4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * Some corrections by tytso.
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/slab.h>
21 #include <linux/namei.h>
22 #include <linux/pagemap.h>
23 #include <linux/fsnotify.h>
24 #include <linux/personality.h>
25 #include <linux/security.h>
26 #include <linux/ima.h>
27 #include <linux/syscalls.h>
28 #include <linux/mount.h>
29 #include <linux/audit.h>
30 #include <linux/capability.h>
31 #include <linux/file.h>
32 #include <linux/fcntl.h>
33 #include <linux/device_cgroup.h>
34 #include <linux/fs_struct.h>
35 #include <asm/uaccess.h>
39 /* [Feb-1997 T. Schoebel-Theuer]
40 * Fundamental changes in the pathname lookup mechanisms (namei)
41 * were necessary because of omirr. The reason is that omirr needs
42 * to know the _real_ pathname, not the user-supplied one, in case
43 * of symlinks (and also when transname replacements occur).
45 * The new code replaces the old recursive symlink resolution with
46 * an iterative one (in case of non-nested symlink chains). It does
47 * this with calls to <fs>_follow_link().
48 * As a side effect, dir_namei(), _namei() and follow_link() are now
49 * replaced with a single function lookup_dentry() that can handle all
50 * the special cases of the former code.
52 * With the new dcache, the pathname is stored at each inode, at least as
53 * long as the refcount of the inode is positive. As a side effect, the
54 * size of the dcache depends on the inode cache and thus is dynamic.
56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57 * resolution to correspond with current state of the code.
59 * Note that the symlink resolution is not *completely* iterative.
60 * There is still a significant amount of tail- and mid- recursion in
61 * the algorithm. Also, note that <fs>_readlink() is not used in
62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63 * may return different results than <fs>_follow_link(). Many virtual
64 * filesystems (including /proc) exhibit this behavior.
67 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
69 * and the name already exists in form of a symlink, try to create the new
70 * name indicated by the symlink. The old code always complained that the
71 * name already exists, due to not following the symlink even if its target
72 * is nonexistent. The new semantics affects also mknod() and link() when
73 * the name is a symlink pointing to a non-existent name.
75 * I don't know which semantics is the right one, since I have no access
76 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78 * "old" one. Personally, I think the new semantics is much more logical.
79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
80 * file does succeed in both HP-UX and SunOs, but not in Solaris
81 * and in the old Linux semantics.
84 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85 * semantics. See the comments in "open_namei" and "do_link" below.
87 * [10-Sep-98 Alan Modra] Another symlink change.
90 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91 * inside the path - always follow.
92 * in the last component in creation/removal/renaming - never follow.
93 * if LOOKUP_FOLLOW passed - follow.
94 * if the pathname has trailing slashes - follow.
95 * otherwise - don't follow.
96 * (applied in that order).
98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100 * During the 2.4 we need to fix the userland stuff depending on it -
101 * hopefully we will be able to get rid of that wart in 2.5. So far only
102 * XEmacs seems to be relying on it...
105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
107 * any extra contention...
110 /* In order to reduce some races, while at the same time doing additional
111 * checking and hopefully speeding things up, we copy filenames to the
112 * kernel data space before using them..
114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115 * PATH_MAX includes the nul terminator --RR.
117 static int do_getname(const char __user *filename, char *page)
120 unsigned long len = PATH_MAX;
122 if (!segment_eq(get_fs(), KERNEL_DS)) {
123 if ((unsigned long) filename >= TASK_SIZE)
125 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
126 len = TASK_SIZE - (unsigned long) filename;
129 retval = strncpy_from_user(page, filename, len);
133 return -ENAMETOOLONG;
139 static char *getname_flags(const char __user *filename, int flags, int *empty)
143 result = ERR_PTR(-ENOMEM);
146 int retval = do_getname(filename, tmp);
150 if (retval == -ENOENT && empty)
152 if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
154 result = ERR_PTR(retval);
158 audit_getname(result);
162 char *getname(const char __user * filename)
164 return getname_flags(filename, 0, 0);
167 #ifdef CONFIG_AUDITSYSCALL
168 void putname(const char *name)
170 if (unlikely(!audit_dummy_context()))
175 EXPORT_SYMBOL(putname);
179 * This does basic POSIX ACL permission checking
181 static int acl_permission_check(struct inode *inode, int mask, unsigned int flags,
182 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
184 unsigned int mode = inode->i_mode;
186 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
188 if (current_user_ns() != inode_userns(inode))
191 if (current_fsuid() == inode->i_uid)
194 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
195 int error = check_acl(inode, mask, flags);
196 if (error != -EAGAIN)
200 if (in_group_p(inode->i_gid))
206 * If the DACs are ok we don't need any capability check.
208 if ((mask & ~mode) == 0)
214 * generic_permission - check for access rights on a Posix-like filesystem
215 * @inode: inode to check access rights for
216 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
217 * @check_acl: optional callback to check for Posix ACLs
218 * @flags: IPERM_FLAG_ flags.
220 * Used to check for read/write/execute permissions on a file.
221 * We use "fsuid" for this, letting us set arbitrary permissions
222 * for filesystem access without changing the "normal" uids which
223 * are used for other things.
225 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
226 * request cannot be satisfied (eg. requires blocking or too much complexity).
227 * It would then be called again in ref-walk mode.
229 int generic_permission(struct inode *inode, int mask, unsigned int flags,
230 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
235 * Do the basic POSIX ACL permission checks.
237 ret = acl_permission_check(inode, mask, flags, check_acl);
242 * Read/write DACs are always overridable.
243 * Executable DACs are overridable for all directories and
244 * for non-directories that have least one exec bit set.
246 if (!(mask & MAY_EXEC) || execute_ok(inode))
247 if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
251 * Searching includes executable on directories, else just read.
253 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
254 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
255 if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
262 * inode_permission - check for access rights to a given inode
263 * @inode: inode to check permission on
264 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
266 * Used to check for read/write/execute permissions on an inode.
267 * We use "fsuid" for this, letting us set arbitrary permissions
268 * for filesystem access without changing the "normal" uids which
269 * are used for other things.
271 int inode_permission(struct inode *inode, int mask)
275 if (mask & MAY_WRITE) {
276 umode_t mode = inode->i_mode;
279 * Nobody gets write access to a read-only fs.
281 if (IS_RDONLY(inode) &&
282 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
286 * Nobody gets write access to an immutable file.
288 if (IS_IMMUTABLE(inode))
292 if (inode->i_op->permission)
293 retval = inode->i_op->permission(inode, mask, 0);
295 retval = generic_permission(inode, mask, 0,
296 inode->i_op->check_acl);
301 retval = devcgroup_inode_permission(inode, mask);
305 return security_inode_permission(inode, mask);
309 * file_permission - check for additional access rights to a given file
310 * @file: file to check access rights for
311 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
313 * Used to check for read/write/execute permissions on an already opened
317 * Do not use this function in new code. All access checks should
318 * be done using inode_permission().
320 int file_permission(struct file *file, int mask)
322 return inode_permission(file->f_path.dentry->d_inode, mask);
326 * get_write_access() gets write permission for a file.
327 * put_write_access() releases this write permission.
328 * This is used for regular files.
329 * We cannot support write (and maybe mmap read-write shared) accesses and
330 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
331 * can have the following values:
332 * 0: no writers, no VM_DENYWRITE mappings
333 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
334 * > 0: (i_writecount) users are writing to the file.
336 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
337 * except for the cases where we don't hold i_writecount yet. Then we need to
338 * use {get,deny}_write_access() - these functions check the sign and refuse
339 * to do the change if sign is wrong. Exclusion between them is provided by
340 * the inode->i_lock spinlock.
343 int get_write_access(struct inode * inode)
345 spin_lock(&inode->i_lock);
346 if (atomic_read(&inode->i_writecount) < 0) {
347 spin_unlock(&inode->i_lock);
350 atomic_inc(&inode->i_writecount);
351 spin_unlock(&inode->i_lock);
356 int deny_write_access(struct file * file)
358 struct inode *inode = file->f_path.dentry->d_inode;
360 spin_lock(&inode->i_lock);
361 if (atomic_read(&inode->i_writecount) > 0) {
362 spin_unlock(&inode->i_lock);
365 atomic_dec(&inode->i_writecount);
366 spin_unlock(&inode->i_lock);
372 * path_get - get a reference to a path
373 * @path: path to get the reference to
375 * Given a path increment the reference count to the dentry and the vfsmount.
377 void path_get(struct path *path)
382 EXPORT_SYMBOL(path_get);
385 * path_put - put a reference to a path
386 * @path: path to put the reference to
388 * Given a path decrement the reference count to the dentry and the vfsmount.
