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fs: allow AT_EMPTY_PATH in linkat(), limit that to CAP_DAC_READ_SEARCH
[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>
18#include <linux/module.h>
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>
1da177e4
LT		 35#include <asm/uaccess.h>
36
e81e3f4d
EP		 37#include "internal.h"
38
1da177e4
LT		 39/* [Feb-1997 T. Schoebel-Theuer]
40 * Fundamental changes in the pathname lookup mechanisms (namei)
41 * were necessary because of omirr. The reason is that omirr needs
42 * to know the _real_ pathname, not the user-supplied one, in case
43 * of symlinks (and also when transname replacements occur).
44 *
45 * The new code replaces the old recursive symlink resolution with
46 * an iterative one (in case of non-nested symlink chains). It does
47 * this with calls to <fs>_follow_link().
48 * As a side effect, dir_namei(), _namei() and follow_link() are now
49 * replaced with a single function lookup_dentry() that can handle all
50 * the special cases of the former code.
51 *
52 * With the new dcache, the pathname is stored at each inode, at least as
53 * long as the refcount of the inode is positive. As a side effect, the
54 * size of the dcache depends on the inode cache and thus is dynamic.
55 *
56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57 * resolution to correspond with current state of the code.
58 *
59 * Note that the symlink resolution is not *completely* iterative.
60 * There is still a significant amount of tail- and mid- recursion in
61 * the algorithm. Also, note that <fs>_readlink() is not used in
62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63 * may return different results than <fs>_follow_link(). Many virtual
64 * filesystems (including /proc) exhibit this behavior.
65 */
66
67/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
69 * and the name already exists in form of a symlink, try to create the new
70 * name indicated by the symlink. The old code always complained that the
71 * name already exists, due to not following the symlink even if its target
72 * is nonexistent. The new semantics affects also mknod() and link() when
73 * the name is a symlink pointing to a non-existant name.
74 *
75 * I don't know which semantics is the right one, since I have no access
76 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78 * "old" one. Personally, I think the new semantics is much more logical.
79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
80 * file does succeed in both HP-UX and SunOs, but not in Solaris
81 * and in the old Linux semantics.
82 */
83
84/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85 * semantics. See the comments in "open_namei" and "do_link" below.
86 *
87 * [10-Sep-98 Alan Modra] Another symlink change.
88 */
89
90/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91 * inside the path - always follow.
92 * in the last component in creation/removal/renaming - never follow.
93 * if LOOKUP_FOLLOW passed - follow.
94 * if the pathname has trailing slashes - follow.
95 * otherwise - don't follow.
96 * (applied in that order).
97 *
98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100 * During the 2.4 we need to fix the userland stuff depending on it -
101 * hopefully we will be able to get rid of that wart in 2.5. So far only
102 * XEmacs seems to be relying on it...
103 */
104/*
105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
a11f3a05 106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
1da177e4
LT		 107 * any extra contention...
108 */
109
110/* In order to reduce some races, while at the same time doing additional
111 * checking and hopefully speeding things up, we copy filenames to the
112 * kernel data space before using them..
113 *
114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115 * PATH_MAX includes the nul terminator --RR.
116 */
858119e1 117static int do_getname(const char __user *filename, char *page)
1da177e4
LT		 118{
119 int retval;
120 unsigned long len = PATH_MAX;
121
122 if (!segment_eq(get_fs(), KERNEL_DS)) {
123 if ((unsigned long) filename >= TASK_SIZE)
124 return -EFAULT;
125 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
126 len = TASK_SIZE - (unsigned long) filename;
127 }
128
129 retval = strncpy_from_user(page, filename, len);
130 if (retval > 0) {
131 if (retval < len)
132 return 0;
133 return -ENAMETOOLONG;
134 } else if (!retval)
135 retval = -ENOENT;
136 return retval;
137}
138
f52e0c11 139static char *getname_flags(const char __user * filename, int flags)
1da177e4
LT		 140{
141 char *tmp, *result;
142
143 result = ERR_PTR(-ENOMEM);
144 tmp = __getname();
145 if (tmp) {
146 int retval = do_getname(filename, tmp);
147
148 result = tmp;
149 if (retval < 0) {
f52e0c11
AV		 150 if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
151 __putname(tmp);
152 result = ERR_PTR(retval);
153 }
1da177e4
LT		 154 }
155 }
156 audit_getname(result);
157 return result;
158}
159
f52e0c11
AV		 160char *getname(const char __user * filename)
161{
162 return getname_flags(filename, 0);
163}
164
1da177e4
LT		 165#ifdef CONFIG_AUDITSYSCALL
166void putname(const char *name)
167{
5ac3a9c2 168 if (unlikely(!audit_dummy_context()))
1da177e4
LT		 169 audit_putname(name);
170 else
171 __putname(name);
172}
173EXPORT_SYMBOL(putname);
174#endif
175
5909ccaa
LT		 176/*
177 * This does basic POSIX ACL permission checking
1da177e4 178 */
b74c79e9
NP		 179static int acl_permission_check(struct inode *inode, int mask, unsigned int flags,
180 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
1da177e4
LT		 181{
182 umode_t mode = inode->i_mode;
183
e6305c43
AV		 184 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
185
da9592ed 186 if (current_fsuid() == inode->i_uid)
1da177e4
LT		 187 mode >>= 6;
188 else {
189 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
b74c79e9
NP		 190 int error = check_acl(inode, mask, flags);
191 if (error != -EAGAIN)
192 return error;
1da177e4
LT		 193 }
194
195 if (in_group_p(inode->i_gid))
196 mode >>= 3;
197 }
198
199 /*
200 * If the DACs are ok we don't need any capability check.
201 */
e6305c43 202 if ((mask & ~mode) == 0)
1da177e4 203 return 0;
5909ccaa
LT		 204 return -EACCES;
205}
206
207/**
b74c79e9 208 * generic_permission - check for access rights on a Posix-like filesystem
5909ccaa
LT		 209 * @inode: inode to check access rights for
210 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
211 * @check_acl: optional callback to check for Posix ACLs
39191628 212 * @flags: IPERM_FLAG_ flags.
5909ccaa
LT		 213 *
214 * Used to check for read/write/execute permissions on a file.
215 * We use "fsuid" for this, letting us set arbitrary permissions
216 * for filesystem access without changing the "normal" uids which
b74c79e9
NP		 217 * are used for other things.
218 *
219 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
220 * request cannot be satisfied (eg. requires blocking or too much complexity).
221 * It would then be called again in ref-walk mode.
5909ccaa 222 */
b74c79e9
NP		 223int generic_permission(struct inode *inode, int mask, unsigned int flags,
224 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
5909ccaa
LT		 225{
226 int ret;
227
228 /*
229 * Do the basic POSIX ACL permission checks.
230 */
b74c79e9 231 ret = acl_permission_check(inode, mask, flags, check_acl);
5909ccaa
LT		 232 if (ret != -EACCES)
233 return ret;
1da177e4 234
1da177e4
LT		 235 /*
236 * Read/write DACs are always overridable.
237 * Executable DACs are overridable if at least one exec bit is set.
238 */
f696a365 239 if (!(mask & MAY_EXEC) || execute_ok(inode))
1da177e4
LT		 240 if (capable(CAP_DAC_OVERRIDE))
241 return 0;
242
243 /*
244 * Searching includes executable on directories, else just read.
245 */
7ea66001 246 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
1da177e4
LT		 247 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
248 if (capable(CAP_DAC_READ_SEARCH))
249 return 0;
250
251 return -EACCES;
252}
253
cb23beb5
CH		 254/**
255 * inode_permission - check for access rights to a given inode
256 * @inode: inode to check permission on
257 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
258 *
259 * Used to check for read/write/execute permissions on an inode.
260 * We use "fsuid" for this, letting us set arbitrary permissions
261 * for filesystem access without changing the "normal" uids which
262 * are used for other things.
263 */
f419a2e3 264int inode_permission(struct inode *inode, int mask)
1da177e4 265{
e6305c43 266 int retval;
1da177e4
LT		 267
268 if (mask & MAY_WRITE) {
22590e41 269 umode_t mode = inode->i_mode;
1da177e4
LT		 270
271 /*
272 * Nobody gets write access to a read-only fs.
273 */
274 if (IS_RDONLY(inode) &&
275 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
276 return -EROFS;
277
278 /*
279 * Nobody gets write access to an immutable file.
280 */
281 if (IS_IMMUTABLE(inode))
282 return -EACCES;
283 }
284
acfa4380 285 if (inode->i_op->permission)
b74c79e9 286 retval = inode->i_op->permission(inode, mask, 0);
f696a365 287 else
b74c79e9
NP		 288 retval = generic_permission(inode, mask, 0,
289 inode->i_op->check_acl);
f696a365 290
1da177e4
LT		 291 if (retval)
292 return retval;
293
08ce5f16
SH		 294 retval = devcgroup_inode_permission(inode, mask);
295 if (retval)
296 return retval;
297
d09ca739 298 return security_inode_permission(inode, mask);
1da177e4
LT		 299}
300
8c744fb8
CH		 301/**
302 * file_permission - check for additional access rights to a given file
303 * @file: file to check access rights for
304 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
305 *
306 * Used to check for read/write/execute permissions on an already opened
307 * file.
308 *
309 * Note:
310 * Do not use this function in new code. All access checks should
cb23beb5 311 * be done using inode_permission().
8c744fb8
CH		 312 */
313int file_permission(struct file *file, int mask)
314{
f419a2e3 315 return inode_permission(file->f_path.dentry->d_inode, mask);
8c744fb8
CH		 316}
317
1da177e4
LT		 318/*
319 * get_write_access() gets write permission for a file.
320 * put_write_access() releases this write permission.
321 * This is used for regular files.
322 * We cannot support write (and maybe mmap read-write shared) accesses and
323 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
324 * can have the following values:
325 * 0: no writers, no VM_DENYWRITE mappings
326 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
327 * > 0: (i_writecount) users are writing to the file.
328 *
329 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
330 * except for the cases where we don't hold i_writecount yet. Then we need to
331 * use {get,deny}_write_access() - these functions check the sign and refuse
332 * to do the change if sign is wrong. Exclusion between them is provided by
333 * the inode->i_lock spinlock.
334 */
335
336int get_write_access(struct inode * inode)
337{
338 spin_lock(&inode->i_lock);
339 if (atomic_read(&inode->i_writecount) < 0) {
340 spin_unlock(&inode->i_lock);
341 return -ETXTBSY;
342 }
343 atomic_inc(&inode->i_writecount);
344 spin_unlock(&inode->i_lock);
345
346 return 0;
347}
348
349int deny_write_access(struct file * file)
350{
0f7fc9e4 351 struct inode *inode = file->f_path.dentry->d_inode;
1da177e4
LT		 352
353 spin_lock(&inode->i_lock);
354 if (atomic_read(&inode->i_writecount) > 0) {
355 spin_unlock(&inode->i_lock);
356 return -ETXTBSY;
357 }
358 atomic_dec(&inode->i_writecount);
359 spin_unlock(&inode->i_lock);
360
361 return 0;
362}
363
5dd784d0
JB		 364/**
365 * path_get - get a reference to a path
366 * @path: path to get the reference to
367 *
368 * Given a path increment the reference count to the dentry and the vfsmount.
369 */
370void path_get(struct path *path)
371{
372 mntget(path->mnt);
373 dget(path->dentry);
374}
375EXPORT_SYMBOL(path_get);
376
1d957f9b
JB		 377/**
378 * path_put - put a reference to a path
379 * @path: path to put the reference to
380 *
381 * Given a path decrement the reference count to the dentry and the vfsmount.
382 */
383void path_put(struct path *path)
1da177e4 384{
1d957f9b
JB		 385 dput(path->dentry);
386 mntput(path->mnt);
1da177e4 387}
1d957f9b 388EXPORT_SYMBOL(path_put);
1da177e4 389
31e6b01f
NP		 390/**
391 * nameidata_drop_rcu - drop this nameidata out of rcu-walk
392 * @nd: nameidata pathwalk data to drop
39191628 393 * Returns: 0 on success, -ECHILD on failure
31e6b01f
NP		 394 *
395 * Path walking has 2 modes, rcu-walk and ref-walk (see
396 * Documentation/filesystems/path-lookup.txt). __drop_rcu* functions attempt
397 * to drop out of rcu-walk mode and take normal reference counts on dentries
398 * and vfsmounts to transition to rcu-walk mode. __drop_rcu* functions take
399 * refcounts at the last known good point before rcu-walk got stuck, so
400 * ref-walk may continue from there. If this is not successful (eg. a seqcount
401 * has changed), then failure is returned and path walk restarts from the
402 * beginning in ref-walk mode.
403 *
404 * nameidata_drop_rcu attempts to drop the current nd->path and nd->root into
405 * ref-walk. Must be called from rcu-walk context.
406 */
407static int nameidata_drop_rcu(struct nameidata *nd)
408{
409 struct fs_struct *fs = current->fs;
410 struct dentry *dentry = nd->path.dentry;
5b6ca027 411 int want_root = 0;
31e6b01f
NP		 412
413 BUG_ON(!(nd->flags & LOOKUP_RCU));
5b6ca027
AV		 414 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
415 want_root = 1;
31e6b01f
NP		 416 spin_lock(&fs->lock);
417 if (nd->root.mnt != fs->root.mnt ||
418 nd->root.dentry != fs->root.dentry)
419 goto err_root;
420 }
421 spin_lock(&dentry->d_lock);
422 if (!__d_rcu_to_refcount(dentry, nd->seq))
423 goto err;
424 BUG_ON(nd->inode != dentry->d_inode);
425 spin_unlock(&dentry->d_lock);
5b6ca027 426 if (want_root) {
31e6b01f
NP		 427 path_get(&nd->root);
428 spin_unlock(&fs->lock);
429 }
430 mntget(nd->path.mnt);
431
432 rcu_read_unlock();
433 br_read_unlock(vfsmount_lock);
434 nd->flags &= ~LOOKUP_RCU;
435 return 0;
436err:
437 spin_unlock(&dentry->d_lock);
438err_root:
5b6ca027 439 if (want_root)
31e6b01f
NP		 440 spin_unlock(&fs->lock);
441 return -ECHILD;
442}
443
444/* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
445static inline int nameidata_drop_rcu_maybe(struct nameidata *nd)
446{
447 if (nd->flags & LOOKUP_RCU)
448 return nameidata_drop_rcu(nd);
449 return 0;
450}
451
452/**
453 * nameidata_dentry_drop_rcu - drop nameidata and dentry out of rcu-walk
454 * @nd: nameidata pathwalk data to drop
455 * @dentry: dentry to drop
39191628 456 * Returns: 0 on success, -ECHILD on failure
31e6b01f
NP		 457 *
458 * nameidata_dentry_drop_rcu attempts to drop the current nd->path and nd->root,
459 * and dentry into ref-walk. @dentry must be a path found by a do_lookup call on
460 * @nd. Must be called from rcu-walk context.
461 */
462static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry)
463{
464 struct fs_struct *fs = current->fs;
465 struct dentry *parent = nd->path.dentry;
5b6ca027 466 int want_root = 0;
31e6b01f
NP		 467
468 BUG_ON(!(nd->flags & LOOKUP_RCU));
5b6ca027
AV		 469 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
470 want_root = 1;
31e6b01f
NP		 471 spin_lock(&fs->lock);
472 if (nd->root.mnt != fs->root.mnt ||
473 nd->root.dentry != fs->root.dentry)
474 goto err_root;
475 }
476 spin_lock(&parent->d_lock);
477 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
478 if (!__d_rcu_to_refcount(dentry, nd->seq))
479 goto err;
480 /*
481 * If the sequence check on the child dentry passed, then the child has
482 * not been removed from its parent. This means the parent dentry must
483 * be valid and able to take a reference at this point.
