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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/export.h> | |
19 | #include <linux/kernel.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/fs.h> | |
22 | #include <linux/namei.h> | |
23 | #include <linux/pagemap.h> | |
24 | #include <linux/fsnotify.h> | |
25 | #include <linux/personality.h> | |
26 | #include <linux/security.h> | |
27 | #include <linux/ima.h> | |
28 | #include <linux/syscalls.h> | |
29 | #include <linux/mount.h> | |
30 | #include <linux/audit.h> | |
31 | #include <linux/capability.h> | |
32 | #include <linux/file.h> | |
33 | #include <linux/fcntl.h> | |
34 | #include <linux/device_cgroup.h> | |
35 | #include <linux/fs_struct.h> | |
36 | #include <linux/posix_acl.h> | |
37 | #include <linux/hash.h> | |
38 | #include <linux/bitops.h> | |
39 | #include <linux/init_task.h> | |
40 | #include <linux/uaccess.h> | |
41 | ||
42 | #include "internal.h" | |
43 | #include "mount.h" | |
44 | ||
45 | /* [Feb-1997 T. Schoebel-Theuer] | |
46 | * Fundamental changes in the pathname lookup mechanisms (namei) | |
47 | * were necessary because of omirr. The reason is that omirr needs | |
48 | * to know the _real_ pathname, not the user-supplied one, in case | |
49 | * of symlinks (and also when transname replacements occur). | |
50 | * | |
51 | * The new code replaces the old recursive symlink resolution with | |
52 | * an iterative one (in case of non-nested symlink chains). It does | |
53 | * this with calls to <fs>_follow_link(). | |
54 | * As a side effect, dir_namei(), _namei() and follow_link() are now | |
55 | * replaced with a single function lookup_dentry() that can handle all | |
56 | * the special cases of the former code. | |
57 | * | |
58 | * With the new dcache, the pathname is stored at each inode, at least as | |
59 | * long as the refcount of the inode is positive. As a side effect, the | |
60 | * size of the dcache depends on the inode cache and thus is dynamic. | |
61 | * | |
62 | * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink | |
63 | * resolution to correspond with current state of the code. | |
64 | * | |
65 | * Note that the symlink resolution is not *completely* iterative. | |
66 | * There is still a significant amount of tail- and mid- recursion in | |
67 | * the algorithm. Also, note that <fs>_readlink() is not used in | |
68 | * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() | |
69 | * may return different results than <fs>_follow_link(). Many virtual | |
70 | * filesystems (including /proc) exhibit this behavior. | |
71 | */ | |
72 | ||
73 | /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: | |
74 | * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL | |
75 | * and the name already exists in form of a symlink, try to create the new | |
76 | * name indicated by the symlink. The old code always complained that the | |
77 | * name already exists, due to not following the symlink even if its target | |
78 | * is nonexistent. The new semantics affects also mknod() and link() when | |
79 | * the name is a symlink pointing to a non-existent name. | |
80 | * | |
81 | * I don't know which semantics is the right one, since I have no access | |
82 | * to standards. But I found by trial that HP-UX 9.0 has the full "new" | |
83 | * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the | |
84 | * "old" one. Personally, I think the new semantics is much more logical. | |
85 | * Note that "ln old new" where "new" is a symlink pointing to a non-existing | |
86 | * file does succeed in both HP-UX and SunOs, but not in Solaris | |
87 | * and in the old Linux semantics. | |
88 | */ | |
89 | ||
90 | /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink | |
91 | * semantics. See the comments in "open_namei" and "do_link" below. | |
92 | * | |
93 | * [10-Sep-98 Alan Modra] Another symlink change. | |
94 | */ | |
95 | ||
96 | /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: | |
97 | * inside the path - always follow. | |
98 | * in the last component in creation/removal/renaming - never follow. | |
99 | * if LOOKUP_FOLLOW passed - follow. | |
100 | * if the pathname has trailing slashes - follow. | |
101 | * otherwise - don't follow. | |
102 | * (applied in that order). | |
103 | * | |
104 | * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT | |
105 | * restored for 2.4. This is the last surviving part of old 4.2BSD bug. | |
106 | * During the 2.4 we need to fix the userland stuff depending on it - | |
107 | * hopefully we will be able to get rid of that wart in 2.5. So far only | |