390 void path_put(struct path *path)
395 EXPORT_SYMBOL(path_put);
398 * Path walking has 2 modes, rcu-walk and ref-walk (see
399 * Documentation/filesystems/path-lookup.txt). In situations when we can't
400 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
401 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
402 * mode. Refcounts are grabbed at the last known good point before rcu-walk
403 * got stuck, so ref-walk may continue from there. If this is not successful
404 * (eg. a seqcount has changed), then failure is returned and it's up to caller
405 * to restart the path walk from the beginning in ref-walk mode.
409 * unlazy_walk - try to switch to ref-walk mode.
410 * @nd: nameidata pathwalk data
411 * @dentry: child of nd->path.dentry or NULL
412 * Returns: 0 on success, -ECHILD on failure
414 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
415 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
416 * @nd or NULL. Must be called from rcu-walk context.
418 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
420 struct fs_struct *fs = current->fs;
421 struct dentry *parent = nd->path.dentry;
424 BUG_ON(!(nd->flags & LOOKUP_RCU));
425 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
427 spin_lock(&fs->lock);
428 if (nd->root.mnt != fs->root.mnt ||
429 nd->root.dentry != fs->root.dentry)
432 spin_lock(&parent->d_lock);
434 if (!__d_rcu_to_refcount(parent, nd->seq))
436 BUG_ON(nd->inode != parent->d_inode);
438 if (dentry->d_parent != parent)
440 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
441 if (!__d_rcu_to_refcount(dentry, nd->seq))
444 * If the sequence check on the child dentry passed, then
445 * the child has not been removed from its parent. This
446 * means the parent dentry must be valid and able to take
447 * a reference at this point.
449 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
450 BUG_ON(!parent->d_count);
452 spin_unlock(&dentry->d_lock);
454 spin_unlock(&parent->d_lock);
457 spin_unlock(&fs->lock);
459 mntget(nd->path.mnt);
462 br_read_unlock(vfsmount_lock);
463 nd->flags &= ~LOOKUP_RCU;
467 spin_unlock(&dentry->d_lock);
469 spin_unlock(&parent->d_lock);
472 spin_unlock(&fs->lock);
477 * release_open_intent - free up open intent resources
478 * @nd: pointer to nameidata
480 void release_open_intent(struct nameidata *nd)
482 struct file *file = nd->intent.open.file;
484 if (file && !IS_ERR(file)) {
485 if (file->f_path.dentry == NULL)
492 static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
494 return dentry->d_op->d_revalidate(dentry, nd);
497 static struct dentry *
498 do_revalidate(struct dentry *dentry, struct nameidata *nd)
500 int status = d_revalidate(dentry, nd);
501 if (unlikely(status <= 0)) {
503 * The dentry failed validation.
504 * If d_revalidate returned 0 attempt to invalidate
505 * the dentry otherwise d_revalidate is asking us
506 * to return a fail status.
510 dentry = ERR_PTR(status);
511 } else if (!d_invalidate(dentry)) {
520 * complete_walk - successful completion of path walk
521 * @nd: pointer nameidata
523 * If we had been in RCU mode, drop out of it and legitimize nd->path.
524 * Revalidate the final result, unless we'd already done that during
525 * the path walk or the filesystem doesn't ask for it. Return 0 on
526 * success, -error on failure. In case of failure caller does not
527 * need to drop nd->path.
529 static int complete_walk(struct nameidata *nd)
531 struct dentry *dentry = nd->path.dentry;
534 if (nd->flags & LOOKUP_RCU) {
535 nd->flags &= ~LOOKUP_RCU;
536 if (!(nd->flags & LOOKUP_ROOT))
538 spin_lock(&dentry->d_lock);
539 if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
540 spin_unlock(&dentry->d_lock);
542 br_read_unlock(vfsmount_lock);
545 BUG_ON(nd->inode != dentry->d_inode);
546 spin_unlock(&dentry->d_lock);
547 mntget(nd->path.mnt);
549 br_read_unlock(vfsmount_lock);
552 if (likely(!(nd->flags & LOOKUP_JUMPED)))
555 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
558 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
561 /* Note: we do not d_invalidate() */
562 status = d_revalidate(dentry, nd);
574 * Short-cut version of permission(), for calling on directories
575 * during pathname resolution. Combines parts of permission()
576 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
578 * If appropriate, check DAC only. If not appropriate, or
579 * short-cut DAC fails, then call ->permission() to do more
580 * complete permission check.
582 static inline int exec_permission(struct inode *inode, unsigned int flags)
585 struct user_namespace *ns = inode_userns(inode);
587 if (inode->i_op->permission) {
588 ret = inode->i_op->permission(inode, MAY_EXEC, flags);
590 ret = acl_permission_check(inode, MAY_EXEC, flags,
591 inode->i_op->check_acl);
598 if (ns_capable(ns, CAP_DAC_OVERRIDE) ||
599 ns_capable(ns, CAP_DAC_READ_SEARCH))
604 return security_inode_exec_permission(inode, flags);
607 static __always_inline void set_root(struct nameidata *nd)
610 get_fs_root(current->fs, &nd->root);
613 static int link_path_walk(const char *, struct nameidata *);
615 static __always_inline void set_root_rcu(struct nameidata *nd)
618 struct fs_struct *fs = current->fs;
622 seq = read_seqcount_begin(&fs->seq);
624 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
625 } while (read_seqcount_retry(&fs->seq, seq));
629 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
641 nd->flags |= LOOKUP_JUMPED;
643 nd->inode = nd->path.dentry->d_inode;
645 ret = link_path_walk(link, nd);
649 return PTR_ERR(link);
652 static void path_put_conditional(struct path *path, struct nameidata *nd)
655 if (path->mnt != nd->path.mnt)
659 static inline void path_to_nameidata(const struct path *path,
660 struct nameidata *nd)
662 if (!(nd->flags & LOOKUP_RCU)) {
663 dput(nd->path.dentry);
664 if (nd->path.mnt != path->mnt)
665 mntput(nd->path.mnt);
667 nd->path.mnt = path->mnt;
668 nd->path.dentry = path->dentry;
671 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
673 struct inode *inode = link->dentry->d_inode;
674 if (!IS_ERR(cookie) && inode->i_op->put_link)
675 inode->i_op->put_link(link->dentry, nd, cookie);
679 static __always_inline int
680 follow_link(struct path *link, struct nameidata *nd, void **p)
683 struct dentry *dentry = link->dentry;
685 BUG_ON(nd->flags & LOOKUP_RCU);
687 if (link->mnt == nd->path.mnt)
690 if (unlikely(current->total_link_count >= 40)) {
691 *p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
696 current->total_link_count++;
698 touch_atime(link->mnt, dentry);
699 nd_set_link(nd, NULL);
701 error = security_inode_follow_link(link->dentry, nd);
703 *p = ERR_PTR(error); /* no ->put_link(), please */
708 nd->last_type = LAST_BIND;
709 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
712 char *s = nd_get_link(nd);
715 error = __vfs_follow_link(nd, s);
716 else if (nd->last_type == LAST_BIND) {
717 nd->flags |= LOOKUP_JUMPED;
718 nd->inode = nd->path.dentry->d_inode;
719 if (nd->inode->i_op->follow_link) {
720 /* stepped on a _really_ weird one */
729 static int follow_up_rcu(struct path *path)
731 struct vfsmount *parent;
732 struct dentry *mountpoint;
734 parent = path->mnt->mnt_parent;
735 if (parent == path->mnt)
737 mountpoint = path->mnt->mnt_mountpoint;
738 path->dentry = mountpoint;
743 int follow_up(struct path *path)
745 struct vfsmount *parent;
746 struct dentry *mountpoint;
748 br_read_lock(vfsmount_lock);
749 parent = path->mnt->mnt_parent;
750 if (parent == path->mnt) {
751 br_read_unlock(vfsmount_lock);
755 mountpoint = dget(path->mnt->mnt_mountpoint);
756 br_read_unlock(vfsmount_lock);
758 path->dentry = mountpoint;
765 * Perform an automount
766 * - return -EISDIR to tell follow_managed() to stop and return the path we
769 static int follow_automount(struct path *path, unsigned flags,
772 struct vfsmount *mnt;
775 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
778 /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
779 * and this is the terminal part of the path.
781 if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
782 return -EISDIR; /* we actually want to stop here */
784 /* We don't want to mount if someone's just doing a stat -
785 * unless they're stat'ing a directory and appended a '/' to
788 * We do, however, want to mount if someone wants to open or
789 * create a file of any type under the mountpoint, wants to
790 * traverse through the mountpoint or wants to open the
791 * mounted directory. Also, autofs may mark negative dentries
792 * as being automount points. These will need the attentions
793 * of the daemon to instantiate them before they can be used.