484 */
485 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
486 BUG_ON(!parent->d_count);
487 parent->d_count++;
488 spin_unlock(&dentry->d_lock);
489 spin_unlock(&parent->d_lock);
5b6ca027 490 if (want_root) {
31e6b01f
NP		 491 path_get(&nd->root);
492 spin_unlock(&fs->lock);
493 }
494 mntget(nd->path.mnt);
495
496 rcu_read_unlock();
497 br_read_unlock(vfsmount_lock);
498 nd->flags &= ~LOOKUP_RCU;
499 return 0;
500err:
501 spin_unlock(&dentry->d_lock);
502 spin_unlock(&parent->d_lock);
503err_root:
5b6ca027 504 if (want_root)
31e6b01f
NP		 505 spin_unlock(&fs->lock);
506 return -ECHILD;
507}
508
509/* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
510static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata *nd, struct dentry *dentry)
511{
a7472bab
AV		 512 if (nd->flags & LOOKUP_RCU) {
513 if (unlikely(nameidata_dentry_drop_rcu(nd, dentry))) {
514 nd->flags &= ~LOOKUP_RCU;
5b6ca027
AV		 515 if (!(nd->flags & LOOKUP_ROOT))
516 nd->root.mnt = NULL;
a7472bab
AV		 517 rcu_read_unlock();
518 br_read_unlock(vfsmount_lock);
519 return -ECHILD;
520 }
521 }
31e6b01f
NP		 522 return 0;
523}
524
525/**
526 * nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
527 * @nd: nameidata pathwalk data to drop
39191628 528 * Returns: 0 on success, -ECHILD on failure
31e6b01f
NP		 529 *
530 * nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
531 * nd->path should be the final element of the lookup, so nd->root is discarded.
532 * Must be called from rcu-walk context.
533 */
534static int nameidata_drop_rcu_last(struct nameidata *nd)
535{
536 struct dentry *dentry = nd->path.dentry;
537
538 BUG_ON(!(nd->flags & LOOKUP_RCU));
539 nd->flags &= ~LOOKUP_RCU;
5b6ca027
AV		 540 if (!(nd->flags & LOOKUP_ROOT))
541 nd->root.mnt = NULL;
31e6b01f
NP		 542 spin_lock(&dentry->d_lock);
543 if (!__d_rcu_to_refcount(dentry, nd->seq))
544 goto err_unlock;
545 BUG_ON(nd->inode != dentry->d_inode);
546 spin_unlock(&dentry->d_lock);
547
548 mntget(nd->path.mnt);
549
550 rcu_read_unlock();
551 br_read_unlock(vfsmount_lock);
552
553 return 0;
554
555err_unlock:
556 spin_unlock(&dentry->d_lock);
557 rcu_read_unlock();
558 br_read_unlock(vfsmount_lock);
559 return -ECHILD;
560}
561
834f2a4a
TM		 562/**
563 * release_open_intent - free up open intent resources
564 * @nd: pointer to nameidata
565 */
566void release_open_intent(struct nameidata *nd)
567{
2dab5974
LT		 568 struct file *file = nd->intent.open.file;
569
570 if (file && !IS_ERR(file)) {
571 if (file->f_path.dentry == NULL)
572 put_filp(file);
573 else
574 fput(file);
575 }
834f2a4a
TM		 576}
577
f60aef7e 578static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
34286d66 579{
f60aef7e 580 return dentry->d_op->d_revalidate(dentry, nd);
34286d66
NP		 581}
582
f5e1c1c1 583static struct dentry *
bcdc5e01
IK		 584do_revalidate(struct dentry *dentry, struct nameidata *nd)
585{
f5e1c1c1 586 int status = d_revalidate(dentry, nd);
bcdc5e01
IK		 587 if (unlikely(status <= 0)) {
588 /*
589 * The dentry failed validation.
590 * If d_revalidate returned 0 attempt to invalidate
591 * the dentry otherwise d_revalidate is asking us
592 * to return a fail status.
593 */
34286d66 594 if (status < 0) {
f5e1c1c1 595 dput(dentry);
34286d66 596 dentry = ERR_PTR(status);
f5e1c1c1
AV		 597 } else if (!d_invalidate(dentry)) {
598 dput(dentry);
599 dentry = NULL;
bcdc5e01
IK		 600 }
601 }
602 return dentry;
603}
604
39159de2 605/*
16c2cd71 606 * handle_reval_path - force revalidation of a dentry
39159de2
JL		 607 *
608 * In some situations the path walking code will trust dentries without
609 * revalidating them. This causes problems for filesystems that depend on
610 * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
611 * (which indicates that it's possible for the dentry to go stale), force
612 * a d_revalidate call before proceeding.
613 *
614 * Returns 0 if the revalidation was successful. If the revalidation fails,
615 * either return the error returned by d_revalidate or -ESTALE if the
616 * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
617 * invalidate the dentry. It's up to the caller to handle putting references
618 * to the path if necessary.
619 */
16c2cd71 620static inline int handle_reval_path(struct nameidata *nd)
39159de2 621{
16c2cd71 622 struct dentry *dentry = nd->path.dentry;
39159de2 623 int status;
39159de2 624
16c2cd71
AV		 625 if (likely(!(nd->flags & LOOKUP_JUMPED)))
626 return 0;
627
628 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
39159de2
JL		 629 return 0;
630
16c2cd71
AV		 631 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
632 return 0;
633
634 /* Note: we do not d_invalidate() */
34286d66 635 status = d_revalidate(dentry, nd);
39159de2
JL		 636 if (status > 0)
637 return 0;
638
16c2cd71 639 if (!status)
39159de2 640 status = -ESTALE;
16c2cd71 641
39159de2
JL		 642 return status;
643}
644
1da177e4 645/*
b75b5086
AV		 646 * Short-cut version of permission(), for calling on directories
647 * during pathname resolution. Combines parts of permission()
648 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
1da177e4
LT		 649 *
650 * If appropriate, check DAC only. If not appropriate, or
b75b5086 651 * short-cut DAC fails, then call ->permission() to do more
1da177e4
LT		 652 * complete permission check.
653 */
b74c79e9 654static inline int exec_permission(struct inode *inode, unsigned int flags)
1da177e4 655{
5909ccaa 656 int ret;
1da177e4 657
cb9179ea 658 if (inode->i_op->permission) {
b74c79e9
NP		 659 ret = inode->i_op->permission(inode, MAY_EXEC, flags);
660 } else {
661 ret = acl_permission_check(inode, MAY_EXEC, flags,
662 inode->i_op->check_acl);
cb9179ea 663 }
b74c79e9 664 if (likely(!ret))
1da177e4 665 goto ok;
b74c79e9 666 if (ret == -ECHILD)
31e6b01f 667 return ret;
1da177e4 668
f1ac9f6b 669 if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
1da177e4
LT		 670 goto ok;
671
5909ccaa 672 return ret;
1da177e4 673ok:
b74c79e9 674 return security_inode_exec_permission(inode, flags);
1da177e4
LT		 675}
676
2a737871
AV		 677static __always_inline void set_root(struct nameidata *nd)
678{
f7ad3c6b
MS		 679 if (!nd->root.mnt)
680 get_fs_root(current->fs, &nd->root);
2a737871
AV		 681}
682
6de88d72
AV		 683static int link_path_walk(const char *, struct nameidata *);
684
31e6b01f
NP		 685static __always_inline void set_root_rcu(struct nameidata *nd)
686{
687 if (!nd->root.mnt) {
688 struct fs_struct *fs = current->fs;
c28cc364
NP		 689 unsigned seq;
690
691 do {
692 seq = read_seqcount_begin(&fs->seq);
693 nd->root = fs->root;
694 } while (read_seqcount_retry(&fs->seq, seq));
31e6b01f
NP		 695 }
696}
697
f1662356 698static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
1da177e4 699{
31e6b01f
NP		 700 int ret;
701
1da177e4
LT		 702 if (IS_ERR(link))
703 goto fail;
704
705 if (*link == '/') {
2a737871 706 set_root(nd);
1d957f9b 707 path_put(&nd->path);
2a737871
AV		 708 nd->path = nd->root;
709 path_get(&nd->root);
16c2cd71 710 nd->flags |= LOOKUP_JUMPED;
1da177e4 711 }
31e6b01f 712 nd->inode = nd->path.dentry->d_inode;
b4091d5f 713
31e6b01f
NP		 714 ret = link_path_walk(link, nd);
715 return ret;
1da177e4 716fail:
1d957f9b 717 path_put(&nd->path);
1da177e4
LT		 718 return PTR_ERR(link);
719}
720
1d957f9b 721static void path_put_conditional(struct path *path, struct nameidata *nd)
051d3812
IK		 722{
723 dput(path->dentry);
4ac91378 724 if (path->mnt != nd->path.mnt)
051d3812
IK		 725 mntput(path->mnt);
726}
727
7b9337aa
NP		 728static inline void path_to_nameidata(const struct path *path,
729 struct nameidata *nd)
051d3812 730{
31e6b01f
NP		 731 if (!(nd->flags & LOOKUP_RCU)) {
732 dput(nd->path.dentry);
733 if (nd->path.mnt != path->mnt)
734 mntput(nd->path.mnt);
9a229683 735 }
31e6b01f 736 nd->path.mnt = path->mnt;
4ac91378 737 nd->path.dentry = path->dentry;
051d3812
IK		 738}
739
def4af30 740static __always_inline int
7b9337aa 741__do_follow_link(const struct path *link, struct nameidata *nd, void **p)
1da177e4
LT		 742{
743 int error;
7b9337aa 744 struct dentry *dentry = link->dentry;
1da177e4 745
844a3917
AV		 746 BUG_ON(nd->flags & LOOKUP_RCU);
747
7b9337aa 748 touch_atime(link->mnt, dentry);
1da177e4 749 nd_set_link(nd, NULL);
cd4e91d3 750
87556ef1
DH		 751 if (link->mnt == nd->path.mnt)
752 mntget(link->mnt);
31e6b01f 753
36f3b4f6
AV		 754 error = security_inode_follow_link(link->dentry, nd);
755 if (error) {
756 *p = ERR_PTR(error); /* no ->put_link(), please */
757 path_put(&nd->path);
758 return error;
759 }
760
86acdca1 761 nd->last_type = LAST_BIND;
def4af30
AV		 762 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
763 error = PTR_ERR(*p);
764 if (!IS_ERR(*p)) {
1da177e4 765 char *s = nd_get_link(nd);
cc314eef 766 error = 0;
1da177e4
LT		 767 if (s)
768 error = __vfs_follow_link(nd, s);
bcda7652 769 else if (nd->last_type == LAST_BIND) {
16c2cd71 770 nd->flags |= LOOKUP_JUMPED;
bcda7652
AV		 771 if (nd->path.dentry->d_inode->i_op->follow_link) {
772 /* stepped on a _really_ weird one */
773 path_put(&nd->path);
774 error = -ELOOP;
775 }
776 }
1da177e4 777 }
1da177e4
LT		 778 return error;
779}
780
781/*
782 * This limits recursive symlink follows to 8, while
783 * limiting consecutive symlinks to 40.
784 *
785 * Without that kind of total limit, nasty chains of consecutive
786 * symlinks can cause almost arbitrarily long lookups.
787 */
3abb17e8 788static inline int do_follow_link(struct inode *inode, struct path *path, struct nameidata *nd)
1da177e4 789{
def4af30 790 void *cookie;
1da177e4 791 int err = -ELOOP;
844a3917
AV		 792
793 /* We drop rcu-walk here */
794 if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
795 return -ECHILD;
3abb17e8 796 BUG_ON(inode != path->dentry->d_inode);
844a3917 797
1da177e4
LT		 798 if (current->link_count >= MAX_NESTED_LINKS)
799 goto loop;
800 if (current->total_link_count >= 40)
801 goto loop;
802 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
803 cond_resched();
1da177e4
LT		 804 current->link_count++;
805 current->total_link_count++;
806 nd->depth++;
def4af30
AV		 807 err = __do_follow_link(path, nd, &cookie);
808 if (!IS_ERR(cookie) && path->dentry->d_inode->i_op->put_link)
809 path->dentry->d_inode->i_op->put_link(path->dentry, nd, cookie);
258fa999 810 path_put(path);
839d9f93
AV		 811 current->link_count--;
812 nd->depth--;
1da177e4
LT		 813 return err;
814loop:
1d957f9b
JB		 815 path_put_conditional(path, nd);
816 path_put(&nd->path);
1da177e4
LT		 817 return err;
818}
819
31e6b01f
NP		 820static int follow_up_rcu(struct path *path)
821{
822 struct vfsmount *parent;
823 struct dentry *mountpoint;
824
825 parent = path->mnt->mnt_parent;
826 if (parent == path->mnt)
827 return 0;
828 mountpoint = path->mnt->mnt_mountpoint;
829 path->dentry = mountpoint;
830 path->mnt = parent;
831 return 1;
832}
833
bab77ebf 834int follow_up(struct path *path)
1da177e4
LT		 835{
836 struct vfsmount *parent;
837 struct dentry *mountpoint;
99b7db7b
NP		 838
839 br_read_lock(vfsmount_lock);
bab77ebf
AV		 840 parent = path->mnt->mnt_parent;
841 if (parent == path->mnt) {
99b7db7b 842 br_read_unlock(vfsmount_lock);
1da177e4
LT		 843 return 0;
844 }
845 mntget(parent);
bab77ebf 846 mountpoint = dget(path->mnt->mnt_mountpoint);
99b7db7b 847 br_read_unlock(vfsmount_lock);
bab77ebf
AV		 848 dput(path->dentry);
849 path->dentry = mountpoint;
850 mntput(path->mnt);
851 path->mnt = parent;
1da177e4
LT		 852 return 1;
853}
854
b5c84bf6 855/*
9875cf80
DH		 856 * Perform an automount
857 * - return -EISDIR to tell follow_managed() to stop and return the path we
858 * were called with.
1da177e4 859 */
9875cf80
DH		 860static int follow_automount(struct path *path, unsigned flags,
861 bool *need_mntput)
31e6b01f 862{
9875cf80 863 struct vfsmount *mnt;
ea5b778a 864 int err;
9875cf80
DH		 865
866 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
867 return -EREMOTE;
868
6f45b656
DH		 869 /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
870 * and this is the terminal part of the path.
871 */
872 if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
873 return -EISDIR; /* we actually want to stop here */
874
9875cf80
DH		 875 /* We want to mount if someone is trying to open/create a file of any
876 * type under the mountpoint, wants to traverse through the mountpoint
877 * or wants to open the mounted directory.
878 *
879 * We don't want to mount if someone's just doing a stat and they've
880 * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
881 * appended a '/' to the name.
882 */
883 if (!(flags & LOOKUP_FOLLOW) &&
884 !(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
885 LOOKUP_OPEN | LOOKUP_CREATE)))
886 return -EISDIR;
887
888 current->total_link_count++;
889 if (current->total_link_count >= 40)
890 return -ELOOP;
891
892 mnt = path->dentry->d_op->d_automount(path);
893 if (IS_ERR(mnt)) {
894 /*
895 * The filesystem is allowed to return -EISDIR here to indicate
896 * it doesn't want to automount. For instance, autofs would do
897 * this so that its userspace daemon can mount on this dentry.
898 *
899 * However, we can only permit this if it's a terminal point in
900 * the path being looked up; if it wasn't then the remainder of
901 * the path is inaccessible and we should say so.
