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vfs: don't revalidate just looked up dentry
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / fs / namei.c
CommitLineData
1da177e4
LT		 1/*
2 * linux/fs/namei.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * Some corrections by tytso.
9 */
10
11/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
12 * lookup logic.
13 */
14/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
15 */
16
17#include <linux/init.h>
630d9c47 18#include <linux/export.h>
1da177e4
LT		 19#include <linux/slab.h>
20#include <linux/fs.h>
21#include <linux/namei.h>
1da177e4 22#include <linux/pagemap.h>
0eeca283 23#include <linux/fsnotify.h>
1da177e4
LT		 24#include <linux/personality.h>
25#include <linux/security.h>
6146f0d5 26#include <linux/ima.h>
1da177e4
LT		 27#include <linux/syscalls.h>
28#include <linux/mount.h>
29#include <linux/audit.h>
16f7e0fe 30#include <linux/capability.h>
834f2a4a 31#include <linux/file.h>
5590ff0d 32#include <linux/fcntl.h>
08ce5f16 33#include <linux/device_cgroup.h>
5ad4e53b 34#include <linux/fs_struct.h>
e77819e5 35#include <linux/posix_acl.h>
1da177e4
LT		 36#include <asm/uaccess.h>
37
e81e3f4d 38#include "internal.h"
c7105365 39#include "mount.h"
e81e3f4d 40
1da177e4
LT		 41/* [Feb-1997 T. Schoebel-Theuer]
42 * Fundamental changes in the pathname lookup mechanisms (namei)
43 * were necessary because of omirr. The reason is that omirr needs
44 * to know the _real_ pathname, not the user-supplied one, in case
45 * of symlinks (and also when transname replacements occur).
46 *
47 * The new code replaces the old recursive symlink resolution with
48 * an iterative one (in case of non-nested symlink chains). It does
49 * this with calls to <fs>_follow_link().
50 * As a side effect, dir_namei(), _namei() and follow_link() are now
51 * replaced with a single function lookup_dentry() that can handle all
52 * the special cases of the former code.
53 *
54 * With the new dcache, the pathname is stored at each inode, at least as
55 * long as the refcount of the inode is positive. As a side effect, the
56 * size of the dcache depends on the inode cache and thus is dynamic.
57 *
58 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
59 * resolution to correspond with current state of the code.
60 *
61 * Note that the symlink resolution is not *completely* iterative.
62 * There is still a significant amount of tail- and mid- recursion in
63 * the algorithm. Also, note that <fs>_readlink() is not used in
64 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
65 * may return different results than <fs>_follow_link(). Many virtual
66 * filesystems (including /proc) exhibit this behavior.
67 */
68
69/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
70 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
71 * and the name already exists in form of a symlink, try to create the new
72 * name indicated by the symlink. The old code always complained that the
73 * name already exists, due to not following the symlink even if its target
74 * is nonexistent. The new semantics affects also mknod() and link() when
25985edc 75 * the name is a symlink pointing to a non-existent name.
1da177e4
LT		 76 *
77 * I don't know which semantics is the right one, since I have no access
78 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
79 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
80 * "old" one. Personally, I think the new semantics is much more logical.
81 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
82 * file does succeed in both HP-UX and SunOs, but not in Solaris
83 * and in the old Linux semantics.
84 */
85
86/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
87 * semantics. See the comments in "open_namei" and "do_link" below.
88 *
89 * [10-Sep-98 Alan Modra] Another symlink change.
90 */
91
92/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
93 * inside the path - always follow.
94 * in the last component in creation/removal/renaming - never follow.
95 * if LOOKUP_FOLLOW passed - follow.
96 * if the pathname has trailing slashes - follow.
97 * otherwise - don't follow.
98 * (applied in that order).
99 *
100 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
101 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
102 * During the 2.4 we need to fix the userland stuff depending on it -
103 * hopefully we will be able to get rid of that wart in 2.5. So far only
104 * XEmacs seems to be relying on it...
105 */
106/*
107 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
a11f3a05 108 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
1da177e4
LT		 109 * any extra contention...
110 */
111
112/* In order to reduce some races, while at the same time doing additional
113 * checking and hopefully speeding things up, we copy filenames to the
114 * kernel data space before using them..
115 *
116 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
117 * PATH_MAX includes the nul terminator --RR.
118 */
858119e1 119static int do_getname(const char __user *filename, char *page)
1da177e4
LT		 120{
121 int retval;
122 unsigned long len = PATH_MAX;
123
124 if (!segment_eq(get_fs(), KERNEL_DS)) {
125 if ((unsigned long) filename >= TASK_SIZE)
126 return -EFAULT;
127 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
128 len = TASK_SIZE - (unsigned long) filename;
129 }
130
131 retval = strncpy_from_user(page, filename, len);
132 if (retval > 0) {
133 if (retval < len)
134 return 0;
135 return -ENAMETOOLONG;
136 } else if (!retval)
137 retval = -ENOENT;
138 return retval;
139}
140
1fa1e7f6 141static char *getname_flags(const char __user *filename, int flags, int *empty)
1da177e4 142{
4043cde8
EP		 143 char *result = __getname();
144 int retval;
145
146 if (!result)
147 return ERR_PTR(-ENOMEM);
148
149 retval = do_getname(filename, result);
150 if (retval < 0) {
151 if (retval == -ENOENT && empty)
152 *empty = 1;
153 if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
154 __putname(result);
155 return ERR_PTR(retval);
1da177e4
LT		 156 }
157 }
158 audit_getname(result);
159 return result;
160}
161
f52e0c11
AV		 162char *getname(const char __user * filename)
163{
f7493e5d 164 return getname_flags(filename, 0, NULL);
f52e0c11
AV		 165}
166
1da177e4
LT		 167#ifdef CONFIG_AUDITSYSCALL
168void putname(const char *name)
169{
5ac3a9c2 170 if (unlikely(!audit_dummy_context()))
1da177e4
LT		 171 audit_putname(name);
172 else
173 __putname(name);
174}
175EXPORT_SYMBOL(putname);
176#endif
177
e77819e5
LT		 178static int check_acl(struct inode *inode, int mask)
179{
84635d68 180#ifdef CONFIG_FS_POSIX_ACL
e77819e5
LT		 181 struct posix_acl *acl;
182
e77819e5 183 if (mask & MAY_NOT_BLOCK) {
3567866b
AV		 184 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
185 if (!acl)
e77819e5 186 return -EAGAIN;
3567866b
AV		 187 /* no ->get_acl() calls in RCU mode... */
188 if (acl == ACL_NOT_CACHED)
189 return -ECHILD;
206b1d09 190 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
e77819e5
LT		 191 }
192
193 acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
194
195 /*
4e34e719
CH		 196 * A filesystem can force a ACL callback by just never filling the
197 * ACL cache. But normally you'd fill the cache either at inode
198 * instantiation time, or on the first ->get_acl call.
e77819e5 199 *
4e34e719
CH		 200 * If the filesystem doesn't have a get_acl() function at all, we'll
201 * just create the negative cache entry.
e77819e5
LT		 202 */
203 if (acl == ACL_NOT_CACHED) {
4e34e719
CH		 204 if (inode->i_op->get_acl) {
205 acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
206 if (IS_ERR(acl))
207 return PTR_ERR(acl);
208 } else {
209 set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
210 return -EAGAIN;
211 }
e77819e5
LT		 212 }
213
214 if (acl) {
215 int error = posix_acl_permission(inode, acl, mask);
216 posix_acl_release(acl);
217 return error;
218 }
84635d68 219#endif
e77819e5
LT		 220
221 return -EAGAIN;
222}
223
5909ccaa 224/*
948409c7 225 * This does the basic permission checking
1da177e4 226 */
7e40145e 227static int acl_permission_check(struct inode *inode, int mask)
1da177e4 228{
26cf46be 229 unsigned int mode = inode->i_mode;
1da177e4 230
e795b717
SH		 231 if (current_user_ns() != inode_userns(inode))
232 goto other_perms;
233
14067ff5 234 if (likely(current_fsuid() == inode->i_uid))
1da177e4
LT		 235 mode >>= 6;
236 else {
e77819e5 237 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
7e40145e 238 int error = check_acl(inode, mask);
b74c79e9
NP		 239 if (error != -EAGAIN)
240 return error;
1da177e4
LT		 241 }
242
243 if (in_group_p(inode->i_gid))
244 mode >>= 3;
245 }
246
e795b717 247other_perms:
1da177e4
LT		 248 /*
249 * If the DACs are ok we don't need any capability check.
250 */
9c2c7039 251 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
1da177e4 252 return 0;
5909ccaa
LT		 253 return -EACCES;
254}
255
256/**
b74c79e9 257 * generic_permission - check for access rights on a Posix-like filesystem
5909ccaa 258 * @inode: inode to check access rights for
8fd90c8d 259 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
5909ccaa
LT		 260 *
261 * Used to check for read/write/execute permissions on a file.
262 * We use "fsuid" for this, letting us set arbitrary permissions
263 * for filesystem access without changing the "normal" uids which
b74c79e9
NP		 264 * are used for other things.
265 *
266 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
267 * request cannot be satisfied (eg. requires blocking or too much complexity).
268 * It would then be called again in ref-walk mode.
5909ccaa 269 */
2830ba7f 270int generic_permission(struct inode *inode, int mask)
5909ccaa
LT		 271{
272 int ret;
273
274 /*
948409c7 275 * Do the basic permission checks.
5909ccaa 276 */
7e40145e 277 ret = acl_permission_check(inode, mask);
5909ccaa
LT		 278 if (ret != -EACCES)
279 return ret;
1da177e4 280
d594e7ec
AV		 281 if (S_ISDIR(inode->i_mode)) {
282 /* DACs are overridable for directories */
283 if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
284 return 0;
285 if (!(mask & MAY_WRITE))
286 if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
287 return 0;
288 return -EACCES;
289 }
1da177e4
LT		 290 /*
291 * Read/write DACs are always overridable.
d594e7ec
AV		 292 * Executable DACs are overridable when there is
293 * at least one exec bit set.
1da177e4 294 */
d594e7ec 295 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
e795b717 296 if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
1da177e4
LT		 297 return 0;
298
299 /*
300 * Searching includes executable on directories, else just read.
301 */
7ea66001 302 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
d594e7ec 303 if (mask == MAY_READ)
e795b717 304 if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
1da177e4
LT		 305 return 0;
306
307 return -EACCES;
308}
309
3ddcd056
LT		 310/*
311 * We _really_ want to just do "generic_permission()" without
312 * even looking at the inode->i_op values. So we keep a cache
313 * flag in inode->i_opflags, that says "this has not special
314 * permission function, use the fast case".
315 */
316static inline int do_inode_permission(struct inode *inode, int mask)
317{
318 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
319 if (likely(inode->i_op->permission))
320 return inode->i_op->permission(inode, mask);
321
322 /* This gets set once for the inode lifetime */
323 spin_lock(&inode->i_lock);
324 inode->i_opflags |= IOP_FASTPERM;
325 spin_unlock(&inode->i_lock);
326 }
327 return generic_permission(inode, mask);
328}
329
cb23beb5
CH		 330/**
331 * inode_permission - check for access rights to a given inode
332 * @inode: inode to check permission on
8fd90c8d 333 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
cb23beb5
CH		 334 *
335 * Used to check for read/write/execute permissions on an inode.
336 * We use "fsuid" for this, letting us set arbitrary permissions
337 * for filesystem access without changing the "normal" uids which
338 * are used for other things.
948409c7
AG		 339 *
340 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
cb23beb5 341 */
f419a2e3 342int inode_permission(struct inode *inode, int mask)
1da177e4 343{
e6305c43 344 int retval;
1da177e4 345
3ddcd056 346 if (unlikely(mask & MAY_WRITE)) {
22590e41 347 umode_t mode = inode->i_mode;
1da177e4
LT		 348
349 /*
350 * Nobody gets write access to a read-only fs.
351 */
352 if (IS_RDONLY(inode) &&
353 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
354 return -EROFS;
355
356 /*
357 * Nobody gets write access to an immutable file.
358 */
359 if (IS_IMMUTABLE(inode))
360 return -EACCES;
361 }
362
3ddcd056 363 retval = do_inode_permission(inode, mask);
1da177e4
LT		 364 if (retval)
365 return retval;
366
08ce5f16
SH		 367 retval = devcgroup_inode_permission(inode, mask);
368 if (retval)
369 return retval;
370
d09ca739 371 return security_inode_permission(inode, mask);
1da177e4
LT		 372}
373
5dd784d0
JB		 374/**
375 * path_get - get a reference to a path
376 * @path: path to get the reference to
377 *
378 * Given a path increment the reference count to the dentry and the vfsmount.
379 */
380void path_get(struct path *path)
381{
382 mntget(path->mnt);
383 dget(path->dentry);
384}
385EXPORT_SYMBOL(path_get);
386
1d957f9b
JB		 387/**
388 * path_put - put a reference to a path
389 * @path: path to put the reference to
390 *
391 * Given a path decrement the reference count to the dentry and the vfsmount.
392 */
393void path_put(struct path *path)
1da177e4 394{
1d957f9b
JB		 395 dput(path->dentry);
396 mntput(path->mnt);
1da177e4 397}
1d957f9b 398EXPORT_SYMBOL(path_put);
1da177e4 399
19660af7 400/*
31e6b01f 401 * Path walking has 2 modes, rcu-walk and ref-walk (see
19660af7
AV		 402 * Documentation/filesystems/path-lookup.txt). In situations when we can't
403 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
404 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
405 * mode. Refcounts are grabbed at the last known good point before rcu-walk
406 * got stuck, so ref-walk may continue from there. If this is not successful
407 * (eg. a seqcount has changed), then failure is returned and it's up to caller
408 * to restart the path walk from the beginning in ref-walk mode.
31e6b01f 409 */
31e6b01f
NP		 410
411/**
19660af7
AV		 412 * unlazy_walk - try to switch to ref-walk mode.
413 * @nd: nameidata pathwalk data
414 * @dentry: child of nd->path.dentry or NULL
39191628 415 * Returns: 0 on success, -ECHILD on failure
31e6b01f 416 *
19660af7
AV		 417 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
418 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
419 * @nd or NULL. Must be called from rcu-walk context.
31e6b01f 420 */
19660af7 421static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
31e6b01f
NP		 422{
423 struct fs_struct *fs = current->fs;
424 struct dentry *parent = nd->path.dentry;
5b6ca027 425 int want_root = 0;
31e6b01f
NP		 426
427 BUG_ON(!(nd->flags & LOOKUP_RCU));
5b6ca027
AV		 428 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
429 want_root = 1;
31e6b01f
NP		 430 spin_lock(&fs->lock);
431 if (nd->root.mnt != fs->root.mnt ||
432 nd->root.dentry != fs->root.dentry)
433 goto err_root;
434 }
435 spin_lock(&parent->d_lock);
19660af7
AV		 436 if (!dentry) {
437 if (!__d_rcu_to_refcount(parent, nd->seq))
438 goto err_parent;
439 BUG_ON(nd->inode != parent->d_inode);
440 } else {
94c0d4ec
AV		 441 if (dentry->d_parent != parent)
442 goto err_parent;
19660af7
AV		 443 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
444 if (!__d_rcu_to_refcount(dentry, nd->seq))
445 goto err_child;
446 /*
447 * If the sequence check on the child dentry passed, then
448 * the child has not been removed from its parent. This
449 * means the parent dentry must be valid and able to take
450 * a reference at this point.
451 */
452 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
453 BUG_ON(!parent->d_count);
454 parent->d_count++;
455 spin_unlock(&dentry->d_lock);
456 }
31e6b01f 457 spin_unlock(&parent->d_lock);
5b6ca027 458 if (want_root) {
31e6b01f
NP		 459 path_get(&nd->root);
460 spin_unlock(&fs->lock);
461 }
462 mntget(nd->path.mnt);
463
464 rcu_read_unlock();
465 br_read_unlock(vfsmount_lock);
466 nd->flags &= ~LOOKUP_RCU;
467 return 0;
19660af7
AV		 468
469err_child:
31e6b01f 470 spin_unlock(&dentry->d_lock);
19660af7 471err_parent:
31e6b01f
NP		 472 spin_unlock(&parent->d_lock);
473err_root:
5b6ca027 474 if (want_root)
31e6b01f
NP		 475 spin_unlock(&fs->lock);
476 return -ECHILD;
477}
478
834f2a4a
TM		 479/**
480 * release_open_intent - free up open intent resources
481 * @nd: pointer to nameidata
482 */
483void release_open_intent(struct nameidata *nd)
484{
2dab5974
LT		 485 struct file *file = nd->intent.open.file;
486
487 if (file && !IS_ERR(file)) {
488 if (file->f_path.dentry == NULL)
489 put_filp(file);
490 else
491 fput(file);
492 }
834f2a4a
TM		 493}
494
f60aef7e 495static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
34286d66 496{
f60aef7e 497 return dentry->d_op->d_revalidate(dentry, nd);
34286d66
NP		 498}
499
9f1fafee
AV		 500/**
501 * complete_walk - successful completion of path walk
502 * @nd: pointer nameidata
39159de2 503 *
9f1fafee
AV		 504 * If we had been in RCU mode, drop out of it and legitimize nd->path.
