APPEND(inode)) {
2942 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2948 /* O_NOATIME can only be set by the owner or superuser */
2949 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2955 static int handle_truncate(struct file *filp)
2957 const struct path *path = &filp->f_path;
2958 struct inode *inode = path->dentry->d_inode;
2959 int error = get_write_access(inode);
2963 * Refuse to truncate files with mandatory locks held on them.
2965 error = locks_verify_locked(filp);
2967 error = security_path_truncate(path);
2969 error = do_truncate(path->dentry, 0,
2970 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2973 put_write_access(inode);
2977 static inline int open_to_namei_flags(int flag)
2979 if ((flag & O_ACCMODE) == 3)
2984 static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode)
2986 struct user_namespace *s_user_ns;
2987 int error = security_path_mknod(dir, dentry, mode, 0);
2991 s_user_ns = dir->dentry->d_sb->s_user_ns;
2992 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
2993 !kgid_has_mapping(s_user_ns, current_fsgid()))
2996 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
3000 return security_inode_create(dir->dentry->d_inode, dentry, mode);
3004 * Attempt to atomically look up, create and open a file from a negative
3007 * Returns 0 if successful. The file will have been created and attached to
3008 * @file by the filesystem calling finish_open().
3010 * Returns 1 if the file was looked up only or didn't need creating. The
3011 * caller will need to perform the open themselves. @path will have been
3012 * updated to point to the new dentry. This may be negative.
3014 * Returns an error code otherwise.
3016 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
3017 struct path *path, struct file *file,
3018 const struct open_flags *op,
3019 int open_flag, umode_t mode,
3022 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3023 struct inode *dir = nd->path.dentry->d_inode;
3026 if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */
3027 open_flag &= ~O_TRUNC;
3029 if (nd->flags & LOOKUP_DIRECTORY)
3030 open_flag |= O_DIRECTORY;
3032 file->f_path.dentry = DENTRY_NOT_SET;
3033 file->f_path.mnt = nd->path.mnt;
3034 error = dir->i_op->atomic_open(dir, dentry, file,
3035 open_to_namei_flags(open_flag),
3037 d_lookup_done(dentry);
3040 * We didn't have the inode before the open, so check open
3043 int acc_mode = op->acc_mode;
3044 if (*opened & FILE_CREATED) {
3045 WARN_ON(!(open_flag & O_CREAT));
3046 fsnotify_create(dir, dentry);
3049 error = may_open(&file->f_path, acc_mode, open_flag);
3050 if (WARN_ON(error > 0))
3052 } else if (error > 0) {
3053 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3056 if (file->f_path.dentry) {
3058 dentry = file->f_path.dentry;
3060 if (*opened & FILE_CREATED)
3061 fsnotify_create(dir, dentry);
3062 if (unlikely(d_is_negative(dentry))) {
3065 path->dentry = dentry;
3066 path->mnt = nd->path.mnt;
3076 * Look up and maybe create and open the last component.
3078 * Must be called with i_mutex held on parent.
3080 * Returns 0 if the file was successfully atomically created (if necessary) and
3081 * opened. In this case the file will be returned attached to @file.
3083 * Returns 1 if the file was not completely opened at this time, though lookups
3084 * and creations will have been performed and the dentry returned in @path will
3085 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
3086 * specified then a negative dentry may be returned.
3088 * An error code is returned otherwise.
3090 * FILE_CREATE will be set in @*opened if the dentry was created and will be
3091 * cleared otherwise prior to returning.
3093 static int lookup_open(struct nameidata *nd, struct path *path,
3095 const struct open_flags *op,
3096 bool got_write, int *opened)
3098 struct dentry *dir = nd->path.dentry;
3099 struct inode *dir_inode = dir->d_inode;
3100 int open_flag = op->open_flag;
3101 struct dentry *dentry;
3102 int error, create_error = 0;
3103 umode_t mode = op->mode;
3104 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3106 if (unlikely(IS_DEADDIR(dir_inode)))
3109 *opened &= ~FILE_CREATED;
3110 dentry = d_lookup(dir, &nd->last);
3113 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3115 return PTR_ERR(dentry);
3117 if (d_in_lookup(dentry))
3120 error = d_revalidate(dentry, nd->flags);
3121 if (likely(error > 0))
3125 d_invalidate(dentry);
3129 if (dentry->d_inode) {
3130 /* Cached positive dentry: will open in f_op->open */
3135 * Checking write permission is tricky, bacuse we don't know if we are
3136 * going to actually need it: O_CREAT opens should work as long as the
3137 * file exists. But checking existence breaks atomicity. The trick is
3138 * to check access and if not granted clear O_CREAT from the flags.
3140 * Another problem is returing the "right" error value (e.g. for an
3141 * O_EXCL open we want to return EEXIST not EROFS).