108 | * XEmacs seems to be relying on it... | |
109 | */ | |
110 | /* | |
111 | * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) | |
112 | * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives | |
113 | * any extra contention... | |
114 | */ | |
115 | ||
116 | /* In order to reduce some races, while at the same time doing additional | |
117 | * checking and hopefully speeding things up, we copy filenames to the | |
118 | * kernel data space before using them.. | |
119 | * | |
120 | * POSIX.1 2.4: an empty pathname is invalid (ENOENT). | |
121 | * PATH_MAX includes the nul terminator --RR. | |
122 | */ | |
123 | ||
124 | #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname)) | |
125 | ||
126 | struct filename * | |
127 | getname_flags(const char __user *filename, int flags, int *empty) | |
128 | { | |
129 | struct filename *result; | |
130 | char *kname; | |
131 | int len; | |
132 | ||
133 | result = audit_reusename(filename); | |
134 | if (result) | |
135 | return result; | |
136 | ||
137 | result = __getname(); | |
138 | if (unlikely(!result)) | |
139 | return ERR_PTR(-ENOMEM); | |
140 | ||
141 | /* | |
142 | * First, try to embed the struct filename inside the names_cache | |
143 | * allocation | |
144 | */ | |
145 | kname = (char *)result->iname; | |
146 | result->name = kname; | |
147 | ||
148 | len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX); | |
149 | if (unlikely(len < 0)) { | |
150 | __putname(result); | |
151 | return ERR_PTR(len); | |
152 | } | |
153 | ||
154 | /* | |
155 | * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a | |
156 | * separate struct filename so we can dedicate the entire | |
157 | * names_cache allocation for the pathname, and re-do the copy from | |
158 | * userland. | |
159 | */ | |
160 | if (unlikely(len == EMBEDDED_NAME_MAX)) { | |
161 | const size_t size = offsetof(struct filename, iname[1]); | |
162 | kname = (char *)result; | |
163 | ||
164 | /* | |
165 | * size is chosen that way we to guarantee that | |
166 | * result->iname[0] is within the same object and that | |
167 | * kname can't be equal to result->iname, no matter what. | |
168 | */ | |
169 | result = kzalloc(size, GFP_KERNEL); | |
170 | if (unlikely(!result)) { | |
171 | __putname(kname); | |
172 | return ERR_PTR(-ENOMEM); | |
173 | } | |
174 | result->name = kname; | |
175 | len = strncpy_from_user(kname, filename, PATH_MAX); | |
176 | if (unlikely(len < 0)) { | |
177 | __putname(kname); | |
178 | kfree(result); | |
179 | return ERR_PTR(len); | |
180 | } | |
181 | if (unlikely(len == PATH_MAX)) { | |
182 | __putname(kname); | |
183 | kfree(result); | |
184 | return ERR_PTR(-ENAMETOOLONG); | |
185 | } | |
186 | } | |
187 | ||
188 | result->refcnt = 1; | |
189 | /* The empty path is special. */ | |
190 | if (unlikely(!len)) { | |
191 | if (empty) | |
192 | *empty = 1; | |
193 | if (!(flags & LOOKUP_EMPTY)) { | |
194 | putname(result); | |
195 | return ERR_PTR(-ENOENT); | |
196 | } | |
197 | } | |
198 | ||
199 | result->uptr = filename; | |
200 | result->aname = NULL; | |
201 | audit_getname(result); | |
202 | return result; | |
203 | } | |
204 | ||
205 | struct filename * | |
206 | getname(const char __user * filename) | |
207 | { | |
208 | return getname_flags(filename, 0, NULL); | |
209 | } | |
210 | ||
211 | struct filename * | |
212 | getname_kernel(const char * filename) | |
213 | { | |
214 | struct filename *result; | |
215 | int len = strlen(filename) + 1; | |
216 | ||
217 | result = __getname(); | |
218 | if (unlikely(!result)) | |
219 | return ERR_PTR(-ENOMEM); | |
220 | ||
221 | if (len <= EMBEDDED_NAME_MAX) { | |
222 | result->name = (char *)result->iname; | |
223 | } else if (len <= PATH_MAX) { | |
224 | struct filename *tmp; | |
225 | ||
226 | tmp = kmalloc(sizeof(*tmp), GFP_KERNEL); | |
227 | if (unlikely(!tmp)) { | |
228 | __putname(result); | |
229 | return ERR_PTR(-ENOMEM); | |
230 | } | |
231 | tmp->name = (char *)result; | |
232 | result = tmp; | |
233 | } else { | |
234 | __putname(result); | |
235 | return ERR_PTR(-ENAMETOOLONG); | |
236 | } | |
237 | memcpy((char *)result->name, filename, len); | |
238 | result->uptr = NULL; | |
239 | result->aname = NULL; | |
240 | result->refcnt = 1; | |
241 | audit_getname(result); | |
242 | ||
243 | return result; | |
244 | } | |
245 | ||
246 | void putname(struct filename *name) | |
247 | { | |
248 | BUG_ON(name->refcnt <= 0); | |
249 | ||
250 | if (--name->refcnt > 0) | |
251 | return; | |
252 | ||
253 | if (name->name != name->iname) { | |
254 | __putname(name->name); | |
255 | kfree(name); | |