505 * Revalidate the final result, unless we'd already done that during
506 * the path walk or the filesystem doesn't ask for it. Return 0 on
507 * success, -error on failure. In case of failure caller does not
508 * need to drop nd->path.
39159de2 509 */
9f1fafee 510static int complete_walk(struct nameidata *nd)
39159de2 511{
16c2cd71 512 struct dentry *dentry = nd->path.dentry;
39159de2 513 int status;
39159de2 514
9f1fafee
AV		 515 if (nd->flags & LOOKUP_RCU) {
516 nd->flags &= ~LOOKUP_RCU;
517 if (!(nd->flags & LOOKUP_ROOT))
518 nd->root.mnt = NULL;
519 spin_lock(&dentry->d_lock);
520 if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
521 spin_unlock(&dentry->d_lock);
522 rcu_read_unlock();
523 br_read_unlock(vfsmount_lock);
524 return -ECHILD;
525 }
526 BUG_ON(nd->inode != dentry->d_inode);
527 spin_unlock(&dentry->d_lock);
528 mntget(nd->path.mnt);
529 rcu_read_unlock();
530 br_read_unlock(vfsmount_lock);
531 }
532
16c2cd71
AV		 533 if (likely(!(nd->flags & LOOKUP_JUMPED)))
534 return 0;
535
536 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
39159de2
JL		 537 return 0;
538
16c2cd71
AV		 539 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
540 return 0;
541
542 /* Note: we do not d_invalidate() */
34286d66 543 status = d_revalidate(dentry, nd);
39159de2
JL		 544 if (status > 0)
545 return 0;
546
16c2cd71 547 if (!status)
39159de2 548 status = -ESTALE;
16c2cd71 549
9f1fafee 550 path_put(&nd->path);
39159de2
JL		 551 return status;
552}
553
2a737871
AV		 554static __always_inline void set_root(struct nameidata *nd)
555{
f7ad3c6b
MS		 556 if (!nd->root.mnt)
557 get_fs_root(current->fs, &nd->root);
2a737871
AV		 558}
559
6de88d72
AV		 560static int link_path_walk(const char *, struct nameidata *);
561
31e6b01f
NP		 562static __always_inline void set_root_rcu(struct nameidata *nd)
563{
564 if (!nd->root.mnt) {
565 struct fs_struct *fs = current->fs;
c28cc364
NP		 566 unsigned seq;
567
568 do {
569 seq = read_seqcount_begin(&fs->seq);
570 nd->root = fs->root;
c1530019 571 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
c28cc364 572 } while (read_seqcount_retry(&fs->seq, seq));
31e6b01f
NP		 573 }
574}
575
f1662356 576static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
1da177e4 577{
31e6b01f
NP		 578 int ret;
579
1da177e4
LT		 580 if (IS_ERR(link))
581 goto fail;
582
583 if (*link == '/') {
2a737871 584 set_root(nd);
1d957f9b 585 path_put(&nd->path);
2a737871
AV		 586 nd->path = nd->root;
587 path_get(&nd->root);
16c2cd71 588 nd->flags |= LOOKUP_JUMPED;
1da177e4 589 }
31e6b01f 590 nd->inode = nd->path.dentry->d_inode;
b4091d5f 591
31e6b01f
NP		 592 ret = link_path_walk(link, nd);
593 return ret;
1da177e4 594fail:
1d957f9b 595 path_put(&nd->path);
1da177e4
LT		 596 return PTR_ERR(link);
597}
598
1d957f9b 599static void path_put_conditional(struct path *path, struct nameidata *nd)
051d3812
IK		 600{
601 dput(path->dentry);
4ac91378 602 if (path->mnt != nd->path.mnt)
051d3812
IK		 603 mntput(path->mnt);
604}
605
7b9337aa
NP		 606static inline void path_to_nameidata(const struct path *path,
607 struct nameidata *nd)
051d3812 608{
31e6b01f
NP		 609 if (!(nd->flags & LOOKUP_RCU)) {
610 dput(nd->path.dentry);
611 if (nd->path.mnt != path->mnt)
612 mntput(nd->path.mnt);
9a229683 613 }
31e6b01f 614 nd->path.mnt = path->mnt;
4ac91378 615 nd->path.dentry = path->dentry;
051d3812
IK		 616}
617
574197e0
AV		 618static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
619{
620 struct inode *inode = link->dentry->d_inode;
621 if (!IS_ERR(cookie) && inode->i_op->put_link)
622 inode->i_op->put_link(link->dentry, nd, cookie);
623 path_put(link);
624}
625
def4af30 626static __always_inline int
574197e0 627follow_link(struct path *link, struct nameidata *nd, void **p)
1da177e4
LT		 628{
629 int error;
7b9337aa 630 struct dentry *dentry = link->dentry;
1da177e4 631
844a3917
AV		 632 BUG_ON(nd->flags & LOOKUP_RCU);
633
0e794589
AV		 634 if (link->mnt == nd->path.mnt)
635 mntget(link->mnt);
636
574197e0
AV		 637 if (unlikely(current->total_link_count >= 40)) {
638 *p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
574197e0
AV		 639 path_put(&nd->path);
640 return -ELOOP;
641 }
642 cond_resched();
643 current->total_link_count++;
644
68ac1234 645 touch_atime(link);
1da177e4 646 nd_set_link(nd, NULL);
cd4e91d3 647
36f3b4f6
AV		 648 error = security_inode_follow_link(link->dentry, nd);
649 if (error) {
650 *p = ERR_PTR(error); /* no ->put_link(), please */
651 path_put(&nd->path);
652 return error;
653 }
654
86acdca1 655 nd->last_type = LAST_BIND;
def4af30
AV		 656 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
657 error = PTR_ERR(*p);
658 if (!IS_ERR(*p)) {
1da177e4 659 char *s = nd_get_link(nd);
cc314eef 660 error = 0;
1da177e4
LT		 661 if (s)
662 error = __vfs_follow_link(nd, s);
bcda7652 663 else if (nd->last_type == LAST_BIND) {
16c2cd71 664 nd->flags |= LOOKUP_JUMPED;
b21041d0
AV		 665 nd->inode = nd->path.dentry->d_inode;
666 if (nd->inode->i_op->follow_link) {
bcda7652
AV		 667 /* stepped on a _really_ weird one */
668 path_put(&nd->path);
669 error = -ELOOP;
670 }
671 }
1da177e4 672 }
1da177e4
LT		 673 return error;
674}
675
31e6b01f
NP		 676static int follow_up_rcu(struct path *path)
677{
0714a533
AV		 678 struct mount *mnt = real_mount(path->mnt);
679 struct mount *parent;
31e6b01f
NP		 680 struct dentry *mountpoint;
681
0714a533
AV		 682 parent = mnt->mnt_parent;
683 if (&parent->mnt == path->mnt)
31e6b01f 684 return 0;
a73324da 685 mountpoint = mnt->mnt_mountpoint;
31e6b01f 686 path->dentry = mountpoint;
0714a533 687 path->mnt = &parent->mnt;
31e6b01f
NP		 688 return 1;
689}
690
bab77ebf 691int follow_up(struct path *path)
1da177e4 692{
0714a533
AV		 693 struct mount *mnt = real_mount(path->mnt);
694 struct mount *parent;
1da177e4 695 struct dentry *mountpoint;
99b7db7b
NP		 696
697 br_read_lock(vfsmount_lock);
0714a533
AV		 698 parent = mnt->mnt_parent;
699 if (&parent->mnt == path->mnt) {
99b7db7b 700 br_read_unlock(vfsmount_lock);
1da177e4
LT		 701 return 0;
702 }
0714a533 703 mntget(&parent->mnt);
a73324da 704 mountpoint = dget(mnt->mnt_mountpoint);
99b7db7b 705 br_read_unlock(vfsmount_lock);
bab77ebf
AV		 706 dput(path->dentry);
707 path->dentry = mountpoint;
708 mntput(path->mnt);
0714a533 709 path->mnt = &parent->mnt;
1da177e4
LT		 710 return 1;
711}
712
b5c84bf6 713/*
9875cf80
DH		 714 * Perform an automount
715 * - return -EISDIR to tell follow_managed() to stop and return the path we
716 * were called with.
1da177e4 717 */
9875cf80
DH		 718static int follow_automount(struct path *path, unsigned flags,
719 bool *need_mntput)
31e6b01f 720{
9875cf80 721 struct vfsmount *mnt;
ea5b778a 722 int err;
9875cf80
DH		 723
724 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
725 return -EREMOTE;
726
0ec26fd0
MS		 727 /* We don't want to mount if someone's just doing a stat -
728 * unless they're stat'ing a directory and appended a '/' to
729 * the name.
730 *
731 * We do, however, want to mount if someone wants to open or
732 * create a file of any type under the mountpoint, wants to
733 * traverse through the mountpoint or wants to open the
734 * mounted directory. Also, autofs may mark negative dentries
735 * as being automount points. These will need the attentions
736 * of the daemon to instantiate them before they can be used.
9875cf80 737 */
0ec26fd0 738 if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
d94c177b 739 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
0ec26fd0
MS		 740 path->dentry->d_inode)
741 return -EISDIR;
742
9875cf80
DH		 743 current->total_link_count++;
744 if (current->total_link_count >= 40)
745 return -ELOOP;
746
747 mnt = path->dentry->d_op->d_automount(path);
748 if (IS_ERR(mnt)) {
749 /*
750 * The filesystem is allowed to return -EISDIR here to indicate
751 * it doesn't want to automount. For instance, autofs would do
752 * this so that its userspace daemon can mount on this dentry.
753 *
754 * However, we can only permit this if it's a terminal point in
755 * the path being looked up; if it wasn't then the remainder of
756 * the path is inaccessible and we should say so.
757 */
49084c3b 758 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
9875cf80
DH		 759 return -EREMOTE;
760 return PTR_ERR(mnt);
31e6b01f 761 }
ea5b778a 762
9875cf80
DH		 763 if (!mnt) /* mount collision */
764 return 0;
31e6b01f 765
8aef1884
AV		 766 if (!*need_mntput) {
767 /* lock_mount() may release path->mnt on error */
768 mntget(path->mnt);
769 *need_mntput = true;
770 }
19a167af 771 err = finish_automount(mnt, path);
9875cf80 772
ea5b778a
DH		 773 switch (err) {
774 case -EBUSY:
775 /* Someone else made a mount here whilst we were busy */
19a167af 776 return 0;
ea5b778a 777 case 0:
8aef1884 778 path_put(path);
ea5b778a
DH		 779 path->mnt = mnt;
780 path->dentry = dget(mnt->mnt_root);
ea5b778a 781 return 0;
19a167af
AV		 782 default:
783 return err;
ea5b778a 784 }
19a167af 785
463ffb2e
AV		 786}
787
9875cf80
DH		 788/*
789 * Handle a dentry that is managed in some way.
cc53ce53 790 * - Flagged for transit management (autofs)
9875cf80
DH		 791 * - Flagged as mountpoint
792 * - Flagged as automount point
793 *
794 * This may only be called in refwalk mode.
795 *
796 * Serialization is taken care of in namespace.c
797 */
798static int follow_managed(struct path *path, unsigned flags)
1da177e4 799{
8aef1884 800 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
9875cf80
DH		 801 unsigned managed;
802 bool need_mntput = false;
8aef1884 803 int ret = 0;
9875cf80
DH		 804
805 /* Given that we're not holding a lock here, we retain the value in a
806 * local variable for each dentry as we look at it so that we don't see
807 * the components of that value change under us */
808 while (managed = ACCESS_ONCE(path->dentry->d_flags),
809 managed &= DCACHE_MANAGED_DENTRY,
810 unlikely(managed != 0)) {
cc53ce53
DH		 811 /* Allow the filesystem to manage the transit without i_mutex
812 * being held. */
813 if (managed & DCACHE_MANAGE_TRANSIT) {
814 BUG_ON(!path->dentry->d_op);
815 BUG_ON(!path->dentry->d_op->d_manage);
1aed3e42 816 ret = path->dentry->d_op->d_manage(path->dentry, false);
cc53ce53 817 if (ret < 0)
8aef1884 818 break;
cc53ce53
DH		 819 }
820
9875cf80
DH		 821 /* Transit to a mounted filesystem. */
822 if (managed & DCACHE_MOUNTED) {
823 struct vfsmount *mounted = lookup_mnt(path);
824 if (mounted) {
825 dput(path->dentry);
826 if (need_mntput)
827 mntput(path->mnt);
828 path->mnt = mounted;
829 path->dentry = dget(mounted->mnt_root);
830 need_mntput = true;
831 continue;
832 }
833
834 /* Something is mounted on this dentry in another
835 * namespace and/or whatever was mounted there in this
836 * namespace got unmounted before we managed to get the
837 * vfsmount_lock */
838 }
839
840 /* Handle an automount point */
841 if (managed & DCACHE_NEED_AUTOMOUNT) {
842 ret = follow_automount(path, flags, &need_mntput);
843 if (ret < 0)
8aef1884 844 break;
9875cf80
DH		 845 continue;
846 }
847
848 /* We didn't change the current path point */
849 break;
1da177e4 850 }
8aef1884
AV		 851
852 if (need_mntput && path->mnt == mnt)
853 mntput(path->mnt);
854 if (ret == -EISDIR)
855 ret = 0;
a3fbbde7 856 return ret < 0 ? ret : need_mntput;
1da177e4
LT		 857}
858
cc53ce53 859int follow_down_one(struct path *path)
1da177e4
LT		 860{
861 struct vfsmount *mounted;
862
1c755af4 863 mounted = lookup_mnt(path);
1da177e4 864 if (mounted) {
9393bd07
AV		 865 dput(path->dentry);
866 mntput(path->mnt);
867 path->mnt = mounted;
868 path->dentry = dget(mounted->mnt_root);
1da177e4
LT		 869 return 1;
870 }
871 return 0;
872}
873
62a7375e
IK		 874static inline bool managed_dentry_might_block(struct dentry *dentry)
875{
876 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
877 dentry->d_op->d_manage(dentry, true) < 0);
878}
879
9875cf80 880/*
287548e4
AV		 881 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
882 * we meet a managed dentry that would need blocking.
9875cf80
DH		 883 */
884static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
287548e4 885 struct inode **inode)
9875cf80 886{
62a7375e 887 for (;;) {
c7105365 888 struct mount *mounted;
62a7375e
IK		 889 /*
890 * Don't forget we might have a non-mountpoint managed dentry
891 * that wants to block transit.
892 */
287548e4 893 if (unlikely(managed_dentry_might_block(path->dentry)))
ab90911f 894 return false;
62a7375e
IK		 895
896 if (!d_mountpoint(path->dentry))
897 break;
898
9875cf80
DH		 899 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
900 if (!mounted)
901 break;
c7105365
AV		 902 path->mnt = &mounted->mnt;
903 path->dentry = mounted->mnt.mnt_root;
a3fbbde7 904 nd->flags |= LOOKUP_JUMPED;
9875cf80 905 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
59430262
LT		 906 /*
907 * Update the inode too. We don't need to re-check the
908 * dentry sequence number here after this d_inode read,
909 * because a mount-point is always pinned.