3143 if (open_flag & O_CREAT) {
3144 if (!IS_POSIXACL(dir->d_inode))
3145 mode &= ~current_umask();
3146 if (unlikely(!got_write)) {
3147 create_error = -EROFS;
3148 open_flag &= ~O_CREAT;
3149 if (open_flag & (O_EXCL | O_TRUNC))
3151 /* No side effects, safe to clear O_CREAT */
3153 create_error = may_o_create(&nd->path, dentry, mode);
3155 open_flag &= ~O_CREAT;
3156 if (open_flag & O_EXCL)
3160 } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) &&
3161 unlikely(!got_write)) {
3163 * No O_CREATE -> atomicity not a requirement -> fall
3164 * back to lookup + open
3169 if (dir_inode->i_op->atomic_open) {
3170 error = atomic_open(nd, dentry, path, file, op, open_flag,
3172 if (unlikely(error == -ENOENT) && create_error)
3173 error = create_error;
3178 if (d_in_lookup(dentry)) {
3179 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3181 d_lookup_done(dentry);
3182 if (unlikely(res)) {
3184 error = PTR_ERR(res);
3192 /* Negative dentry, just create the file */
3193 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3194 *opened |= FILE_CREATED;
3195 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3196 if (!dir_inode->i_op->create) {
3200 error = dir_inode->i_op->create(dir_inode, dentry, mode,
3201 open_flag & O_EXCL);
3204 fsnotify_create(dir_inode, dentry);
3206 if (unlikely(create_error) && !dentry->d_inode) {
3207 error = create_error;
3211 path->dentry = dentry;
3212 path->mnt = nd->path.mnt;
3221 * Handle the last step of open()
3223 static int do_last(struct nameidata *nd,
3224 struct file *file, const struct open_flags *op,
3227 struct dentry *dir = nd->path.dentry;
3228 int open_flag = op->open_flag;
3229 bool will_truncate = (open_flag & O_TRUNC) != 0;
3230 bool got_write = false;
3231 int acc_mode = op->acc_mode;
3233 struct inode *inode;
3237 nd->flags &= ~LOOKUP_PARENT;
3238 nd->flags |= op->intent;
3240 if (nd->last_type != LAST_NORM) {
3241 error = handle_dots(nd, nd->last_type);
3242 if (unlikely(error))
3247 if (!(open_flag & O_CREAT)) {
3248 if (nd->last.name[nd->last.len])
3249 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3250 /* we _can_ be in RCU mode here */
3251 error = lookup_fast(nd, &path, &inode, &seq);
3252 if (likely(error > 0))
3258 BUG_ON(nd->inode != dir->d_inode);
3259 BUG_ON(nd->flags & LOOKUP_RCU);
3261 /* create side of things */
3263 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3264 * has been cleared when we got to the last component we are
3267 error = complete_walk(nd);
3271 audit_inode(nd->name, dir, LOOKUP_PARENT);
3272 /* trailing slashes? */
3273 if (unlikely(nd->last.name[nd->last.len]))
3277 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3278 error = mnt_want_write(nd->path.mnt);
3282 * do _not_ fail yet - we might not need that or fail with
3283 * a different error; let lookup_open() decide; we'll be
3284 * dropping this one anyway.
3287 if (open_flag & O_CREAT)
3288 inode_lock(dir->d_inode);
3290 inode_lock_shared(dir->d_inode);
3291 error = lookup_open(nd, &path, file, op, got_write, opened);
3292 if (open_flag & O_CREAT)
3293 inode_unlock(dir->d_inode);
3295 inode_unlock_shared(dir->d_inode);
3301 if ((*opened & FILE_CREATED) ||
3302 !S_ISREG(file_inode(file)->i_mode))
3303 will_truncate = false;
3305 audit_inode(nd->name, file->f_path.dentry, 0);
3309 if (*opened & FILE_CREATED) {
3310 /* Don't check for write permission, don't truncate */
3311 open_flag &= ~O_TRUNC;
3312 will_truncate = false;
3314 path_to_nameidata(&path, nd);
3315 goto finish_open_created;
3319 * If atomic_open() acquired write access it is dropped now due to
3320 * possible mount and symlink following (this might be optimized away if
3324 mnt_drop_write(nd->path.mnt);
3328 error = follow_managed(&path, nd);
3329 if (unlikely(error < 0))
3332 if (unlikely(d_is_negative(path.dentry))) {
3333 path_to_nameidata(&path, nd);
3338 * create/update audit record if it already exists.