795 if (!(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
796 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
797 path->dentry->d_inode)
800 current->total_link_count++;
801 if (current->total_link_count >= 40)
804 mnt = path->dentry->d_op->d_automount(path);
807 * The filesystem is allowed to return -EISDIR here to indicate
808 * it doesn't want to automount. For instance, autofs would do
809 * this so that its userspace daemon can mount on this dentry.
811 * However, we can only permit this if it's a terminal point in
812 * the path being looked up; if it wasn't then the remainder of
813 * the path is inaccessible and we should say so.
815 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_CONTINUE))
820 if (!mnt) /* mount collision */
824 /* lock_mount() may release path->mnt on error */
828 err = finish_automount(mnt, path);
832 /* Someone else made a mount here whilst we were busy */
837 path->dentry = dget(mnt->mnt_root);
846 * Handle a dentry that is managed in some way.
847 * - Flagged for transit management (autofs)
848 * - Flagged as mountpoint
849 * - Flagged as automount point
851 * This may only be called in refwalk mode.
853 * Serialization is taken care of in namespace.c
855 static int follow_managed(struct path *path, unsigned flags)
857 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
859 bool need_mntput = false;
862 /* Given that we're not holding a lock here, we retain the value in a
863 * local variable for each dentry as we look at it so that we don't see
864 * the components of that value change under us */
865 while (managed = ACCESS_ONCE(path->dentry->d_flags),
866 managed &= DCACHE_MANAGED_DENTRY,
867 unlikely(managed != 0)) {
868 /* Allow the filesystem to manage the transit without i_mutex
870 if (managed & DCACHE_MANAGE_TRANSIT) {
871 BUG_ON(!path->dentry->d_op);
872 BUG_ON(!path->dentry->d_op->d_manage);
873 ret = path->dentry->d_op->d_manage(path->dentry, false);
878 /* Transit to a mounted filesystem. */
879 if (managed & DCACHE_MOUNTED) {
880 struct vfsmount *mounted = lookup_mnt(path);
886 path->dentry = dget(mounted->mnt_root);
891 /* Something is mounted on this dentry in another
892 * namespace and/or whatever was mounted there in this
893 * namespace got unmounted before we managed to get the
897 /* Handle an automount point */
898 if (managed & DCACHE_NEED_AUTOMOUNT) {
899 ret = follow_automount(path, flags, &need_mntput);
905 /* We didn't change the current path point */
909 if (need_mntput && path->mnt == mnt)
916 int follow_down_one(struct path *path)
918 struct vfsmount *mounted;
920 mounted = lookup_mnt(path);
925 path->dentry = dget(mounted->mnt_root);
931 static inline bool managed_dentry_might_block(struct dentry *dentry)
933 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
934 dentry->d_op->d_manage(dentry, true) < 0);
938 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
939 * we meet a managed dentry that would need blocking.
941 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
942 struct inode **inode)
945 struct vfsmount *mounted;
947 * Don't forget we might have a non-mountpoint managed dentry
948 * that wants to block transit.
950 if (unlikely(managed_dentry_might_block(path->dentry)))
953 if (!d_mountpoint(path->dentry))
956 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
960 path->dentry = mounted->mnt_root;
961 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
963 * Update the inode too. We don't need to re-check the
964 * dentry sequence number here after this d_inode read,
965 * because a mount-point is always pinned.
967 *inode = path->dentry->d_inode;
972 static void follow_mount_rcu(struct nameidata *nd)
974 while (d_mountpoint(nd->path.dentry)) {
975 struct vfsmount *mounted;
976 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
979 nd->path.mnt = mounted;
980 nd->path.dentry = mounted->mnt_root;
981 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
985 static int follow_dotdot_rcu(struct nameidata *nd)
990 if (nd->path.dentry == nd->root.dentry &&
991 nd->path.mnt == nd->root.mnt) {
994 if (nd->path.dentry != nd->path.mnt->mnt_root) {
995 struct dentry *old = nd->path.dentry;
996 struct dentry *parent = old->d_parent;
999 seq = read_seqcount_begin(&parent->d_seq);
1000 if (read_seqcount_retry(&old->d_seq, nd->seq))
1002 nd->path.dentry = parent;
1006 if (!follow_up_rcu(&nd->path))
1008 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1010 follow_mount_rcu(nd);
1011 nd->inode = nd->path.dentry->d_inode;
1015 nd->flags &= ~LOOKUP_RCU;
1016 if (!(nd->flags & LOOKUP_ROOT))
1017 nd->root.mnt = NULL;
1019 br_read_unlock(vfsmount_lock);
1024 * Follow down to the covering mount currently visible to userspace. At each
1025 * point, the filesystem owning that dentry may be queried as to whether the
1026 * caller is permitted to proceed or not.
1028 int follow_down(struct path *path)
1033 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1034 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1035 /* Allow the filesystem to manage the transit without i_mutex
1038 * We indicate to the filesystem if someone is trying to mount
1039 * something here. This gives autofs the chance to deny anyone
1040 * other than its daemon the right to mount on its
1043 * The filesystem may sleep at this point.
1045 if (managed & DCACHE_MANAGE_TRANSIT) {
1046 BUG_ON(!path->dentry->d_op);
1047 BUG_ON(!path->dentry->d_op->d_manage);
1048 ret = path->dentry->d_op->d_manage(
1049 path->dentry, false);
1051 return ret == -EISDIR ? 0 : ret;
1054 /* Transit to a mounted filesystem. */
1055 if (managed & DCACHE_MOUNTED) {
1056 struct vfsmount *mounted = lookup_mnt(path);
1061 path->mnt = mounted;
1062 path->dentry = dget(mounted->mnt_root);
1066 /* Don't handle automount points here */
1073 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1075 static void follow_mount(struct path *path)
1077 while (d_mountpoint(path->dentry)) {
1078 struct vfsmount *mounted = lookup_mnt(path);
1083 path->mnt = mounted;
1084 path->dentry = dget(mounted->mnt_root);
1088 static void follow_dotdot(struct nameidata *nd)
1093 struct dentry *old = nd->path.dentry;
1095 if (nd->path.dentry == nd->root.dentry &&
1096 nd->path.mnt == nd->root.mnt) {
1099 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1100 /* rare case of legitimate dget_parent()... */
1101 nd->path.dentry = dget_parent(nd->path.dentry);
1105 if (!follow_up(&nd->path))
1108 follow_mount(&nd->path);
1109 nd->inode = nd->path.dentry->d_inode;
1113 * Allocate a dentry with name and parent, and perform a parent
1114 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1115 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1116 * have verified that no child exists while under i_mutex.
1118 static struct dentry *d_alloc_and_lookup(struct dentry *parent,
1119 struct qstr *name, struct nameidata *nd)
1121 struct inode *inode = parent->d_inode;
1122 struct dentry *dentry;
1125 /* Don't create child dentry for a dead directory. */
1126 if (unlikely(IS_DEADDIR(inode)))
1127 return ERR_PTR(-ENOENT);
1129 dentry = d_alloc(parent, name);
1130 if (unlikely(!dentry))
1131 return ERR_PTR(-ENOMEM);
1133 old = inode->i_op->lookup(inode, dentry, nd);
1134 if (unlikely(old)) {
1142 * It's more convoluted than I'd like it to be, but... it's still fairly
1143 * small and for now I'd prefer to have fast path as straight as possible.
1144 * It _is_ time-critical.
1146 static int do_lookup(struct nameidata *nd, struct qstr *name,
1147 struct path *path, struct inode **inode)
1149 struct vfsmount *mnt = nd->path.mnt;
1150 struct dentry *dentry, *parent = nd->path.dentry;
1156 * Rename seqlock is not required here because in the off chance
1157 * of a false negative due to a concurrent rename, we're going to
1158 * do the non-racy lookup, below.