910 */
911 *inode = path->dentry->d_inode;
9875cf80 912 }
9875cf80
DH		 913 return true;
914}
915
dea39376 916static void follow_mount_rcu(struct nameidata *nd)
287548e4 917{
dea39376 918 while (d_mountpoint(nd->path.dentry)) {
c7105365 919 struct mount *mounted;
dea39376 920 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
287548e4
AV		 921 if (!mounted)
922 break;
c7105365
AV		 923 nd->path.mnt = &mounted->mnt;
924 nd->path.dentry = mounted->mnt.mnt_root;
dea39376 925 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
287548e4
AV		 926 }
927}
928
31e6b01f
NP		 929static int follow_dotdot_rcu(struct nameidata *nd)
930{
31e6b01f
NP		 931 set_root_rcu(nd);
932
9875cf80 933 while (1) {
31e6b01f
NP		 934 if (nd->path.dentry == nd->root.dentry &&
935 nd->path.mnt == nd->root.mnt) {
936 break;
937 }
938 if (nd->path.dentry != nd->path.mnt->mnt_root) {
939 struct dentry *old = nd->path.dentry;
940 struct dentry *parent = old->d_parent;
941 unsigned seq;
942
943 seq = read_seqcount_begin(&parent->d_seq);
944 if (read_seqcount_retry(&old->d_seq, nd->seq))
ef7562d5 945 goto failed;
31e6b01f
NP		 946 nd->path.dentry = parent;
947 nd->seq = seq;
948 break;
949 }
950 if (!follow_up_rcu(&nd->path))
951 break;
952 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
31e6b01f 953 }
dea39376
AV		 954 follow_mount_rcu(nd);
955 nd->inode = nd->path.dentry->d_inode;
31e6b01f 956 return 0;
ef7562d5
AV		 957
958failed:
959 nd->flags &= ~LOOKUP_RCU;
5b6ca027
AV		 960 if (!(nd->flags & LOOKUP_ROOT))
961 nd->root.mnt = NULL;
ef7562d5
AV		 962 rcu_read_unlock();
963 br_read_unlock(vfsmount_lock);
964 return -ECHILD;
31e6b01f
NP		 965}
966
cc53ce53
DH		 967/*
968 * Follow down to the covering mount currently visible to userspace. At each
969 * point, the filesystem owning that dentry may be queried as to whether the
970 * caller is permitted to proceed or not.
cc53ce53 971 */
7cc90cc3 972int follow_down(struct path *path)
cc53ce53
DH		 973{
974 unsigned managed;
975 int ret;
976
977 while (managed = ACCESS_ONCE(path->dentry->d_flags),
978 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
979 /* Allow the filesystem to manage the transit without i_mutex
980 * being held.
981 *
982 * We indicate to the filesystem if someone is trying to mount
983 * something here. This gives autofs the chance to deny anyone
984 * other than its daemon the right to mount on its
985 * superstructure.
986 *
987 * The filesystem may sleep at this point.
988 */
989 if (managed & DCACHE_MANAGE_TRANSIT) {
990 BUG_ON(!path->dentry->d_op);
991 BUG_ON(!path->dentry->d_op->d_manage);
ab90911f 992 ret = path->dentry->d_op->d_manage(
1aed3e42 993 path->dentry, false);
cc53ce53
DH		 994 if (ret < 0)
995 return ret == -EISDIR ? 0 : ret;
996 }
997
998 /* Transit to a mounted filesystem. */
999 if (managed & DCACHE_MOUNTED) {
1000 struct vfsmount *mounted = lookup_mnt(path);
1001 if (!mounted)
1002 break;
1003 dput(path->dentry);
1004 mntput(path->mnt);
1005 path->mnt = mounted;
1006 path->dentry = dget(mounted->mnt_root);
1007 continue;
1008 }
1009
1010 /* Don't handle automount points here */
1011 break;
1012 }
1013 return 0;
1014}
1015
9875cf80
DH		 1016/*
1017 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1018 */
1019static void follow_mount(struct path *path)
1020{
1021 while (d_mountpoint(path->dentry)) {
1022 struct vfsmount *mounted = lookup_mnt(path);
1023 if (!mounted)
1024 break;
1025 dput(path->dentry);
1026 mntput(path->mnt);
1027 path->mnt = mounted;
1028 path->dentry = dget(mounted->mnt_root);
1029 }
1030}
1031
31e6b01f 1032static void follow_dotdot(struct nameidata *nd)
1da177e4 1033{
2a737871 1034 set_root(nd);
e518ddb7 1035
1da177e4 1036 while(1) {
4ac91378 1037 struct dentry *old = nd->path.dentry;
1da177e4 1038
2a737871
AV		 1039 if (nd->path.dentry == nd->root.dentry &&
1040 nd->path.mnt == nd->root.mnt) {
1da177e4
LT		 1041 break;
1042 }
4ac91378 1043 if (nd->path.dentry != nd->path.mnt->mnt_root) {
3088dd70
AV		 1044 /* rare case of legitimate dget_parent()... */
1045 nd->path.dentry = dget_parent(nd->path.dentry);
1da177e4
LT		 1046 dput(old);
1047 break;
1048 }
3088dd70 1049 if (!follow_up(&nd->path))
1da177e4 1050 break;
1da177e4 1051 }
79ed0226 1052 follow_mount(&nd->path);
31e6b01f 1053 nd->inode = nd->path.dentry->d_inode;
1da177e4
LT		 1054}
1055
baa03890
NP		 1056/*
1057 * Allocate a dentry with name and parent, and perform a parent
1058 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1059 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1060 * have verified that no child exists while under i_mutex.
1061 */
1062static struct dentry *d_alloc_and_lookup(struct dentry *parent,
1063 struct qstr *name, struct nameidata *nd)
1064{
1065 struct inode *inode = parent->d_inode;
1066 struct dentry *dentry;
1067 struct dentry *old;
1068
1069 /* Don't create child dentry for a dead directory. */
1070 if (unlikely(IS_DEADDIR(inode)))
1071 return ERR_PTR(-ENOENT);
1072
1073 dentry = d_alloc(parent, name);
1074 if (unlikely(!dentry))
1075 return ERR_PTR(-ENOMEM);
1076
1077 old = inode->i_op->lookup(inode, dentry, nd);
1078 if (unlikely(old)) {
1079 dput(dentry);
1080 dentry = old;
1081 }
1082 return dentry;
1083}
1084
44396f4b
JB		 1085/*
1086 * We already have a dentry, but require a lookup to be performed on the parent
1087 * directory to fill in d_inode. Returns the new dentry, or ERR_PTR on error.
1088 * parent->d_inode->i_mutex must be held. d_lookup must have verified that no
1089 * child exists while under i_mutex.
1090 */
1091static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentry,
1092 struct nameidata *nd)
1093{
1094 struct inode *inode = parent->d_inode;
1095 struct dentry *old;
1096
1097 /* Don't create child dentry for a dead directory. */
e188dc02
MS		 1098 if (unlikely(IS_DEADDIR(inode))) {
1099 dput(dentry);
44396f4b 1100 return ERR_PTR(-ENOENT);
e188dc02 1101 }
44396f4b
JB		 1102
1103 old = inode->i_op->lookup(inode, dentry, nd);
1104 if (unlikely(old)) {
1105 dput(dentry);
1106 dentry = old;
1107 }
1108 return dentry;
1109}
1110
1da177e4
LT		 1111/*
1112 * It's more convoluted than I'd like it to be, but... it's still fairly
1113 * small and for now I'd prefer to have fast path as straight as possible.
1114 * It _is_ time-critical.
1115 */
1116static int do_lookup(struct nameidata *nd, struct qstr *name,
31e6b01f 1117 struct path *path, struct inode **inode)
1da177e4 1118{
4ac91378 1119 struct vfsmount *mnt = nd->path.mnt;
31e6b01f 1120 struct dentry *dentry, *parent = nd->path.dentry;
5a18fff2
AV		 1121 int need_reval = 1;
1122 int status = 1;
9875cf80
DH		 1123 int err;
1124
b04f784e
NP		 1125 /*
1126 * Rename seqlock is not required here because in the off chance
1127 * of a false negative due to a concurrent rename, we're going to
1128 * do the non-racy lookup, below.
1129 */
31e6b01f
NP		 1130 if (nd->flags & LOOKUP_RCU) {
1131 unsigned seq;
31e6b01f
NP		 1132 *inode = nd->inode;
1133 dentry = __d_lookup_rcu(parent, name, &seq, inode);
5a18fff2
AV		 1134 if (!dentry)
1135 goto unlazy;
1136
31e6b01f
NP		 1137 /* Memory barrier in read_seqcount_begin of child is enough */
1138 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1139 return -ECHILD;
31e6b01f 1140 nd->seq = seq;
5a18fff2 1141
fa4ee159
MS		 1142 if (unlikely(d_need_lookup(dentry)))
1143 goto unlazy;
24643087 1144 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
5a18fff2
AV		 1145 status = d_revalidate(dentry, nd);
1146 if (unlikely(status <= 0)) {
1147 if (status != -ECHILD)
1148 need_reval = 0;
1149 goto unlazy;
1150 }
24643087 1151 }
31e6b01f
NP		 1152 path->mnt = mnt;
1153 path->dentry = dentry;
d6e9bd25
AV		 1154 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1155 goto unlazy;
1156 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1157 goto unlazy;
1158 return 0;
5a18fff2 1159unlazy:
19660af7
AV		 1160 if (unlazy_walk(nd, dentry))
1161 return -ECHILD;
5a18fff2
AV		 1162 } else {
1163 dentry = __d_lookup(parent, name);
9875cf80 1164 }
5a18fff2 1165
44396f4b
JB		 1166 if (dentry && unlikely(d_need_lookup(dentry))) {
1167 dput(dentry);
1168 dentry = NULL;
1169 }
5a18fff2
AV		 1170retry:
1171 if (unlikely(!dentry)) {
1172 struct inode *dir = parent->d_inode;
1173 BUG_ON(nd->inode != dir);
1174
1175 mutex_lock(&dir->i_mutex);
1176 dentry = d_lookup(parent, name);
1177 if (likely(!dentry)) {
1178 dentry = d_alloc_and_lookup(parent, name, nd);
1179 if (IS_ERR(dentry)) {
1180 mutex_unlock(&dir->i_mutex);
1181 return PTR_ERR(dentry);
1182 }
1183 /* known good */
1184 need_reval = 0;
1185 status = 1;
44396f4b
JB		 1186 } else if (unlikely(d_need_lookup(dentry))) {
1187 dentry = d_inode_lookup(parent, dentry, nd);
1188 if (IS_ERR(dentry)) {
1189 mutex_unlock(&dir->i_mutex);
1190 return PTR_ERR(dentry);
1191 }
1192 /* known good */
1193 need_reval = 0;
1194 status = 1;
5a18fff2
AV		 1195 }
1196 mutex_unlock(&dir->i_mutex);
1197 }
1198 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1199 status = d_revalidate(dentry, nd);
1200 if (unlikely(status <= 0)) {
1201 if (status < 0) {
1202 dput(dentry);
1203 return status;
1204 }
1205 if (!d_invalidate(dentry)) {
1206 dput(dentry);
1207 dentry = NULL;
1208 need_reval = 1;
1209 goto retry;
1210 }
24643087 1211 }
5a18fff2 1212
9875cf80
DH		 1213 path->mnt = mnt;
1214 path->dentry = dentry;
1215 err = follow_managed(path, nd->flags);
89312214
IK		 1216 if (unlikely(err < 0)) {
1217 path_put_conditional(path, nd);
9875cf80 1218 return err;
89312214 1219 }
a3fbbde7
AV		 1220 if (err)
1221 nd->flags |= LOOKUP_JUMPED;
9875cf80 1222 *inode = path->dentry->d_inode;
1da177e4 1223 return 0;
1da177e4
LT		 1224}
1225
52094c8a
AV		 1226static inline int may_lookup(struct nameidata *nd)
1227{
1228 if (nd->flags & LOOKUP_RCU) {
4ad5abb3 1229 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
52094c8a
AV		 1230 if (err != -ECHILD)
1231 return err;
19660af7 1232 if (unlazy_walk(nd, NULL))
52094c8a
AV		 1233 return -ECHILD;
1234 }
4ad5abb3 1235 return inode_permission(nd->inode, MAY_EXEC);
52094c8a
AV		 1236}
1237
9856fa1b
AV		 1238static inline int handle_dots(struct nameidata *nd, int type)
1239{
1240 if (type == LAST_DOTDOT) {
1241 if (nd->flags & LOOKUP_RCU) {
1242 if (follow_dotdot_rcu(nd))
1243 return -ECHILD;
1244 } else
1245 follow_dotdot(nd);
1246 }
1247 return 0;
1248}
1249
951361f9
AV		 1250static void terminate_walk(struct nameidata *nd)
1251{
1252 if (!(nd->flags & LOOKUP_RCU)) {
1253 path_put(&nd->path);
1254 } else {
1255 nd->flags &= ~LOOKUP_RCU;
5b6ca027
AV		 1256 if (!(nd->flags & LOOKUP_ROOT))
1257 nd->root.mnt = NULL;
951361f9
AV		 1258 rcu_read_unlock();
1259 br_read_unlock(vfsmount_lock);
1260 }
1261}
1262
3ddcd056
LT		 1263/*
1264 * Do we need to follow links? We _really_ want to be able
1265 * to do this check without having to look at inode->i_op,
1266 * so we keep a cache of "no, this doesn't need follow_link"
1267 * for the common case.
1268 */
7813b94a 1269static inline int should_follow_link(struct inode *inode, int follow)
3ddcd056
LT		 1270{
1271 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1272 if (likely(inode->i_op->follow_link))
1273 return follow;
1274
1275 /* This gets set once for the inode lifetime */
1276 spin_lock(&inode->i_lock);
1277 inode->i_opflags |= IOP_NOFOLLOW;
1278 spin_unlock(&inode->i_lock);
1279 }
1280 return 0;
1281}
1282
ce57dfc1
AV		 1283static inline int walk_component(struct nameidata *nd, struct path *path,
1284 struct qstr *name, int type, int follow)
1285{
1286 struct inode *inode;
1287 int err;
1288 /*
1289 * "." and ".." are special - ".." especially so because it has
1290 * to be able to know about the current root directory and
1291 * parent relationships.
1292 */
1293 if (unlikely(type != LAST_NORM))
1294 return handle_dots(nd, type);
1295 err = do_lookup(nd, name, path, &inode);
1296 if (unlikely(err)) {
1297 terminate_walk(nd);
1298 return err;
1299 }
1300 if (!inode) {
1301 path_to_nameidata(path, nd);
1302 terminate_walk(nd);
1303 return -ENOENT;
1304 }
7813b94a 1305 if (should_follow_link(inode, follow)) {
19660af7
AV		 1306 if (nd->flags & LOOKUP_RCU) {
1307 if (unlikely(unlazy_walk(nd, path->dentry))) {
1308 terminate_walk(nd);
1309 return -ECHILD;
1310 }
1311 }
ce57dfc1
AV		 1312 BUG_ON(inode != path->dentry->d_inode);
1313 return 1;
1314 }
1315 path_to_nameidata(path, nd);
1316 nd->inode = inode;
1317 return 0;
1318}
1319
b356379a
AV		 1320/*
1321 * This limits recursive symlink follows to 8, while
1322 * limiting consecutive symlinks to 40.
1323 *
1324 * Without that kind of total limit, nasty chains of consecutive
1325 * symlinks can cause almost arbitrarily long lookups.
1326 */
1327static inline int nested_symlink(struct path *path, struct nameidata *nd)
1328{
1329 int res;
1330
b356379a
AV		 1331 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1332 path_put_conditional(path, nd);
1333 path_put(&nd->path);
1334 return -ELOOP;
1335 }
1a4022f8 1336 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
b356379a
AV		 1337
1338 nd->depth++;
1339 current->link_count++;
1340
1341 do {
1342 struct path link = *path;
1343 void *cookie;
574197e0
AV		 1344
1345 res = follow_link(&link, nd, &cookie);
b356379a
AV		 1346 if (!res)
1347 res = walk_component(nd, path, &nd->last,
1348 nd->last_type, LOOKUP_FOLLOW);
574197e0 1349 put_link(nd, &link, cookie);
b356379a
AV		 1350 } while (res > 0);
1351
1352 current->link_count--;
1353 nd->depth--;
1354 return res;
1355}
1356
3ddcd056
LT		 1357/*
1358 * We really don't want to look at inode->i_op->lookup
1359 * when we don't have to. So we keep a cache bit in
1360 * the inode ->i_opflags field that says "yes, we can
1361 * do lookup on this inode".
1362 */
1363static inline int can_lookup(struct inode *inode)
1364{
1365 if (likely(inode->i_opflags & IOP_LOOKUP))
1366 return 1;
1367 if (likely(!inode->i_op->lookup))
1368 return 0;
1369
1370 /* We do this once for the lifetime of the inode */
1371 spin_lock(&inode->i_lock);
1372 inode->i_opflags |= IOP_LOOKUP;
1373 spin_unlock(&inode->i_lock);
1374 return 1;
1375}
1376
bfcfaa77
LT		 1377/*
1378 * We can do the critical dentry name comparison and hashing
1379 * operations one word at a time, but we are limited to:
1380 *
1381 * - Architectures with fast unaligned word accesses. We could
1382 * do a "get_unaligned()" if this helps and is sufficiently
1383 * fast.