3340 audit_inode(nd->name, path.dentry, 0);
3342 if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
3343 path_to_nameidata(&path, nd);
3347 seq = 0; /* out of RCU mode, so the value doesn't matter */
3348 inode = d_backing_inode(path.dentry);
3350 error = step_into(nd, &path, 0, inode, seq);
3351 if (unlikely(error))
3354 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3355 error = complete_walk(nd);
3358 audit_inode(nd->name, nd->path.dentry, 0);
3360 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
3363 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3365 if (!d_is_reg(nd->path.dentry))
3366 will_truncate = false;
3368 if (will_truncate) {
3369 error = mnt_want_write(nd->path.mnt);
3374 finish_open_created:
3375 error = may_open(&nd->path, acc_mode, open_flag);
3378 BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
3379 error = vfs_open(&nd->path, file, current_cred());
3382 *opened |= FILE_OPENED;
3384 error = open_check_o_direct(file);
3386 error = ima_file_check(file, op->acc_mode, *opened);
3387 if (!error && will_truncate)
3388 error = handle_truncate(file);
3390 if (unlikely(error) && (*opened & FILE_OPENED))
3392 if (unlikely(error > 0)) {
3397 mnt_drop_write(nd->path.mnt);
3401 struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode, int open_flag)
3403 struct dentry *child = NULL;
3404 struct inode *dir = dentry->d_inode;
3405 struct inode *inode;
3408 /* we want directory to be writable */
3409 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
3412 error = -EOPNOTSUPP;
3413 if (!dir->i_op->tmpfile)
3416 child = d_alloc(dentry, &slash_name);
3417 if (unlikely(!child))
3419 error = dir->i_op->tmpfile(dir, child, mode);
3423 inode = child->d_inode;
3424 if (unlikely(!inode))
3426 if (!(open_flag & O_EXCL)) {
3427 spin_lock(&inode->i_lock);
3428 inode->i_state |= I_LINKABLE;
3429 spin_unlock(&inode->i_lock);
3435 return ERR_PTR(error);
3437 EXPORT_SYMBOL(vfs_tmpfile);
3439 static int do_tmpfile(struct nameidata *nd, unsigned flags,
3440 const struct open_flags *op,
3441 struct file *file, int *opened)
3443 struct dentry *child;
3445 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3446 if (unlikely(error))
3448 error = mnt_want_write(path.mnt);
3449 if (unlikely(error))
3451 child = vfs_tmpfile(path.dentry, op->mode, op->open_flag);
3452 error = PTR_ERR(child);
3456 path.dentry = child;
3457 audit_inode(nd->name, child, 0);
3458 /* Don't check for other permissions, the inode was just created */
3459 error = may_open(&path, 0, op->open_flag);
3462 file->f_path.mnt = path.mnt;
3463 error = finish_open(file, child, NULL, opened);
3466 error = open_check_o_direct(file);
3470 mnt_drop_write(path.mnt);
3476 static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3479 int error = path_lookupat(nd, flags, &path);
3481 audit_inode(nd->name, path.dentry, 0);
3482 error = vfs_open(&path, file, current_cred());
3488 static struct file *path_openat(struct nameidata *nd,
3489 const struct open_flags *op, unsigned flags)
3496 file = get_empty_filp();
3500 file->f_flags = op->open_flag;
3502 if (unlikely(file->f_flags & __O_TMPFILE)) {
3503 error = do_tmpfile(nd, flags, op, file, &opened);
3507 if (unlikely(file->f_flags & O_PATH)) {
3508 error = do_o_path(nd, flags, file);
3510 opened |= FILE_OPENED;
3514 s = path_init(nd, flags);
3519 while (!(error = link_path_walk(s, nd)) &&
3520 (error = do_last(nd, file, op, &opened)) > 0) {
3521 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3522 s = trailing_symlink(nd);
3530 if (!(opened & FILE_OPENED)) {
3534 if (unlikely(error)) {
3535 if (error == -EOPENSTALE) {
3536 if (flags & LOOKUP_RCU)
3541 file = ERR_PTR(error);
3546 struct file *do_filp_open(int dfd, struct filename *pathname,
3547 const struct open_flags *op)
3549 struct nameidata nd;
3550 int flags = op->lookup_flags;
3553 set_nameidata(&nd, dfd, pathname);
3554 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3555 if (unlikely(filp == ERR_PTR(-ECHILD)))
3556 filp = path_openat(&nd, op, flags);
3557 if (unlikely(filp == ERR_PTR(-ESTALE)))
3558 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3559 restore_nameidata();
3563 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3564 const char *name, const struct open_flags *op)
3566 struct nameidata nd;
3568 struct filename *filename;
3569 int flags = op->lookup_flags | LOOKUP_ROOT;
3572 nd.root.dentry = dentry;
3574 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
3575 return ERR_PTR(-ELOOP);
3577 filename = getname_kernel(name);
3578 if (IS_ERR(filename))
3579 return ERR_CAST(filename);
3581 set_nameidata(&nd, -1, filename);
3582 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3583 if (unlikely(file == ERR_PTR(-ECHILD)))
3584 file = path_openat(&nd, op, flags);
3585 if (unlikely(file == ERR_PTR(-ESTALE)))
3586 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3587 restore_nameidata();
3592 static struct dentry *filename_create(int dfd, struct filename *name,
3593 struct path *path, unsigned int lookup_flags)
3595 struct dentry *dentry = ERR_PTR(-EEXIST);
3600 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3603 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3604 * other flags passed in are ignored!
3606 lookup_flags &= LOOKUP_REVAL;
3608 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
3610 return ERR_CAST(name);
3613 * Yucky last component or no last component at all?
3614 * (foo/., foo/.., /////)
3616 if (unlikely(type != LAST_NORM))
3619 /* don't fail immediately if it's r/o, at least try to report other errors */
3620 err2 = mnt_want_write(path->mnt);
3622 * Do the final lookup.