256 | } else | |
257 | __putname(name); | |
258 | } | |
259 | ||
260 | static int check_acl(struct inode *inode, int mask) | |
261 | { | |
262 | #ifdef CONFIG_FS_POSIX_ACL | |
263 | struct posix_acl *acl; | |
264 | ||
265 | if (mask & MAY_NOT_BLOCK) { | |
266 | acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); | |
267 | if (!acl) | |
268 | return -EAGAIN; | |
269 | /* no ->get_acl() calls in RCU mode... */ | |
270 | if (is_uncached_acl(acl)) | |
271 | return -ECHILD; | |
272 | return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); | |
273 | } | |
274 | ||
275 | acl = get_acl(inode, ACL_TYPE_ACCESS); | |
276 | if (IS_ERR(acl)) | |
277 | return PTR_ERR(acl); | |
278 | if (acl) { | |
279 | int error = posix_acl_permission(inode, acl, mask); | |
280 | posix_acl_release(acl); | |
281 | return error; | |
282 | } | |
283 | #endif | |
284 | ||
285 | return -EAGAIN; | |
286 | } | |
287 | ||
288 | /* | |
289 | * This does the basic permission checking | |
290 | */ | |
291 | static int acl_permission_check(struct inode *inode, int mask) | |
292 | { | |
293 | unsigned int mode = inode->i_mode; | |
294 | ||
295 | if (likely(uid_eq(current_fsuid(), inode->i_uid))) | |
296 | mode >>= 6; | |
297 | else { | |
298 | if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { | |
299 | int error = check_acl(inode, mask); | |
300 | if (error != -EAGAIN) | |
301 | return error; | |
302 | } | |
303 | ||
304 | if (in_group_p(inode->i_gid)) | |
305 | mode >>= 3; | |
306 | } | |
307 | ||
308 | /* | |
309 | * If the DACs are ok we don't need any capability check. | |
310 | */ | |
311 | if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) | |
312 | return 0; | |
313 | return -EACCES; | |
314 | } | |
315 | ||
316 | /** | |
317 | * generic_permission - check for access rights on a Posix-like filesystem | |
318 | * @inode: inode to check access rights for | |
319 | * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) | |
320 | * | |
321 | * Used to check for read/write/execute permissions on a file. | |
322 | * We use "fsuid" for this, letting us set arbitrary permissions | |
323 | * for filesystem access without changing the "normal" uids which | |
324 | * are used for other things. | |
325 | * | |
326 | * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk | |
327 | * request cannot be satisfied (eg. requires blocking or too much complexity). | |
328 | * It would then be called again in ref-walk mode. | |
329 | */ | |
330 | int generic_permission(struct inode *inode, int mask) | |
331 | { | |
332 | int ret; | |
333 | ||
334 | /* | |
335 | * Do the basic permission checks. | |
336 | */ | |
337 | ret = acl_permission_check(inode, mask); | |
338 | if (ret != -EACCES) | |
339 | return ret; | |
340 | ||
341 | if (S_ISDIR(inode->i_mode)) { | |
342 | /* DACs are overridable for directories */ | |
343 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) | |
344 | return 0; | |
345 | if (!(mask & MAY_WRITE)) | |
346 | if (capable_wrt_inode_uidgid(inode, | |
347 | CAP_DAC_READ_SEARCH)) | |
348 | return 0; | |
349 | return -EACCES; | |
350 | } | |
351 | /* | |
352 | * Read/write DACs are always overridable. | |
353 | * Executable DACs are overridable when there is | |
354 | * at least one exec bit set. | |
355 | */ | |
356 | if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) | |
357 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) | |
358 | return 0; | |
359 | ||
360 | /* | |
361 | * Searching includes executable on directories, else just read. | |
362 | */ | |
363 | mask &= MAY_READ | MAY_WRITE | MAY_EXEC; | |
364 | if (mask == MAY_READ) | |
365 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) | |
366 | return 0; | |
367 | ||
368 | return -EACCES; | |
369 | } | |
370 | EXPORT_SYMBOL(generic_permission); | |
371 | ||
372 | /* | |
373 | * We _really_ want to just do "generic_permission()" without | |
374 | * even looking at the inode->i_op values. So we keep a cache | |
375 | * flag in inode->i_opflags, that says "this has not special | |
376 | * permission function, use the fast case". | |
377 | */ | |
378 | static inline int do_inode_permission(struct inode *inode, int mask) | |
379 | { | |
380 | if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { | |
381 | if (likely(inode->i_op->permission)) | |
382 | return inode->i_op->permission(inode, mask); | |
383 | ||
384 | /* This gets set once for the inode lifetime */ | |
385 | spin_lock(&inode->i_lock); | |
386 | inode->i_opflags |= IOP_FASTPERM; | |
387 | spin_unlock(&inode->i_lock); | |
388 | } | |
389 | return generic_permission(inode, mask); | |