1384 *
1385 * - Little-endian machines (so that we can generate the mask
1386 * of low bytes efficiently). Again, we *could* do a byte
1387 * swapping load on big-endian architectures if that is not
1388 * expensive enough to make the optimization worthless.
1389 *
1390 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1391 * do not trap on the (extremely unlikely) case of a page
1392 * crossing operation.
1393 *
1394 * - Furthermore, we need an efficient 64-bit compile for the
1395 * 64-bit case in order to generate the "number of bytes in
1396 * the final mask". Again, that could be replaced with a
1397 * efficient population count instruction or similar.
1398 */
1399#ifdef CONFIG_DCACHE_WORD_ACCESS
1400
1401#ifdef CONFIG_64BIT
1402
1403/*
1404 * Jan Achrenius on G+: microoptimized version of
1405 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
1406 * that works for the bytemasks without having to
1407 * mask them first.
1408 */
1409static inline long count_masked_bytes(unsigned long mask)
1410{
f7493e5d 1411 return mask*0x0001020304050608ul >> 56;
bfcfaa77
LT		 1412}
1413
1414static inline unsigned int fold_hash(unsigned long hash)
1415{
1416 hash += hash >> (8*sizeof(int));
1417 return hash;
1418}
1419
1420#else /* 32-bit case */
1421
1422/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
1423static inline long count_masked_bytes(long mask)
1424{
1425 /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
1426 long a = (0x0ff0001+mask) >> 23;
1427 /* Fix the 1 for 00 case */
1428 return a & mask;
1429}
1430
1431#define fold_hash(x) (x)
1432
1433#endif
1434
1435unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1436{
1437 unsigned long a, mask;
1438 unsigned long hash = 0;
1439
1440 for (;;) {
1441 a = *(unsigned long *)name;
bfcfaa77
LT		 1442 if (len < sizeof(unsigned long))
1443 break;
1444 hash += a;
f132c5be 1445 hash *= 9;
bfcfaa77
LT		 1446 name += sizeof(unsigned long);
1447 len -= sizeof(unsigned long);
1448 if (!len)
1449 goto done;
1450 }
1451 mask = ~(~0ul << len*8);
1452 hash += mask & a;
1453done:
1454 return fold_hash(hash);
1455}
1456EXPORT_SYMBOL(full_name_hash);
1457
989412bb
LT		 1458#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
1459#define ONEBYTES REPEAT_BYTE(0x01)
1460#define SLASHBYTES REPEAT_BYTE('/')
1461#define HIGHBITS REPEAT_BYTE(0x80)
bfcfaa77
LT		 1462
1463/* Return the high bit set in the first byte that is a zero */
1464static inline unsigned long has_zero(unsigned long a)
1465{
1466 return ((a - ONEBYTES) & ~a) & HIGHBITS;
1467}
1468
1469/*
1470 * Calculate the length and hash of the path component, and
1471 * return the length of the component;
1472 */
1473static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1474{
1475 unsigned long a, mask, hash, len;
1476
1477 hash = a = 0;
1478 len = -sizeof(unsigned long);
1479 do {
1480 hash = (hash + a) * 9;
1481 len += sizeof(unsigned long);
1482 a = *(unsigned long *)(name+len);
1483 /* Do we have any NUL or '/' bytes in this word? */
1484 mask = has_zero(a) | has_zero(a ^ SLASHBYTES);
1485 } while (!mask);
1486
1487 /* The mask *below* the first high bit set */
1488 mask = (mask - 1) & ~mask;
1489 mask >>= 7;
1490 hash += a & mask;
1491 *hashp = fold_hash(hash);
1492
1493 return len + count_masked_bytes(mask);
1494}
1495
1496#else
1497
0145acc2
LT		 1498unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1499{
1500 unsigned long hash = init_name_hash();
1501 while (len--)
1502 hash = partial_name_hash(*name++, hash);
1503 return end_name_hash(hash);
1504}
ae942ae7 1505EXPORT_SYMBOL(full_name_hash);
0145acc2 1506
200e9ef7
LT		 1507/*
1508 * We know there's a real path component here of at least
1509 * one character.
1510 */
1511static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1512{
1513 unsigned long hash = init_name_hash();
1514 unsigned long len = 0, c;
1515
1516 c = (unsigned char)*name;
1517 do {
1518 len++;
1519 hash = partial_name_hash(c, hash);
1520 c = (unsigned char)name[len];
1521 } while (c && c != '/');
1522 *hashp = end_name_hash(hash);
1523 return len;
1524}
1525
bfcfaa77
LT		 1526#endif
1527
1da177e4
LT		 1528/*
1529 * Name resolution.
ea3834d9
PM		 1530 * This is the basic name resolution function, turning a pathname into
1531 * the final dentry. We expect 'base' to be positive and a directory.
1da177e4 1532 *
ea3834d9
PM		 1533 * Returns 0 and nd will have valid dentry and mnt on success.
1534 * Returns error and drops reference to input namei data on failure.
1da177e4 1535 */
6de88d72 1536static int link_path_walk(const char *name, struct nameidata *nd)
1da177e4
LT		 1537{
1538 struct path next;
1da177e4 1539 int err;
1da177e4
LT		 1540
1541 while (*name=='/')
1542 name++;
1543 if (!*name)
086e183a 1544 return 0;
1da177e4 1545
1da177e4
LT		 1546 /* At this point we know we have a real path component. */
1547 for(;;) {
1da177e4 1548 struct qstr this;
200e9ef7 1549 long len;
fe479a58 1550 int type;
1da177e4 1551
52094c8a 1552 err = may_lookup(nd);
1da177e4
LT		 1553 if (err)
1554 break;
1555
200e9ef7 1556 len = hash_name(name, &this.hash);
1da177e4 1557 this.name = name;
200e9ef7 1558 this.len = len;
1da177e4 1559
fe479a58 1560 type = LAST_NORM;
200e9ef7 1561 if (name[0] == '.') switch (len) {
fe479a58 1562 case 2:
200e9ef7 1563 if (name[1] == '.') {
fe479a58 1564 type = LAST_DOTDOT;
16c2cd71
AV		 1565 nd->flags |= LOOKUP_JUMPED;
1566 }
fe479a58
AV		 1567 break;
1568 case 1:
1569 type = LAST_DOT;
1570 }
5a202bcd
AV		 1571 if (likely(type == LAST_NORM)) {
1572 struct dentry *parent = nd->path.dentry;
16c2cd71 1573 nd->flags &= ~LOOKUP_JUMPED;
5a202bcd
AV		 1574 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1575 err = parent->d_op->d_hash(parent, nd->inode,
1576 &this);
1577 if (err < 0)
1578 break;
1579 }
1580 }
fe479a58 1581
200e9ef7 1582 if (!name[len])
1da177e4 1583 goto last_component;
200e9ef7
LT		 1584 /*
1585 * If it wasn't NUL, we know it was '/'. Skip that
1586 * slash, and continue until no more slashes.
1587 */
1588 do {
1589 len++;
1590 } while (unlikely(name[len] == '/'));
1591 if (!name[len])
b356379a 1592 goto last_component;
200e9ef7 1593 name += len;
1da177e4 1594
ce57dfc1
AV		 1595 err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
1596 if (err < 0)
1597 return err;
1da177e4 1598
ce57dfc1 1599 if (err) {
b356379a 1600 err = nested_symlink(&next, nd);
1da177e4 1601 if (err)
a7472bab 1602 return err;
31e6b01f 1603 }
3ddcd056
LT		 1604 if (can_lookup(nd->inode))
1605 continue;
1da177e4 1606 err = -ENOTDIR;
3ddcd056 1607 break;
1da177e4
LT		 1608 /* here ends the main loop */
1609
1da177e4 1610last_component:
b356379a
AV		 1611 nd->last = this;
1612 nd->last_type = type;
086e183a 1613 return 0;
1da177e4 1614 }
951361f9 1615 terminate_walk(nd);
1da177e4
LT		 1616 return err;
1617}
1618
70e9b357
AV		 1619static int path_init(int dfd, const char *name, unsigned int flags,
1620 struct nameidata *nd, struct file **fp)
31e6b01f
NP		 1621{
1622 int retval = 0;
1623 int fput_needed;
1624 struct file *file;
1625
1626 nd->last_type = LAST_ROOT; /* if there are only slashes... */
16c2cd71 1627 nd->flags = flags | LOOKUP_JUMPED;
31e6b01f 1628 nd->depth = 0;
5b6ca027
AV		 1629 if (flags & LOOKUP_ROOT) {
1630 struct inode *inode = nd->root.dentry->d_inode;
73d049a4
AV		 1631 if (*name) {
1632 if (!inode->i_op->lookup)
1633 return -ENOTDIR;
1634 retval = inode_permission(inode, MAY_EXEC);
1635 if (retval)
1636 return retval;
1637 }
5b6ca027
AV		 1638 nd->path = nd->root;
1639 nd->inode = inode;
1640 if (flags & LOOKUP_RCU) {
1641 br_read_lock(vfsmount_lock);
1642 rcu_read_lock();
1643 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1644 } else {
1645 path_get(&nd->path);
1646 }
1647 return 0;
1648 }
1649
31e6b01f 1650 nd->root.mnt = NULL;
31e6b01f
NP		 1651
1652 if (*name=='/') {
e41f7d4e
AV		 1653 if (flags & LOOKUP_RCU) {
1654 br_read_lock(vfsmount_lock);
1655 rcu_read_lock();
1656 set_root_rcu(nd);
1657 } else {
1658 set_root(nd);
1659 path_get(&nd->root);
1660 }
1661 nd->path = nd->root;
31e6b01f 1662 } else if (dfd == AT_FDCWD) {
e41f7d4e
AV		 1663 if (flags & LOOKUP_RCU) {
1664 struct fs_struct *fs = current->fs;
1665 unsigned seq;
31e6b01f 1666
e41f7d4e
AV		 1667 br_read_lock(vfsmount_lock);
1668 rcu_read_lock();
c28cc364 1669
e41f7d4e
AV		 1670 do {
1671 seq = read_seqcount_begin(&fs->seq);
1672 nd->path = fs->pwd;
1673 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1674 } while (read_seqcount_retry(&fs->seq, seq));
1675 } else {
1676 get_fs_pwd(current->fs, &nd->path);
1677 }
31e6b01f
NP		 1678 } else {
1679 struct dentry *dentry;
1680
1abf0c71 1681 file = fget_raw_light(dfd, &fput_needed);
31e6b01f
NP		 1682 retval = -EBADF;
1683 if (!file)
1684 goto out_fail;
1685
1686 dentry = file->f_path.dentry;
1687
f52e0c11
AV		 1688 if (*name) {
1689 retval = -ENOTDIR;
1690 if (!S_ISDIR(dentry->d_inode->i_mode))
1691 goto fput_fail;
31e6b01f 1692
4ad5abb3 1693 retval = inode_permission(dentry->d_inode, MAY_EXEC);
f52e0c11
AV		 1694 if (retval)
1695 goto fput_fail;
1696 }
31e6b01f
NP		 1697
1698 nd->path = file->f_path;
e41f7d4e
AV		 1699 if (flags & LOOKUP_RCU) {
1700 if (fput_needed)
70e9b357 1701 *fp = file;
e41f7d4e
AV		 1702 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1703 br_read_lock(vfsmount_lock);
1704 rcu_read_lock();
1705 } else {
1706 path_get(&file->f_path);
1707 fput_light(file, fput_needed);
1708 }
31e6b01f 1709 }
31e6b01f 1710
31e6b01f 1711 nd->inode = nd->path.dentry->d_inode;
9b4a9b14 1712 return 0;
2dfdd266 1713
9b4a9b14
AV		 1714fput_fail:
1715 fput_light(file, fput_needed);
1716out_fail:
1717 return retval;
1718}
1719
bd92d7fe
AV		 1720static inline int lookup_last(struct nameidata *nd, struct path *path)
1721{
1722 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1723 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1724
1725 nd->flags &= ~LOOKUP_PARENT;
1726 return walk_component(nd, path, &nd->last, nd->last_type,
1727 nd->flags & LOOKUP_FOLLOW);
1728}
1729
9b4a9b14 1730/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
ee0827cd 1731static int path_lookupat(int dfd, const char *name,
9b4a9b14
AV		 1732 unsigned int flags, struct nameidata *nd)
1733{
70e9b357 1734 struct file *base = NULL;
bd92d7fe
AV		 1735 struct path path;
1736 int err;
31e6b01f
NP		 1737
1738 /*
1739 * Path walking is largely split up into 2 different synchronisation
1740 * schemes, rcu-walk and ref-walk (explained in
1741 * Documentation/filesystems/path-lookup.txt). These share much of the
1742 * path walk code, but some things particularly setup, cleanup, and
1743 * following mounts are sufficiently divergent that functions are
1744 * duplicated. Typically there is a function foo(), and its RCU
1745 * analogue, foo_rcu().
1746 *
1747 * -ECHILD is the error number of choice (just to avoid clashes) that
1748 * is returned if some aspect of an rcu-walk fails. Such an error must
1749 * be handled by restarting a traditional ref-walk (which will always
1750 * be able to complete).
1751 */
bd92d7fe 1752 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
ee0827cd 1753
bd92d7fe
AV		 1754 if (unlikely(err))
1755 return err;
ee0827cd
AV		 1756
1757 current->total_link_count = 0;
bd92d7fe
AV		 1758 err = link_path_walk(name, nd);
1759
1760 if (!err && !(flags & LOOKUP_PARENT)) {
bd92d7fe
AV		 1761 err = lookup_last(nd, &path);
1762 while (err > 0) {
1763 void *cookie;
1764 struct path link = path;
bd92d7fe 1765 nd->flags |= LOOKUP_PARENT;
574197e0 1766 err = follow_link(&link, nd, &cookie);
bd92d7fe
AV		 1767 if (!err)
1768 err = lookup_last(nd, &path);
574197e0 1769 put_link(nd, &link, cookie);
bd92d7fe
AV		 1770 }
1771 }
ee0827cd 1772
9f1fafee
AV		 1773 if (!err)
1774 err = complete_walk(nd);
bd92d7fe
AV		 1775
1776 if (!err && nd->flags & LOOKUP_DIRECTORY) {
1777 if (!nd->inode->i_op->lookup) {
1778 path_put(&nd->path);
bd23a539 1779 err = -ENOTDIR;
bd92d7fe
AV		 1780 }
1781 }
16c2cd71 1782
70e9b357
AV		 1783 if (base)
1784 fput(base);
ee0827cd 1785
5b6ca027 1786 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
2a737871
AV		 1787 path_put(&nd->root);
1788 nd->root.mnt = NULL;
1789 }
bd92d7fe 1790 return err;
ee0827cd 1791}
31e6b01f 1792
ee0827cd
AV		 1793static int do_path_lookup(int dfd, const char *name,
1794 unsigned int flags, struct nameidata *nd)
1795{
1796 int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
1797 if (unlikely(retval == -ECHILD))
1798 retval = path_lookupat(dfd, name, flags, nd);
1799 if (unlikely(retval == -ESTALE))
1800 retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
31e6b01f
NP		 1801
1802 if (likely(!retval)) {
1803 if (unlikely(!audit_dummy_context())) {
1804 if (nd->path.dentry && nd->inode)
1805 audit_inode(name, nd->path.dentry);
1806 }
1807 }
170aa3d0 1808 return retval;
1da177e4
LT		 1809}
1810
c9c6cac0 1811int kern_path_parent(const char *name, struct nameidata *nd)
5590ff0d 1812{
c9c6cac0 1813 return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
5590ff0d
UD		 1814}
1815
d1811465
AV		 1816int kern_path(const char *name, unsigned int flags, struct path *path)
1817{
1818 struct nameidata nd;
1819 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1820 if (!res)
1821 *path = nd.path;
1822 return res;
1823}
1824
16f18200
JJS		 1825/**
1826 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1827 * @dentry: pointer to dentry of the base directory
1828 * @mnt: pointer to vfs mount of the base directory
1829 * @name: pointer to file name
1830 * @flags: lookup flags
e0a01249 1831 * @path: pointer to struct path to fill
16f18200
JJS		 1832 */
1833int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1834 const char *name, unsigned int flags,
e0a01249 1835 struct path *path)
16f18200 1836{
e0a01249
AV		 1837 struct nameidata nd;
1838 int err;
1839 nd.root.dentry = dentry;
1840 nd.root.mnt = mnt;
1841 BUG_ON(flags & LOOKUP_PARENT);
5b6ca027 1842 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
e0a01249
AV		 1843 err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
1844 if (!err)
1845 *path = nd.path;
1846 return err;
16f18200
JJS		 1847}
1848
eead1911
CH		 1849static struct dentry *__lookup_hash(struct qstr *name,
1850 struct dentry *base, struct nameidata *nd)
1da177e4 1851{
81fca444 1852 struct inode *inode = base->d_inode;
057f6c01 1853 struct dentry *dentry;
1da177e4
LT		 1854 int err;
1855
4ad5abb3 1856 err = inode_permission(inode, MAY_EXEC);
81fca444
CH		 1857 if (err)
1858 return ERR_PTR(err);
1da177e4 1859
b04f784e
NP		 1860 /*
1861 * Don't bother with __d_lookup: callers are for creat as
1862 * well as unlink, so a lot of the time it would cost
1863 * a double lookup.