3624 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3625 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3626 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
3631 if (d_is_positive(dentry))
3635 * Special case - lookup gave negative, but... we had foo/bar/
3636 * From the vfs_mknod() POV we just have a negative dentry -
3637 * all is fine. Let's be bastards - you had / on the end, you've
3638 * been asking for (non-existent) directory. -ENOENT for you.
3640 if (unlikely(!is_dir && last.name[last.len])) {
3644 if (unlikely(err2)) {
3652 dentry = ERR_PTR(error);
3654 inode_unlock(path->dentry->d_inode);
3656 mnt_drop_write(path->mnt);
3663 struct dentry *kern_path_create(int dfd, const char *pathname,
3664 struct path *path, unsigned int lookup_flags)
3666 return filename_create(dfd, getname_kernel(pathname),
3667 path, lookup_flags);
3669 EXPORT_SYMBOL(kern_path_create);
3671 void done_path_create(struct path *path, struct dentry *dentry)
3674 inode_unlock(path->dentry->d_inode);
3675 mnt_drop_write(path->mnt);
3678 EXPORT_SYMBOL(done_path_create);
3680 inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3681 struct path *path, unsigned int lookup_flags)
3683 return filename_create(dfd, getname(pathname), path, lookup_flags);
3685 EXPORT_SYMBOL(user_path_create);
3687 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3689 int error = may_create(dir, dentry);
3694 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3697 if (!dir->i_op->mknod)
3700 error = devcgroup_inode_mknod(mode, dev);
3704 error = security_inode_mknod(dir, dentry, mode, dev);
3708 error = dir->i_op->mknod(dir, dentry, mode, dev);
3710 fsnotify_create(dir, dentry);
3713 EXPORT_SYMBOL(vfs_mknod);
3715 static int may_mknod(umode_t mode)
3717 switch (mode & S_IFMT) {
3723 case 0: /* zero mode translates to S_IFREG */
3732 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3735 struct dentry *dentry;
3738 unsigned int lookup_flags = 0;
3740 error = may_mknod(mode);
3744 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3746 return PTR_ERR(dentry);
3748 if (!IS_POSIXACL(path.dentry->d_inode))
3749 mode &= ~current_umask();
3750 error = security_path_mknod(&path, dentry, mode, dev);
3753 switch (mode & S_IFMT) {
3754 case 0: case S_IFREG:
3755 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3757 ima_post_path_mknod(dentry);
3759 case S_IFCHR: case S_IFBLK:
3760 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3761 new_decode_dev(dev));
3763 case S_IFIFO: case S_IFSOCK:
3764 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3768 done_path_create(&path, dentry);
3769 if (retry_estale(error, lookup_flags)) {
3770 lookup_flags |= LOOKUP_REVAL;
3776 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3778 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3781 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3783 int error = may_create(dir, dentry);
3784 unsigned max_links = dir->i_sb->s_max_links;
3789 if (!dir->i_op->mkdir)
3792 mode &= (S_IRWXUGO|S_ISVTX);
3793 error = security_inode_mkdir(dir, dentry, mode);
3797 if (max_links && dir->i_nlink >= max_links)
3800 error = dir->i_op->mkdir(dir, dentry, mode);
3802 fsnotify_mkdir(dir, dentry);
3805 EXPORT_SYMBOL(vfs_mkdir);
3807 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3809 struct dentry *dentry;
3812 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3815 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3817 return PTR_ERR(dentry);
3819 if (!IS_POSIXACL(path.dentry->d_inode))
3820 mode &= ~current_umask();
3821 error = security_path_mkdir(&path, dentry, mode);
3823 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3824 done_path_create(&path, dentry);
3825 if (retry_estale(error, lookup_flags)) {
3826 lookup_flags |= LOOKUP_REVAL;
3832 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3834 return sys_mkdirat(AT_FDCWD, pathname, mode);
3837 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3839 int error = may_delete(dir, dentry, 1);
3844 if (!dir->i_op->rmdir)
3848 inode_lock(dentry->d_inode);
3851 if (is_local_mountpoint(dentry))
3854 error = security_inode_rmdir(dir, dentry);
3858 shrink_dcache_parent(dentry);
3859 error = dir->i_op->rmdir(dir, dentry);
3863 dentry->d_inode->i_flags |= S_DEAD;
3865 detach_mounts(dentry);
3868 inode_unlock(dentry->d_inode);
3874 EXPORT_SYMBOL(vfs_rmdir);
3876 static long do_rmdir(int dfd, const char __user *pathname)
3879 struct filename *name;
3880 struct dentry *dentry;
3884 unsigned int lookup_flags = 0;
3886 name = filename_parentat(dfd, getname(pathname), lookup_flags,
3887 &path, &last, &type);
3889 return PTR_ERR(name);
3903 error = mnt_want_write(path.mnt);
3907 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3908 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3909 error = PTR_ERR(dentry);
3912 if (!dentry->d_inode) {
3916 error = security_path_rmdir(&path, dentry);
3919 error = vfs_rmdir(path.dentry->d_inode, dentry);
3923 inode_unlock(path.dentry->d_inode);
3924 mnt_drop_write(path.mnt);
3928 if (retry_estale(error, lookup_flags)) {
3929 lookup_flags |= LOOKUP_REVAL;
3935 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3937 return do_rmdir(AT_FDCWD, pathname);
3941 * vfs_unlink - unlink a filesystem object
3942 * @dir: parent directory
3944 * @delegated_inode: returns victim inode, if the inode is delegated.