902 */
903 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_CONTINUE))
904 return -EREMOTE;
905 return PTR_ERR(mnt);
31e6b01f 906 }
ea5b778a 907
9875cf80
DH		 908 if (!mnt) /* mount collision */
909 return 0;
31e6b01f 910
19a167af 911 err = finish_automount(mnt, path);
9875cf80 912
ea5b778a
DH		 913 switch (err) {
914 case -EBUSY:
915 /* Someone else made a mount here whilst we were busy */
19a167af 916 return 0;
ea5b778a 917 case 0:
ea5b778a
DH		 918 dput(path->dentry);
919 if (*need_mntput)
920 mntput(path->mnt);
921 path->mnt = mnt;
922 path->dentry = dget(mnt->mnt_root);
923 *need_mntput = true;
924 return 0;
19a167af
AV		 925 default:
926 return err;
ea5b778a 927 }
19a167af 928
463ffb2e
AV		 929}
930
9875cf80
DH		 931/*
932 * Handle a dentry that is managed in some way.
cc53ce53 933 * - Flagged for transit management (autofs)
9875cf80
DH		 934 * - Flagged as mountpoint
935 * - Flagged as automount point
936 *
937 * This may only be called in refwalk mode.
938 *
939 * Serialization is taken care of in namespace.c
940 */
941static int follow_managed(struct path *path, unsigned flags)
1da177e4 942{
9875cf80
DH		 943 unsigned managed;
944 bool need_mntput = false;
945 int ret;
946
947 /* Given that we're not holding a lock here, we retain the value in a
948 * local variable for each dentry as we look at it so that we don't see
949 * the components of that value change under us */
950 while (managed = ACCESS_ONCE(path->dentry->d_flags),
951 managed &= DCACHE_MANAGED_DENTRY,
952 unlikely(managed != 0)) {
cc53ce53
DH		 953 /* Allow the filesystem to manage the transit without i_mutex
954 * being held. */
955 if (managed & DCACHE_MANAGE_TRANSIT) {
956 BUG_ON(!path->dentry->d_op);
957 BUG_ON(!path->dentry->d_op->d_manage);
ab90911f
DH		 958 ret = path->dentry->d_op->d_manage(path->dentry,
959 false, false);
cc53ce53
DH		 960 if (ret < 0)
961 return ret == -EISDIR ? 0 : ret;
962 }
963
9875cf80
DH		 964 /* Transit to a mounted filesystem. */
965 if (managed & DCACHE_MOUNTED) {
966 struct vfsmount *mounted = lookup_mnt(path);
967 if (mounted) {
968 dput(path->dentry);
969 if (need_mntput)
970 mntput(path->mnt);
971 path->mnt = mounted;
972 path->dentry = dget(mounted->mnt_root);
973 need_mntput = true;
974 continue;
975 }
976
977 /* Something is mounted on this dentry in another
978 * namespace and/or whatever was mounted there in this
979 * namespace got unmounted before we managed to get the
980 * vfsmount_lock */
981 }
982
983 /* Handle an automount point */
984 if (managed & DCACHE_NEED_AUTOMOUNT) {
985 ret = follow_automount(path, flags, &need_mntput);
986 if (ret < 0)
987 return ret == -EISDIR ? 0 : ret;
988 continue;
989 }
990
991 /* We didn't change the current path point */
992 break;
1da177e4 993 }
9875cf80 994 return 0;
1da177e4
LT		 995}
996
cc53ce53 997int follow_down_one(struct path *path)
1da177e4
LT		 998{
999 struct vfsmount *mounted;
1000
1c755af4 1001 mounted = lookup_mnt(path);
1da177e4 1002 if (mounted) {
9393bd07
AV		 1003 dput(path->dentry);
1004 mntput(path->mnt);
1005 path->mnt = mounted;
1006 path->dentry = dget(mounted->mnt_root);
1da177e4
LT		 1007 return 1;
1008 }
1009 return 0;
1010}
1011
9875cf80
DH		 1012/*
1013 * Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
cc53ce53 1014 * meet a managed dentry and we're not walking to "..". True is returned to
9875cf80
DH		 1015 * continue, false to abort.
1016 */
1017static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1018 struct inode **inode, bool reverse_transit)
1019{
1020 while (d_mountpoint(path->dentry)) {
1021 struct vfsmount *mounted;
ab90911f
DH		 1022 if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
1023 !reverse_transit &&
1024 path->dentry->d_op->d_manage(path->dentry, false, true) < 0)
1025 return false;
9875cf80
DH		 1026 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1027 if (!mounted)
1028 break;
1029 path->mnt = mounted;
1030 path->dentry = mounted->mnt_root;
1031 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1032 *inode = path->dentry->d_inode;
1033 }
1034
1035 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1036 return reverse_transit;
1037 return true;
1038}
1039
31e6b01f
NP		 1040static int follow_dotdot_rcu(struct nameidata *nd)
1041{
1042 struct inode *inode = nd->inode;
1043
1044 set_root_rcu(nd);
1045
9875cf80 1046 while (1) {
31e6b01f
NP		 1047 if (nd->path.dentry == nd->root.dentry &&
1048 nd->path.mnt == nd->root.mnt) {
1049 break;
1050 }
1051 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1052 struct dentry *old = nd->path.dentry;
1053 struct dentry *parent = old->d_parent;
1054 unsigned seq;
1055
1056 seq = read_seqcount_begin(&parent->d_seq);
1057 if (read_seqcount_retry(&old->d_seq, nd->seq))
ef7562d5 1058 goto failed;
31e6b01f
NP		 1059 inode = parent->d_inode;
1060 nd->path.dentry = parent;
1061 nd->seq = seq;
1062 break;
1063 }
1064 if (!follow_up_rcu(&nd->path))
1065 break;
1066 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1067 inode = nd->path.dentry->d_inode;
1068 }
9875cf80 1069 __follow_mount_rcu(nd, &nd->path, &inode, true);
31e6b01f 1070 nd->inode = inode;
31e6b01f 1071 return 0;
ef7562d5
AV		 1072
1073failed:
1074 nd->flags &= ~LOOKUP_RCU;
5b6ca027
AV		 1075 if (!(nd->flags & LOOKUP_ROOT))
1076 nd->root.mnt = NULL;
ef7562d5
AV		 1077 rcu_read_unlock();
1078 br_read_unlock(vfsmount_lock);
1079 return -ECHILD;
31e6b01f
NP		 1080}
1081
cc53ce53
DH		 1082/*
1083 * Follow down to the covering mount currently visible to userspace. At each
1084 * point, the filesystem owning that dentry may be queried as to whether the
1085 * caller is permitted to proceed or not.
1086 *
1087 * Care must be taken as namespace_sem may be held (indicated by mounting_here
1088 * being true).
1089 */
1090int follow_down(struct path *path, bool mounting_here)
1091{
1092 unsigned managed;
1093 int ret;
1094
1095 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1096 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1097 /* Allow the filesystem to manage the transit without i_mutex
1098 * being held.
1099 *
1100 * We indicate to the filesystem if someone is trying to mount
1101 * something here. This gives autofs the chance to deny anyone
1102 * other than its daemon the right to mount on its
1103 * superstructure.
1104 *
1105 * The filesystem may sleep at this point.
1106 */
1107 if (managed & DCACHE_MANAGE_TRANSIT) {
1108 BUG_ON(!path->dentry->d_op);
1109 BUG_ON(!path->dentry->d_op->d_manage);
ab90911f
DH		 1110 ret = path->dentry->d_op->d_manage(
1111 path->dentry, mounting_here, false);
cc53ce53
DH		 1112 if (ret < 0)
1113 return ret == -EISDIR ? 0 : ret;
1114 }
1115
1116 /* Transit to a mounted filesystem. */
1117 if (managed & DCACHE_MOUNTED) {
1118 struct vfsmount *mounted = lookup_mnt(path);
1119 if (!mounted)
1120 break;
1121 dput(path->dentry);
1122 mntput(path->mnt);
1123 path->mnt = mounted;
1124 path->dentry = dget(mounted->mnt_root);
1125 continue;
1126 }
1127
1128 /* Don't handle automount points here */
1129 break;
1130 }
1131 return 0;
1132}
1133
9875cf80
DH		 1134/*
1135 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1136 */
1137static void follow_mount(struct path *path)
1138{
1139 while (d_mountpoint(path->dentry)) {
1140 struct vfsmount *mounted = lookup_mnt(path);
1141 if (!mounted)
1142 break;
1143 dput(path->dentry);
1144 mntput(path->mnt);
1145 path->mnt = mounted;
1146 path->dentry = dget(mounted->mnt_root);
1147 }
1148}
1149
31e6b01f 1150static void follow_dotdot(struct nameidata *nd)
1da177e4 1151{
2a737871 1152 set_root(nd);
e518ddb7 1153
1da177e4 1154 while(1) {
4ac91378 1155 struct dentry *old = nd->path.dentry;
1da177e4 1156
2a737871
AV		 1157 if (nd->path.dentry == nd->root.dentry &&
1158 nd->path.mnt == nd->root.mnt) {
1da177e4
LT		 1159 break;
1160 }
4ac91378 1161 if (nd->path.dentry != nd->path.mnt->mnt_root) {
3088dd70
AV		 1162 /* rare case of legitimate dget_parent()... */
1163 nd->path.dentry = dget_parent(nd->path.dentry);
1da177e4
LT		 1164 dput(old);
1165 break;
1166 }
3088dd70 1167 if (!follow_up(&nd->path))
1da177e4 1168 break;
1da177e4 1169 }
79ed0226 1170 follow_mount(&nd->path);
31e6b01f 1171 nd->inode = nd->path.dentry->d_inode;
1da177e4
LT		 1172}
1173
baa03890
NP		 1174/*
1175 * Allocate a dentry with name and parent, and perform a parent
1176 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1177 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1178 * have verified that no child exists while under i_mutex.
1179 */
1180static struct dentry *d_alloc_and_lookup(struct dentry *parent,
1181 struct qstr *name, struct nameidata *nd)
1182{
1183 struct inode *inode = parent->d_inode;
1184 struct dentry *dentry;
1185 struct dentry *old;
1186
1187 /* Don't create child dentry for a dead directory. */
1188 if (unlikely(IS_DEADDIR(inode)))
1189 return ERR_PTR(-ENOENT);
1190
1191 dentry = d_alloc(parent, name);
1192 if (unlikely(!dentry))
1193 return ERR_PTR(-ENOMEM);
1194
1195 old = inode->i_op->lookup(inode, dentry, nd);
1196 if (unlikely(old)) {
1197 dput(dentry);
1198 dentry = old;
1199 }
1200 return dentry;
1201}
1202
1da177e4
LT		 1203/*
1204 * It's more convoluted than I'd like it to be, but... it's still fairly
1205 * small and for now I'd prefer to have fast path as straight as possible.
1206 * It _is_ time-critical.
1207 */
1208static int do_lookup(struct nameidata *nd, struct qstr *name,
31e6b01f 1209 struct path *path, struct inode **inode)
1da177e4 1210{
4ac91378 1211 struct vfsmount *mnt = nd->path.mnt;
31e6b01f 1212 struct dentry *dentry, *parent = nd->path.dentry;
5a18fff2
AV		 1213 int need_reval = 1;
1214 int status = 1;
9875cf80
DH		 1215 int err;
1216
b04f784e
NP		 1217 /*
1218 * Rename seqlock is not required here because in the off chance
1219 * of a false negative due to a concurrent rename, we're going to
1220 * do the non-racy lookup, below.
1221 */
31e6b01f
NP		 1222 if (nd->flags & LOOKUP_RCU) {
1223 unsigned seq;
31e6b01f
NP		 1224 *inode = nd->inode;
1225 dentry = __d_lookup_rcu(parent, name, &seq, inode);
5a18fff2
AV		 1226 if (!dentry)
1227 goto unlazy;
1228
31e6b01f
NP		 1229 /* Memory barrier in read_seqcount_begin of child is enough */
1230 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1231 return -ECHILD;
31e6b01f 1232 nd->seq = seq;
5a18fff2 1233
24643087 1234 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
5a18fff2
AV		 1235 status = d_revalidate(dentry, nd);
1236 if (unlikely(status <= 0)) {
1237 if (status != -ECHILD)
1238 need_reval = 0;
1239 goto unlazy;
1240 }
24643087 1241 }
31e6b01f
NP		 1242 path->mnt = mnt;
1243 path->dentry = dentry;
9875cf80
DH		 1244 if (likely(__follow_mount_rcu(nd, path, inode, false)))
1245 return 0;
5a18fff2
AV		 1246unlazy:
1247 if (dentry) {
1248 if (nameidata_dentry_drop_rcu(nd, dentry))
1249 return -ECHILD;
1250 } else {
1251 if (nameidata_drop_rcu(nd))
1252 return -ECHILD;
1253 }
1254 } else {
1255 dentry = __d_lookup(parent, name);
9875cf80 1256 }
5a18fff2
AV		 1257
1258retry:
1259 if (unlikely(!dentry)) {
1260 struct inode *dir = parent->d_inode;
1261 BUG_ON(nd->inode != dir);
1262
1263 mutex_lock(&dir->i_mutex);
1264 dentry = d_lookup(parent, name);
1265 if (likely(!dentry)) {
1266 dentry = d_alloc_and_lookup(parent, name, nd);
1267 if (IS_ERR(dentry)) {
1268 mutex_unlock(&dir->i_mutex);
1269 return PTR_ERR(dentry);
1270 }
1271 /* known good */
1272 need_reval = 0;
1273 status = 1;
1274 }
1275 mutex_unlock(&dir->i_mutex);
1276 }
1277 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1278 status = d_revalidate(dentry, nd);
1279 if (unlikely(status <= 0)) {
1280 if (status < 0) {
1281 dput(dentry);
1282 return status;
1283 }
1284 if (!d_invalidate(dentry)) {
1285 dput(dentry);
1286 dentry = NULL;
1287 need_reval = 1;
1288 goto retry;
1289 }
24643087 1290 }
5a18fff2 1291
9875cf80
DH		 1292 path->mnt = mnt;
1293 path->dentry = dentry;
1294 err = follow_managed(path, nd->flags);
89312214
IK		 1295 if (unlikely(err < 0)) {
1296 path_put_conditional(path, nd);
9875cf80 1297 return err;
89312214 1298 }
9875cf80 1299 *inode = path->dentry->d_inode;
1da177e4 1300 return 0;
1da177e4
LT		 1301}
1302
52094c8a
AV		 1303static inline int may_lookup(struct nameidata *nd)
1304{
1305 if (nd->flags & LOOKUP_RCU) {
1306 int err = exec_permission(nd->inode, IPERM_FLAG_RCU);
1307 if (err != -ECHILD)
1308 return err;
1309 if (nameidata_drop_rcu(nd))
1310 return -ECHILD;
1311 }
1312 return exec_permission(nd->inode, 0);
1313}
1314
9856fa1b
AV		 1315static inline int handle_dots(struct nameidata *nd, int type)
1316{
1317 if (type == LAST_DOTDOT) {
1318 if (nd->flags & LOOKUP_RCU) {
1319 if (follow_dotdot_rcu(nd))
1320 return -ECHILD;
1321 } else
1322 follow_dotdot(nd);
1323 }
1324 return 0;
1325}
1326
951361f9
AV		 1327static void terminate_walk(struct nameidata *nd)
1328{
1329 if (!(nd->flags & LOOKUP_RCU)) {
1330 path_put(&nd->path);
1331 } else {
1332 nd->flags &= ~LOOKUP_RCU;
5b6ca027
AV		 1333 if (!(nd->flags & LOOKUP_ROOT))
1334 nd->root.mnt = NULL;
951361f9
AV		 1335 rcu_read_unlock();
1336 br_read_unlock(vfsmount_lock);
1337 }
1338}
1339
1da177e4
LT		 1340/*
1341 * Name resolution.
ea3834d9
PM		 1342 * This is the basic name resolution function, turning a pathname into
1343 * the final dentry. We expect 'base' to be positive and a directory.
1da177e4 1344 *
ea3834d9
PM		 1345 * Returns 0 and nd will have valid dentry and mnt on success.