1160 if (nd->flags & LOOKUP_RCU) {
1163 dentry = __d_lookup_rcu(parent, name, &seq, inode);
1167 /* Memory barrier in read_seqcount_begin of child is enough */
1168 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1172 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1173 status = d_revalidate(dentry, nd);
1174 if (unlikely(status <= 0)) {
1175 if (status != -ECHILD)
1181 path->dentry = dentry;
1182 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1184 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1188 if (unlazy_walk(nd, dentry))
1191 dentry = __d_lookup(parent, name);
1195 if (unlikely(!dentry)) {
1196 struct inode *dir = parent->d_inode;
1197 BUG_ON(nd->inode != dir);
1199 mutex_lock(&dir->i_mutex);
1200 dentry = d_lookup(parent, name);
1201 if (likely(!dentry)) {
1202 dentry = d_alloc_and_lookup(parent, name, nd);
1203 if (IS_ERR(dentry)) {
1204 mutex_unlock(&dir->i_mutex);
1205 return PTR_ERR(dentry);
1211 mutex_unlock(&dir->i_mutex);
1213 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1214 status = d_revalidate(dentry, nd);
1215 if (unlikely(status <= 0)) {
1220 if (!d_invalidate(dentry)) {
1229 path->dentry = dentry;
1230 err = follow_managed(path, nd->flags);
1231 if (unlikely(err < 0)) {
1232 path_put_conditional(path, nd);
1235 *inode = path->dentry->d_inode;
1239 static inline int may_lookup(struct nameidata *nd)
1241 if (nd->flags & LOOKUP_RCU) {
1242 int err = exec_permission(nd->inode, IPERM_FLAG_RCU);
1245 if (unlazy_walk(nd, NULL))
1248 return exec_permission(nd->inode, 0);
1251 static inline int handle_dots(struct nameidata *nd, int type)
1253 if (type == LAST_DOTDOT) {
1254 if (nd->flags & LOOKUP_RCU) {
1255 if (follow_dotdot_rcu(nd))
1263 static void terminate_walk(struct nameidata *nd)
1265 if (!(nd->flags & LOOKUP_RCU)) {
1266 path_put(&nd->path);
1268 nd->flags &= ~LOOKUP_RCU;
1269 if (!(nd->flags & LOOKUP_ROOT))
1270 nd->root.mnt = NULL;
1272 br_read_unlock(vfsmount_lock);
1276 static inline int walk_component(struct nameidata *nd, struct path *path,
1277 struct qstr *name, int type, int follow)
1279 struct inode *inode;
1282 * "." and ".." are special - ".." especially so because it has
1283 * to be able to know about the current root directory and
1284 * parent relationships.
1286 if (unlikely(type != LAST_NORM))
1287 return handle_dots(nd, type);
1288 err = do_lookup(nd, name, path, &inode);
1289 if (unlikely(err)) {
1294 path_to_nameidata(path, nd);
1298 if (unlikely(inode->i_op->follow_link) && follow) {
1299 if (nd->flags & LOOKUP_RCU) {
1300 if (unlikely(unlazy_walk(nd, path->dentry))) {
1305 BUG_ON(inode != path->dentry->d_inode);
1308 path_to_nameidata(path, nd);
1314 * This limits recursive symlink follows to 8, while
1315 * limiting consecutive symlinks to 40.
1317 * Without that kind of total limit, nasty chains of consecutive
1318 * symlinks can cause almost arbitrarily long lookups.
1320 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1324 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1325 path_put_conditional(path, nd);
1326 path_put(&nd->path);
1329 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1332 current->link_count++;
1335 struct path link = *path;
1338 res = follow_link(&link, nd, &cookie);
1340 res = walk_component(nd, path, &nd->last,
1341 nd->last_type, LOOKUP_FOLLOW);
1342 put_link(nd, &link, cookie);
1345 current->link_count--;
1352 * This is the basic name resolution function, turning a pathname into
1353 * the final dentry. We expect 'base' to be positive and a directory.
1355 * Returns 0 and nd will have valid dentry and mnt on success.
1356 * Returns error and drops reference to input namei data on failure.
1358 static int link_path_walk(const char *name, struct nameidata *nd)
1362 unsigned int lookup_flags = nd->flags;
1369 /* At this point we know we have a real path component. */
1376 nd->flags |= LOOKUP_CONTINUE;
1378 err = may_lookup(nd);
1383 c = *(const unsigned char *)name;
1385 hash = init_name_hash();
1388 hash = partial_name_hash(c, hash);
1389 c = *(const unsigned char *)name;
1390 } while (c && (c != '/'));
1391 this.len = name - (const char *) this.name;
1392 this.hash = end_name_hash(hash);
1395 if (this.name[0] == '.') switch (this.len) {
1397 if (this.name[1] == '.') {
1399 nd->flags |= LOOKUP_JUMPED;
1405 if (likely(type == LAST_NORM)) {
1406 struct dentry *parent = nd->path.dentry;
1407 nd->flags &= ~LOOKUP_JUMPED;
1408 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1409 err = parent->d_op->d_hash(parent, nd->inode,
1416 /* remove trailing slashes? */
1418 goto last_component;
1419 while (*++name == '/');
1421 goto last_component;
1423 err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
1428 err = nested_symlink(&next, nd);
1433 if (!nd->inode->i_op->lookup)
1436 /* here ends the main loop */
1439 /* Clear LOOKUP_CONTINUE iff it was previously unset */
1440 nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
1442 nd->last_type = type;
1449 static int path_init(int dfd, const char *name, unsigned int flags,
1450 struct nameidata *nd, struct file **fp)
1456 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1457 nd->flags = flags | LOOKUP_JUMPED;
1459 if (flags & LOOKUP_ROOT) {
1460 struct inode *inode = nd->root.dentry->d_inode;
1462 if (!inode->i_op->lookup)
1464 retval = inode_permission(inode, MAY_EXEC);
1468 nd->path = nd->root;
1470 if (flags & LOOKUP_RCU) {
1471 br_read_lock(vfsmount_lock);
1473 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1475 path_get(&nd->path);
1480 nd->root.mnt = NULL;
1483 if (flags & LOOKUP_RCU) {
1484 br_read_lock(vfsmount_lock);
1489 path_get(&nd->root);
1491 nd->path = nd->root;
1492 } else if (dfd == AT_FDCWD) {
1493 if (flags & LOOKUP_RCU) {
1494 struct fs_struct *fs = current->fs;
1497 br_read_lock(vfsmount_lock);
1501 seq = read_seqcount_begin(&fs->seq);
1503 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1504 } while (read_seqcount_retry(&fs->seq, seq));
1506 get_fs_pwd(current->fs, &nd->path);
1509 struct dentry *dentry;
1511 file = fget_raw_light(dfd, &fput_needed);
1516 dentry = file->f_path.dentry;
1520 if (!S_ISDIR(dentry->d_inode->i_mode))
1523 retval = file_permission(file, MAY_EXEC);
1528 nd->path = file->f_path;
1529 if (flags & LOOKUP_RCU) {
1532 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1533 br_read_lock(vfsmount_lock);
1536 path_get(&file->f_path);
1537 fput_light(file, fput_needed);
1541 nd->inode = nd->path.dentry->d_inode;
1545 fput_light(file, fput_needed);
1550 static inline int lookup_last(struct nameidata *nd, struct path *path)
1552 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1553 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1555 nd->flags &= ~LOOKUP_PARENT;
1556 return walk_component(nd, path, &nd->last, nd->last_type,
1557 nd->flags & LOOKUP_FOLLOW);
1560 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1561 static int path_lookupat(int dfd, const char *name,
1562 unsigned int flags, struct nameidata *nd)
1564 struct file *base = NULL;
1569 * Path walking is largely split up into 2 different synchronisation
1570 * schemes, rcu-walk and ref-walk (explained in
1571 * Documentation/filesystems/path-lookup.txt). These share much of the
1572 * path walk code, but some things particularly setup, cleanup, and
1573 * following mounts are sufficiently divergent that functions are
1574 * duplicated. Typically there is a function foo(), and its RCU
1575 * analogue, foo_rcu().
1577 * -ECHILD is the error number of choice (just to avoid clashes) that
1578 * is returned if some aspect of an rcu-walk fails. Such an error must
1579 * be handled by restarting a traditional ref-walk (which will always
1580 * be able to complete).