6e6b1bd1 1864 */
b04f784e 1865 dentry = d_lookup(base, name);
6e6b1bd1 1866
44396f4b
JB		 1867 if (dentry && d_need_lookup(dentry)) {
1868 /*
1869 * __lookup_hash is called with the parent dir's i_mutex already
1870 * held, so we are good to go here.
1871 */
3637c05d 1872 return d_inode_lookup(base, dentry, nd);
44396f4b
JB		 1873 }
1874
d2d9e9fb
AV		 1875 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1876 int status = d_revalidate(dentry, nd);
1877 if (unlikely(status <= 0)) {
1878 /*
1879 * The dentry failed validation.
1880 * If d_revalidate returned 0 attempt to invalidate
1881 * the dentry otherwise d_revalidate is asking us
1882 * to return a fail status.
1883 */
1884 if (status < 0) {
1885 dput(dentry);
1886 return ERR_PTR(status);
1887 } else if (!d_invalidate(dentry)) {
1888 dput(dentry);
1889 dentry = NULL;
1890 }
1891 }
1892 }
6e6b1bd1 1893
baa03890
NP		 1894 if (!dentry)
1895 dentry = d_alloc_and_lookup(base, name, nd);
5a202bcd 1896
1da177e4
LT		 1897 return dentry;
1898}
1899
057f6c01
JM		 1900/*
1901 * Restricted form of lookup. Doesn't follow links, single-component only,
1902 * needs parent already locked. Doesn't follow mounts.
1903 * SMP-safe.
1904 */
eead1911 1905static struct dentry *lookup_hash(struct nameidata *nd)
057f6c01 1906{
4ac91378 1907 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1da177e4
LT		 1908}
1909
eead1911 1910/**
a6b91919 1911 * lookup_one_len - filesystem helper to lookup single pathname component
eead1911
CH		 1912 * @name: pathname component to lookup
1913 * @base: base directory to lookup from
1914 * @len: maximum length @len should be interpreted to
1915 *
a6b91919
RD		 1916 * Note that this routine is purely a helper for filesystem usage and should
1917 * not be called by generic code. Also note that by using this function the
eead1911
CH		 1918 * nameidata argument is passed to the filesystem methods and a filesystem
1919 * using this helper needs to be prepared for that.
1920 */
057f6c01
JM		 1921struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1922{
057f6c01 1923 struct qstr this;
6a96ba54 1924 unsigned int c;
057f6c01 1925
2f9092e1
DW		 1926 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1927
6a96ba54
AV		 1928 this.name = name;
1929 this.len = len;
0145acc2 1930 this.hash = full_name_hash(name, len);
6a96ba54
AV		 1931 if (!len)
1932 return ERR_PTR(-EACCES);
1933
6a96ba54
AV		 1934 while (len--) {
1935 c = *(const unsigned char *)name++;
1936 if (c == '/' || c == '\0')
1937 return ERR_PTR(-EACCES);
6a96ba54 1938 }
5a202bcd
AV		 1939 /*
1940 * See if the low-level filesystem might want
1941 * to use its own hash..
1942 */
1943 if (base->d_flags & DCACHE_OP_HASH) {
1944 int err = base->d_op->d_hash(base, base->d_inode, &this);
1945 if (err < 0)
1946 return ERR_PTR(err);
1947 }
eead1911 1948
49705b77 1949 return __lookup_hash(&this, base, NULL);
057f6c01
JM		 1950}
1951
1fa1e7f6
AW		 1952int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
1953 struct path *path, int *empty)
1da177e4 1954{
2d8f3038 1955 struct nameidata nd;
1fa1e7f6 1956 char *tmp = getname_flags(name, flags, empty);
1da177e4 1957 int err = PTR_ERR(tmp);
1da177e4 1958 if (!IS_ERR(tmp)) {
2d8f3038
AV		 1959
1960 BUG_ON(flags & LOOKUP_PARENT);
1961
1962 err = do_path_lookup(dfd, tmp, flags, &nd);
1da177e4 1963 putname(tmp);
2d8f3038
AV		 1964 if (!err)
1965 *path = nd.path;
1da177e4
LT		 1966 }
1967 return err;
1968}
1969
1fa1e7f6
AW		 1970int user_path_at(int dfd, const char __user *name, unsigned flags,
1971 struct path *path)
1972{
f7493e5d 1973 return user_path_at_empty(dfd, name, flags, path, NULL);
1fa1e7f6
AW		 1974}
1975
2ad94ae6
AV		 1976static int user_path_parent(int dfd, const char __user *path,
1977 struct nameidata *nd, char **name)
1978{
1979 char *s = getname(path);
1980 int error;
1981
1982 if (IS_ERR(s))
1983 return PTR_ERR(s);
1984
1985 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1986 if (error)
1987 putname(s);
1988 else
1989 *name = s;
1990
1991 return error;
1992}
1993
1da177e4
LT		 1994/*
1995 * It's inline, so penalty for filesystems that don't use sticky bit is
1996 * minimal.
1997 */
1998static inline int check_sticky(struct inode *dir, struct inode *inode)
1999{
da9592ed
DH		 2000 uid_t fsuid = current_fsuid();
2001
1da177e4
LT		 2002 if (!(dir->i_mode & S_ISVTX))
2003 return 0;
e795b717
SH		 2004 if (current_user_ns() != inode_userns(inode))
2005 goto other_userns;
da9592ed 2006 if (inode->i_uid == fsuid)
1da177e4 2007 return 0;
da9592ed 2008 if (dir->i_uid == fsuid)
1da177e4 2009 return 0;
e795b717
SH		 2010
2011other_userns:
2012 return !ns_capable(inode_userns(inode), CAP_FOWNER);
1da177e4
LT		 2013}
2014
2015/*
2016 * Check whether we can remove a link victim from directory dir, check
2017 * whether the type of victim is right.
2018 * 1. We can't do it if dir is read-only (done in permission())
2019 * 2. We should have write and exec permissions on dir
2020 * 3. We can't remove anything from append-only dir
2021 * 4. We can't do anything with immutable dir (done in permission())
2022 * 5. If the sticky bit on dir is set we should either
2023 * a. be owner of dir, or
2024 * b. be owner of victim, or
2025 * c. have CAP_FOWNER capability
2026 * 6. If the victim is append-only or immutable we can't do antyhing with
2027 * links pointing to it.
2028 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2029 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2030 * 9. We can't remove a root or mountpoint.
2031 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2032 * nfs_async_unlink().
2033 */
858119e1 2034static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1da177e4
LT		 2035{
2036 int error;
2037
2038 if (!victim->d_inode)
2039 return -ENOENT;
2040
2041 BUG_ON(victim->d_parent->d_inode != dir);
cccc6bba 2042 audit_inode_child(victim, dir);
1da177e4 2043
f419a2e3 2044 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1da177e4
LT		 2045 if (error)
2046 return error;
2047 if (IS_APPEND(dir))
2048 return -EPERM;
2049 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
f9454548 2050 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1da177e4
LT		 2051 return -EPERM;
2052 if (isdir) {
2053 if (!S_ISDIR(victim->d_inode->i_mode))
2054 return -ENOTDIR;
2055 if (IS_ROOT(victim))
2056 return -EBUSY;
2057 } else if (S_ISDIR(victim->d_inode->i_mode))
2058 return -EISDIR;
2059 if (IS_DEADDIR(dir))
2060 return -ENOENT;
2061 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2062 return -EBUSY;
2063 return 0;
2064}
2065
2066/* Check whether we can create an object with dentry child in directory
2067 * dir.
2068 * 1. We can't do it if child already exists (open has special treatment for
2069 * this case, but since we are inlined it's OK)
2070 * 2. We can't do it if dir is read-only (done in permission())
2071 * 3. We should have write and exec permissions on dir
2072 * 4. We can't do it if dir is immutable (done in permission())
2073 */
a95164d9 2074static inline int may_create(struct inode *dir, struct dentry *child)
1da177e4
LT		 2075{
2076 if (child->d_inode)
2077 return -EEXIST;
2078 if (IS_DEADDIR(dir))
2079 return -ENOENT;
f419a2e3 2080 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
1da177e4
LT		 2081}
2082
1da177e4
LT		 2083/*
2084 * p1 and p2 should be directories on the same fs.
2085 */
2086struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2087{
2088 struct dentry *p;
2089
2090 if (p1 == p2) {
f2eace23 2091 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1da177e4
LT		 2092 return NULL;
2093 }
2094
a11f3a05 2095 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1da177e4 2096
e2761a11
OH		 2097 p = d_ancestor(p2, p1);
2098 if (p) {
2099 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2100 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2101 return p;
1da177e4
LT		 2102 }
2103
e2761a11
OH		 2104 p = d_ancestor(p1, p2);
2105 if (p) {
2106 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2107 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2108 return p;
1da177e4
LT		 2109 }
2110
f2eace23
IM		 2111 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2112 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1da177e4
LT		 2113 return NULL;
2114}
2115
2116void unlock_rename(struct dentry *p1, struct dentry *p2)
2117{
1b1dcc1b 2118 mutex_unlock(&p1->d_inode->i_mutex);
1da177e4 2119 if (p1 != p2) {
1b1dcc1b 2120 mutex_unlock(&p2->d_inode->i_mutex);
a11f3a05 2121 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1da177e4
LT		 2122 }
2123}
2124
4acdaf27 2125int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1da177e4
LT		 2126 struct nameidata *nd)
2127{
a95164d9 2128 int error = may_create(dir, dentry);
1da177e4
LT		 2129
2130 if (error)
2131 return error;
2132
acfa4380 2133 if (!dir->i_op->create)
1da177e4
LT		 2134 return -EACCES; /* shouldn't it be ENOSYS? */
2135 mode &= S_IALLUGO;
2136 mode |= S_IFREG;
2137 error = security_inode_create(dir, dentry, mode);
2138 if (error)
2139 return error;
1da177e4 2140 error = dir->i_op->create(dir, dentry, mode, nd);
a74574aa 2141 if (!error)
f38aa942 2142 fsnotify_create(dir, dentry);
1da177e4
LT		 2143 return error;
2144}
2145
73d049a4 2146static int may_open(struct path *path, int acc_mode, int flag)
1da177e4 2147{
3fb64190 2148 struct dentry *dentry = path->dentry;
1da177e4
LT		 2149 struct inode *inode = dentry->d_inode;
2150 int error;
2151
bcda7652
AV		 2152 /* O_PATH? */
2153 if (!acc_mode)
2154 return 0;
2155
1da177e4
LT		 2156 if (!inode)
2157 return -ENOENT;
2158
c8fe8f30
CH		 2159 switch (inode->i_mode & S_IFMT) {
2160 case S_IFLNK:
1da177e4 2161 return -ELOOP;
c8fe8f30
CH		 2162 case S_IFDIR:
2163 if (acc_mode & MAY_WRITE)
2164 return -EISDIR;
2165 break;
2166 case S_IFBLK:
2167 case S_IFCHR:
3fb64190 2168 if (path->mnt->mnt_flags & MNT_NODEV)
1da177e4 2169 return -EACCES;
c8fe8f30
CH		 2170 /*FALLTHRU*/
2171 case S_IFIFO:
2172 case S_IFSOCK:
1da177e4 2173 flag &= ~O_TRUNC;
c8fe8f30 2174 break;
4a3fd211 2175 }
b41572e9 2176
3fb64190 2177 error = inode_permission(inode, acc_mode);
b41572e9
DH		 2178 if (error)
2179 return error;
6146f0d5 2180
1da177e4
LT		 2181 /*
2182 * An append-only file must be opened in append mode for writing.
2183 */
2184 if (IS_APPEND(inode)) {
8737c930 2185 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
7715b521 2186 return -EPERM;
1da177e4 2187 if (flag & O_TRUNC)
7715b521 2188 return -EPERM;
1da177e4
LT		 2189 }
2190
2191 /* O_NOATIME can only be set by the owner or superuser */
2e149670 2192 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
7715b521 2193 return -EPERM;
1da177e4 2194
f3c7691e 2195 return 0;
7715b521 2196}
1da177e4 2197
e1181ee6 2198static int handle_truncate(struct file *filp)
7715b521 2199{
e1181ee6 2200 struct path *path = &filp->f_path;
7715b521
AV		 2201 struct inode *inode = path->dentry->d_inode;
2202 int error = get_write_access(inode);
2203 if (error)
2204 return error;
2205 /*
2206 * Refuse to truncate files with mandatory locks held on them.
2207 */
2208 error = locks_verify_locked(inode);
2209 if (!error)
ea0d3ab2 2210 error = security_path_truncate(path);
7715b521
AV		 2211 if (!error) {
2212 error = do_truncate(path->dentry, 0,
2213 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
e1181ee6 2214 filp);
7715b521
AV		 2215 }
2216 put_write_access(inode);
acd0c935 2217 return error;
1da177e4
LT		 2218}
2219
d57999e1
DH		 2220static inline int open_to_namei_flags(int flag)
2221{
8a5e929d
AV		 2222 if ((flag & O_ACCMODE) == 3)
2223 flag--;
d57999e1
DH		 2224 return flag;
2225}
2226
31e6b01f 2227/*
fe2d35ff 2228 * Handle the last step of open()
31e6b01f 2229 */
fb1cc555 2230static struct file *do_last(struct nameidata *nd, struct path *path,
c3e380b0 2231 const struct open_flags *op, const char *pathname)
fb1cc555 2232{
a1e28038 2233 struct dentry *dir = nd->path.dentry;
6c0d46c4 2234 struct dentry *dentry;
ca344a89 2235 int open_flag = op->open_flag;
6c0d46c4 2236 int will_truncate = open_flag & O_TRUNC;
ca344a89 2237 int want_write = 0;
bcda7652 2238 int acc_mode = op->acc_mode;
fb1cc555 2239 struct file *filp;
16c2cd71 2240 int error;
1f36f774 2241
c3e380b0
AV		 2242 nd->flags &= ~LOOKUP_PARENT;
2243 nd->flags |= op->intent;
2244
1f36f774
AV		 2245 switch (nd->last_type) {
2246 case LAST_DOTDOT:
176306f5 2247 case LAST_DOT:
fe2d35ff
AV		 2248 error = handle_dots(nd, nd->last_type);
2249 if (error)
2250 return ERR_PTR(error);
1f36f774 2251 /* fallthrough */
1f36f774 2252 case LAST_ROOT:
9f1fafee 2253 error = complete_walk(nd);
16c2cd71 2254 if (error)
9f1fafee 2255 return ERR_PTR(error);
fe2d35ff 2256 audit_inode(pathname, nd->path.dentry);
ca344a89 2257 if (open_flag & O_CREAT) {
fe2d35ff
AV		 2258 error = -EISDIR;
2259 goto exit;
2260 }
2261 goto ok;
1f36f774 2262 case LAST_BIND:
9f1fafee 2263 error = complete_walk(nd);
16c2cd71 2264 if (error)
9f1fafee 2265 return ERR_PTR(error);
1f36f774 2266 audit_inode(pathname, dir);
67ee3ad2 2267 goto ok;
1f36f774 2268 }
67ee3ad2 2269
ca344a89 2270 if (!(open_flag & O_CREAT)) {
bcda7652 2271 int symlink_ok = 0;
fe2d35ff
AV		 2272 if (nd->last.name[nd->last.len])
2273 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
bcda7652
AV		 2274 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2275 symlink_ok = 1;
fe2d35ff 2276 /* we _can_ be in RCU mode here */
ce57dfc1
AV		 2277 error = walk_component(nd, path, &nd->last, LAST_NORM,
2278 !symlink_ok);
2279 if (error < 0)
fe2d35ff 2280 return ERR_PTR(error);
ce57dfc1 2281 if (error) /* symlink */
fe2d35ff 2282 return NULL;
fe2d35ff 2283 /* sayonara */
9f1fafee
AV		 2284 error = complete_walk(nd);
2285 if (error)
7f6c7e62 2286 return ERR_PTR(error);
fe2d35ff
AV		 2287
2288 error = -ENOTDIR;
2289 if (nd->flags & LOOKUP_DIRECTORY) {
ce57dfc1 2290 if (!nd->inode->i_op->lookup)
fe2d35ff
AV		 2291 goto exit;
2292 }
2293 audit_inode(pathname, nd->path.dentry);
2294 goto ok;
2295 }
2296
2297 /* create side of things */
a3fbbde7
AV		 2298 /*
2299 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been
2300 * cleared when we got to the last component we are about to look up
2301 */
9f1fafee
AV		 2302 error = complete_walk(nd);
2303 if (error)
2304 return ERR_PTR(error);
fe2d35ff
AV		 2305
2306 audit_inode(pathname, dir);
16c2cd71 2307 error = -EISDIR;
1f36f774 2308 /* trailing slashes? */
31e6b01f
NP		 2309 if (nd->last.name[nd->last.len])
2310 goto exit;
a2c36b45 2311
a1e28038
AV		 2312 mutex_lock(&dir->d_inode->i_mutex);
2313
6c0d46c4
AV		 2314 dentry = lookup_hash(nd);
2315 error = PTR_ERR(dentry);
2316 if (IS_ERR(dentry)) {
fb1cc555
AV		 2317 mutex_unlock(&dir->d_inode->i_mutex);
2318 goto exit;
2319 }
2320
6c0d46c4
AV		 2321 path->dentry = dentry;
2322 path->mnt = nd->path.mnt;
2323
fb1cc555 2324 /* Negative dentry, just create the file */
6c0d46c4 2325 if (!dentry->d_inode) {
a218d0fd 2326 umode_t mode = op->mode;
6c0d46c4
AV		 2327 if (!IS_POSIXACL(dir->d_inode))
2328 mode &= ~current_umask();
fb1cc555
AV		 2329 /*
2330 * This write is needed to ensure that a
6c0d46c4 2331 * rw->ro transition does not occur between
fb1cc555
AV		 2332 * the time when the file is created and when
2333 * a permanent write count is taken through
2334 * the 'struct file' in nameidata_to_filp().