1346 * Returns error and drops reference to input namei data on failure.
1da177e4 1347 */
6de88d72 1348static int link_path_walk(const char *name, struct nameidata *nd)
1da177e4
LT		 1349{
1350 struct path next;
1da177e4
LT		 1351 int err;
1352 unsigned int lookup_flags = nd->flags;
1353
1354 while (*name=='/')
1355 name++;
1356 if (!*name)
086e183a 1357 return 0;
1da177e4 1358
1da177e4 1359 if (nd->depth)
f55eab82 1360 lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
1da177e4
LT		 1361
1362 /* At this point we know we have a real path component. */
1363 for(;;) {
31e6b01f 1364 struct inode *inode;
1da177e4
LT		 1365 unsigned long hash;
1366 struct qstr this;
1367 unsigned int c;
fe479a58 1368 int type;
1da177e4 1369
cdce5d6b 1370 nd->flags |= LOOKUP_CONTINUE;
52094c8a
AV		 1371
1372 err = may_lookup(nd);
1da177e4
LT		 1373 if (err)
1374 break;
1375
1376 this.name = name;
1377 c = *(const unsigned char *)name;
1378
1379 hash = init_name_hash();
1380 do {
1381 name++;
1382 hash = partial_name_hash(c, hash);
1383 c = *(const unsigned char *)name;
1384 } while (c && (c != '/'));
1385 this.len = name - (const char *) this.name;
1386 this.hash = end_name_hash(hash);
1387
fe479a58
AV		 1388 type = LAST_NORM;
1389 if (this.name[0] == '.') switch (this.len) {
1390 case 2:
16c2cd71 1391 if (this.name[1] == '.') {
fe479a58 1392 type = LAST_DOTDOT;
16c2cd71
AV		 1393 nd->flags |= LOOKUP_JUMPED;
1394 }
fe479a58
AV		 1395 break;
1396 case 1:
1397 type = LAST_DOT;
1398 }
5a202bcd
AV		 1399 if (likely(type == LAST_NORM)) {
1400 struct dentry *parent = nd->path.dentry;
16c2cd71 1401 nd->flags &= ~LOOKUP_JUMPED;
5a202bcd
AV		 1402 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1403 err = parent->d_op->d_hash(parent, nd->inode,
1404 &this);
1405 if (err < 0)
1406 break;
1407 }
1408 }
fe479a58 1409
1da177e4
LT		 1410 /* remove trailing slashes? */
1411 if (!c)
1412 goto last_component;
1413 while (*++name == '/');
1414 if (!*name)
1415 goto last_with_slashes;
1416
1417 /*
1418 * "." and ".." are special - ".." especially so because it has
1419 * to be able to know about the current root directory and
1420 * parent relationships.
1421 */
fe479a58 1422 if (unlikely(type != LAST_NORM)) {
ef7562d5
AV		 1423 if (handle_dots(nd, type))
1424 return -ECHILD;
fe479a58 1425 continue;
1da177e4 1426 }
fe479a58 1427
1da177e4 1428 /* This does the actual lookups.. */
31e6b01f 1429 err = do_lookup(nd, &this, &next, &inode);
1da177e4
LT		 1430 if (err)
1431 break;
1da177e4 1432
7bc055d1 1433 if (inode && inode->i_op->follow_link) {
3abb17e8 1434 err = do_follow_link(inode, &next, nd);
1da177e4 1435 if (err)
a7472bab 1436 return err;
31e6b01f 1437 nd->inode = nd->path.dentry->d_inode;
31e6b01f 1438 } else {
09dd17d3 1439 path_to_nameidata(&next, nd);
31e6b01f
NP		 1440 nd->inode = inode;
1441 }
7bc055d1
AV		 1442 err = -ENOENT;
1443 if (!nd->inode)
1444 break;
1da177e4 1445 err = -ENOTDIR;
31e6b01f 1446 if (!nd->inode->i_op->lookup)
1da177e4
LT		 1447 break;
1448 continue;
1449 /* here ends the main loop */
1450
1451last_with_slashes:
1452 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1453last_component:
f55eab82
TM		 1454 /* Clear LOOKUP_CONTINUE iff it was previously unset */
1455 nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
1da177e4
LT		 1456 if (lookup_flags & LOOKUP_PARENT)
1457 goto lookup_parent;
ef7562d5
AV		 1458 if (unlikely(type != LAST_NORM))
1459 return handle_dots(nd, type);
31e6b01f 1460 err = do_lookup(nd, &this, &next, &inode);
1da177e4
LT		 1461 if (err)
1462 break;
db372915
DH		 1463 if (inode && unlikely(inode->i_op->follow_link) &&
1464 (lookup_flags & LOOKUP_FOLLOW)) {
3abb17e8 1465 err = do_follow_link(inode, &next, nd);
1da177e4 1466 if (err)
a7472bab 1467 return err;
31e6b01f
NP		 1468 nd->inode = nd->path.dentry->d_inode;
1469 } else {
09dd17d3 1470 path_to_nameidata(&next, nd);
31e6b01f
NP		 1471 nd->inode = inode;
1472 }
1da177e4 1473 err = -ENOENT;
31e6b01f 1474 if (!nd->inode)
1da177e4
LT		 1475 break;
1476 if (lookup_flags & LOOKUP_DIRECTORY) {
1477 err = -ENOTDIR;
31e6b01f 1478 if (!nd->inode->i_op->lookup)
1da177e4
LT		 1479 break;
1480 }
086e183a 1481 return 0;
1da177e4
LT		 1482lookup_parent:
1483 nd->last = this;
fe479a58 1484 nd->last_type = type;
1da177e4 1485 return 0;
1da177e4 1486 }
951361f9 1487 terminate_walk(nd);
1da177e4
LT		 1488 return err;
1489}
1490
70e9b357
AV		 1491static int path_init(int dfd, const char *name, unsigned int flags,
1492 struct nameidata *nd, struct file **fp)
31e6b01f
NP		 1493{
1494 int retval = 0;
1495 int fput_needed;
1496 struct file *file;
1497
1498 nd->last_type = LAST_ROOT; /* if there are only slashes... */
16c2cd71 1499 nd->flags = flags | LOOKUP_JUMPED;
31e6b01f 1500 nd->depth = 0;
5b6ca027
AV		 1501 if (flags & LOOKUP_ROOT) {
1502 struct inode *inode = nd->root.dentry->d_inode;
73d049a4
AV		 1503 if (*name) {
1504 if (!inode->i_op->lookup)
1505 return -ENOTDIR;
1506 retval = inode_permission(inode, MAY_EXEC);
1507 if (retval)
1508 return retval;
1509 }
5b6ca027
AV		 1510 nd->path = nd->root;
1511 nd->inode = inode;
1512 if (flags & LOOKUP_RCU) {
1513 br_read_lock(vfsmount_lock);
1514 rcu_read_lock();
1515 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1516 } else {
1517 path_get(&nd->path);
1518 }
1519 return 0;
1520 }
1521
31e6b01f 1522 nd->root.mnt = NULL;
31e6b01f
NP		 1523
1524 if (*name=='/') {
e41f7d4e
AV		 1525 if (flags & LOOKUP_RCU) {
1526 br_read_lock(vfsmount_lock);
1527 rcu_read_lock();
1528 set_root_rcu(nd);
1529 } else {
1530 set_root(nd);
1531 path_get(&nd->root);
1532 }
1533 nd->path = nd->root;
31e6b01f 1534 } else if (dfd == AT_FDCWD) {
e41f7d4e
AV		 1535 if (flags & LOOKUP_RCU) {
1536 struct fs_struct *fs = current->fs;
1537 unsigned seq;
31e6b01f 1538
e41f7d4e
AV		 1539 br_read_lock(vfsmount_lock);
1540 rcu_read_lock();
c28cc364 1541
e41f7d4e
AV		 1542 do {
1543 seq = read_seqcount_begin(&fs->seq);
1544 nd->path = fs->pwd;
1545 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1546 } while (read_seqcount_retry(&fs->seq, seq));
1547 } else {
1548 get_fs_pwd(current->fs, &nd->path);
1549 }
31e6b01f
NP		 1550 } else {
1551 struct dentry *dentry;
1552
1abf0c71 1553 file = fget_raw_light(dfd, &fput_needed);
31e6b01f
NP		 1554 retval = -EBADF;
1555 if (!file)
1556 goto out_fail;
1557
1558 dentry = file->f_path.dentry;
1559
f52e0c11
AV		 1560 if (*name) {
1561 retval = -ENOTDIR;
1562 if (!S_ISDIR(dentry->d_inode->i_mode))
1563 goto fput_fail;
31e6b01f 1564
f52e0c11
AV		 1565 retval = file_permission(file, MAY_EXEC);
1566 if (retval)
1567 goto fput_fail;
1568 }
31e6b01f
NP		 1569
1570 nd->path = file->f_path;
e41f7d4e
AV		 1571 if (flags & LOOKUP_RCU) {
1572 if (fput_needed)
70e9b357 1573 *fp = file;
e41f7d4e
AV		 1574 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1575 br_read_lock(vfsmount_lock);
1576 rcu_read_lock();
1577 } else {
1578 path_get(&file->f_path);
1579 fput_light(file, fput_needed);
1580 }
31e6b01f 1581 }
31e6b01f 1582
31e6b01f 1583 nd->inode = nd->path.dentry->d_inode;
9b4a9b14 1584 return 0;
2dfdd266 1585
9b4a9b14
AV		 1586fput_fail:
1587 fput_light(file, fput_needed);
1588out_fail:
1589 return retval;
1590}
1591
1592/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
ee0827cd 1593static int path_lookupat(int dfd, const char *name,
9b4a9b14
AV		 1594 unsigned int flags, struct nameidata *nd)
1595{
70e9b357 1596 struct file *base = NULL;
31e6b01f
NP		 1597 int retval;
1598
1599 /*
1600 * Path walking is largely split up into 2 different synchronisation
1601 * schemes, rcu-walk and ref-walk (explained in
1602 * Documentation/filesystems/path-lookup.txt). These share much of the
1603 * path walk code, but some things particularly setup, cleanup, and
1604 * following mounts are sufficiently divergent that functions are
1605 * duplicated. Typically there is a function foo(), and its RCU
1606 * analogue, foo_rcu().
1607 *
1608 * -ECHILD is the error number of choice (just to avoid clashes) that
1609 * is returned if some aspect of an rcu-walk fails. Such an error must
1610 * be handled by restarting a traditional ref-walk (which will always
1611 * be able to complete).
1612 */
70e9b357 1613 retval = path_init(dfd, name, flags, nd, &base);
ee0827cd 1614
31e6b01f
NP		 1615 if (unlikely(retval))
1616 return retval;
ee0827cd
AV		 1617
1618 current->total_link_count = 0;
1619 retval = link_path_walk(name, nd);
1620
1621 if (nd->flags & LOOKUP_RCU) {
4455ca62
AV		 1622 /* went all way through without dropping RCU */
1623 BUG_ON(retval);
1624 if (nameidata_drop_rcu_last(nd))
1625 retval = -ECHILD;
ee0827cd
AV		 1626 }
1627
16c2cd71
AV		 1628 if (!retval)
1629 retval = handle_reval_path(nd);
1630
70e9b357
AV		 1631 if (base)
1632 fput(base);
ee0827cd 1633
5b6ca027 1634 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
2a737871
AV		 1635 path_put(&nd->root);
1636 nd->root.mnt = NULL;
1637 }
ee0827cd
AV		 1638 return retval;
1639}
31e6b01f 1640
ee0827cd
AV		 1641static int do_path_lookup(int dfd, const char *name,
1642 unsigned int flags, struct nameidata *nd)
1643{
1644 int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
1645 if (unlikely(retval == -ECHILD))
1646 retval = path_lookupat(dfd, name, flags, nd);
1647 if (unlikely(retval == -ESTALE))
1648 retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
31e6b01f
NP		 1649
1650 if (likely(!retval)) {
1651 if (unlikely(!audit_dummy_context())) {
1652 if (nd->path.dentry && nd->inode)
1653 audit_inode(name, nd->path.dentry);
1654 }
1655 }
170aa3d0 1656 return retval;
1da177e4
LT		 1657}
1658
c9c6cac0 1659int kern_path_parent(const char *name, struct nameidata *nd)
5590ff0d 1660{
c9c6cac0 1661 return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
5590ff0d
UD		 1662}
1663
d1811465
AV		 1664int kern_path(const char *name, unsigned int flags, struct path *path)
1665{
1666 struct nameidata nd;
1667 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1668 if (!res)
1669 *path = nd.path;
1670 return res;
1671}
1672
16f18200
JJS		 1673/**
1674 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1675 * @dentry: pointer to dentry of the base directory
1676 * @mnt: pointer to vfs mount of the base directory
1677 * @name: pointer to file name
1678 * @flags: lookup flags
1679 * @nd: pointer to nameidata
1680 */
1681int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1682 const char *name, unsigned int flags,
1683 struct nameidata *nd)
1684{
5b6ca027
AV		 1685 nd->root.dentry = dentry;
1686 nd->root.mnt = mnt;
1687 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1688 return do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, nd);
16f18200
JJS		 1689}
1690
eead1911
CH		 1691static struct dentry *__lookup_hash(struct qstr *name,
1692 struct dentry *base, struct nameidata *nd)
1da177e4 1693{
81fca444 1694 struct inode *inode = base->d_inode;
057f6c01 1695 struct dentry *dentry;
1da177e4
LT		 1696 int err;
1697
b74c79e9 1698 err = exec_permission(inode, 0);
81fca444
CH		 1699 if (err)
1700 return ERR_PTR(err);
1da177e4 1701
b04f784e
NP		 1702 /*
1703 * Don't bother with __d_lookup: callers are for creat as
1704 * well as unlink, so a lot of the time it would cost
1705 * a double lookup.
6e6b1bd1 1706 */
b04f784e 1707 dentry = d_lookup(base, name);
6e6b1bd1 1708
fb045adb 1709 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
6e6b1bd1
AV		 1710 dentry = do_revalidate(dentry, nd);
1711
baa03890
NP		 1712 if (!dentry)
1713 dentry = d_alloc_and_lookup(base, name, nd);
5a202bcd 1714
1da177e4
LT		 1715 return dentry;
1716}
1717
057f6c01
JM		 1718/*
1719 * Restricted form of lookup. Doesn't follow links, single-component only,
1720 * needs parent already locked. Doesn't follow mounts.
1721 * SMP-safe.
1722 */
eead1911 1723static struct dentry *lookup_hash(struct nameidata *nd)
057f6c01 1724{
4ac91378 1725 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1da177e4
LT		 1726}
1727
eead1911 1728/**
a6b91919 1729 * lookup_one_len - filesystem helper to lookup single pathname component
eead1911
CH		 1730 * @name: pathname component to lookup
1731 * @base: base directory to lookup from
1732 * @len: maximum length @len should be interpreted to
1733 *
a6b91919
RD		 1734 * Note that this routine is purely a helper for filesystem usage and should
1735 * not be called by generic code. Also note that by using this function the
eead1911
CH		 1736 * nameidata argument is passed to the filesystem methods and a filesystem
1737 * using this helper needs to be prepared for that.
1738 */
057f6c01
JM		 1739struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1740{
057f6c01 1741 struct qstr this;
6a96ba54
AV		 1742 unsigned long hash;
1743 unsigned int c;
057f6c01 1744
2f9092e1
DW		 1745 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1746
6a96ba54
AV		 1747 this.name = name;
1748 this.len = len;
1749 if (!len)
1750 return ERR_PTR(-EACCES);
1751
1752 hash = init_name_hash();
1753 while (len--) {
1754 c = *(const unsigned char *)name++;
1755 if (c == '/' || c == '\0')
1756 return ERR_PTR(-EACCES);
1757 hash = partial_name_hash(c, hash);
1758 }
1759 this.hash = end_name_hash(hash);
5a202bcd
AV		 1760 /*
1761 * See if the low-level filesystem might want
1762 * to use its own hash..