1582 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1587 current->total_link_count = 0;
1588 err = link_path_walk(name, nd);
1590 if (!err && !(flags & LOOKUP_PARENT)) {
1591 err = lookup_last(nd, &path);
1594 struct path link = path;
1595 nd->flags |= LOOKUP_PARENT;
1596 err = follow_link(&link, nd, &cookie);
1598 err = lookup_last(nd, &path);
1599 put_link(nd, &link, cookie);
1604 err = complete_walk(nd);
1606 if (!err && nd->flags & LOOKUP_DIRECTORY) {
1607 if (!nd->inode->i_op->lookup) {
1608 path_put(&nd->path);
1616 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
1617 path_put(&nd->root);
1618 nd->root.mnt = NULL;
1623 static int do_path_lookup(int dfd, const char *name,
1624 unsigned int flags, struct nameidata *nd)
1626 int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
1627 if (unlikely(retval == -ECHILD))
1628 retval = path_lookupat(dfd, name, flags, nd);
1629 if (unlikely(retval == -ESTALE))
1630 retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
1632 if (likely(!retval)) {
1633 if (unlikely(!audit_dummy_context())) {
1634 if (nd->path.dentry && nd->inode)
1635 audit_inode(name, nd->path.dentry);
1641 int kern_path_parent(const char *name, struct nameidata *nd)
1643 return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
1646 int kern_path(const char *name, unsigned int flags, struct path *path)
1648 struct nameidata nd;
1649 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1656 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1657 * @dentry: pointer to dentry of the base directory
1658 * @mnt: pointer to vfs mount of the base directory
1659 * @name: pointer to file name
1660 * @flags: lookup flags
1661 * @nd: pointer to nameidata
1663 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1664 const char *name, unsigned int flags,
1665 struct nameidata *nd)
1667 nd->root.dentry = dentry;
1669 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1670 return do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, nd);
1673 static struct dentry *__lookup_hash(struct qstr *name,
1674 struct dentry *base, struct nameidata *nd)
1676 struct inode *inode = base->d_inode;
1677 struct dentry *dentry;
1680 err = exec_permission(inode, 0);
1682 return ERR_PTR(err);
1685 * Don't bother with __d_lookup: callers are for creat as
1686 * well as unlink, so a lot of the time it would cost
1689 dentry = d_lookup(base, name);
1691 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
1692 dentry = do_revalidate(dentry, nd);
1695 dentry = d_alloc_and_lookup(base, name, nd);
1701 * Restricted form of lookup. Doesn't follow links, single-component only,
1702 * needs parent already locked. Doesn't follow mounts.
1705 static struct dentry *lookup_hash(struct nameidata *nd)
1707 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1711 * lookup_one_len - filesystem helper to lookup single pathname component
1712 * @name: pathname component to lookup
1713 * @base: base directory to lookup from
1714 * @len: maximum length @len should be interpreted to
1716 * Note that this routine is purely a helper for filesystem usage and should
1717 * not be called by generic code. Also note that by using this function the
1718 * nameidata argument is passed to the filesystem methods and a filesystem
1719 * using this helper needs to be prepared for that.
1721 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1727 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1732 return ERR_PTR(-EACCES);
1734 hash = init_name_hash();
1736 c = *(const unsigned char *)name++;
1737 if (c == '/' || c == '\0')
1738 return ERR_PTR(-EACCES);
1739 hash = partial_name_hash(c, hash);
1741 this.hash = end_name_hash(hash);
1743 * See if the low-level filesystem might want
1744 * to use its own hash..
1746 if (base->d_flags & DCACHE_OP_HASH) {
1747 int err = base->d_op->d_hash(base, base->d_inode, &this);
1749 return ERR_PTR(err);
1752 return __lookup_hash(&this, base, NULL);
1755 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
1756 struct path *path, int *empty)
1758 struct nameidata nd;
1759 char *tmp = getname_flags(name, flags, empty);
1760 int err = PTR_ERR(tmp);
1763 BUG_ON(flags & LOOKUP_PARENT);
1765 err = do_path_lookup(dfd, tmp, flags, &nd);
1773 int user_path_at(int dfd, const char __user *name, unsigned flags,
1776 return user_path_at_empty(dfd, name, flags, path, 0);
1779 static int user_path_parent(int dfd, const char __user *path,
1780 struct nameidata *nd, char **name)
1782 char *s = getname(path);
1788 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1798 * It's inline, so penalty for filesystems that don't use sticky bit is
1801 static inline int check_sticky(struct inode *dir, struct inode *inode)
1803 uid_t fsuid = current_fsuid();
1805 if (!(dir->i_mode & S_ISVTX))
1807 if (current_user_ns() != inode_userns(inode))
1809 if (inode->i_uid == fsuid)
1811 if (dir->i_uid == fsuid)
1815 return !ns_capable(inode_userns(inode), CAP_FOWNER);
1819 * Check whether we can remove a link victim from directory dir, check
1820 * whether the type of victim is right.
1821 * 1. We can't do it if dir is read-only (done in permission())
1822 * 2. We should have write and exec permissions on dir
1823 * 3. We can't remove anything from append-only dir
1824 * 4. We can't do anything with immutable dir (done in permission())
1825 * 5. If the sticky bit on dir is set we should either
1826 * a. be owner of dir, or
1827 * b. be owner of victim, or
1828 * c. have CAP_FOWNER capability
1829 * 6. If the victim is append-only or immutable we can't do antyhing with
1830 * links pointing to it.
1831 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1832 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1833 * 9. We can't remove a root or mountpoint.
1834 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1835 * nfs_async_unlink().
1837 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1841 if (!victim->d_inode)
1844 BUG_ON(victim->d_parent->d_inode != dir);
1845 audit_inode_child(victim, dir);
1847 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1852 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1853 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1856 if (!S_ISDIR(victim->d_inode->i_mode))
1858 if (IS_ROOT(victim))
1860 } else if (S_ISDIR(victim->d_inode->i_mode))
1862 if (IS_DEADDIR(dir))
1864 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1869 /* Check whether we can create an object with dentry child in directory
1871 * 1. We can't do it if child already exists (open has special treatment for
1872 * this case, but since we are inlined it's OK)
1873 * 2. We can't do it if dir is read-only (done in permission())
1874 * 3. We should have write and exec permissions on dir
1875 * 4. We can't do it if dir is immutable (done in permission())
1877 static inline int may_create(struct inode *dir, struct dentry *child)
1881 if (IS_DEADDIR(dir))
1883 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
1887 * p1 and p2 should be directories on the same fs.
1889 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1894 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1898 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1900 p = d_ancestor(p2, p1);
1902 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
1903 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
1907 p = d_ancestor(p1, p2);
1909 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1910 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1914 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1915 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1919 void unlock_rename(struct dentry *p1, struct dentry *p2)
1921 mutex_unlock(&p1->d_inode->i_mutex);
1923 mutex_unlock(&p2->d_inode->i_mutex);
1924 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1928 int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1929 struct nameidata *nd)
1931 int error = may_create(dir, dentry);
1936 if (!dir->i_op->create)
1937 return -EACCES; /* shouldn't it be ENOSYS? */
1940 error = security_inode_create(dir, dentry, mode);
1943 error = dir->i_op->create(dir, dentry, mode, nd);
1945 fsnotify_create(dir, dentry);
1949 static int may_open(struct path *path, int acc_mode, int flag)
1951 struct dentry *dentry = path->dentry;
1952 struct inode *inode = dentry->d_inode;
1962 switch (inode->i_mode & S_IFMT) {
1966 if (acc_mode & MAY_WRITE)
1971 if (path->mnt->mnt_flags & MNT_NODEV)
1980 error = inode_permission(inode, acc_mode);
1985 * An append-only file must be opened in append mode for writing.
1987 if (IS_APPEND(inode)) {
1988 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
1994 /* O_NOATIME can only be set by the owner or superuser */
1995 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
1999 * Ensure there are no outstanding leases on the file.
2001 return break_lease(inode, flag);
2004 static int handle_truncate(struct file *filp)
2006 struct path *path = &filp->f_path;
2007 struct inode *inode = path->dentry->d_inode;
2008 int error = get_write_access(inode);
2012 * Refuse to truncate files with mandatory locks held on them.