2335 */
2336 error = mnt_want_write(nd->path.mnt);
2337 if (error)
2338 goto exit_mutex_unlock;
ca344a89 2339 want_write = 1;
9b44f1b3 2340 /* Don't check for write permission, don't truncate */
ca344a89 2341 open_flag &= ~O_TRUNC;
6c0d46c4 2342 will_truncate = 0;
bcda7652 2343 acc_mode = MAY_OPEN;
6c0d46c4
AV		 2344 error = security_path_mknod(&nd->path, dentry, mode, 0);
2345 if (error)
2346 goto exit_mutex_unlock;
2347 error = vfs_create(dir->d_inode, dentry, mode, nd);
2348 if (error)
2349 goto exit_mutex_unlock;
2350 mutex_unlock(&dir->d_inode->i_mutex);
2351 dput(nd->path.dentry);
2352 nd->path.dentry = dentry;
ca344a89 2353 goto common;
fb1cc555
AV		 2354 }
2355
2356 /*
2357 * It already exists.
2358 */
2359 mutex_unlock(&dir->d_inode->i_mutex);
2360 audit_inode(pathname, path->dentry);
2361
2362 error = -EEXIST;
ca344a89 2363 if (open_flag & O_EXCL)
fb1cc555
AV		 2364 goto exit_dput;
2365
9875cf80
DH		 2366 error = follow_managed(path, nd->flags);
2367 if (error < 0)
2368 goto exit_dput;
fb1cc555 2369
a3fbbde7
AV		 2370 if (error)
2371 nd->flags |= LOOKUP_JUMPED;
2372
fb1cc555
AV		 2373 error = -ENOENT;
2374 if (!path->dentry->d_inode)
2375 goto exit_dput;
9e67f361
AV		 2376
2377 if (path->dentry->d_inode->i_op->follow_link)
fb1cc555 2378 return NULL;
fb1cc555
AV		 2379
2380 path_to_nameidata(path, nd);
31e6b01f 2381 nd->inode = path->dentry->d_inode;
a3fbbde7
AV		 2382 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
2383 error = complete_walk(nd);
2384 if (error)
097b180c 2385 return ERR_PTR(error);
fb1cc555 2386 error = -EISDIR;
31e6b01f 2387 if (S_ISDIR(nd->inode->i_mode))
fb1cc555 2388 goto exit;
67ee3ad2 2389ok:
6c0d46c4
AV		 2390 if (!S_ISREG(nd->inode->i_mode))
2391 will_truncate = 0;
2392
0f9d1a10
AV		 2393 if (will_truncate) {
2394 error = mnt_want_write(nd->path.mnt);
2395 if (error)
2396 goto exit;
ca344a89 2397 want_write = 1;
0f9d1a10 2398 }
ca344a89 2399common:
bcda7652 2400 error = may_open(&nd->path, acc_mode, open_flag);
ca344a89 2401 if (error)
0f9d1a10 2402 goto exit;
0f9d1a10
AV		 2403 filp = nameidata_to_filp(nd);
2404 if (!IS_ERR(filp)) {
2405 error = ima_file_check(filp, op->acc_mode);
2406 if (error) {
2407 fput(filp);
2408 filp = ERR_PTR(error);
2409 }
2410 }
2411 if (!IS_ERR(filp)) {
2412 if (will_truncate) {
2413 error = handle_truncate(filp);
2414 if (error) {
2415 fput(filp);
2416 filp = ERR_PTR(error);
2417 }
2418 }
2419 }
ca344a89
AV		 2420out:
2421 if (want_write)
0f9d1a10
AV		 2422 mnt_drop_write(nd->path.mnt);
2423 path_put(&nd->path);
fb1cc555
AV		 2424 return filp;
2425
2426exit_mutex_unlock:
2427 mutex_unlock(&dir->d_inode->i_mutex);
2428exit_dput:
2429 path_put_conditional(path, nd);
2430exit:
ca344a89
AV		 2431 filp = ERR_PTR(error);
2432 goto out;
fb1cc555
AV		 2433}
2434
13aab428 2435static struct file *path_openat(int dfd, const char *pathname,
73d049a4 2436 struct nameidata *nd, const struct open_flags *op, int flags)
1da177e4 2437{
fe2d35ff 2438 struct file *base = NULL;
4a3fd211 2439 struct file *filp;
9850c056 2440 struct path path;
13aab428 2441 int error;
31e6b01f
NP		 2442
2443 filp = get_empty_filp();
2444 if (!filp)
2445 return ERR_PTR(-ENFILE);
2446
47c805dc 2447 filp->f_flags = op->open_flag;
73d049a4
AV		 2448 nd->intent.open.file = filp;
2449 nd->intent.open.flags = open_to_namei_flags(op->open_flag);
2450 nd->intent.open.create_mode = op->mode;
31e6b01f 2451
73d049a4 2452 error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
31e6b01f 2453 if (unlikely(error))
13aab428 2454 goto out_filp;
31e6b01f 2455
fe2d35ff 2456 current->total_link_count = 0;
73d049a4 2457 error = link_path_walk(pathname, nd);
31e6b01f
NP		 2458 if (unlikely(error))
2459 goto out_filp;
1da177e4 2460
73d049a4 2461 filp = do_last(nd, &path, op, pathname);
806b681c 2462 while (unlikely(!filp)) { /* trailing symlink */
7b9337aa 2463 struct path link = path;
def4af30 2464 void *cookie;
574197e0 2465 if (!(nd->flags & LOOKUP_FOLLOW)) {
73d049a4
AV		 2466 path_put_conditional(&path, nd);
2467 path_put(&nd->path);
40b39136
AV		 2468 filp = ERR_PTR(-ELOOP);
2469 break;
2470 }
73d049a4
AV		 2471 nd->flags |= LOOKUP_PARENT;
2472 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
574197e0 2473 error = follow_link(&link, nd, &cookie);
c3e380b0 2474 if (unlikely(error))
f1afe9ef 2475 filp = ERR_PTR(error);
c3e380b0 2476 else
73d049a4 2477 filp = do_last(nd, &path, op, pathname);
574197e0 2478 put_link(nd, &link, cookie);
806b681c 2479 }
10fa8e62 2480out:
73d049a4
AV		 2481 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2482 path_put(&nd->root);
fe2d35ff
AV		 2483 if (base)
2484 fput(base);
73d049a4 2485 release_open_intent(nd);
10fa8e62 2486 return filp;
1da177e4 2487
31e6b01f 2488out_filp:
806b681c 2489 filp = ERR_PTR(error);
10fa8e62 2490 goto out;
1da177e4
LT		 2491}
2492
13aab428
AV		 2493struct file *do_filp_open(int dfd, const char *pathname,
2494 const struct open_flags *op, int flags)
2495{
73d049a4 2496 struct nameidata nd;
13aab428
AV		 2497 struct file *filp;
2498
73d049a4 2499 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
13aab428 2500 if (unlikely(filp == ERR_PTR(-ECHILD)))
73d049a4 2501 filp = path_openat(dfd, pathname, &nd, op, flags);
13aab428 2502 if (unlikely(filp == ERR_PTR(-ESTALE)))
73d049a4 2503 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
13aab428
AV		 2504 return filp;
2505}
2506
73d049a4
AV		 2507struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
2508 const char *name, const struct open_flags *op, int flags)
2509{
2510 struct nameidata nd;
2511 struct file *file;
2512
2513 nd.root.mnt = mnt;
2514 nd.root.dentry = dentry;
2515
2516 flags |= LOOKUP_ROOT;
2517
bcda7652 2518 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
73d049a4
AV		 2519 return ERR_PTR(-ELOOP);
2520
2521 file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
2522 if (unlikely(file == ERR_PTR(-ECHILD)))
2523 file = path_openat(-1, name, &nd, op, flags);
2524 if (unlikely(file == ERR_PTR(-ESTALE)))
2525 file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
2526 return file;
2527}
2528
ed75e95d 2529struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir)
1da177e4 2530{
c663e5d8 2531 struct dentry *dentry = ERR_PTR(-EEXIST);
ed75e95d
AV		 2532 struct nameidata nd;
2533 int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd);
2534 if (error)
2535 return ERR_PTR(error);
1da177e4 2536
c663e5d8
CH		 2537 /*
2538 * Yucky last component or no last component at all?
2539 * (foo/., foo/.., /////)
2540 */
ed75e95d
AV		 2541 if (nd.last_type != LAST_NORM)
2542 goto out;
2543 nd.flags &= ~LOOKUP_PARENT;
2544 nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
2545 nd.intent.open.flags = O_EXCL;
c663e5d8
CH		 2546
2547 /*
2548 * Do the final lookup.
2549 */
ed75e95d
AV		 2550 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2551 dentry = lookup_hash(&nd);
1da177e4
LT		 2552 if (IS_ERR(dentry))
2553 goto fail;
c663e5d8 2554
e9baf6e5
AV		 2555 if (dentry->d_inode)
2556 goto eexist;
c663e5d8
CH		 2557 /*
2558 * Special case - lookup gave negative, but... we had foo/bar/
2559 * From the vfs_mknod() POV we just have a negative dentry -
2560 * all is fine. Let's be bastards - you had / on the end, you've
2561 * been asking for (non-existent) directory. -ENOENT for you.
2562 */
ed75e95d 2563 if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
e9baf6e5
AV		 2564 dput(dentry);
2565 dentry = ERR_PTR(-ENOENT);
ed75e95d 2566 goto fail;
e9baf6e5 2567 }
ed75e95d 2568 *path = nd.path;
1da177e4 2569 return dentry;
e9baf6e5 2570eexist:
1da177e4 2571 dput(dentry);
e9baf6e5 2572 dentry = ERR_PTR(-EEXIST);
1da177e4 2573fail:
ed75e95d
AV		 2574 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2575out:
2576 path_put(&nd.path);
1da177e4
LT		 2577 return dentry;
2578}
dae6ad8f
AV		 2579EXPORT_SYMBOL(kern_path_create);
2580
2581struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir)
2582{
2583 char *tmp = getname(pathname);
2584 struct dentry *res;
2585 if (IS_ERR(tmp))
2586 return ERR_CAST(tmp);
2587 res = kern_path_create(dfd, tmp, path, is_dir);
2588 putname(tmp);
2589 return res;
2590}
2591EXPORT_SYMBOL(user_path_create);
2592
1a67aafb 2593int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1da177e4 2594{
a95164d9 2595 int error = may_create(dir, dentry);
1da177e4
LT		 2596
2597 if (error)
2598 return error;
2599
e795b717
SH		 2600 if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
2601 !ns_capable(inode_userns(dir), CAP_MKNOD))
1da177e4
LT		 2602 return -EPERM;
2603
acfa4380 2604 if (!dir->i_op->mknod)
1da177e4
LT		 2605 return -EPERM;
2606
08ce5f16
SH		 2607 error = devcgroup_inode_mknod(mode, dev);
2608 if (error)
2609 return error;
2610
1da177e4
LT		 2611 error = security_inode_mknod(dir, dentry, mode, dev);
2612 if (error)
2613 return error;
2614
1da177e4 2615 error = dir->i_op->mknod(dir, dentry, mode, dev);
a74574aa 2616 if (!error)
f38aa942 2617 fsnotify_create(dir, dentry);
1da177e4
LT		 2618 return error;
2619}
2620
f69aac00 2621static int may_mknod(umode_t mode)
463c3197
DH		 2622{
2623 switch (mode & S_IFMT) {
2624 case S_IFREG:
2625 case S_IFCHR:
2626 case S_IFBLK:
2627 case S_IFIFO:
2628 case S_IFSOCK:
2629 case 0: /* zero mode translates to S_IFREG */
2630 return 0;
2631 case S_IFDIR:
2632 return -EPERM;
2633 default:
2634 return -EINVAL;
2635 }
2636}
2637
8208a22b 2638SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
2e4d0924 2639 unsigned, dev)
1da177e4 2640{
2ad94ae6 2641 struct dentry *dentry;
dae6ad8f
AV		 2642 struct path path;
2643 int error;
1da177e4
LT		 2644
2645 if (S_ISDIR(mode))
2646 return -EPERM;
1da177e4 2647
dae6ad8f
AV		 2648 dentry = user_path_create(dfd, filename, &path, 0);
2649 if (IS_ERR(dentry))
2650 return PTR_ERR(dentry);
2ad94ae6 2651
dae6ad8f 2652 if (!IS_POSIXACL(path.dentry->d_inode))
ce3b0f8d 2653 mode &= ~current_umask();
463c3197
DH		 2654 error = may_mknod(mode);
2655 if (error)
2656 goto out_dput;
dae6ad8f 2657 error = mnt_want_write(path.mnt);
463c3197
DH		 2658 if (error)
2659 goto out_dput;
dae6ad8f 2660 error = security_path_mknod(&path, dentry, mode, dev);
be6d3e56
KT		 2661 if (error)
2662 goto out_drop_write;
463c3197 2663 switch (mode & S_IFMT) {
1da177e4 2664 case 0: case S_IFREG:
dae6ad8f 2665 error = vfs_create(path.dentry->d_inode,dentry,mode,NULL);
1da177e4
LT		 2666 break;
2667 case S_IFCHR: case S_IFBLK:
dae6ad8f 2668 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
1da177e4
LT		 2669 new_decode_dev(dev));
2670 break;
2671 case S_IFIFO: case S_IFSOCK:
dae6ad8f 2672 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
1da177e4 2673 break;
1da177e4 2674 }
be6d3e56 2675out_drop_write:
dae6ad8f 2676 mnt_drop_write(path.mnt);
463c3197
DH		 2677out_dput:
2678 dput(dentry);
dae6ad8f
AV		 2679 mutex_unlock(&path.dentry->d_inode->i_mutex);
2680 path_put(&path);
1da177e4
LT		 2681
2682 return error;
2683}
2684
8208a22b 2685SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
5590ff0d
UD		 2686{
2687 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2688}
2689
18bb1db3 2690int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1da177e4 2691{
a95164d9 2692 int error = may_create(dir, dentry);
8de52778 2693 unsigned max_links = dir->i_sb->s_max_links;
1da177e4
LT		 2694
2695 if (error)
2696 return error;
2697
acfa4380 2698 if (!dir->i_op->mkdir)
1da177e4
LT		 2699 return -EPERM;
2700
2701 mode &= (S_IRWXUGO|S_ISVTX);
2702 error = security_inode_mkdir(dir, dentry, mode);
2703 if (error)
2704 return error;
2705
8de52778
AV		 2706 if (max_links && dir->i_nlink >= max_links)
2707 return -EMLINK;
2708
1da177e4 2709 error = dir->i_op->mkdir(dir, dentry, mode);
a74574aa 2710 if (!error)
f38aa942 2711 fsnotify_mkdir(dir, dentry);
1da177e4
LT		 2712 return error;
2713}
2714
a218d0fd 2715SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
1da177e4 2716{
6902d925 2717 struct dentry *dentry;
dae6ad8f
AV		 2718 struct path path;
2719 int error;
1da177e4 2720
dae6ad8f 2721 dentry = user_path_create(dfd, pathname, &path, 1);
6902d925 2722 if (IS_ERR(dentry))
dae6ad8f 2723 return PTR_ERR(dentry);
1da177e4 2724
dae6ad8f 2725 if (!IS_POSIXACL(path.dentry->d_inode))
ce3b0f8d 2726 mode &= ~current_umask();
dae6ad8f 2727 error = mnt_want_write(path.mnt);
463c3197
DH		 2728 if (error)
2729 goto out_dput;
dae6ad8f 2730 error = security_path_mkdir(&path, dentry, mode);
be6d3e56
KT		 2731 if (error)
2732 goto out_drop_write;
dae6ad8f 2733 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
be6d3e56 2734out_drop_write:
dae6ad8f 2735 mnt_drop_write(path.mnt);
463c3197 2736out_dput:
6902d925 2737 dput(dentry);
dae6ad8f
AV		 2738 mutex_unlock(&path.dentry->d_inode->i_mutex);
2739 path_put(&path);
1da177e4
LT		 2740 return error;
2741}
2742
a218d0fd 2743SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
5590ff0d
UD		 2744{
2745 return sys_mkdirat(AT_FDCWD, pathname, mode);
2746}
2747
1da177e4 2748/*
a71905f0
SW		 2749 * The dentry_unhash() helper will try to drop the dentry early: we
2750 * should have a usage count of 2 if we're the only user of this
2751 * dentry, and if that is true (possibly after pruning the dcache),
2752 * then we drop the dentry now.