1763 */
1764 if (base->d_flags & DCACHE_OP_HASH) {
1765 int err = base->d_op->d_hash(base, base->d_inode, &this);
1766 if (err < 0)
1767 return ERR_PTR(err);
1768 }
eead1911 1769
49705b77 1770 return __lookup_hash(&this, base, NULL);
057f6c01
JM		 1771}
1772
2d8f3038
AV		 1773int user_path_at(int dfd, const char __user *name, unsigned flags,
1774 struct path *path)
1da177e4 1775{
2d8f3038 1776 struct nameidata nd;
f52e0c11 1777 char *tmp = getname_flags(name, flags);
1da177e4 1778 int err = PTR_ERR(tmp);
1da177e4 1779 if (!IS_ERR(tmp)) {
2d8f3038
AV		 1780
1781 BUG_ON(flags & LOOKUP_PARENT);
1782
1783 err = do_path_lookup(dfd, tmp, flags, &nd);
1da177e4 1784 putname(tmp);
2d8f3038
AV		 1785 if (!err)
1786 *path = nd.path;
1da177e4
LT		 1787 }
1788 return err;
1789}
1790
2ad94ae6
AV		 1791static int user_path_parent(int dfd, const char __user *path,
1792 struct nameidata *nd, char **name)
1793{
1794 char *s = getname(path);
1795 int error;
1796
1797 if (IS_ERR(s))
1798 return PTR_ERR(s);
1799
1800 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1801 if (error)
1802 putname(s);
1803 else
1804 *name = s;
1805
1806 return error;
1807}
1808
1da177e4
LT		 1809/*
1810 * It's inline, so penalty for filesystems that don't use sticky bit is
1811 * minimal.
1812 */
1813static inline int check_sticky(struct inode *dir, struct inode *inode)
1814{
da9592ed
DH		 1815 uid_t fsuid = current_fsuid();
1816
1da177e4
LT		 1817 if (!(dir->i_mode & S_ISVTX))
1818 return 0;
da9592ed 1819 if (inode->i_uid == fsuid)
1da177e4 1820 return 0;
da9592ed 1821 if (dir->i_uid == fsuid)
1da177e4
LT		 1822 return 0;
1823 return !capable(CAP_FOWNER);
1824}
1825
1826/*
1827 * Check whether we can remove a link victim from directory dir, check
1828 * whether the type of victim is right.
1829 * 1. We can't do it if dir is read-only (done in permission())
1830 * 2. We should have write and exec permissions on dir
1831 * 3. We can't remove anything from append-only dir
1832 * 4. We can't do anything with immutable dir (done in permission())
1833 * 5. If the sticky bit on dir is set we should either
1834 * a. be owner of dir, or
1835 * b. be owner of victim, or
1836 * c. have CAP_FOWNER capability
1837 * 6. If the victim is append-only or immutable we can't do antyhing with
1838 * links pointing to it.
1839 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1840 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1841 * 9. We can't remove a root or mountpoint.
1842 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1843 * nfs_async_unlink().
1844 */
858119e1 1845static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1da177e4
LT		 1846{
1847 int error;
1848
1849 if (!victim->d_inode)
1850 return -ENOENT;
1851
1852 BUG_ON(victim->d_parent->d_inode != dir);
cccc6bba 1853 audit_inode_child(victim, dir);
1da177e4 1854
f419a2e3 1855 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1da177e4
LT		 1856 if (error)
1857 return error;
1858 if (IS_APPEND(dir))
1859 return -EPERM;
1860 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
f9454548 1861 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1da177e4
LT		 1862 return -EPERM;
1863 if (isdir) {
1864 if (!S_ISDIR(victim->d_inode->i_mode))
1865 return -ENOTDIR;
1866 if (IS_ROOT(victim))
1867 return -EBUSY;
1868 } else if (S_ISDIR(victim->d_inode->i_mode))
1869 return -EISDIR;
1870 if (IS_DEADDIR(dir))
1871 return -ENOENT;
1872 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1873 return -EBUSY;
1874 return 0;
1875}
1876
1877/* Check whether we can create an object with dentry child in directory
1878 * dir.
1879 * 1. We can't do it if child already exists (open has special treatment for
1880 * this case, but since we are inlined it's OK)
1881 * 2. We can't do it if dir is read-only (done in permission())
1882 * 3. We should have write and exec permissions on dir
1883 * 4. We can't do it if dir is immutable (done in permission())
1884 */
a95164d9 1885static inline int may_create(struct inode *dir, struct dentry *child)
1da177e4
LT		 1886{
1887 if (child->d_inode)
1888 return -EEXIST;
1889 if (IS_DEADDIR(dir))
1890 return -ENOENT;
f419a2e3 1891 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
1da177e4
LT		 1892}
1893
1da177e4
LT		 1894/*
1895 * p1 and p2 should be directories on the same fs.
1896 */
1897struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1898{
1899 struct dentry *p;
1900
1901 if (p1 == p2) {
f2eace23 1902 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1da177e4
LT		 1903 return NULL;
1904 }
1905
a11f3a05 1906 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1da177e4 1907
e2761a11
OH		 1908 p = d_ancestor(p2, p1);
1909 if (p) {
1910 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
1911 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
1912 return p;
1da177e4
LT		 1913 }
1914
e2761a11
OH		 1915 p = d_ancestor(p1, p2);
1916 if (p) {
1917 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1918 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1919 return p;
1da177e4
LT		 1920 }
1921
f2eace23
IM		 1922 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1923 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1da177e4
LT		 1924 return NULL;
1925}
1926
1927void unlock_rename(struct dentry *p1, struct dentry *p2)
1928{
1b1dcc1b 1929 mutex_unlock(&p1->d_inode->i_mutex);
1da177e4 1930 if (p1 != p2) {
1b1dcc1b 1931 mutex_unlock(&p2->d_inode->i_mutex);
a11f3a05 1932 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1da177e4
LT		 1933 }
1934}
1935
1936int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1937 struct nameidata *nd)
1938{
a95164d9 1939 int error = may_create(dir, dentry);
1da177e4
LT		 1940
1941 if (error)
1942 return error;
1943
acfa4380 1944 if (!dir->i_op->create)
1da177e4
LT		 1945 return -EACCES; /* shouldn't it be ENOSYS? */
1946 mode &= S_IALLUGO;
1947 mode |= S_IFREG;
1948 error = security_inode_create(dir, dentry, mode);
1949 if (error)
1950 return error;
1da177e4 1951 error = dir->i_op->create(dir, dentry, mode, nd);
a74574aa 1952 if (!error)
f38aa942 1953 fsnotify_create(dir, dentry);
1da177e4
LT		 1954 return error;
1955}
1956
73d049a4 1957static int may_open(struct path *path, int acc_mode, int flag)
1da177e4 1958{
3fb64190 1959 struct dentry *dentry = path->dentry;
1da177e4
LT		 1960 struct inode *inode = dentry->d_inode;
1961 int error;
1962
bcda7652
AV		 1963 /* O_PATH? */
1964 if (!acc_mode)
1965 return 0;
1966
1da177e4
LT		 1967 if (!inode)
1968 return -ENOENT;
1969
c8fe8f30
CH		 1970 switch (inode->i_mode & S_IFMT) {
1971 case S_IFLNK:
1da177e4 1972 return -ELOOP;
c8fe8f30
CH		 1973 case S_IFDIR:
1974 if (acc_mode & MAY_WRITE)
1975 return -EISDIR;
1976 break;
1977 case S_IFBLK:
1978 case S_IFCHR:
3fb64190 1979 if (path->mnt->mnt_flags & MNT_NODEV)
1da177e4 1980 return -EACCES;
c8fe8f30
CH		 1981 /*FALLTHRU*/
1982 case S_IFIFO:
1983 case S_IFSOCK:
1da177e4 1984 flag &= ~O_TRUNC;
c8fe8f30 1985 break;
4a3fd211 1986 }
b41572e9 1987
3fb64190 1988 error = inode_permission(inode, acc_mode);
b41572e9
DH		 1989 if (error)
1990 return error;
6146f0d5 1991
1da177e4
LT		 1992 /*
1993 * An append-only file must be opened in append mode for writing.
1994 */
1995 if (IS_APPEND(inode)) {
8737c930 1996 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
7715b521 1997 return -EPERM;
1da177e4 1998 if (flag & O_TRUNC)
7715b521 1999 return -EPERM;
1da177e4
LT		 2000 }
2001
2002 /* O_NOATIME can only be set by the owner or superuser */
7715b521
AV		 2003 if (flag & O_NOATIME && !is_owner_or_cap(inode))
2004 return -EPERM;
1da177e4
LT		 2005
2006 /*
2007 * Ensure there are no outstanding leases on the file.
2008 */
b65a9cfc 2009 return break_lease(inode, flag);
7715b521 2010}
1da177e4 2011
e1181ee6 2012static int handle_truncate(struct file *filp)
7715b521 2013{
e1181ee6 2014 struct path *path = &filp->f_path;
7715b521
AV		 2015 struct inode *inode = path->dentry->d_inode;
2016 int error = get_write_access(inode);
2017 if (error)
2018 return error;
2019 /*
2020 * Refuse to truncate files with mandatory locks held on them.
2021 */
2022 error = locks_verify_locked(inode);
2023 if (!error)
ea0d3ab2 2024 error = security_path_truncate(path);
7715b521
AV		 2025 if (!error) {
2026 error = do_truncate(path->dentry, 0,
2027 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
e1181ee6 2028 filp);
7715b521
AV		 2029 }
2030 put_write_access(inode);
acd0c935 2031 return error;
1da177e4
LT		 2032}
2033
d57999e1
DH		 2034/*
2035 * Note that while the flag value (low two bits) for sys_open means:
2036 * 00 - read-only
2037 * 01 - write-only
2038 * 10 - read-write
2039 * 11 - special
2040 * it is changed into
2041 * 00 - no permissions needed
2042 * 01 - read-permission
2043 * 10 - write-permission
2044 * 11 - read-write
2045 * for the internal routines (ie open_namei()/follow_link() etc)
2046 * This is more logical, and also allows the 00 "no perm needed"
2047 * to be used for symlinks (where the permissions are checked
2048 * later).
2049 *
2050*/
2051static inline int open_to_namei_flags(int flag)
2052{
2053 if ((flag+1) & O_ACCMODE)
2054 flag++;
2055 return flag;
2056}
2057
31e6b01f 2058/*
fe2d35ff 2059 * Handle the last step of open()
31e6b01f 2060 */
fb1cc555 2061static struct file *do_last(struct nameidata *nd, struct path *path,
c3e380b0 2062 const struct open_flags *op, const char *pathname)
fb1cc555 2063{
a1e28038 2064 struct dentry *dir = nd->path.dentry;
6c0d46c4 2065 struct dentry *dentry;
ca344a89 2066 int open_flag = op->open_flag;
6c0d46c4 2067 int will_truncate = open_flag & O_TRUNC;
ca344a89 2068 int want_write = 0;
bcda7652 2069 int acc_mode = op->acc_mode;
fb1cc555 2070 struct file *filp;
fe2d35ff 2071 struct inode *inode;
16c2cd71 2072 int error;
1f36f774 2073
c3e380b0
AV		 2074 nd->flags &= ~LOOKUP_PARENT;
2075 nd->flags |= op->intent;
2076
1f36f774
AV		 2077 switch (nd->last_type) {
2078 case LAST_DOTDOT:
176306f5 2079 case LAST_DOT:
fe2d35ff
AV		 2080 error = handle_dots(nd, nd->last_type);
2081 if (error)
2082 return ERR_PTR(error);
1f36f774 2083 /* fallthrough */
1f36f774 2084 case LAST_ROOT:
fe2d35ff
AV		 2085 if (nd->flags & LOOKUP_RCU) {
2086 if (nameidata_drop_rcu_last(nd))
2087 return ERR_PTR(-ECHILD);
2088 }
16c2cd71
AV		 2089 error = handle_reval_path(nd);
2090 if (error)
2091 goto exit;
fe2d35ff 2092 audit_inode(pathname, nd->path.dentry);
ca344a89 2093 if (open_flag & O_CREAT) {
fe2d35ff
AV		 2094 error = -EISDIR;
2095 goto exit;
2096 }
2097 goto ok;
1f36f774 2098 case LAST_BIND:
fe2d35ff 2099 /* can't be RCU mode here */
16c2cd71
AV		 2100 error = handle_reval_path(nd);
2101 if (error)
2102 goto exit;
1f36f774 2103 audit_inode(pathname, dir);
67ee3ad2 2104 goto ok;
1f36f774 2105 }
67ee3ad2 2106
ca344a89 2107 if (!(open_flag & O_CREAT)) {
bcda7652 2108 int symlink_ok = 0;
fe2d35ff
AV		 2109 if (nd->last.name[nd->last.len])
2110 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
bcda7652
AV		 2111 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2112 symlink_ok = 1;
fe2d35ff
AV		 2113 /* we _can_ be in RCU mode here */
2114 error = do_lookup(nd, &nd->last, path, &inode);
2115 if (error) {
2116 terminate_walk(nd);
2117 return ERR_PTR(error);
2118 }
2119 if (!inode) {
2120 path_to_nameidata(path, nd);
2121 terminate_walk(nd);
2122 return ERR_PTR(-ENOENT);
2123 }
bcda7652 2124 if (unlikely(inode->i_op->follow_link && !symlink_ok)) {
fe2d35ff
AV		 2125 /* We drop rcu-walk here */
2126 if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
2127 return ERR_PTR(-ECHILD);
2128 return NULL;
2129 }
2130 path_to_nameidata(path, nd);
2131 nd->inode = inode;
2132 /* sayonara */
2133 if (nd->flags & LOOKUP_RCU) {
2134 if (nameidata_drop_rcu_last(nd))
2135 return ERR_PTR(-ECHILD);
2136 }
2137
2138 error = -ENOTDIR;
2139 if (nd->flags & LOOKUP_DIRECTORY) {
2140 if (!inode->i_op->lookup)
2141 goto exit;
2142 }
2143 audit_inode(pathname, nd->path.dentry);
2144 goto ok;
2145 }
2146
2147 /* create side of things */
2148
2149 if (nd->flags & LOOKUP_RCU) {
2150 if (nameidata_drop_rcu_last(nd))
2151 return ERR_PTR(-ECHILD);
2152 }
2153
2154 audit_inode(pathname, dir);
16c2cd71 2155 error = -EISDIR;
1f36f774 2156 /* trailing slashes? */
31e6b01f
NP		 2157 if (nd->last.name[nd->last.len])
2158 goto exit;
a2c36b45 2159
a1e28038
AV		 2160 mutex_lock(&dir->d_inode->i_mutex);
2161
6c0d46c4
AV		 2162 dentry = lookup_hash(nd);
2163 error = PTR_ERR(dentry);
2164 if (IS_ERR(dentry)) {
fb1cc555
AV		 2165 mutex_unlock(&dir->d_inode->i_mutex);
2166 goto exit;
2167 }
2168
6c0d46c4
AV		 2169 path->dentry = dentry;
2170 path->mnt = nd->path.mnt;
2171
fb1cc555 2172 /* Negative dentry, just create the file */
6c0d46c4
AV		 2173 if (!dentry->d_inode) {
2174 int mode = op->mode;
2175 if (!IS_POSIXACL(dir->d_inode))
2176 mode &= ~current_umask();
fb1cc555
AV		 2177 /*
2178 * This write is needed to ensure that a
6c0d46c4 2179 * rw->ro transition does not occur between
fb1cc555
AV		 2180 * the time when the file is created and when
2181 * a permanent write count is taken through
2182 * the 'struct file' in nameidata_to_filp().