2014 error = locks_verify_locked(inode);
2016 error = security_path_truncate(path);
2018 error = do_truncate(path->dentry, 0,
2019 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2022 put_write_access(inode);
2027 * Note that while the flag value (low two bits) for sys_open means:
2032 * it is changed into
2033 * 00 - no permissions needed
2034 * 01 - read-permission
2035 * 10 - write-permission
2037 * for the internal routines (ie open_namei()/follow_link() etc)
2038 * This is more logical, and also allows the 00 "no perm needed"
2039 * to be used for symlinks (where the permissions are checked
2043 static inline int open_to_namei_flags(int flag)
2045 if ((flag+1) & O_ACCMODE)
2051 * Handle the last step of open()
2053 static struct file *do_last(struct nameidata *nd, struct path *path,
2054 const struct open_flags *op, const char *pathname)
2056 struct dentry *dir = nd->path.dentry;
2057 struct dentry *dentry;
2058 int open_flag = op->open_flag;
2059 int will_truncate = open_flag & O_TRUNC;
2061 int acc_mode = op->acc_mode;
2065 nd->flags &= ~LOOKUP_PARENT;
2066 nd->flags |= op->intent;
2068 switch (nd->last_type) {
2071 error = handle_dots(nd, nd->last_type);
2073 return ERR_PTR(error);
2076 error = complete_walk(nd);
2078 return ERR_PTR(error);
2079 audit_inode(pathname, nd->path.dentry);
2080 if (open_flag & O_CREAT) {
2086 error = complete_walk(nd);
2088 return ERR_PTR(error);
2089 audit_inode(pathname, dir);
2093 if (!(open_flag & O_CREAT)) {
2095 if (nd->last.name[nd->last.len])
2096 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2097 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2099 /* we _can_ be in RCU mode here */
2100 error = walk_component(nd, path, &nd->last, LAST_NORM,
2103 return ERR_PTR(error);
2104 if (error) /* symlink */
2107 error = complete_walk(nd);
2109 return ERR_PTR(-ECHILD);
2112 if (nd->flags & LOOKUP_DIRECTORY) {
2113 if (!nd->inode->i_op->lookup)
2116 audit_inode(pathname, nd->path.dentry);
2120 /* create side of things */
2121 error = complete_walk(nd);
2123 return ERR_PTR(error);
2125 audit_inode(pathname, dir);
2127 /* trailing slashes? */
2128 if (nd->last.name[nd->last.len])
2131 mutex_lock(&dir->d_inode->i_mutex);
2133 dentry = lookup_hash(nd);
2134 error = PTR_ERR(dentry);
2135 if (IS_ERR(dentry)) {
2136 mutex_unlock(&dir->d_inode->i_mutex);
2140 path->dentry = dentry;
2141 path->mnt = nd->path.mnt;
2143 /* Negative dentry, just create the file */
2144 if (!dentry->d_inode) {
2145 int mode = op->mode;
2146 if (!IS_POSIXACL(dir->d_inode))
2147 mode &= ~current_umask();
2149 * This write is needed to ensure that a
2150 * rw->ro transition does not occur between
2151 * the time when the file is created and when
2152 * a permanent write count is taken through
2153 * the 'struct file' in nameidata_to_filp().
2155 error = mnt_want_write(nd->path.mnt);
2157 goto exit_mutex_unlock;
2159 /* Don't check for write permission, don't truncate */
2160 open_flag &= ~O_TRUNC;
2162 acc_mode = MAY_OPEN;
2163 error = security_path_mknod(&nd->path, dentry, mode, 0);
2165 goto exit_mutex_unlock;
2166 error = vfs_create(dir->d_inode, dentry, mode, nd);
2168 goto exit_mutex_unlock;
2169 mutex_unlock(&dir->d_inode->i_mutex);
2170 dput(nd->path.dentry);
2171 nd->path.dentry = dentry;
2176 * It already exists.
2178 mutex_unlock(&dir->d_inode->i_mutex);
2179 audit_inode(pathname, path->dentry);
2182 if (open_flag & O_EXCL)
2185 error = follow_managed(path, nd->flags);
2190 if (!path->dentry->d_inode)
2193 if (path->dentry->d_inode->i_op->follow_link)
2196 path_to_nameidata(path, nd);
2197 nd->inode = path->dentry->d_inode;
2199 if (S_ISDIR(nd->inode->i_mode))
2202 if (!S_ISREG(nd->inode->i_mode))
2205 if (will_truncate) {
2206 error = mnt_want_write(nd->path.mnt);
2212 error = may_open(&nd->path, acc_mode, open_flag);
2215 filp = nameidata_to_filp(nd);
2216 if (!IS_ERR(filp)) {
2217 error = ima_file_check(filp, op->acc_mode);
2220 filp = ERR_PTR(error);
2223 if (!IS_ERR(filp)) {
2224 if (will_truncate) {
2225 error = handle_truncate(filp);
2228 filp = ERR_PTR(error);
2234 mnt_drop_write(nd->path.mnt);
2235 path_put(&nd->path);
2239 mutex_unlock(&dir->d_inode->i_mutex);
2241 path_put_conditional(path, nd);
2243 filp = ERR_PTR(error);
2247 static struct file *path_openat(int dfd, const char *pathname,
2248 struct nameidata *nd, const struct open_flags *op, int flags)
2250 struct file *base = NULL;
2255 filp = get_empty_filp();
2257 return ERR_PTR(-ENFILE);
2259 filp->f_flags = op->open_flag;
2260 nd->intent.open.file = filp;
2261 nd->intent.open.flags = open_to_namei_flags(op->open_flag);
2262 nd->intent.open.create_mode = op->mode;
2264 error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
2265 if (unlikely(error))
2268 current->total_link_count = 0;
2269 error = link_path_walk(pathname, nd);
2270 if (unlikely(error))
2273 filp = do_last(nd, &path, op, pathname);
2274 while (unlikely(!filp)) { /* trailing symlink */
2275 struct path link = path;
2277 if (!(nd->flags & LOOKUP_FOLLOW)) {
2278 path_put_conditional(&path, nd);
2279 path_put(&nd->path);
2280 filp = ERR_PTR(-ELOOP);
2283 nd->flags |= LOOKUP_PARENT;
2284 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
2285 error = follow_link(&link, nd, &cookie);
2286 if (unlikely(error))
2287 filp = ERR_PTR(error);
2289 filp = do_last(nd, &path, op, pathname);
2290 put_link(nd, &link, cookie);
2293 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2294 path_put(&nd->root);
2297 release_open_intent(nd);
2301 filp = ERR_PTR(error);
2305 struct file *do_filp_open(int dfd, const char *pathname,
2306 const struct open_flags *op, int flags)
2308 struct nameidata nd;
2311 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
2312 if (unlikely(filp == ERR_PTR(-ECHILD)))
2313 filp = path_openat(dfd, pathname, &nd, op, flags);
2314 if (unlikely(filp == ERR_PTR(-ESTALE)))
2315 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
2319 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
2320 const char *name, const struct open_flags *op, int flags)
2322 struct nameidata nd;
2326 nd.root.dentry = dentry;
2328 flags |= LOOKUP_ROOT;
2330 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
2331 return ERR_PTR(-ELOOP);
2333 file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
2334 if (unlikely(file == ERR_PTR(-ECHILD)))
2335 file = path_openat(-1, name, &nd, op, flags);
2336 if (unlikely(file == ERR_PTR(-ESTALE)))
2337 file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
2342 * lookup_create - lookup a dentry, creating it if it doesn't exist
2343 * @nd: nameidata info
2344 * @is_dir: directory flag
2346 * Simple function to lookup and return a dentry and create it
2347 * if it doesn't exist. Is SMP-safe.
2349 * Returns with nd->path.dentry->d_inode->i_mutex locked.
2351 struct dentry *lookup_create(struct nameidata *nd, int is_dir)
2353 struct dentry *dentry = ERR_PTR(-EEXIST);
2355 mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2357 * Yucky last component or no last component at all?
2358 * (foo/., foo/.., /////)
2360 if (nd->last_type != LAST_NORM)
2362 nd->flags &= ~LOOKUP_PARENT;
2363 nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
2364 nd->intent.open.flags = O_EXCL;
2367 * Do the final lookup.
2369 dentry = lookup_hash(nd);
2373 if (dentry->d_inode)
2376 * Special case - lookup gave negative, but... we had foo/bar/
2377 * From the vfs_mknod() POV we just have a negative dentry -
2378 * all is fine. Let's be bastards - you had / on the end, you've
2379 * been asking for (non-existent) directory. -ENOENT for you.