1da177e4
LT		 2753 *
2754 * A low-level filesystem can, if it choses, legally
2755 * do a
2756 *
2757 * if (!d_unhashed(dentry))
2758 * return -EBUSY;
2759 *
2760 * if it cannot handle the case of removing a directory
2761 * that is still in use by something else..
2762 */
2763void dentry_unhash(struct dentry *dentry)
2764{
dc168427 2765 shrink_dcache_parent(dentry);
1da177e4 2766 spin_lock(&dentry->d_lock);
64252c75 2767 if (dentry->d_count == 1)
1da177e4
LT		 2768 __d_drop(dentry);
2769 spin_unlock(&dentry->d_lock);
1da177e4
LT		 2770}
2771
2772int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2773{
2774 int error = may_delete(dir, dentry, 1);
2775
2776 if (error)
2777 return error;
2778
acfa4380 2779 if (!dir->i_op->rmdir)
1da177e4
LT		 2780 return -EPERM;
2781
1d2ef590 2782 dget(dentry);
1b1dcc1b 2783 mutex_lock(&dentry->d_inode->i_mutex);
912dbc15
SW		 2784
2785 error = -EBUSY;
1da177e4 2786 if (d_mountpoint(dentry))
912dbc15
SW		 2787 goto out;
2788
2789 error = security_inode_rmdir(dir, dentry);
2790 if (error)
2791 goto out;
2792
3cebde24 2793 shrink_dcache_parent(dentry);
912dbc15
SW		 2794 error = dir->i_op->rmdir(dir, dentry);
2795 if (error)
2796 goto out;
2797
2798 dentry->d_inode->i_flags |= S_DEAD;
2799 dont_mount(dentry);
2800
2801out:
1b1dcc1b 2802 mutex_unlock(&dentry->d_inode->i_mutex);
1d2ef590 2803 dput(dentry);
912dbc15 2804 if (!error)
1da177e4 2805 d_delete(dentry);
1da177e4
LT		 2806 return error;
2807}
2808
5590ff0d 2809static long do_rmdir(int dfd, const char __user *pathname)
1da177e4
LT		 2810{
2811 int error = 0;
2812 char * name;
2813 struct dentry *dentry;
2814 struct nameidata nd;
2815
2ad94ae6 2816 error = user_path_parent(dfd, pathname, &nd, &name);
1da177e4 2817 if (error)
2ad94ae6 2818 return error;
1da177e4
LT		 2819
2820 switch(nd.last_type) {
0612d9fb
OH		 2821 case LAST_DOTDOT:
2822 error = -ENOTEMPTY;
2823 goto exit1;
2824 case LAST_DOT:
2825 error = -EINVAL;
2826 goto exit1;
2827 case LAST_ROOT:
2828 error = -EBUSY;
2829 goto exit1;
1da177e4 2830 }
0612d9fb
OH		 2831
2832 nd.flags &= ~LOOKUP_PARENT;
2833
4ac91378 2834 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
49705b77 2835 dentry = lookup_hash(&nd);
1da177e4 2836 error = PTR_ERR(dentry);
6902d925
DH		 2837 if (IS_ERR(dentry))
2838 goto exit2;
e6bc45d6
TT		 2839 if (!dentry->d_inode) {
2840 error = -ENOENT;
2841 goto exit3;
2842 }
0622753b
DH		 2843 error = mnt_want_write(nd.path.mnt);
2844 if (error)
2845 goto exit3;
be6d3e56
KT		 2846 error = security_path_rmdir(&nd.path, dentry);
2847 if (error)
2848 goto exit4;
4ac91378 2849 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
be6d3e56 2850exit4:
0622753b
DH		 2851 mnt_drop_write(nd.path.mnt);
2852exit3:
6902d925
DH		 2853 dput(dentry);
2854exit2:
4ac91378 2855 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1da177e4 2856exit1:
1d957f9b 2857 path_put(&nd.path);
1da177e4
LT		 2858 putname(name);
2859 return error;
2860}
2861
3cdad428 2862SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
5590ff0d
UD		 2863{
2864 return do_rmdir(AT_FDCWD, pathname);
2865}
2866
1da177e4
LT		 2867int vfs_unlink(struct inode *dir, struct dentry *dentry)
2868{
2869 int error = may_delete(dir, dentry, 0);
2870
2871 if (error)
2872 return error;
2873
acfa4380 2874 if (!dir->i_op->unlink)
1da177e4
LT		 2875 return -EPERM;
2876
1b1dcc1b 2877 mutex_lock(&dentry->d_inode->i_mutex);
1da177e4
LT		 2878 if (d_mountpoint(dentry))
2879 error = -EBUSY;
2880 else {
2881 error = security_inode_unlink(dir, dentry);
bec1052e 2882 if (!error) {
1da177e4 2883 error = dir->i_op->unlink(dir, dentry);
bec1052e 2884 if (!error)
d83c49f3 2885 dont_mount(dentry);
bec1052e 2886 }
1da177e4 2887 }
1b1dcc1b 2888 mutex_unlock(&dentry->d_inode->i_mutex);
1da177e4
LT		 2889
2890 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2891 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
ece95912 2892 fsnotify_link_count(dentry->d_inode);
e234f35c 2893 d_delete(dentry);
1da177e4 2894 }
0eeca283 2895
1da177e4
LT		 2896 return error;
2897}
2898
2899/*
2900 * Make sure that the actual truncation of the file will occur outside its
1b1dcc1b 2901 * directory's i_mutex. Truncate can take a long time if there is a lot of
1da177e4
LT		 2902 * writeout happening, and we don't want to prevent access to the directory
2903 * while waiting on the I/O.
2904 */
5590ff0d 2905static long do_unlinkat(int dfd, const char __user *pathname)
1da177e4 2906{
2ad94ae6
AV		 2907 int error;
2908 char *name;
1da177e4
LT		 2909 struct dentry *dentry;
2910 struct nameidata nd;
2911 struct inode *inode = NULL;
2912
2ad94ae6 2913 error = user_path_parent(dfd, pathname, &nd, &name);
1da177e4 2914 if (error)
2ad94ae6
AV		 2915 return error;
2916
1da177e4
LT		 2917 error = -EISDIR;
2918 if (nd.last_type != LAST_NORM)
2919 goto exit1;
0612d9fb
OH		 2920
2921 nd.flags &= ~LOOKUP_PARENT;
2922
4ac91378 2923 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
49705b77 2924 dentry = lookup_hash(&nd);
1da177e4
LT		 2925 error = PTR_ERR(dentry);
2926 if (!IS_ERR(dentry)) {
2927 /* Why not before? Because we want correct error value */
50338b88
TE		 2928 if (nd.last.name[nd.last.len])
2929 goto slashes;
1da177e4 2930 inode = dentry->d_inode;
50338b88 2931 if (!inode)
e6bc45d6
TT		 2932 goto slashes;
2933 ihold(inode);
0622753b
DH		 2934 error = mnt_want_write(nd.path.mnt);
2935 if (error)
2936 goto exit2;
be6d3e56
KT		 2937 error = security_path_unlink(&nd.path, dentry);
2938 if (error)
2939 goto exit3;
4ac91378 2940 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
be6d3e56 2941exit3:
0622753b 2942 mnt_drop_write(nd.path.mnt);
1da177e4
LT		 2943 exit2:
2944 dput(dentry);
2945 }
4ac91378 2946 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1da177e4
LT		 2947 if (inode)
2948 iput(inode); /* truncate the inode here */
2949exit1:
1d957f9b 2950 path_put(&nd.path);
1da177e4
LT		 2951 putname(name);
2952 return error;
2953
2954slashes:
2955 error = !dentry->d_inode ? -ENOENT :
2956 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2957 goto exit2;
2958}
2959
2e4d0924 2960SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
5590ff0d
UD		 2961{
2962 if ((flag & ~AT_REMOVEDIR) != 0)
2963 return -EINVAL;
2964
2965 if (flag & AT_REMOVEDIR)
2966 return do_rmdir(dfd, pathname);
2967
2968 return do_unlinkat(dfd, pathname);
2969}
2970
3480b257 2971SYSCALL_DEFINE1(unlink, const char __user *, pathname)
5590ff0d
UD		 2972{
2973 return do_unlinkat(AT_FDCWD, pathname);
2974}
2975
db2e747b 2976int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
1da177e4 2977{
a95164d9 2978 int error = may_create(dir, dentry);
1da177e4
LT		 2979
2980 if (error)
2981 return error;
2982
acfa4380 2983 if (!dir->i_op->symlink)
1da177e4
LT		 2984 return -EPERM;
2985
2986 error = security_inode_symlink(dir, dentry, oldname);
2987 if (error)
2988 return error;
2989
1da177e4 2990 error = dir->i_op->symlink(dir, dentry, oldname);
a74574aa 2991 if (!error)
f38aa942 2992 fsnotify_create(dir, dentry);
1da177e4
LT		 2993 return error;
2994}
2995
2e4d0924
HC		 2996SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2997 int, newdfd, const char __user *, newname)
1da177e4 2998{
2ad94ae6
AV		 2999 int error;
3000 char *from;
6902d925 3001 struct dentry *dentry;
dae6ad8f 3002 struct path path;
1da177e4
LT		 3003
3004 from = getname(oldname);
2ad94ae6 3005 if (IS_ERR(from))
1da177e4 3006 return PTR_ERR(from);
1da177e4 3007
dae6ad8f 3008 dentry = user_path_create(newdfd, newname, &path, 0);
6902d925
DH		 3009 error = PTR_ERR(dentry);
3010 if (IS_ERR(dentry))
dae6ad8f 3011 goto out_putname;
6902d925 3012
dae6ad8f 3013 error = mnt_want_write(path.mnt);
75c3f29d
DH		 3014 if (error)
3015 goto out_dput;
dae6ad8f 3016 error = security_path_symlink(&path, dentry, from);
be6d3e56
KT		 3017 if (error)
3018 goto out_drop_write;
dae6ad8f 3019 error = vfs_symlink(path.dentry->d_inode, dentry, from);
be6d3e56 3020out_drop_write:
dae6ad8f 3021 mnt_drop_write(path.mnt);
75c3f29d 3022out_dput:
6902d925 3023 dput(dentry);
dae6ad8f
AV		 3024 mutex_unlock(&path.dentry->d_inode->i_mutex);
3025 path_put(&path);
6902d925 3026out_putname:
1da177e4
LT		 3027 putname(from);
3028 return error;
3029}
3030
3480b257 3031SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
5590ff0d
UD		 3032{
3033 return sys_symlinkat(oldname, AT_FDCWD, newname);
3034}
3035
1da177e4
LT		 3036int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3037{
3038 struct inode *inode = old_dentry->d_inode;
8de52778 3039 unsigned max_links = dir->i_sb->s_max_links;
1da177e4
LT		 3040 int error;
3041
3042 if (!inode)
3043 return -ENOENT;
3044
a95164d9 3045 error = may_create(dir, new_dentry);
1da177e4
LT		 3046 if (error)
3047 return error;
3048
3049 if (dir->i_sb != inode->i_sb)
3050 return -EXDEV;
3051
3052 /*
3053 * A link to an append-only or immutable file cannot be created.
3054 */
3055 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3056 return -EPERM;
acfa4380 3057 if (!dir->i_op->link)
1da177e4 3058 return -EPERM;
7e79eedb 3059 if (S_ISDIR(inode->i_mode))
1da177e4
LT		 3060 return -EPERM;
3061
3062 error = security_inode_link(old_dentry, dir, new_dentry);
3063 if (error)
3064 return error;
3065
7e79eedb 3066 mutex_lock(&inode->i_mutex);
aae8a97d
AK		 3067 /* Make sure we don't allow creating hardlink to an unlinked file */
3068 if (inode->i_nlink == 0)
3069 error = -ENOENT;
8de52778
AV		 3070 else if (max_links && inode->i_nlink >= max_links)
3071 error = -EMLINK;
aae8a97d
AK		 3072 else
3073 error = dir->i_op->link(old_dentry, dir, new_dentry);
7e79eedb 3074 mutex_unlock(&inode->i_mutex);
e31e14ec 3075 if (!error)
7e79eedb 3076 fsnotify_link(dir, inode, new_dentry);
1da177e4
LT		 3077 return error;
3078}
3079
3080/*
3081 * Hardlinks are often used in delicate situations. We avoid
3082 * security-related surprises by not following symlinks on the
3083 * newname. --KAB
3084 *
3085 * We don't follow them on the oldname either to be compatible
3086 * with linux 2.0, and to avoid hard-linking to directories
3087 * and other special files. --ADM
3088 */
2e4d0924
HC		 3089SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3090 int, newdfd, const char __user *, newname, int, flags)
1da177e4
LT		 3091{
3092 struct dentry *new_dentry;
dae6ad8f 3093 struct path old_path, new_path;
11a7b371 3094 int how = 0;
1da177e4 3095 int error;
1da177e4 3096
11a7b371 3097 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
c04030e1 3098 return -EINVAL;
11a7b371
AK		 3099 /*
3100 * To use null names we require CAP_DAC_READ_SEARCH
3101 * This ensures that not everyone will be able to create
3102 * handlink using the passed filedescriptor.
3103 */
3104 if (flags & AT_EMPTY_PATH) {
3105 if (!capable(CAP_DAC_READ_SEARCH))
3106 return -ENOENT;
3107 how = LOOKUP_EMPTY;
3108 }
3109
3110 if (flags & AT_SYMLINK_FOLLOW)
3111 how |= LOOKUP_FOLLOW;
c04030e1 3112
11a7b371 3113 error = user_path_at(olddfd, oldname, how, &old_path);
1da177e4 3114 if (error)
2ad94ae6
AV		 3115 return error;
3116
dae6ad8f 3117 new_dentry = user_path_create(newdfd, newname, &new_path, 0);
1da177e4 3118 error = PTR_ERR(new_dentry);
6902d925 3119 if (IS_ERR(new_dentry))
dae6ad8f
AV		 3120 goto out;
3121
3122 error = -EXDEV;
3123 if (old_path.mnt != new_path.mnt)
3124 goto out_dput;
3125 error = mnt_want_write(new_path.mnt);
75c3f29d
DH		 3126 if (error)
3127 goto out_dput;
dae6ad8f 3128 error = security_path_link(old_path.dentry, &new_path, new_dentry);
be6d3e56
KT		 3129 if (error)
3130 goto out_drop_write;
dae6ad8f 3131 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
be6d3e56 3132out_drop_write:
dae6ad8f 3133 mnt_drop_write(new_path.mnt);
75c3f29d 3134out_dput:
6902d925 3135 dput(new_dentry);
dae6ad8f
AV		 3136 mutex_unlock(&new_path.dentry->d_inode->i_mutex);
3137 path_put(&new_path);
1da177e4 3138out:
2d8f3038 3139 path_put(&old_path);
1da177e4
LT		 3140
3141 return error;
3142}
3143
3480b257 3144SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
5590ff0d 3145{
c04030e1 3146 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
5590ff0d
UD		 3147}
3148
1da177e4
LT		 3149/*
3150 * The worst of all namespace operations - renaming directory. "Perverted"
3151 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3152 * Problems:
3153 * a) we can get into loop creation. Check is done in is_subdir().