3946 * The caller must hold dir->i_mutex.
3948 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3949 * return a reference to the inode in delegated_inode. The caller
3950 * should then break the delegation on that inode and retry. Because
3951 * breaking a delegation may take a long time, the caller should drop
3952 * dir->i_mutex before doing so.
3954 * Alternatively, a caller may pass NULL for delegated_inode. This may
3955 * be appropriate for callers that expect the underlying filesystem not
3956 * to be NFS exported.
3958 int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
3960 struct inode *target = dentry->d_inode;
3961 int error = may_delete(dir, dentry, 0);
3966 if (!dir->i_op->unlink)
3970 if (is_local_mountpoint(dentry))
3973 error = security_inode_unlink(dir, dentry);
3975 error = try_break_deleg(target, delegated_inode);
3978 error = dir->i_op->unlink(dir, dentry);
3981 detach_mounts(dentry);
3986 inode_unlock(target);
3988 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3989 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3990 fsnotify_link_count(target);
3996 EXPORT_SYMBOL(vfs_unlink);
3999 * Make sure that the actual truncation of the file will occur outside its
4000 * directory's i_mutex. Truncate can take a long time if there is a lot of
4001 * writeout happening, and we don't want to prevent access to the directory
4002 * while waiting on the I/O.
4004 long do_unlinkat(int dfd, struct filename *name)
4007 struct dentry *dentry;
4011 struct inode *inode = NULL;
4012 struct inode *delegated_inode = NULL;
4013 unsigned int lookup_flags = 0;
4015 name = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4017 return PTR_ERR(name);
4020 if (type != LAST_NORM)
4023 error = mnt_want_write(path.mnt);
4027 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4028 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4029 error = PTR_ERR(dentry);
4030 if (!IS_ERR(dentry)) {
4031 /* Why not before? Because we want correct error value */
4032 if (last.name[last.len])
4034 inode = dentry->d_inode;
4035 if (d_is_negative(dentry))
4038 error = security_path_unlink(&path, dentry);
4041 error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode);
4045 inode_unlock(path.dentry->d_inode);
4047 iput(inode); /* truncate the inode here */
4049 if (delegated_inode) {
4050 error = break_deleg_wait(&delegated_inode);
4054 mnt_drop_write(path.mnt);
4057 if (retry_estale(error, lookup_flags)) {
4058 lookup_flags |= LOOKUP_REVAL;
4066 if (d_is_negative(dentry))
4068 else if (d_is_dir(dentry))
4075 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4077 if ((flag & ~AT_REMOVEDIR) != 0)
4080 if (flag & AT_REMOVEDIR)
4081 return do_rmdir(dfd, pathname);
4083 return do_unlinkat(dfd, getname(pathname));
4086 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4088 return do_unlinkat(AT_FDCWD, getname(pathname));
4091 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
4093 int error = may_create(dir, dentry);
4098 if (!dir->i_op->symlink)
4101 error = security_inode_symlink(dir, dentry, oldname);
4105 error = dir->i_op->symlink(dir, dentry, oldname);
4107 fsnotify_create(dir, dentry);
4110 EXPORT_SYMBOL(vfs_symlink);
4112 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4113 int, newdfd, const char __user *, newname)
4116 struct filename *from;
4117 struct dentry *dentry;
4119 unsigned int lookup_flags = 0;
4121 from = getname(oldname);
4123 return PTR_ERR(from);
4125 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
4126 error = PTR_ERR(dentry);
4130 error = security_path_symlink(&path, dentry, from->name);
4132 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
4133 done_path_create(&path, dentry);
4134 if (retry_estale(error, lookup_flags)) {
4135 lookup_flags |= LOOKUP_REVAL;
4143 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4145 return sys_symlinkat(oldname, AT_FDCWD, newname);
4149 * vfs_link - create a new link
4150 * @old_dentry: object to be linked
4152 * @new_dentry: where to create the new link
4153 * @delegated_inode: returns inode needing a delegation break
4155 * The caller must hold dir->i_mutex
4157 * If vfs_link discovers a delegation on the to-be-linked file in need
4158 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4159 * inode in delegated_inode. The caller should then break the delegation
4160 * and retry. Because breaking a delegation may take a long time, the
4161 * caller should drop the i_mutex before doing so.
4163 * Alternatively, a caller may pass NULL for delegated_inode. This may
4164 * be appropriate for callers that expect the underlying filesystem not
4165 * to be NFS exported.