2183 */
2184 error = mnt_want_write(nd->path.mnt);
2185 if (error)
2186 goto exit_mutex_unlock;
ca344a89 2187 want_write = 1;
9b44f1b3 2188 /* Don't check for write permission, don't truncate */
ca344a89 2189 open_flag &= ~O_TRUNC;
6c0d46c4 2190 will_truncate = 0;
bcda7652 2191 acc_mode = MAY_OPEN;
6c0d46c4
AV		 2192 error = security_path_mknod(&nd->path, dentry, mode, 0);
2193 if (error)
2194 goto exit_mutex_unlock;
2195 error = vfs_create(dir->d_inode, dentry, mode, nd);
2196 if (error)
2197 goto exit_mutex_unlock;
2198 mutex_unlock(&dir->d_inode->i_mutex);
2199 dput(nd->path.dentry);
2200 nd->path.dentry = dentry;
ca344a89 2201 goto common;
fb1cc555
AV		 2202 }
2203
2204 /*
2205 * It already exists.
2206 */
2207 mutex_unlock(&dir->d_inode->i_mutex);
2208 audit_inode(pathname, path->dentry);
2209
2210 error = -EEXIST;
ca344a89 2211 if (open_flag & O_EXCL)
fb1cc555
AV		 2212 goto exit_dput;
2213
9875cf80
DH		 2214 error = follow_managed(path, nd->flags);
2215 if (error < 0)
2216 goto exit_dput;
fb1cc555
AV		 2217
2218 error = -ENOENT;
2219 if (!path->dentry->d_inode)
2220 goto exit_dput;
9e67f361
AV		 2221
2222 if (path->dentry->d_inode->i_op->follow_link)
fb1cc555 2223 return NULL;
fb1cc555
AV		 2224
2225 path_to_nameidata(path, nd);
31e6b01f 2226 nd->inode = path->dentry->d_inode;
fb1cc555 2227 error = -EISDIR;
31e6b01f 2228 if (S_ISDIR(nd->inode->i_mode))
fb1cc555 2229 goto exit;
67ee3ad2 2230ok:
6c0d46c4
AV		 2231 if (!S_ISREG(nd->inode->i_mode))
2232 will_truncate = 0;
2233
0f9d1a10
AV		 2234 if (will_truncate) {
2235 error = mnt_want_write(nd->path.mnt);
2236 if (error)
2237 goto exit;
ca344a89 2238 want_write = 1;
0f9d1a10 2239 }
ca344a89 2240common:
bcda7652 2241 error = may_open(&nd->path, acc_mode, open_flag);
ca344a89 2242 if (error)
0f9d1a10 2243 goto exit;
0f9d1a10
AV		 2244 filp = nameidata_to_filp(nd);
2245 if (!IS_ERR(filp)) {
2246 error = ima_file_check(filp, op->acc_mode);
2247 if (error) {
2248 fput(filp);
2249 filp = ERR_PTR(error);
2250 }
2251 }
2252 if (!IS_ERR(filp)) {
2253 if (will_truncate) {
2254 error = handle_truncate(filp);
2255 if (error) {
2256 fput(filp);
2257 filp = ERR_PTR(error);
2258 }
2259 }
2260 }
ca344a89
AV		 2261out:
2262 if (want_write)
0f9d1a10
AV		 2263 mnt_drop_write(nd->path.mnt);
2264 path_put(&nd->path);
fb1cc555
AV		 2265 return filp;
2266
2267exit_mutex_unlock:
2268 mutex_unlock(&dir->d_inode->i_mutex);
2269exit_dput:
2270 path_put_conditional(path, nd);
2271exit:
ca344a89
AV		 2272 filp = ERR_PTR(error);
2273 goto out;
fb1cc555
AV		 2274}
2275
13aab428 2276static struct file *path_openat(int dfd, const char *pathname,
73d049a4 2277 struct nameidata *nd, const struct open_flags *op, int flags)
1da177e4 2278{
fe2d35ff 2279 struct file *base = NULL;
4a3fd211 2280 struct file *filp;
9850c056 2281 struct path path;
1da177e4 2282 int count = 0;
13aab428 2283 int error;
31e6b01f
NP		 2284
2285 filp = get_empty_filp();
2286 if (!filp)
2287 return ERR_PTR(-ENFILE);
2288
47c805dc 2289 filp->f_flags = op->open_flag;
73d049a4
AV		 2290 nd->intent.open.file = filp;
2291 nd->intent.open.flags = open_to_namei_flags(op->open_flag);
2292 nd->intent.open.create_mode = op->mode;
31e6b01f 2293
73d049a4 2294 error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
31e6b01f 2295 if (unlikely(error))
13aab428 2296 goto out_filp;
31e6b01f 2297
fe2d35ff 2298 current->total_link_count = 0;
73d049a4 2299 error = link_path_walk(pathname, nd);
31e6b01f
NP		 2300 if (unlikely(error))
2301 goto out_filp;
1da177e4 2302
73d049a4 2303 filp = do_last(nd, &path, op, pathname);
806b681c 2304 while (unlikely(!filp)) { /* trailing symlink */
7b9337aa
NP		 2305 struct path link = path;
2306 struct inode *linki = link.dentry->d_inode;
def4af30 2307 void *cookie;
73d049a4
AV		 2308 if (!(nd->flags & LOOKUP_FOLLOW) || count++ == 32) {
2309 path_put_conditional(&path, nd);
2310 path_put(&nd->path);
40b39136
AV		 2311 filp = ERR_PTR(-ELOOP);
2312 break;
2313 }
806b681c
AV		 2314 /*
2315 * This is subtle. Instead of calling do_follow_link() we do
2316 * the thing by hands. The reason is that this way we have zero
2317 * link_count and path_walk() (called from ->follow_link)
2318 * honoring LOOKUP_PARENT. After that we have the parent and
2319 * last component, i.e. we are in the same situation as after
2320 * the first path_walk(). Well, almost - if the last component
2321 * is normal we get its copy stored in nd->last.name and we will
2322 * have to putname() it when we are done. Procfs-like symlinks
2323 * just set LAST_BIND.
2324 */
73d049a4
AV		 2325 nd->flags |= LOOKUP_PARENT;
2326 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
2327 error = __do_follow_link(&link, nd, &cookie);
c3e380b0 2328 if (unlikely(error))
f1afe9ef 2329 filp = ERR_PTR(error);
c3e380b0 2330 else
73d049a4 2331 filp = do_last(nd, &path, op, pathname);
f1afe9ef 2332 if (!IS_ERR(cookie) && linki->i_op->put_link)
73d049a4 2333 linki->i_op->put_link(link.dentry, nd, cookie);
7b9337aa 2334 path_put(&link);
806b681c 2335 }
10fa8e62 2336out:
73d049a4
AV		 2337 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2338 path_put(&nd->root);
fe2d35ff
AV		 2339 if (base)
2340 fput(base);
73d049a4 2341 release_open_intent(nd);
10fa8e62 2342 return filp;
1da177e4 2343
31e6b01f 2344out_filp:
806b681c 2345 filp = ERR_PTR(error);
10fa8e62 2346 goto out;
1da177e4
LT		 2347}
2348
13aab428
AV		 2349struct file *do_filp_open(int dfd, const char *pathname,
2350 const struct open_flags *op, int flags)
2351{
73d049a4 2352 struct nameidata nd;
13aab428
AV		 2353 struct file *filp;
2354
73d049a4 2355 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
13aab428 2356 if (unlikely(filp == ERR_PTR(-ECHILD)))
73d049a4 2357 filp = path_openat(dfd, pathname, &nd, op, flags);
13aab428 2358 if (unlikely(filp == ERR_PTR(-ESTALE)))
73d049a4 2359 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
13aab428
AV		 2360 return filp;
2361}
2362
73d049a4
AV		 2363struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
2364 const char *name, const struct open_flags *op, int flags)
2365{
2366 struct nameidata nd;
2367 struct file *file;
2368
2369 nd.root.mnt = mnt;
2370 nd.root.dentry = dentry;
2371
2372 flags |= LOOKUP_ROOT;
2373
bcda7652 2374 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
73d049a4
AV		 2375 return ERR_PTR(-ELOOP);
2376
2377 file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
2378 if (unlikely(file == ERR_PTR(-ECHILD)))
2379 file = path_openat(-1, name, &nd, op, flags);
2380 if (unlikely(file == ERR_PTR(-ESTALE)))
2381 file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
2382 return file;
2383}
2384
1da177e4
LT		 2385/**
2386 * lookup_create - lookup a dentry, creating it if it doesn't exist
2387 * @nd: nameidata info
2388 * @is_dir: directory flag
2389 *
2390 * Simple function to lookup and return a dentry and create it
2391 * if it doesn't exist. Is SMP-safe.
c663e5d8 2392 *
4ac91378 2393 * Returns with nd->path.dentry->d_inode->i_mutex locked.
1da177e4
LT		 2394 */
2395struct dentry *lookup_create(struct nameidata *nd, int is_dir)
2396{
c663e5d8 2397 struct dentry *dentry = ERR_PTR(-EEXIST);
1da177e4 2398
4ac91378 2399 mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
c663e5d8
CH		 2400 /*
2401 * Yucky last component or no last component at all?
2402 * (foo/., foo/.., /////)
2403 */
1da177e4
LT		 2404 if (nd->last_type != LAST_NORM)
2405 goto fail;
2406 nd->flags &= ~LOOKUP_PARENT;
3516586a 2407 nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
a634904a 2408 nd->intent.open.flags = O_EXCL;
c663e5d8
CH		 2409
2410 /*
2411 * Do the final lookup.
2412 */
49705b77 2413 dentry = lookup_hash(nd);
1da177e4
LT		 2414 if (IS_ERR(dentry))
2415 goto fail;
c663e5d8 2416
e9baf6e5
AV		 2417 if (dentry->d_inode)
2418 goto eexist;
c663e5d8
CH		 2419 /*
2420 * Special case - lookup gave negative, but... we had foo/bar/
2421 * From the vfs_mknod() POV we just have a negative dentry -
2422 * all is fine. Let's be bastards - you had / on the end, you've
2423 * been asking for (non-existent) directory. -ENOENT for you.
2424 */
e9baf6e5
AV		 2425 if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
2426 dput(dentry);
2427 dentry = ERR_PTR(-ENOENT);
2428 }
1da177e4 2429 return dentry;
e9baf6e5 2430eexist:
1da177e4 2431 dput(dentry);
e9baf6e5 2432 dentry = ERR_PTR(-EEXIST);
1da177e4
LT		 2433fail:
2434 return dentry;
2435}
f81a0bff 2436EXPORT_SYMBOL_GPL(lookup_create);
1da177e4
LT		 2437
2438int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
2439{
a95164d9 2440 int error = may_create(dir, dentry);
1da177e4
LT		 2441
2442 if (error)
2443 return error;
2444
2445 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
2446 return -EPERM;
2447
acfa4380 2448 if (!dir->i_op->mknod)
1da177e4
LT		 2449 return -EPERM;
2450
08ce5f16
SH		 2451 error = devcgroup_inode_mknod(mode, dev);
2452 if (error)
2453 return error;
2454
1da177e4
LT		 2455 error = security_inode_mknod(dir, dentry, mode, dev);
2456 if (error)
2457 return error;
2458
1da177e4 2459 error = dir->i_op->mknod(dir, dentry, mode, dev);
a74574aa 2460 if (!error)
f38aa942 2461 fsnotify_create(dir, dentry);
1da177e4
LT		 2462 return error;
2463}
2464
463c3197
DH		 2465static int may_mknod(mode_t mode)
2466{
2467 switch (mode & S_IFMT) {
2468 case S_IFREG:
2469 case S_IFCHR:
2470 case S_IFBLK:
2471 case S_IFIFO:
2472 case S_IFSOCK:
2473 case 0: /* zero mode translates to S_IFREG */
2474 return 0;
2475 case S_IFDIR:
2476 return -EPERM;
2477 default:
2478 return -EINVAL;
2479 }
2480}
2481
2e4d0924
HC		 2482SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2483 unsigned, dev)
1da177e4 2484{
2ad94ae6
AV		 2485 int error;
2486 char *tmp;
2487 struct dentry *dentry;
1da177e4
LT		 2488 struct nameidata nd;
2489
2490 if (S_ISDIR(mode))
2491 return -EPERM;
1da177e4 2492
2ad94ae6 2493 error = user_path_parent(dfd, filename, &nd, &tmp);
1da177e4 2494 if (error)
2ad94ae6
AV		 2495 return error;
2496
1da177e4 2497 dentry = lookup_create(&nd, 0);
463c3197
DH		 2498 if (IS_ERR(dentry)) {
2499 error = PTR_ERR(dentry);
2500 goto out_unlock;
2501 }
4ac91378 2502 if (!IS_POSIXACL(nd.path.dentry->d_inode))
ce3b0f8d 2503 mode &= ~current_umask();
463c3197
DH		 2504 error = may_mknod(mode);
2505 if (error)
2506 goto out_dput;
2507 error = mnt_want_write(nd.path.mnt);
2508 if (error)
2509 goto out_dput;
be6d3e56
KT		 2510 error = security_path_mknod(&nd.path, dentry, mode, dev);
2511 if (error)
2512 goto out_drop_write;
463c3197 2513 switch (mode & S_IFMT) {
1da177e4 2514 case 0: case S_IFREG:
4ac91378 2515 error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
1da177e4
LT		 2516 break;
2517 case S_IFCHR: case S_IFBLK:
4ac91378 2518 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
1da177e4
LT		 2519 new_decode_dev(dev));
2520 break;
2521 case S_IFIFO: case S_IFSOCK:
4ac91378 2522 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
1da177e4 2523 break;
1da177e4 2524 }
be6d3e56 2525out_drop_write:
463c3197
DH		 2526 mnt_drop_write(nd.path.mnt);
2527out_dput:
2528 dput(dentry);
2529out_unlock:
4ac91378 2530 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1d957f9b 2531 path_put(&nd.path);
1da177e4
LT		 2532 putname(tmp);
2533
2534 return error;
2535}
2536
3480b257 2537SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
5590ff0d
UD		 2538{
2539 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2540}
2541
1da177e4
LT		 2542int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2543{
a95164d9 2544 int error = may_create(dir, dentry);
1da177e4
LT		 2545
2546 if (error)
2547 return error;
2548
acfa4380 2549 if (!dir->i_op->mkdir)
1da177e4
LT		 2550 return -EPERM;
2551
2552 mode &= (S_IRWXUGO|S_ISVTX);
2553 error = security_inode_mkdir(dir, dentry, mode);
2554 if (error)
2555 return error;
2556
1da177e4 2557 error = dir->i_op->mkdir(dir, dentry, mode);
a74574aa 2558 if (!error)
f38aa942 2559 fsnotify_mkdir(dir, dentry);
1da177e4
LT		 2560 return error;
2561}
2562
2e4d0924 2563SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
1da177e4
LT		 2564{
2565 int error = 0;
2566 char * tmp;
6902d925
DH		 2567 struct dentry *dentry;
2568 struct nameidata nd;
1da177e4 2569
2ad94ae6
AV		 2570 error = user_path_parent(dfd, pathname, &nd, &tmp);
2571 if (error)
6902d925 2572 goto out_err;
1da177e4 2573
6902d925
DH		 2574 dentry = lookup_create(&nd, 1);
2575 error = PTR_ERR(dentry);
2576 if (IS_ERR(dentry))
2577 goto out_unlock;
1da177e4 2578
4ac91378 2579 if (!IS_POSIXACL(nd.path.dentry->d_inode))
ce3b0f8d 2580 mode &= ~current_umask();
463c3197
DH		 2581 error = mnt_want_write(nd.path.mnt);
2582 if (error)
2583 goto out_dput;
be6d3e56
KT		 2584 error = security_path_mkdir(&nd.path, dentry, mode);
2585 if (error)
2586 goto out_drop_write;
4ac91378 2587 error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
be6d3e56 2588out_drop_write:
463c3197
DH		 2589 mnt_drop_write(nd.path.mnt);
2590out_dput:
6902d925
DH		 2591 dput(dentry);
2592out_unlock:
4ac91378 2593 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1d957f9b 2594 path_put(&nd.path);
6902d925
DH		 2595 putname(tmp);
2596out_err:
1da177e4
LT		 2597 return error;
2598}
2599
3cdad428 2600SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
5590ff0d
UD		 2601{
2602 return sys_mkdirat(AT_FDCWD, pathname, mode);
2603}
2604
1da177e4
LT		 2605/*
2606 * We try to drop the dentry early: we should have
2607 * a usage count of 2 if we're the only user of this
2608 * dentry, and if that is true (possibly after pruning
2609 * the dcache), then we drop the dentry now.