2381 if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
2383 dentry = ERR_PTR(-ENOENT);
2388 dentry = ERR_PTR(-EEXIST);
2392 EXPORT_SYMBOL_GPL(lookup_create);
2394 int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
2396 int error = may_create(dir, dentry);
2401 if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
2402 !ns_capable(inode_userns(dir), CAP_MKNOD))
2405 if (!dir->i_op->mknod)
2408 error = devcgroup_inode_mknod(mode, dev);
2412 error = security_inode_mknod(dir, dentry, mode, dev);
2416 error = dir->i_op->mknod(dir, dentry, mode, dev);
2418 fsnotify_create(dir, dentry);
2422 static int may_mknod(mode_t mode)
2424 switch (mode & S_IFMT) {
2430 case 0: /* zero mode translates to S_IFREG */
2439 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2444 struct dentry *dentry;
2445 struct nameidata nd;
2450 error = user_path_parent(dfd, filename, &nd, &tmp);
2454 dentry = lookup_create(&nd, 0);
2455 if (IS_ERR(dentry)) {
2456 error = PTR_ERR(dentry);
2459 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2460 mode &= ~current_umask();
2461 error = may_mknod(mode);
2464 error = mnt_want_write(nd.path.mnt);
2467 error = security_path_mknod(&nd.path, dentry, mode, dev);
2469 goto out_drop_write;
2470 switch (mode & S_IFMT) {
2471 case 0: case S_IFREG:
2472 error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
2474 case S_IFCHR: case S_IFBLK:
2475 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
2476 new_decode_dev(dev));
2478 case S_IFIFO: case S_IFSOCK:
2479 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
2483 mnt_drop_write(nd.path.mnt);
2487 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2494 SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
2496 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2499 int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2501 int error = may_create(dir, dentry);
2506 if (!dir->i_op->mkdir)
2509 mode &= (S_IRWXUGO|S_ISVTX);
2510 error = security_inode_mkdir(dir, dentry, mode);
2514 error = dir->i_op->mkdir(dir, dentry, mode);
2516 fsnotify_mkdir(dir, dentry);
2520 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
2524 struct dentry *dentry;
2525 struct nameidata nd;
2527 error = user_path_parent(dfd, pathname, &nd, &tmp);
2531 dentry = lookup_create(&nd, 1);
2532 error = PTR_ERR(dentry);
2536 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2537 mode &= ~current_umask();
2538 error = mnt_want_write(nd.path.mnt);
2541 error = security_path_mkdir(&nd.path, dentry, mode);
2543 goto out_drop_write;
2544 error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2546 mnt_drop_write(nd.path.mnt);
2550 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2557 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
2559 return sys_mkdirat(AT_FDCWD, pathname, mode);
2563 * The dentry_unhash() helper will try to drop the dentry early: we
2564 * should have a usage count of 2 if we're the only user of this
2565 * dentry, and if that is true (possibly after pruning the dcache),
2566 * then we drop the dentry now.
2568 * A low-level filesystem can, if it choses, legally
2571 * if (!d_unhashed(dentry))
2574 * if it cannot handle the case of removing a directory
2575 * that is still in use by something else..
2577 void dentry_unhash(struct dentry *dentry)
2579 shrink_dcache_parent(dentry);
2580 spin_lock(&dentry->d_lock);
2581 if (dentry->d_count == 1)
2583 spin_unlock(&dentry->d_lock);
2586 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2588 int error = may_delete(dir, dentry, 1);
2593 if (!dir->i_op->rmdir)
2597 mutex_lock(&dentry->d_inode->i_mutex);
2600 if (d_mountpoint(dentry))
2603 error = security_inode_rmdir(dir, dentry);
2607 shrink_dcache_parent(dentry);
2608 error = dir->i_op->rmdir(dir, dentry);
2612 dentry->d_inode->i_flags |= S_DEAD;
2616 mutex_unlock(&dentry->d_inode->i_mutex);
2623 static long do_rmdir(int dfd, const char __user *pathname)
2627 struct dentry *dentry;
2628 struct nameidata nd;
2630 error = user_path_parent(dfd, pathname, &nd, &name);
2634 switch(nd.last_type) {
2646 nd.flags &= ~LOOKUP_PARENT;
2648 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2649 dentry = lookup_hash(&nd);
2650 error = PTR_ERR(dentry);
2653 if (!dentry->d_inode) {
2657 error = mnt_want_write(nd.path.mnt);
2660 error = security_path_rmdir(&nd.path, dentry);
2663 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2665 mnt_drop_write(nd.path.mnt);
2669 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2676 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2678 return do_rmdir(AT_FDCWD, pathname);
2681 int vfs_unlink(struct inode *dir, struct dentry *dentry)
2683 int error = may_delete(dir, dentry, 0);
2688 if (!dir->i_op->unlink)
2691 mutex_lock(&dentry->d_inode->i_mutex);
2692 if (d_mountpoint(dentry))
2695 error = security_inode_unlink(dir, dentry);
2697 error = dir->i_op->unlink(dir, dentry);
2702 mutex_unlock(&dentry->d_inode->i_mutex);
2704 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2705 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2706 fsnotify_link_count(dentry->d_inode);
2714 * Make sure that the actual truncation of the file will occur outside its
2715 * directory's i_mutex. Truncate can take a long time if there is a lot of
2716 * writeout happening, and we don't want to prevent access to the directory
2717 * while waiting on the I/O.
2719 static long do_unlinkat(int dfd, const char __user *pathname)
2723 struct dentry *dentry;
2724 struct nameidata nd;
2725 struct inode *inode = NULL;
2727 error = user_path_parent(dfd, pathname, &nd, &name);
2732 if (nd.last_type != LAST_NORM)
2735 nd.flags &= ~LOOKUP_PARENT;
2737 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2738 dentry = lookup_hash(&nd);
2739 error = PTR_ERR(dentry);
2740 if (!IS_ERR(dentry)) {
2741 /* Why not before? Because we want correct error value */
2742 if (nd.last.name[nd.last.len])
2744 inode = dentry->d_inode;
2748 error = mnt_want_write(nd.path.mnt);
2751 error = security_path_unlink(&nd.path, dentry);
2754 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2756 mnt_drop_write(nd.path.mnt);
2760 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2762 iput(inode); /* truncate the inode here */
2769 error = !dentry->d_inode ? -ENOENT :
2770 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2774 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
2776 if ((flag & ~AT_REMOVEDIR) != 0)
2779 if (flag & AT_REMOVEDIR)
2780 return do_rmdir(dfd, pathname);
2782 return do_unlinkat(dfd, pathname);
2785 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
2787 return do_unlinkat(AT_FDCWD, pathname);
2790 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
2792 int error = may_create(dir, dentry);
2797 if (!dir->i_op->symlink)
2800 error = security_inode_symlink(dir, dentry, oldname);
2804 error = dir->i_op->symlink(dir, dentry, oldname);
2806 fsnotify_create(dir, dentry);
2810 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2811 int, newdfd, const char __user *, newname)
2816 struct dentry *dentry;
2817 struct nameidata nd;
2819 from = getname(oldname);
2821 return PTR_ERR(from);
2823 error = user_path_parent(newdfd, newname, &nd, &to);
2827 dentry = lookup_create(&nd, 0);
2828 error = PTR_ERR(dentry);
2832 error = mnt_want_write(nd.path.mnt);
2835 error = security_path_symlink(&nd.path, dentry, from);
2837 goto out_drop_write;
2838 error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
2840 mnt_drop_write(nd.path.mnt);
2844 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2852 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
2854 return sys_symlinkat(oldname, AT_FDCWD, newname);
2857 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
2859 struct inode *inode = old_dentry->d_inode;
2865 error = may_create(dir, new_dentry);
2869 if (dir->i_sb != inode->i_sb)
2873 * A link to an append-only or immutable file cannot be created.
2875 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
2877 if (!dir->i_op->link)
2879 if (S_ISDIR(inode->i_mode))
2882 error = security_inode_link(old_dentry, dir, new_dentry);
2886 mutex_lock(&inode->i_mutex);
2887 /* Make sure we don't allow creating hardlink to an unlinked file */
2888 if (inode->i_nlink == 0)
2891 error = dir->i_op->link(old_dentry, dir, new_dentry);
2892 mutex_unlock(&inode->i_mutex);
2894 fsnotify_link(dir, inode, new_dentry);
2899 * Hardlinks are often used in delicate situations. We avoid
2900 * security-related surprises by not following symlinks on the
2903 * We don't follow them on the oldname either to be compatible
2904 * with linux 2.0, and to avoid hard-linking to directories
2905 * and other special files. --ADM
2907 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
2908 int, newdfd, const char __user *, newname, int, flags)
2910 struct dentry *new_dentry;
2911 struct nameidata nd;
2912 struct path old_path;
2917 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
2920 * To use null names we require CAP_DAC_READ_SEARCH
2921 * This ensures that not everyone will be able to create
2922 * handlink using the passed filedescriptor.
2924 if (flags & AT_EMPTY_PATH) {
2925 if (!capable(CAP_DAC_READ_SEARCH))
2930 if (flags & AT_SYMLINK_FOLLOW)
2931 how |= LOOKUP_FOLLOW;
2933 error = user_path_at(olddfd, oldname, how, &old_path);
2937 error = user_path_parent(newdfd, newname, &nd, &to);
2941 if (old_path.mnt != nd.path.mnt)
2943 new_dentry = lookup_create(&nd, 0);
2944 error = PTR_ERR(new_dentry);
2945 if (IS_ERR(new_dentry))
2947 error = mnt_want_write(nd.path.mnt);
2950 error = security_path_link(old_path.dentry, &nd.path, new_dentry);
2952 goto out_drop_write;
2953 error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
2955 mnt_drop_write(nd.path.mnt);
2959 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2964 path_put(&old_path);
2969 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
2971 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
2975 * The worst of all namespace operations - renaming directory. "Perverted"
2976 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2978 * a) we can get into loop creation. Check is done in is_subdir().
2979 * b) race potential - two innocent renames can create a loop together.