4167 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
4169 struct inode *inode = old_dentry->d_inode;
4170 unsigned max_links = dir->i_sb->s_max_links;
4176 error = may_create(dir, new_dentry);
4180 if (dir->i_sb != inode->i_sb)
4184 * A link to an append-only or immutable file cannot be created.
4186 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4189 * Updating the link count will likely cause i_uid and i_gid to
4190 * be writen back improperly if their true value is unknown to
4193 if (HAS_UNMAPPED_ID(inode))
4195 if (!dir->i_op->link)
4197 if (S_ISDIR(inode->i_mode))
4200 error = security_inode_link(old_dentry, dir, new_dentry);
4205 /* Make sure we don't allow creating hardlink to an unlinked file */
4206 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4208 else if (max_links && inode->i_nlink >= max_links)
4211 error = try_break_deleg(inode, delegated_inode);
4213 error = dir->i_op->link(old_dentry, dir, new_dentry);
4216 if (!error && (inode->i_state & I_LINKABLE)) {
4217 spin_lock(&inode->i_lock);
4218 inode->i_state &= ~I_LINKABLE;
4219 spin_unlock(&inode->i_lock);
4221 inode_unlock(inode);
4223 fsnotify_link(dir, inode, new_dentry);
4226 EXPORT_SYMBOL(vfs_link);
4229 * Hardlinks are often used in delicate situations. We avoid
4230 * security-related surprises by not following symlinks on the
4233 * We don't follow them on the oldname either to be compatible
4234 * with linux 2.0, and to avoid hard-linking to directories
4235 * and other special files. --ADM
4237 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4238 int, newdfd, const char __user *, newname, int, flags)
4240 struct dentry *new_dentry;
4241 struct path old_path, new_path;
4242 struct inode *delegated_inode = NULL;
4246 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
4249 * To use null names we require CAP_DAC_READ_SEARCH
4250 * This ensures that not everyone will be able to create
4251 * handlink using the passed filedescriptor.
4253 if (flags & AT_EMPTY_PATH) {
4254 if (!capable(CAP_DAC_READ_SEARCH))
4259 if (flags & AT_SYMLINK_FOLLOW)
4260 how |= LOOKUP_FOLLOW;
4262 error = user_path_at(olddfd, oldname, how, &old_path);
4266 new_dentry = user_path_create(newdfd, newname, &new_path,
4267 (how & LOOKUP_REVAL));
4268 error = PTR_ERR(new_dentry);
4269 if (IS_ERR(new_dentry))
4273 if (old_path.mnt != new_path.mnt)
4275 error = may_linkat(&old_path);
4276 if (unlikely(error))
4278 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4281 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
4283 done_path_create(&new_path, new_dentry);
4284 if (delegated_inode) {
4285 error = break_deleg_wait(&delegated_inode);
4287 path_put(&old_path);
4291 if (retry_estale(error, how)) {
4292 path_put(&old_path);
4293 how |= LOOKUP_REVAL;
4297 path_put(&old_path);
4302 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4304 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4308 * vfs_rename - rename a filesystem object
4309 * @old_dir: parent of source
4310 * @old_dentry: source
4311 * @new_dir: parent of destination
4312 * @new_dentry: destination
4313 * @delegated_inode: returns an inode needing a delegation break
4314 * @flags: rename flags
4316 * The caller must hold multiple mutexes--see lock_rename()).
4318 * If vfs_rename discovers a delegation in need of breaking at either
4319 * the source or destination, it will return -EWOULDBLOCK and return a
4320 * reference to the inode in delegated_inode. The caller should then
4321 * break the delegation and retry. Because breaking a delegation may
4322 * take a long time, the caller should drop all locks before doing
4325 * Alternatively, a caller may pass NULL for delegated_inode. This may
4326 * be appropriate for callers that expect the underlying filesystem not
4327 * to be NFS exported.
4329 * The worst of all namespace operations - renaming directory. "Perverted"
4330 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4333 * a) we can get into loop creation.
4334 * b) race potential - two innocent renames can create a loop together.
4335 * That's where 4.4 screws up. Current fix: serialization on
4336 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4338 * c) we have to lock _four_ objects - parents and victim (if it exists),
4339 * and source (if it is not a directory).
4340 * And that - after we got ->i_mutex on parents (until then we don't know
4341 * whether the target exists). Solution: try to be smart with locking
4342 * order for inodes. We rely on the fact that tree topology may change
4343 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4344 * move will be locked. Thus we can rank directories by the tree
4345 * (ancestors first) and rank all non-directories after them.
4346 * That works since everybody except rename does "lock parent, lookup,
4347 * lock child" and rename is under ->s_vfs_rename_mutex.
4348 * HOWEVER, it relies on the assumption that any object with ->lookup()
4349 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4350 * we'd better make sure that there's no link(2) for them.