2610 *
2611 * A low-level filesystem can, if it choses, legally
2612 * do a
2613 *
2614 * if (!d_unhashed(dentry))
2615 * return -EBUSY;
2616 *
2617 * if it cannot handle the case of removing a directory
2618 * that is still in use by something else..
2619 */
2620void dentry_unhash(struct dentry *dentry)
2621{
2622 dget(dentry);
dc168427 2623 shrink_dcache_parent(dentry);
1da177e4 2624 spin_lock(&dentry->d_lock);
b7ab39f6 2625 if (dentry->d_count == 2)
1da177e4
LT		 2626 __d_drop(dentry);
2627 spin_unlock(&dentry->d_lock);
1da177e4
LT		 2628}
2629
2630int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2631{
2632 int error = may_delete(dir, dentry, 1);
2633
2634 if (error)
2635 return error;
2636
acfa4380 2637 if (!dir->i_op->rmdir)
1da177e4
LT		 2638 return -EPERM;
2639
1b1dcc1b 2640 mutex_lock(&dentry->d_inode->i_mutex);
1da177e4
LT		 2641 dentry_unhash(dentry);
2642 if (d_mountpoint(dentry))
2643 error = -EBUSY;
2644 else {
2645 error = security_inode_rmdir(dir, dentry);
2646 if (!error) {
2647 error = dir->i_op->rmdir(dir, dentry);
d83c49f3 2648 if (!error) {
1da177e4 2649 dentry->d_inode->i_flags |= S_DEAD;
d83c49f3
AV		 2650 dont_mount(dentry);
2651 }
1da177e4
LT		 2652 }
2653 }
1b1dcc1b 2654 mutex_unlock(&dentry->d_inode->i_mutex);
1da177e4 2655 if (!error) {
1da177e4
LT		 2656 d_delete(dentry);
2657 }
2658 dput(dentry);
2659
2660 return error;
2661}
2662
5590ff0d 2663static long do_rmdir(int dfd, const char __user *pathname)
1da177e4
LT		 2664{
2665 int error = 0;
2666 char * name;
2667 struct dentry *dentry;
2668 struct nameidata nd;
2669
2ad94ae6 2670 error = user_path_parent(dfd, pathname, &nd, &name);
1da177e4 2671 if (error)
2ad94ae6 2672 return error;
1da177e4
LT		 2673
2674 switch(nd.last_type) {
0612d9fb
OH		 2675 case LAST_DOTDOT:
2676 error = -ENOTEMPTY;
2677 goto exit1;
2678 case LAST_DOT:
2679 error = -EINVAL;
2680 goto exit1;
2681 case LAST_ROOT:
2682 error = -EBUSY;
2683 goto exit1;
1da177e4 2684 }
0612d9fb
OH		 2685
2686 nd.flags &= ~LOOKUP_PARENT;
2687
4ac91378 2688 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
49705b77 2689 dentry = lookup_hash(&nd);
1da177e4 2690 error = PTR_ERR(dentry);
6902d925
DH		 2691 if (IS_ERR(dentry))
2692 goto exit2;
0622753b
DH		 2693 error = mnt_want_write(nd.path.mnt);
2694 if (error)
2695 goto exit3;
be6d3e56
KT		 2696 error = security_path_rmdir(&nd.path, dentry);
2697 if (error)
2698 goto exit4;
4ac91378 2699 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
be6d3e56 2700exit4:
0622753b
DH		 2701 mnt_drop_write(nd.path.mnt);
2702exit3:
6902d925
DH		 2703 dput(dentry);
2704exit2:
4ac91378 2705 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1da177e4 2706exit1:
1d957f9b 2707 path_put(&nd.path);
1da177e4
LT		 2708 putname(name);
2709 return error;
2710}
2711
3cdad428 2712SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
5590ff0d
UD		 2713{
2714 return do_rmdir(AT_FDCWD, pathname);
2715}
2716
1da177e4
LT		 2717int vfs_unlink(struct inode *dir, struct dentry *dentry)
2718{
2719 int error = may_delete(dir, dentry, 0);
2720
2721 if (error)
2722 return error;
2723
acfa4380 2724 if (!dir->i_op->unlink)
1da177e4
LT		 2725 return -EPERM;
2726
1b1dcc1b 2727 mutex_lock(&dentry->d_inode->i_mutex);
1da177e4
LT		 2728 if (d_mountpoint(dentry))
2729 error = -EBUSY;
2730 else {
2731 error = security_inode_unlink(dir, dentry);
bec1052e 2732 if (!error) {
1da177e4 2733 error = dir->i_op->unlink(dir, dentry);
bec1052e 2734 if (!error)
d83c49f3 2735 dont_mount(dentry);
bec1052e 2736 }
1da177e4 2737 }
1b1dcc1b 2738 mutex_unlock(&dentry->d_inode->i_mutex);
1da177e4
LT		 2739
2740 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2741 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
ece95912 2742 fsnotify_link_count(dentry->d_inode);
e234f35c 2743 d_delete(dentry);
1da177e4 2744 }
0eeca283 2745
1da177e4
LT		 2746 return error;
2747}
2748
2749/*
2750 * Make sure that the actual truncation of the file will occur outside its
1b1dcc1b 2751 * directory's i_mutex. Truncate can take a long time if there is a lot of
1da177e4
LT		 2752 * writeout happening, and we don't want to prevent access to the directory
2753 * while waiting on the I/O.
2754 */
5590ff0d 2755static long do_unlinkat(int dfd, const char __user *pathname)
1da177e4 2756{
2ad94ae6
AV		 2757 int error;
2758 char *name;
1da177e4
LT		 2759 struct dentry *dentry;
2760 struct nameidata nd;
2761 struct inode *inode = NULL;
2762
2ad94ae6 2763 error = user_path_parent(dfd, pathname, &nd, &name);
1da177e4 2764 if (error)
2ad94ae6
AV		 2765 return error;
2766
1da177e4
LT		 2767 error = -EISDIR;
2768 if (nd.last_type != LAST_NORM)
2769 goto exit1;
0612d9fb
OH		 2770
2771 nd.flags &= ~LOOKUP_PARENT;
2772
4ac91378 2773 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
49705b77 2774 dentry = lookup_hash(&nd);
1da177e4
LT		 2775 error = PTR_ERR(dentry);
2776 if (!IS_ERR(dentry)) {
2777 /* Why not before? Because we want correct error value */
2778 if (nd.last.name[nd.last.len])
2779 goto slashes;
2780 inode = dentry->d_inode;
2781 if (inode)
7de9c6ee 2782 ihold(inode);
0622753b
DH		 2783 error = mnt_want_write(nd.path.mnt);
2784 if (error)
2785 goto exit2;
be6d3e56
KT		 2786 error = security_path_unlink(&nd.path, dentry);
2787 if (error)
2788 goto exit3;
4ac91378 2789 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
be6d3e56 2790exit3:
0622753b 2791 mnt_drop_write(nd.path.mnt);
1da177e4
LT		 2792 exit2:
2793 dput(dentry);
2794 }
4ac91378 2795 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1da177e4
LT		 2796 if (inode)
2797 iput(inode); /* truncate the inode here */
2798exit1:
1d957f9b 2799 path_put(&nd.path);
1da177e4
LT		 2800 putname(name);
2801 return error;
2802
2803slashes:
2804 error = !dentry->d_inode ? -ENOENT :
2805 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2806 goto exit2;
2807}
2808
2e4d0924 2809SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
5590ff0d
UD		 2810{
2811 if ((flag & ~AT_REMOVEDIR) != 0)
2812 return -EINVAL;
2813
2814 if (flag & AT_REMOVEDIR)
2815 return do_rmdir(dfd, pathname);
2816
2817 return do_unlinkat(dfd, pathname);
2818}
2819
3480b257 2820SYSCALL_DEFINE1(unlink, const char __user *, pathname)
5590ff0d
UD		 2821{
2822 return do_unlinkat(AT_FDCWD, pathname);
2823}
2824
db2e747b 2825int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
1da177e4 2826{
a95164d9 2827 int error = may_create(dir, dentry);
1da177e4
LT		 2828
2829 if (error)
2830 return error;
2831
acfa4380 2832 if (!dir->i_op->symlink)
1da177e4
LT		 2833 return -EPERM;
2834
2835 error = security_inode_symlink(dir, dentry, oldname);
2836 if (error)
2837 return error;
2838
1da177e4 2839 error = dir->i_op->symlink(dir, dentry, oldname);
a74574aa 2840 if (!error)
f38aa942 2841 fsnotify_create(dir, dentry);
1da177e4
LT		 2842 return error;
2843}
2844
2e4d0924
HC		 2845SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2846 int, newdfd, const char __user *, newname)
1da177e4 2847{
2ad94ae6
AV		 2848 int error;
2849 char *from;
2850 char *to;
6902d925
DH		 2851 struct dentry *dentry;
2852 struct nameidata nd;
1da177e4
LT		 2853
2854 from = getname(oldname);
2ad94ae6 2855 if (IS_ERR(from))
1da177e4 2856 return PTR_ERR(from);
1da177e4 2857
2ad94ae6 2858 error = user_path_parent(newdfd, newname, &nd, &to);
6902d925 2859 if (error)
2ad94ae6
AV		 2860 goto out_putname;
2861
6902d925
DH		 2862 dentry = lookup_create(&nd, 0);
2863 error = PTR_ERR(dentry);
2864 if (IS_ERR(dentry))
2865 goto out_unlock;
2866
75c3f29d
DH		 2867 error = mnt_want_write(nd.path.mnt);
2868 if (error)
2869 goto out_dput;
be6d3e56
KT		 2870 error = security_path_symlink(&nd.path, dentry, from);
2871 if (error)
2872 goto out_drop_write;
db2e747b 2873 error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
be6d3e56 2874out_drop_write:
75c3f29d
DH		 2875 mnt_drop_write(nd.path.mnt);
2876out_dput:
6902d925
DH		 2877 dput(dentry);
2878out_unlock:
4ac91378 2879 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1d957f9b 2880 path_put(&nd.path);
6902d925
DH		 2881 putname(to);
2882out_putname:
1da177e4
LT		 2883 putname(from);
2884 return error;
2885}
2886
3480b257 2887SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
5590ff0d
UD		 2888{
2889 return sys_symlinkat(oldname, AT_FDCWD, newname);
2890}
2891
1da177e4
LT		 2892int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
2893{
2894 struct inode *inode = old_dentry->d_inode;
2895 int error;
2896
2897 if (!inode)
2898 return -ENOENT;
2899
a95164d9 2900 error = may_create(dir, new_dentry);
1da177e4
LT		 2901 if (error)
2902 return error;
2903
2904 if (dir->i_sb != inode->i_sb)
2905 return -EXDEV;
2906
2907 /*
2908 * A link to an append-only or immutable file cannot be created.
2909 */
2910 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
2911 return -EPERM;
acfa4380 2912 if (!dir->i_op->link)
1da177e4 2913 return -EPERM;
7e79eedb 2914 if (S_ISDIR(inode->i_mode))
1da177e4
LT		 2915 return -EPERM;
2916
2917 error = security_inode_link(old_dentry, dir, new_dentry);
2918 if (error)
2919 return error;
2920
7e79eedb 2921 mutex_lock(&inode->i_mutex);
aae8a97d
AK		 2922 /* Make sure we don't allow creating hardlink to an unlinked file */
2923 if (inode->i_nlink == 0)
2924 error = -ENOENT;
2925 else
2926 error = dir->i_op->link(old_dentry, dir, new_dentry);
7e79eedb 2927 mutex_unlock(&inode->i_mutex);
e31e14ec 2928 if (!error)
7e79eedb 2929 fsnotify_link(dir, inode, new_dentry);
1da177e4
LT		 2930 return error;
2931}
2932
2933/*
2934 * Hardlinks are often used in delicate situations. We avoid
2935 * security-related surprises by not following symlinks on the
2936 * newname. --KAB
2937 *
2938 * We don't follow them on the oldname either to be compatible
2939 * with linux 2.0, and to avoid hard-linking to directories
2940 * and other special files. --ADM
2941 */
2e4d0924
HC		 2942SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
2943 int, newdfd, const char __user *, newname, int, flags)
1da177e4
LT		 2944{
2945 struct dentry *new_dentry;
2d8f3038
AV		 2946 struct nameidata nd;
2947 struct path old_path;
11a7b371 2948 int how = 0;
1da177e4 2949 int error;
2ad94ae6 2950 char *to;
1da177e4 2951
11a7b371 2952 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
c04030e1 2953 return -EINVAL;
11a7b371
AK		 2954 /*
2955 * To use null names we require CAP_DAC_READ_SEARCH
2956 * This ensures that not everyone will be able to create
2957 * handlink using the passed filedescriptor.
2958 */
2959 if (flags & AT_EMPTY_PATH) {
2960 if (!capable(CAP_DAC_READ_SEARCH))
2961 return -ENOENT;
2962 how = LOOKUP_EMPTY;
2963 }
2964
2965 if (flags & AT_SYMLINK_FOLLOW)
2966 how |= LOOKUP_FOLLOW;
c04030e1 2967
11a7b371 2968 error = user_path_at(olddfd, oldname, how, &old_path);
1da177e4 2969 if (error)
2ad94ae6
AV		 2970 return error;
2971
2972 error = user_path_parent(newdfd, newname, &nd, &to);
1da177e4
LT		 2973 if (error)
2974 goto out;
2975 error = -EXDEV;
2d8f3038 2976 if (old_path.mnt != nd.path.mnt)
1da177e4
LT		 2977 goto out_release;
2978 new_dentry = lookup_create(&nd, 0);
2979 error = PTR_ERR(new_dentry);
6902d925
DH		 2980 if (IS_ERR(new_dentry))
2981 goto out_unlock;
75c3f29d
DH		 2982 error = mnt_want_write(nd.path.mnt);
2983 if (error)
2984 goto out_dput;
be6d3e56
KT		 2985 error = security_path_link(old_path.dentry, &nd.path, new_dentry);
2986 if (error)
2987 goto out_drop_write;
2d8f3038 2988 error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
be6d3e56 2989out_drop_write:
75c3f29d
DH		 2990 mnt_drop_write(nd.path.mnt);
2991out_dput:
6902d925
DH		 2992 dput(new_dentry);
2993out_unlock:
4ac91378 2994 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
1da177e4 2995out_release:
1d957f9b 2996 path_put(&nd.path);
2ad94ae6 2997 putname(to);
1da177e4 2998out:
2d8f3038 2999 path_put(&old_path);
1da177e4
LT		 3000
3001 return error;
3002}
3003
3480b257 3004SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
5590ff0d 3005{
c04030e1 3006 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
5590ff0d
UD		 3007}
3008
1da177e4
LT		 3009/*
3010 * The worst of all namespace operations - renaming directory. "Perverted"
3011 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3012 * Problems:
3013 * a) we can get into loop creation. Check is done in is_subdir().