2980 * That's where 4.4 screws up. Current fix: serialization on
2981 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
2983 * c) we have to lock _three_ objects - parents and victim (if it exists).
2984 * And that - after we got ->i_mutex on parents (until then we don't know
2985 * whether the target exists). Solution: try to be smart with locking
2986 * order for inodes. We rely on the fact that tree topology may change
2987 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
2988 * move will be locked. Thus we can rank directories by the tree
2989 * (ancestors first) and rank all non-directories after them.
2990 * That works since everybody except rename does "lock parent, lookup,
2991 * lock child" and rename is under ->s_vfs_rename_mutex.
2992 * HOWEVER, it relies on the assumption that any object with ->lookup()
2993 * has no more than 1 dentry. If "hybrid" objects will ever appear,
2994 * we'd better make sure that there's no link(2) for them.
2995 * d) conversion from fhandle to dentry may come in the wrong moment - when
2996 * we are removing the target. Solution: we will have to grab ->i_mutex
2997 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2998 * ->i_mutex on parents, which works but leads to some truly excessive
3001 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3002 struct inode *new_dir, struct dentry *new_dentry)
3005 struct inode *target = new_dentry->d_inode;
3008 * If we are going to change the parent - check write permissions,
3009 * we'll need to flip '..'.
3011 if (new_dir != old_dir) {
3012 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3017 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3023 mutex_lock(&target->i_mutex);
3026 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3030 shrink_dcache_parent(new_dentry);
3031 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3036 target->i_flags |= S_DEAD;
3037 dont_mount(new_dentry);
3041 mutex_unlock(&target->i_mutex);
3044 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3045 d_move(old_dentry,new_dentry);
3049 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3050 struct inode *new_dir, struct dentry *new_dentry)
3052 struct inode *target = new_dentry->d_inode;
3055 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3061 mutex_lock(&target->i_mutex);
3064 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3067 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3072 dont_mount(new_dentry);
3073 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3074 d_move(old_dentry, new_dentry);
3077 mutex_unlock(&target->i_mutex);
3082 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3083 struct inode *new_dir, struct dentry *new_dentry)
3086 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3087 const unsigned char *old_name;
3089 if (old_dentry->d_inode == new_dentry->d_inode)
3092 error = may_delete(old_dir, old_dentry, is_dir);
3096 if (!new_dentry->d_inode)
3097 error = may_create(new_dir, new_dentry);
3099 error = may_delete(new_dir, new_dentry, is_dir);
3103 if (!old_dir->i_op->rename)
3106 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3109 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3111 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3113 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3114 new_dentry->d_inode, old_dentry);
3115 fsnotify_oldname_free(old_name);
3120 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3121 int, newdfd, const char __user *, newname)
3123 struct dentry *old_dir, *new_dir;
3124 struct dentry *old_dentry, *new_dentry;
3125 struct dentry *trap;
3126 struct nameidata oldnd, newnd;
3131 error = user_path_parent(olddfd, oldname, &oldnd, &from);
3135 error = user_path_parent(newdfd, newname, &newnd, &to);
3140 if (oldnd.path.mnt != newnd.path.mnt)
3143 old_dir = oldnd.path.dentry;
3145 if (oldnd.last_type != LAST_NORM)
3148 new_dir = newnd.path.dentry;
3149 if (newnd.last_type != LAST_NORM)
3152 oldnd.flags &= ~LOOKUP_PARENT;
3153 newnd.flags &= ~LOOKUP_PARENT;
3154 newnd.flags |= LOOKUP_RENAME_TARGET;
3156 trap = lock_rename(new_dir, old_dir);
3158 old_dentry = lookup_hash(&oldnd);
3159 error = PTR_ERR(old_dentry);
3160 if (IS_ERR(old_dentry))
3162 /* source must exist */
3164 if (!old_dentry->d_inode)
3166 /* unless the source is a directory trailing slashes give -ENOTDIR */
3167 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3169 if (oldnd.last.name[oldnd.last.len])
3171 if (newnd.last.name[newnd.last.len])
3174 /* source should not be ancestor of target */
3176 if (old_dentry == trap)
3178 new_dentry = lookup_hash(&newnd);
3179 error = PTR_ERR(new_dentry);
3180 if (IS_ERR(new_dentry))
3182 /* target should not be an ancestor of source */
3184 if (new_dentry == trap)
3187 error = mnt_want_write(oldnd.path.mnt);
3190 error = security_path_rename(&oldnd.path, old_dentry,
3191 &newnd.path, new_dentry);
3194 error = vfs_rename(old_dir->d_inode, old_dentry,
3195 new_dir->d_inode, new_dentry);
3197 mnt_drop_write(oldnd.path.mnt);
3203 unlock_rename(new_dir, old_dir);
3205 path_put(&newnd.path);
3208 path_put(&oldnd.path);
3214 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3216 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3219 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3223 len = PTR_ERR(link);
3228 if (len > (unsigned) buflen)
3230 if (copy_to_user(buffer, link, len))
3237 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3238 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3239 * using) it for any given inode is up to filesystem.
3241 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3243 struct nameidata nd;
3248 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3250 return PTR_ERR(cookie);
3252 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3253 if (dentry->d_inode->i_op->put_link)
3254 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3258 int vfs_follow_link(struct nameidata *nd, const char *link)
3260 return __vfs_follow_link(nd, link);
3263 /* get the link contents into pagecache */
3264 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3268 struct address_space *mapping = dentry->d_inode->i_mapping;
3269 page = read_mapping_page(mapping, 0, NULL);
3274 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3278 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3280 struct page *page = NULL;
3281 char *s = page_getlink(dentry, &page);
3282 int res = vfs_readlink(dentry,buffer,buflen,s);
3285 page_cache_release(page);
3290 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
3292 struct page *page = NULL;
3293 nd_set_link(nd, page_getlink(dentry, &page));
3297 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
3299 struct page *page = cookie;
3303 page_cache_release(page);
3308 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3310 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
3312 struct address_space *mapping = inode->i_mapping;
3317 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3319 flags |= AOP_FLAG_NOFS;
3322 err = pagecache_write_begin(NULL, mapping, 0, len-1,
3323 flags, &page, &fsdata);
3327 kaddr = kmap_atomic(page, KM_USER0);
3328 memcpy(kaddr, symname, len-1);
3329 kunmap_atomic(kaddr, KM_USER0);
3331 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3338 mark_inode_dirty(inode);
3344 int page_symlink(struct inode *inode, const char *symname, int len)
3346 return __page_symlink(inode, symname, len,
3347 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
3350 const struct inode_operations page_symlink_inode_operations = {
3351 .readlink = generic_readlink,
3352 .follow_link = page_follow_link_light,
3353 .put_link = page_put_link,
3356 EXPORT_SYMBOL(user_path_at);
3357 EXPORT_SYMBOL(follow_down_one);
3358 EXPORT_SYMBOL(follow_down);
3359 EXPORT_SYMBOL(follow_up);
3360 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3361 EXPORT_SYMBOL(getname);
3362 EXPORT_SYMBOL(lock_rename);
3363 EXPORT_SYMBOL(lookup_one_len);
3364 EXPORT_SYMBOL(page_follow_link_light);
3365 EXPORT_SYMBOL(page_put_link);
3366 EXPORT_SYMBOL(page_readlink);
3367 EXPORT_SYMBOL(__page_symlink);
3368 EXPORT_SYMBOL(page_symlink);
3369 EXPORT_SYMBOL(page_symlink_inode_operations);
3370 EXPORT_SYMBOL(kern_path_parent);
3371 EXPORT_SYMBOL(kern_path);
3372 EXPORT_SYMBOL(vfs_path_lookup);
3373 EXPORT_SYMBOL(inode_permission);
3374 EXPORT_SYMBOL(file_permission);
3375 EXPORT_SYMBOL(unlock_rename);
3376 EXPORT_SYMBOL(vfs_create);
3377 EXPORT_SYMBOL(vfs_follow_link);
3378 EXPORT_SYMBOL(vfs_link);
3379 EXPORT_SYMBOL(vfs_mkdir);
3380 EXPORT_SYMBOL(vfs_mknod);
3381 EXPORT_SYMBOL(generic_permission);
3382 EXPORT_SYMBOL(vfs_readlink);
3383 EXPORT_SYMBOL(vfs_rename);
3384 EXPORT_SYMBOL(vfs_rmdir);
3385 EXPORT_SYMBOL(vfs_symlink);
3386 EXPORT_SYMBOL(vfs_unlink);
3387 EXPORT_SYMBOL(dentry_unhash);
3388 EXPORT_SYMBOL(generic_readlink);