4351 * d) conversion from fhandle to dentry may come in the wrong moment - when
4352 * we are removing the target. Solution: we will have to grab ->i_mutex
4353 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4354 * ->i_mutex on parents, which works but leads to some truly excessive
4357 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
4358 struct inode *new_dir, struct dentry *new_dentry,
4359 struct inode **delegated_inode, unsigned int flags)
4362 bool is_dir = d_is_dir(old_dentry);
4363 struct inode *source = old_dentry->d_inode;
4364 struct inode *target = new_dentry->d_inode;
4365 bool new_is_dir = false;
4366 unsigned max_links = new_dir->i_sb->s_max_links;
4367 struct name_snapshot old_name;
4369 if (source == target)
4372 error = may_delete(old_dir, old_dentry, is_dir);
4377 error = may_create(new_dir, new_dentry);
4379 new_is_dir = d_is_dir(new_dentry);
4381 if (!(flags & RENAME_EXCHANGE))
4382 error = may_delete(new_dir, new_dentry, is_dir);
4384 error = may_delete(new_dir, new_dentry, new_is_dir);
4389 if (!old_dir->i_op->rename)
4393 * If we are going to change the parent - check write permissions,
4394 * we'll need to flip '..'.
4396 if (new_dir != old_dir) {
4398 error = inode_permission(source, MAY_WRITE);
4402 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4403 error = inode_permission(target, MAY_WRITE);
4409 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4414 take_dentry_name_snapshot(&old_name, old_dentry);
4416 if (!is_dir || (flags & RENAME_EXCHANGE))
4417 lock_two_nondirectories(source, target);
4422 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4425 if (max_links && new_dir != old_dir) {
4427 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4429 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4430 old_dir->i_nlink >= max_links)
4433 if (is_dir && !(flags & RENAME_EXCHANGE) && target)
4434 shrink_dcache_parent(new_dentry);
4436 error = try_break_deleg(source, delegated_inode);
4440 if (target && !new_is_dir) {
4441 error = try_break_deleg(target, delegated_inode);
4445 error = old_dir->i_op->rename(old_dir, old_dentry,
4446 new_dir, new_dentry, flags);
4450 if (!(flags & RENAME_EXCHANGE) && target) {
4452 target->i_flags |= S_DEAD;
4453 dont_mount(new_dentry);
4454 detach_mounts(new_dentry);
4456 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4457 if (!(flags & RENAME_EXCHANGE))
4458 d_move(old_dentry, new_dentry);
4460 d_exchange(old_dentry, new_dentry);
4463 if (!is_dir || (flags & RENAME_EXCHANGE))
4464 unlock_two_nondirectories(source, target);
4466 inode_unlock(target);
4469 fsnotify_move(old_dir, new_dir, old_name.name, is_dir,
4470 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4471 if (flags & RENAME_EXCHANGE) {
4472 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
4473 new_is_dir, NULL, new_dentry);
4476 release_dentry_name_snapshot(&old_name);
4480 EXPORT_SYMBOL(vfs_rename);
4482 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4483 int, newdfd, const char __user *, newname, unsigned int, flags)
4485 struct dentry *old_dentry, *new_dentry;
4486 struct dentry *trap;
4487 struct path old_path, new_path;
4488 struct qstr old_last, new_last;
4489 int old_type, new_type;
4490 struct inode *delegated_inode = NULL;
4491 struct filename *from;
4492 struct filename *to;
4493 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4494 bool should_retry = false;
4497 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4500 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4501 (flags & RENAME_EXCHANGE))
4504 if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
4507 if (flags & RENAME_EXCHANGE)
4511 from = filename_parentat(olddfd, getname(oldname), lookup_flags,
4512 &old_path, &old_last, &old_type);
4514 error = PTR_ERR(from);
4518 to = filename_parentat(newdfd, getname(newname), lookup_flags,
4519 &new_path, &new_last, &new_type);
4521 error = PTR_ERR(to);
4526 if (old_path.mnt != new_path.mnt)
4530 if (old_type != LAST_NORM)
4533 if (flags & RENAME_NOREPLACE)
4535 if (new_type != LAST_NORM)
4538 error = mnt_want_write(old_path.mnt);
4543 trap = lock_rename(new_path.dentry, old_path.dentry);
4545 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4546 error = PTR_ERR(old_dentry);
4547 if (IS_ERR(old_dentry))
4549 /* source must exist */
4551 if (d_is_negative(old_dentry))
4553 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4554 error = PTR_ERR(new_dentry);
4555 if (IS_ERR(new_dentry))
4558 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4560 if (flags & RENAME_EXCHANGE) {
4562 if (d_is_negative(new_dentry))
4565 if (!d_is_dir(new_dentry)) {
4567 if (new_last.name[new_last.len])
4571 /* unless the source is a directory trailing slashes give -ENOTDIR */
4572 if (!d_is_dir(old_dentry)) {
4574 if (old_last.name[old_last.len])
4576 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4579 /* source should not be ancestor of target */
4581 if (old_dentry == trap)
4583 /* target should not be an ancestor of source */
4584 if (!(flags & RENAME_EXCHANGE))
4586 if (new_dentry == trap)
4589 error = security_path_rename(&old_path, old_dentry,
4590 &new_path, new_dentry, flags);
4593 error = vfs_rename(old_path.dentry->d_inode, old_dentry,
4594 new_path.dentry->d_inode, new_dentry,
4595 &delegated_inode, flags);
4601 unlock_rename(new_path.dentry, old_path.dentry);
4602 if (delegated_inode) {
4603 error = break_deleg_wait(&delegated_inode);
4607 mnt_drop_write(old_path.mnt);
4609 if (retry_estale(error, lookup_flags))
4610 should_retry = true;
4611 path_put(&new_path);
4614 path_put(&old_path);
4617 should_retry = false;
4618 lookup_flags |= LOOKUP_REVAL;
4625 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4626 int, newdfd, const char __user *, newname)
4628 return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
4631 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4633 return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4636 int vfs_whiteout(struct inode *dir, struct dentry *dentry)
4638 int error = may_create(dir, dentry);
4642 if (!dir->i_op->mknod)
4645 return dir->i_op->mknod(dir, dentry,
4646 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
4648 EXPORT_SYMBOL(vfs_whiteout);
4650 int readlink_copy(char __user *buffer, int buflen, const char *link)
4652 int len = PTR_ERR(link);
4657 if (len > (unsigned) buflen)
4659 if (copy_to_user(buffer, link, len))
4666 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4667 * have ->get_link() not calling nd_jump_link(). Using (or not using) it
4668 * for any given inode is up to filesystem.