3014 * b) race potential - two innocent renames can create a loop together.
3015 * That's where 4.4 screws up. Current fix: serialization on
a11f3a05 3016 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
1da177e4
LT		 3017 * story.
3018 * c) we have to lock _three_ objects - parents and victim (if it exists).
1b1dcc1b 3019 * And that - after we got ->i_mutex on parents (until then we don't know
1da177e4
LT		 3020 * whether the target exists). Solution: try to be smart with locking
3021 * order for inodes. We rely on the fact that tree topology may change
a11f3a05 3022 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
1da177e4
LT		 3023 * move will be locked. Thus we can rank directories by the tree
3024 * (ancestors first) and rank all non-directories after them.
3025 * That works since everybody except rename does "lock parent, lookup,
a11f3a05 3026 * lock child" and rename is under ->s_vfs_rename_mutex.
1da177e4
LT		 3027 * HOWEVER, it relies on the assumption that any object with ->lookup()
3028 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3029 * we'd better make sure that there's no link(2) for them.
3030 * d) some filesystems don't support opened-but-unlinked directories,
3031 * either because of layout or because they are not ready to deal with
3032 * all cases correctly. The latter will be fixed (taking this sort of
3033 * stuff into VFS), but the former is not going away. Solution: the same
3034 * trick as in rmdir().
3035 * e) conversion from fhandle to dentry may come in the wrong moment - when
1b1dcc1b 3036 * we are removing the target. Solution: we will have to grab ->i_mutex
1da177e4 3037 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
c41b20e7 3038 * ->i_mutex on parents, which works but leads to some truly excessive
1da177e4
LT		 3039 * locking].
3040 */
75c96f85
AB		 3041static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3042 struct inode *new_dir, struct dentry *new_dentry)
1da177e4
LT		 3043{
3044 int error = 0;
3045 struct inode *target;
3046
3047 /*
3048 * If we are going to change the parent - check write permissions,
3049 * we'll need to flip '..'.
3050 */
3051 if (new_dir != old_dir) {
f419a2e3 3052 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
1da177e4
LT		 3053 if (error)
3054 return error;
3055 }
3056
3057 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3058 if (error)
3059 return error;
3060
3061 target = new_dentry->d_inode;
d83c49f3 3062 if (target)
1b1dcc1b 3063 mutex_lock(&target->i_mutex);
1da177e4
LT		 3064 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3065 error = -EBUSY;
d83c49f3
AV		 3066 else {
3067 if (target)
3068 dentry_unhash(new_dentry);
1da177e4 3069 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
d83c49f3 3070 }
1da177e4 3071 if (target) {
d83c49f3 3072 if (!error) {
1da177e4 3073 target->i_flags |= S_DEAD;
d83c49f3
AV		 3074 dont_mount(new_dentry);
3075 }
1b1dcc1b 3076 mutex_unlock(&target->i_mutex);
1da177e4
LT		 3077 if (d_unhashed(new_dentry))
3078 d_rehash(new_dentry);
3079 dput(new_dentry);
3080 }
e31e14ec 3081 if (!error)
349457cc
MF		 3082 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3083 d_move(old_dentry,new_dentry);
1da177e4
LT		 3084 return error;
3085}
3086
75c96f85
AB		 3087static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3088 struct inode *new_dir, struct dentry *new_dentry)
1da177e4
LT		 3089{
3090 struct inode *target;
3091 int error;
3092
3093 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3094 if (error)
3095 return error;
3096
3097 dget(new_dentry);
3098 target = new_dentry->d_inode;
3099 if (target)
1b1dcc1b 3100 mutex_lock(&target->i_mutex);
1da177e4
LT		 3101 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3102 error = -EBUSY;
3103 else
3104 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3105 if (!error) {
bec1052e 3106 if (target)
d83c49f3 3107 dont_mount(new_dentry);
349457cc 3108 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
1da177e4 3109 d_move(old_dentry, new_dentry);
1da177e4
LT		 3110 }
3111 if (target)
1b1dcc1b 3112 mutex_unlock(&target->i_mutex);
1da177e4
LT		 3113 dput(new_dentry);
3114 return error;
3115}
3116
3117int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3118 struct inode *new_dir, struct dentry *new_dentry)
3119{
3120 int error;
3121 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
59b0df21 3122 const unsigned char *old_name;
1da177e4
LT		 3123
3124 if (old_dentry->d_inode == new_dentry->d_inode)
3125 return 0;
3126
3127 error = may_delete(old_dir, old_dentry, is_dir);
3128 if (error)
3129 return error;
3130
3131 if (!new_dentry->d_inode)
a95164d9 3132 error = may_create(new_dir, new_dentry);
1da177e4
LT		 3133 else
3134 error = may_delete(new_dir, new_dentry, is_dir);
3135 if (error)
3136 return error;
3137
acfa4380 3138 if (!old_dir->i_op->rename)
1da177e4
LT		 3139 return -EPERM;
3140
0eeca283
RL		 3141 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3142
1da177e4
LT		 3143 if (is_dir)
3144 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3145 else
3146 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
123df294
AV		 3147 if (!error)
3148 fsnotify_move(old_dir, new_dir, old_name, is_dir,
5a190ae6 3149 new_dentry->d_inode, old_dentry);
0eeca283
RL		 3150 fsnotify_oldname_free(old_name);
3151
1da177e4
LT		 3152 return error;
3153}
3154
2e4d0924
HC		 3155SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3156 int, newdfd, const char __user *, newname)
1da177e4 3157{
2ad94ae6
AV		 3158 struct dentry *old_dir, *new_dir;
3159 struct dentry *old_dentry, *new_dentry;
3160 struct dentry *trap;
1da177e4 3161 struct nameidata oldnd, newnd;
2ad94ae6
AV		 3162 char *from;
3163 char *to;
3164 int error;
1da177e4 3165
2ad94ae6 3166 error = user_path_parent(olddfd, oldname, &oldnd, &from);
1da177e4
LT		 3167 if (error)
3168 goto exit;
3169
2ad94ae6 3170 error = user_path_parent(newdfd, newname, &newnd, &to);
1da177e4
LT		 3171 if (error)
3172 goto exit1;
3173
3174 error = -EXDEV;
4ac91378 3175 if (oldnd.path.mnt != newnd.path.mnt)
1da177e4
LT		 3176 goto exit2;
3177
4ac91378 3178 old_dir = oldnd.path.dentry;
1da177e4
LT		 3179 error = -EBUSY;
3180 if (oldnd.last_type != LAST_NORM)
3181 goto exit2;
3182
4ac91378 3183 new_dir = newnd.path.dentry;
1da177e4
LT		 3184 if (newnd.last_type != LAST_NORM)
3185 goto exit2;
3186
0612d9fb
OH		 3187 oldnd.flags &= ~LOOKUP_PARENT;
3188 newnd.flags &= ~LOOKUP_PARENT;
4e9ed2f8 3189 newnd.flags |= LOOKUP_RENAME_TARGET;
0612d9fb 3190
1da177e4
LT		 3191 trap = lock_rename(new_dir, old_dir);
3192
49705b77 3193 old_dentry = lookup_hash(&oldnd);
1da177e4
LT		 3194 error = PTR_ERR(old_dentry);
3195 if (IS_ERR(old_dentry))
3196 goto exit3;
3197 /* source must exist */
3198 error = -ENOENT;
3199 if (!old_dentry->d_inode)
3200 goto exit4;
3201 /* unless the source is a directory trailing slashes give -ENOTDIR */
3202 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3203 error = -ENOTDIR;
3204 if (oldnd.last.name[oldnd.last.len])
3205 goto exit4;
3206 if (newnd.last.name[newnd.last.len])
3207 goto exit4;
3208 }
3209 /* source should not be ancestor of target */
3210 error = -EINVAL;
3211 if (old_dentry == trap)
3212 goto exit4;
49705b77 3213 new_dentry = lookup_hash(&newnd);
1da177e4
LT		 3214 error = PTR_ERR(new_dentry);
3215 if (IS_ERR(new_dentry))
3216 goto exit4;
3217 /* target should not be an ancestor of source */
3218 error = -ENOTEMPTY;
3219 if (new_dentry == trap)
3220 goto exit5;
3221
9079b1eb
DH		 3222 error = mnt_want_write(oldnd.path.mnt);
3223 if (error)
3224 goto exit5;
be6d3e56
KT		 3225 error = security_path_rename(&oldnd.path, old_dentry,
3226 &newnd.path, new_dentry);
3227 if (error)
3228 goto exit6;
1da177e4
LT		 3229 error = vfs_rename(old_dir->d_inode, old_dentry,
3230 new_dir->d_inode, new_dentry);
be6d3e56 3231exit6:
9079b1eb 3232 mnt_drop_write(oldnd.path.mnt);
1da177e4
LT		 3233exit5:
3234 dput(new_dentry);
3235exit4:
3236 dput(old_dentry);
3237exit3:
3238 unlock_rename(new_dir, old_dir);
3239exit2:
1d957f9b 3240 path_put(&newnd.path);
2ad94ae6 3241 putname(to);
1da177e4 3242exit1:
1d957f9b 3243 path_put(&oldnd.path);
1da177e4 3244 putname(from);
2ad94ae6 3245exit:
1da177e4
LT		 3246 return error;
3247}
3248
a26eab24 3249SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
5590ff0d
UD		 3250{
3251 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3252}
3253
1da177e4
LT		 3254int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3255{
3256 int len;
3257
3258 len = PTR_ERR(link);
3259 if (IS_ERR(link))
3260 goto out;
3261
3262 len = strlen(link);
3263 if (len > (unsigned) buflen)
3264 len = buflen;
3265 if (copy_to_user(buffer, link, len))
3266 len = -EFAULT;
3267out:
3268 return len;
3269}
3270
3271/*
3272 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3273 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3274 * using) it for any given inode is up to filesystem.
3275 */
3276int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3277{
3278 struct nameidata nd;
cc314eef 3279 void *cookie;
694a1764 3280 int res;
cc314eef 3281
1da177e4 3282 nd.depth = 0;
cc314eef 3283 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
694a1764
MS		 3284 if (IS_ERR(cookie))
3285 return PTR_ERR(cookie);
3286
3287 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3288 if (dentry->d_inode->i_op->put_link)
3289 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3290 return res;
1da177e4
LT		 3291}
3292
3293int vfs_follow_link(struct nameidata *nd, const char *link)
3294{
3295 return __vfs_follow_link(nd, link);
3296}
3297
3298/* get the link contents into pagecache */
3299static char *page_getlink(struct dentry * dentry, struct page **ppage)
3300{
ebd09abb
DG		 3301 char *kaddr;
3302 struct page *page;
1da177e4 3303 struct address_space *mapping = dentry->d_inode->i_mapping;
090d2b18 3304 page = read_mapping_page(mapping, 0, NULL);
1da177e4 3305 if (IS_ERR(page))
6fe6900e 3306 return (char*)page;
1da177e4 3307 *ppage = page;
ebd09abb
DG		 3308 kaddr = kmap(page);
3309 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3310 return kaddr;
1da177e4
LT		 3311}
3312
3313int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3314{
3315 struct page *page = NULL;
3316 char *s = page_getlink(dentry, &page);
3317 int res = vfs_readlink(dentry,buffer,buflen,s);
3318 if (page) {
3319 kunmap(page);
3320 page_cache_release(page);
3321 }
3322 return res;
3323}
3324
cc314eef 3325void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
1da177e4 3326{
cc314eef 3327 struct page *page = NULL;
1da177e4 3328 nd_set_link(nd, page_getlink(dentry, &page));
cc314eef 3329 return page;
1da177e4
LT		 3330}
3331
cc314eef 3332void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1da177e4 3333{
cc314eef
LT		 3334 struct page *page = cookie;
3335
3336 if (page) {
1da177e4
LT		 3337 kunmap(page);
3338 page_cache_release(page);
1da177e4
LT		 3339 }
3340}
3341
54566b2c
NP		 3342/*
3343 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3344 */
3345int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
1da177e4
LT		 3346{
3347 struct address_space *mapping = inode->i_mapping;
0adb25d2 3348 struct page *page;
afddba49 3349 void *fsdata;
beb497ab 3350 int err;
1da177e4 3351 char *kaddr;
54566b2c
NP		 3352 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3353 if (nofs)
3354 flags |= AOP_FLAG_NOFS;
1da177e4 3355
7e53cac4 3356retry:
afddba49 3357 err = pagecache_write_begin(NULL, mapping, 0, len-1,
54566b2c 3358 flags, &page, &fsdata);
1da177e4 3359 if (err)
afddba49
NP		 3360 goto fail;
3361
1da177e4
LT		 3362 kaddr = kmap_atomic(page, KM_USER0);
3363 memcpy(kaddr, symname, len-1);
3364 kunmap_atomic(kaddr, KM_USER0);
afddba49
NP		 3365
3366 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3367 page, fsdata);
1da177e4
LT		 3368 if (err < 0)
3369 goto fail;
afddba49
NP		 3370 if (err < len-1)
3371 goto retry;
3372
1da177e4
LT		 3373 mark_inode_dirty(inode);
3374 return 0;
1da177e4
LT		 3375fail:
3376 return err;
3377}
3378
0adb25d2
KK		 3379int page_symlink(struct inode *inode, const char *symname, int len)
3380{
3381 return __page_symlink(inode, symname, len,
54566b2c 3382 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
0adb25d2
KK		 3383}
3384
92e1d5be 3385const struct inode_operations page_symlink_inode_operations = {
1da177e4
LT		 3386 .readlink = generic_readlink,
3387 .follow_link = page_follow_link_light,
3388 .put_link = page_put_link,
3389};
3390
2d8f3038 3391EXPORT_SYMBOL(user_path_at);
cc53ce53 3392EXPORT_SYMBOL(follow_down_one);
1da177e4
LT		 3393EXPORT_SYMBOL(follow_down);
3394EXPORT_SYMBOL(follow_up);
3395EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3396EXPORT_SYMBOL(getname);
3397EXPORT_SYMBOL(lock_rename);
1da177e4
LT		 3398EXPORT_SYMBOL(lookup_one_len);
3399EXPORT_SYMBOL(page_follow_link_light);
3400EXPORT_SYMBOL(page_put_link);
3401EXPORT_SYMBOL(page_readlink);
0adb25d2 3402EXPORT_SYMBOL(__page_symlink);
1da177e4
LT		 3403EXPORT_SYMBOL(page_symlink);
3404EXPORT_SYMBOL(page_symlink_inode_operations);
c9c6cac0 3405EXPORT_SYMBOL(kern_path_parent);
d1811465 3406EXPORT_SYMBOL(kern_path);
16f18200 3407EXPORT_SYMBOL(vfs_path_lookup);
f419a2e3 3408EXPORT_SYMBOL(inode_permission);
8c744fb8 3409EXPORT_SYMBOL(file_permission);
1da177e4
LT		 3410EXPORT_SYMBOL(unlock_rename);
3411EXPORT_SYMBOL(vfs_create);
3412EXPORT_SYMBOL(vfs_follow_link);
3413EXPORT_SYMBOL(vfs_link);
3414EXPORT_SYMBOL(vfs_mkdir);
3415EXPORT_SYMBOL(vfs_mknod);
3416EXPORT_SYMBOL(generic_permission);
3417EXPORT_SYMBOL(vfs_readlink);
3418EXPORT_SYMBOL(vfs_rename);
3419EXPORT_SYMBOL(vfs_rmdir);
3420EXPORT_SYMBOL(vfs_symlink);
3421EXPORT_SYMBOL(vfs_unlink);
3422EXPORT_SYMBOL(dentry_unhash);
3423EXPORT_SYMBOL(generic_readlink);
kernel source for telekom puls (alcatel/mediatek)