3154 * b) race potential - two innocent renames can create a loop together.
3155 * That's where 4.4 screws up. Current fix: serialization on
a11f3a05 3156 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
1da177e4
LT		 3157 * story.
3158 * c) we have to lock _three_ objects - parents and victim (if it exists).
1b1dcc1b 3159 * And that - after we got ->i_mutex on parents (until then we don't know
1da177e4
LT		 3160 * whether the target exists). Solution: try to be smart with locking
3161 * order for inodes. We rely on the fact that tree topology may change
a11f3a05 3162 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
1da177e4
LT		 3163 * move will be locked. Thus we can rank directories by the tree
3164 * (ancestors first) and rank all non-directories after them.
3165 * That works since everybody except rename does "lock parent, lookup,
a11f3a05 3166 * lock child" and rename is under ->s_vfs_rename_mutex.
1da177e4
LT		 3167 * HOWEVER, it relies on the assumption that any object with ->lookup()
3168 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3169 * we'd better make sure that there's no link(2) for them.
e4eaac06 3170 * d) conversion from fhandle to dentry may come in the wrong moment - when
1b1dcc1b 3171 * we are removing the target. Solution: we will have to grab ->i_mutex
1da177e4 3172 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
c41b20e7 3173 * ->i_mutex on parents, which works but leads to some truly excessive
1da177e4
LT		 3174 * locking].
3175 */
75c96f85
AB		 3176static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3177 struct inode *new_dir, struct dentry *new_dentry)
1da177e4
LT		 3178{
3179 int error = 0;
9055cba7 3180 struct inode *target = new_dentry->d_inode;
8de52778 3181 unsigned max_links = new_dir->i_sb->s_max_links;
1da177e4
LT		 3182
3183 /*
3184 * If we are going to change the parent - check write permissions,
3185 * we'll need to flip '..'.
3186 */
3187 if (new_dir != old_dir) {
f419a2e3 3188 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
1da177e4
LT		 3189 if (error)
3190 return error;
3191 }
3192
3193 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3194 if (error)
3195 return error;
3196
1d2ef590 3197 dget(new_dentry);
d83c49f3 3198 if (target)
1b1dcc1b 3199 mutex_lock(&target->i_mutex);
9055cba7
SW		 3200
3201 error = -EBUSY;
3202 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3203 goto out;
3204
8de52778
AV		 3205 error = -EMLINK;
3206 if (max_links && !target && new_dir != old_dir &&
3207 new_dir->i_nlink >= max_links)
3208 goto out;
3209
3cebde24
SW		 3210 if (target)
3211 shrink_dcache_parent(new_dentry);
9055cba7
SW		 3212 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3213 if (error)
3214 goto out;
3215
1da177e4 3216 if (target) {
9055cba7
SW		 3217 target->i_flags |= S_DEAD;
3218 dont_mount(new_dentry);
1da177e4 3219 }
9055cba7
SW		 3220out:
3221 if (target)
3222 mutex_unlock(&target->i_mutex);
1d2ef590 3223 dput(new_dentry);
e31e14ec 3224 if (!error)
349457cc
MF		 3225 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3226 d_move(old_dentry,new_dentry);
1da177e4
LT		 3227 return error;
3228}
3229
75c96f85
AB		 3230static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3231 struct inode *new_dir, struct dentry *new_dentry)
1da177e4 3232{
51892bbb 3233 struct inode *target = new_dentry->d_inode;
1da177e4
LT		 3234 int error;
3235
3236 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3237 if (error)
3238 return error;
3239
3240 dget(new_dentry);
1da177e4 3241 if (target)
1b1dcc1b 3242 mutex_lock(&target->i_mutex);
51892bbb
SW		 3243
3244 error = -EBUSY;
1da177e4 3245 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
51892bbb
SW		 3246 goto out;
3247
3248 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3249 if (error)
3250 goto out;
3251
3252 if (target)
3253 dont_mount(new_dentry);
3254 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3255 d_move(old_dentry, new_dentry);
3256out:
1da177e4 3257 if (target)
1b1dcc1b 3258 mutex_unlock(&target->i_mutex);
1da177e4
LT		 3259 dput(new_dentry);
3260 return error;
3261}
3262
3263int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3264 struct inode *new_dir, struct dentry *new_dentry)
3265{
3266 int error;
3267 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
59b0df21 3268 const unsigned char *old_name;
1da177e4
LT		 3269
3270 if (old_dentry->d_inode == new_dentry->d_inode)
3271 return 0;
3272
3273 error = may_delete(old_dir, old_dentry, is_dir);
3274 if (error)
3275 return error;
3276
3277 if (!new_dentry->d_inode)
a95164d9 3278 error = may_create(new_dir, new_dentry);
1da177e4
LT		 3279 else
3280 error = may_delete(new_dir, new_dentry, is_dir);
3281 if (error)
3282 return error;
3283
acfa4380 3284 if (!old_dir->i_op->rename)
1da177e4
LT		 3285 return -EPERM;
3286
0eeca283
RL		 3287 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3288
1da177e4
LT		 3289 if (is_dir)
3290 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3291 else
3292 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
123df294
AV		 3293 if (!error)
3294 fsnotify_move(old_dir, new_dir, old_name, is_dir,
5a190ae6 3295 new_dentry->d_inode, old_dentry);
0eeca283
RL		 3296 fsnotify_oldname_free(old_name);
3297
1da177e4
LT		 3298 return error;
3299}
3300
2e4d0924
HC		 3301SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3302 int, newdfd, const char __user *, newname)
1da177e4 3303{
2ad94ae6
AV		 3304 struct dentry *old_dir, *new_dir;
3305 struct dentry *old_dentry, *new_dentry;
3306 struct dentry *trap;
1da177e4 3307 struct nameidata oldnd, newnd;
2ad94ae6
AV		 3308 char *from;
3309 char *to;
3310 int error;
1da177e4 3311
2ad94ae6 3312 error = user_path_parent(olddfd, oldname, &oldnd, &from);
1da177e4
LT		 3313 if (error)
3314 goto exit;
3315
2ad94ae6 3316 error = user_path_parent(newdfd, newname, &newnd, &to);
1da177e4
LT		 3317 if (error)
3318 goto exit1;
3319
3320 error = -EXDEV;
4ac91378 3321 if (oldnd.path.mnt != newnd.path.mnt)
1da177e4
LT		 3322 goto exit2;
3323
4ac91378 3324 old_dir = oldnd.path.dentry;
1da177e4
LT		 3325 error = -EBUSY;
3326 if (oldnd.last_type != LAST_NORM)
3327 goto exit2;
3328
4ac91378 3329 new_dir = newnd.path.dentry;
1da177e4
LT		 3330 if (newnd.last_type != LAST_NORM)
3331 goto exit2;
3332
0612d9fb
OH		 3333 oldnd.flags &= ~LOOKUP_PARENT;
3334 newnd.flags &= ~LOOKUP_PARENT;
4e9ed2f8 3335 newnd.flags |= LOOKUP_RENAME_TARGET;
0612d9fb 3336
1da177e4
LT		 3337 trap = lock_rename(new_dir, old_dir);
3338
49705b77 3339 old_dentry = lookup_hash(&oldnd);
1da177e4
LT		 3340 error = PTR_ERR(old_dentry);
3341 if (IS_ERR(old_dentry))
3342 goto exit3;
3343 /* source must exist */
3344 error = -ENOENT;
3345 if (!old_dentry->d_inode)
3346 goto exit4;
3347 /* unless the source is a directory trailing slashes give -ENOTDIR */
3348 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3349 error = -ENOTDIR;
3350 if (oldnd.last.name[oldnd.last.len])
3351 goto exit4;
3352 if (newnd.last.name[newnd.last.len])
3353 goto exit4;
3354 }
3355 /* source should not be ancestor of target */
3356 error = -EINVAL;
3357 if (old_dentry == trap)
3358 goto exit4;
49705b77 3359 new_dentry = lookup_hash(&newnd);
1da177e4
LT		 3360 error = PTR_ERR(new_dentry);
3361 if (IS_ERR(new_dentry))
3362 goto exit4;
3363 /* target should not be an ancestor of source */
3364 error = -ENOTEMPTY;
3365 if (new_dentry == trap)
3366 goto exit5;
3367
9079b1eb
DH		 3368 error = mnt_want_write(oldnd.path.mnt);
3369 if (error)
3370 goto exit5;
be6d3e56
KT		 3371 error = security_path_rename(&oldnd.path, old_dentry,
3372 &newnd.path, new_dentry);
3373 if (error)
3374 goto exit6;
1da177e4
LT		 3375 error = vfs_rename(old_dir->d_inode, old_dentry,
3376 new_dir->d_inode, new_dentry);
be6d3e56 3377exit6:
9079b1eb 3378 mnt_drop_write(oldnd.path.mnt);
1da177e4
LT		 3379exit5:
3380 dput(new_dentry);
3381exit4:
3382 dput(old_dentry);
3383exit3:
3384 unlock_rename(new_dir, old_dir);
3385exit2:
1d957f9b 3386 path_put(&newnd.path);
2ad94ae6 3387 putname(to);
1da177e4 3388exit1:
1d957f9b 3389 path_put(&oldnd.path);
1da177e4 3390 putname(from);
2ad94ae6 3391exit:
1da177e4
LT		 3392 return error;
3393}
3394
a26eab24 3395SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
5590ff0d
UD		 3396{
3397 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3398}
3399
1da177e4
LT		 3400int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3401{
3402 int len;
3403
3404 len = PTR_ERR(link);
3405 if (IS_ERR(link))
3406 goto out;
3407
3408 len = strlen(link);
3409 if (len > (unsigned) buflen)
3410 len = buflen;
3411 if (copy_to_user(buffer, link, len))
3412 len = -EFAULT;
3413out:
3414 return len;
3415}
3416
3417/*
3418 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3419 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3420 * using) it for any given inode is up to filesystem.
3421 */
3422int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3423{
3424 struct nameidata nd;
cc314eef 3425 void *cookie;
694a1764 3426 int res;
cc314eef 3427
1da177e4 3428 nd.depth = 0;
cc314eef 3429 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
694a1764
MS		 3430 if (IS_ERR(cookie))
3431 return PTR_ERR(cookie);
3432
3433 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3434 if (dentry->d_inode->i_op->put_link)
3435 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3436 return res;
1da177e4
LT		 3437}
3438
3439int vfs_follow_link(struct nameidata *nd, const char *link)
3440{
3441 return __vfs_follow_link(nd, link);
3442}
3443
3444/* get the link contents into pagecache */
3445static char *page_getlink(struct dentry * dentry, struct page **ppage)
3446{
ebd09abb
DG		 3447 char *kaddr;
3448 struct page *page;
1da177e4 3449 struct address_space *mapping = dentry->d_inode->i_mapping;
090d2b18 3450 page = read_mapping_page(mapping, 0, NULL);
1da177e4 3451 if (IS_ERR(page))
6fe6900e 3452 return (char*)page;
1da177e4 3453 *ppage = page;
ebd09abb
DG		 3454 kaddr = kmap(page);
3455 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3456 return kaddr;
1da177e4
LT		 3457}
3458
3459int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3460{
3461 struct page *page = NULL;
3462 char *s = page_getlink(dentry, &page);
3463 int res = vfs_readlink(dentry,buffer,buflen,s);
3464 if (page) {
3465 kunmap(page);
3466 page_cache_release(page);
3467 }
3468 return res;
3469}
3470
cc314eef 3471void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
1da177e4 3472{
cc314eef 3473 struct page *page = NULL;
1da177e4 3474 nd_set_link(nd, page_getlink(dentry, &page));
cc314eef 3475 return page;
1da177e4
LT		 3476}
3477
cc314eef 3478void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1da177e4 3479{
cc314eef
LT		 3480 struct page *page = cookie;
3481
3482 if (page) {
1da177e4
LT		 3483 kunmap(page);
3484 page_cache_release(page);
1da177e4
LT		 3485 }
3486}
3487
54566b2c
NP		 3488/*
3489 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3490 */
3491int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
1da177e4
LT		 3492{
3493 struct address_space *mapping = inode->i_mapping;
0adb25d2 3494 struct page *page;
afddba49 3495 void *fsdata;
beb497ab 3496 int err;
1da177e4 3497 char *kaddr;
54566b2c
NP		 3498 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3499 if (nofs)
3500 flags |= AOP_FLAG_NOFS;
1da177e4 3501
7e53cac4 3502retry:
afddba49 3503 err = pagecache_write_begin(NULL, mapping, 0, len-1,
54566b2c 3504 flags, &page, &fsdata);
1da177e4 3505 if (err)
afddba49
NP		 3506 goto fail;
3507
e8e3c3d6 3508 kaddr = kmap_atomic(page);
1da177e4 3509 memcpy(kaddr, symname, len-1);
e8e3c3d6 3510 kunmap_atomic(kaddr);
afddba49
NP		 3511
3512 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3513 page, fsdata);
1da177e4
LT		 3514 if (err < 0)
3515 goto fail;
afddba49
NP		 3516 if (err < len-1)
3517 goto retry;
3518
1da177e4
LT		 3519 mark_inode_dirty(inode);
3520 return 0;
1da177e4
LT		 3521fail:
3522 return err;
3523}
3524
0adb25d2
KK		 3525int page_symlink(struct inode *inode, const char *symname, int len)
3526{
3527 return __page_symlink(inode, symname, len,
54566b2c 3528 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
0adb25d2
KK		 3529}
3530
92e1d5be 3531const struct inode_operations page_symlink_inode_operations = {
1da177e4
LT		 3532 .readlink = generic_readlink,
3533 .follow_link = page_follow_link_light,
3534 .put_link = page_put_link,
3535};
3536
2d8f3038 3537EXPORT_SYMBOL(user_path_at);
cc53ce53 3538EXPORT_SYMBOL(follow_down_one);
1da177e4
LT		 3539EXPORT_SYMBOL(follow_down);
3540EXPORT_SYMBOL(follow_up);
3541EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3542EXPORT_SYMBOL(getname);
3543EXPORT_SYMBOL(lock_rename);
1da177e4
LT		 3544EXPORT_SYMBOL(lookup_one_len);
3545EXPORT_SYMBOL(page_follow_link_light);
3546EXPORT_SYMBOL(page_put_link);
3547EXPORT_SYMBOL(page_readlink);
0adb25d2 3548EXPORT_SYMBOL(__page_symlink);
1da177e4
LT		 3549EXPORT_SYMBOL(page_symlink);
3550EXPORT_SYMBOL(page_symlink_inode_operations);
d1811465 3551EXPORT_SYMBOL(kern_path);
16f18200 3552EXPORT_SYMBOL(vfs_path_lookup);
f419a2e3 3553EXPORT_SYMBOL(inode_permission);
1da177e4
LT		 3554EXPORT_SYMBOL(unlock_rename);
3555EXPORT_SYMBOL(vfs_create);
3556EXPORT_SYMBOL(vfs_follow_link);
3557EXPORT_SYMBOL(vfs_link);
3558EXPORT_SYMBOL(vfs_mkdir);
3559EXPORT_SYMBOL(vfs_mknod);
3560EXPORT_SYMBOL(generic_permission);
3561EXPORT_SYMBOL(vfs_readlink);
3562EXPORT_SYMBOL(vfs_rename);
3563EXPORT_SYMBOL(vfs_rmdir);
3564EXPORT_SYMBOL(vfs_symlink);
3565EXPORT_SYMBOL(vfs_unlink);
3566EXPORT_SYMBOL(dentry_unhash);
3567EXPORT_SYMBOL(generic_readlink);
kernel source for telekom puls (alcatel/mediatek)