4670 static int generic_readlink(struct dentry *dentry, char __user *buffer,
4673 DEFINE_DELAYED_CALL(done);
4674 struct inode *inode = d_inode(dentry);
4675 const char *link = inode->i_link;
4679 link = inode->i_op->get_link(dentry, inode, &done);
4681 return PTR_ERR(link);
4683 res = readlink_copy(buffer, buflen, link);
4684 do_delayed_call(&done);
4689 * vfs_readlink - copy symlink body into userspace buffer
4690 * @dentry: dentry on which to get symbolic link
4691 * @buffer: user memory pointer
4692 * @buflen: size of buffer
4694 * Does not touch atime. That's up to the caller if necessary
4696 * Does not call security hook.
4698 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4700 struct inode *inode = d_inode(dentry);
4702 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
4703 if (unlikely(inode->i_op->readlink))
4704 return inode->i_op->readlink(dentry, buffer, buflen);
4706 if (!d_is_symlink(dentry))
4709 spin_lock(&inode->i_lock);
4710 inode->i_opflags |= IOP_DEFAULT_READLINK;
4711 spin_unlock(&inode->i_lock);
4714 return generic_readlink(dentry, buffer, buflen);
4716 EXPORT_SYMBOL(vfs_readlink);
4719 * vfs_get_link - get symlink body
4720 * @dentry: dentry on which to get symbolic link
4721 * @done: caller needs to free returned data with this
4723 * Calls security hook and i_op->get_link() on the supplied inode.
4725 * It does not touch atime. That's up to the caller if necessary.
4727 * Does not work on "special" symlinks like /proc/$$/fd/N
4729 const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
4731 const char *res = ERR_PTR(-EINVAL);
4732 struct inode *inode = d_inode(dentry);
4734 if (d_is_symlink(dentry)) {
4735 res = ERR_PTR(security_inode_readlink(dentry));
4737 res = inode->i_op->get_link(dentry, inode, done);
4741 EXPORT_SYMBOL(vfs_get_link);
4743 /* get the link contents into pagecache */
4744 const char *page_get_link(struct dentry *dentry, struct inode *inode,
4745 struct delayed_call *callback)
4749 struct address_space *mapping = inode->i_mapping;
4752 page = find_get_page(mapping, 0);
4754 return ERR_PTR(-ECHILD);
4755 if (!PageUptodate(page)) {
4757 return ERR_PTR(-ECHILD);
4760 page = read_mapping_page(mapping, 0, NULL);
4764 set_delayed_call(callback, page_put_link, page);
4765 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
4766 kaddr = page_address(page);
4767 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
4771 EXPORT_SYMBOL(page_get_link);
4773 void page_put_link(void *arg)
4777 EXPORT_SYMBOL(page_put_link);
4779 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4781 DEFINE_DELAYED_CALL(done);
4782 int res = readlink_copy(buffer, buflen,
4783 page_get_link(dentry, d_inode(dentry),
4785 do_delayed_call(&done);
4788 EXPORT_SYMBOL(page_readlink);
4791 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4793 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4795 struct address_space *mapping = inode->i_mapping;
4799 unsigned int flags = 0;
4801 flags |= AOP_FLAG_NOFS;
4804 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4805 flags, &page, &fsdata);
4809 memcpy(page_address(page), symname, len-1);
4811 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4818 mark_inode_dirty(inode);
4823 EXPORT_SYMBOL(__page_symlink);
4825 int page_symlink(struct inode *inode, const char *symname, int len)
4827 return __page_symlink(inode, symname, len,
4828 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
4830 EXPORT_SYMBOL(page_symlink);
4832 const struct inode_operations page_symlink_inode_operations = {
4833 .get_link = page_get_link,
4835 EXPORT_SYMBOL(page_symlink_inode_operations);