390 | } | |
391 | ||
392 | /** | |
393 | * __inode_permission - Check for access rights to a given inode | |
394 | * @inode: Inode to check permission on | |
395 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) | |
396 | * | |
397 | * Check for read/write/execute permissions on an inode. | |
398 | * | |
399 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. | |
400 | * | |
401 | * This does not check for a read-only file system. You probably want | |
402 | * inode_permission(). | |
403 | */ | |
404 | int __inode_permission(struct inode *inode, int mask) | |
405 | { | |
406 | int retval; | |
407 | ||
408 | if (unlikely(mask & MAY_WRITE)) { | |
409 | /* | |
410 | * Nobody gets write access to an immutable file. | |
411 | */ | |
412 | if (IS_IMMUTABLE(inode)) | |
413 | return -EPERM; | |
414 | ||
415 | /* | |
416 | * Updating mtime will likely cause i_uid and i_gid to be | |
417 | * written back improperly if their true value is unknown | |
418 | * to the vfs. | |
419 | */ | |
420 | if (HAS_UNMAPPED_ID(inode)) | |
421 | return -EACCES; | |
422 | } | |
423 | ||
424 | retval = do_inode_permission(inode, mask); | |
425 | if (retval) | |
426 | return retval; | |
427 | ||
428 | retval = devcgroup_inode_permission(inode, mask); | |
429 | if (retval) | |
430 | return retval; | |
431 | ||
432 | return security_inode_permission(inode, mask); | |
433 | } | |
434 | EXPORT_SYMBOL(__inode_permission); | |
435 | ||
436 | /** | |
437 | * sb_permission - Check superblock-level permissions | |
438 | * @sb: Superblock of inode to check permission on | |
439 | * @inode: Inode to check permission on | |
440 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) | |
441 | * | |
442 | * Separate out file-system wide checks from inode-specific permission checks. | |
443 | */ | |
444 | static int sb_permission(struct super_block *sb, struct inode *inode, int mask) | |
445 | { | |
446 | if (unlikely(mask & MAY_WRITE)) { | |
447 | umode_t mode = inode->i_mode; | |
448 | ||
449 | /* Nobody gets write access to a read-only fs. */ | |
450 | if ((sb->s_flags & MS_RDONLY) && | |
451 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) | |
452 | return -EROFS; | |
453 | } | |
454 | return 0; | |
455 | } | |
456 | ||
457 | /** | |
458 | * inode_permission - Check for access rights to a given inode | |
459 | * @inode: Inode to check permission on | |
460 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) | |
461 | * | |
462 | * Check for read/write/execute permissions on an inode. We use fs[ug]id for | |
463 | * this, letting us set arbitrary permissions for filesystem access without | |
464 | * changing the "normal" UIDs which are used for other things. | |
465 | * | |
466 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. | |
467 | */ | |
468 | int inode_permission(struct inode *inode, int mask) | |
469 | { | |
470 | int retval; | |
471 | ||
472 | retval = sb_permission(inode->i_sb, inode, mask); | |
473 | if (retval) | |
474 | return retval; | |
475 | return __inode_permission(inode, mask); | |
476 | } | |
477 | EXPORT_SYMBOL(inode_permission); | |
478 | ||
479 | /** | |
480 | * path_get - get a reference to a path | |
481 | * @path: path to get the reference to | |
482 | * | |
483 | * Given a path increment the reference count to the dentry and the vfsmount. | |
484 | */ | |
485 | void path_get(const struct path *path) | |
486 | { | |
487 | mntget(path->mnt); | |
488 | dget(path->dentry); | |
489 | } | |
490 | EXPORT_SYMBOL(path_get); | |
491 | ||
492 | /** | |
493 | * path_put - put a reference to a path | |
494 | * @path: path to put the reference to | |
495 | * | |
496 | * Given a path decrement the reference count to the dentry and the vfsmount. | |
497 | */ | |
498 | void path_put(const struct path *path) | |
499 | { | |
500 | dput(path->dentry); | |
501 | mntput(path->mnt); | |
502 | } | |
503 | EXPORT_SYMBOL(path_put); | |
504 | ||
505 | #define EMBEDDED_LEVELS 2 | |
506 | struct nameidata { | |
507 | struct path path; | |
508 | struct qstr last; | |
509 | struct path root; | |
510 | struct inode *inode; /* path.dentry.d_inode */ | |
511 | unsigned int flags; | |
512 | unsigned seq, m_seq; | |
513 | int last_type; | |
514 | unsigned depth; | |
515 | int total_link_count; | |
516 | struct saved { | |
517 | struct path link; | |
518 | struct delayed_call done; | |
519 | const char *name; | |
520 | unsigned seq; | |
521 | } *stack, internal[EMBEDDED_LEVELS]; | |
522 | struct filename *name; | |
523 | struct nameidata *saved; | |
524 | struct inode *link_inode; | |
525 | unsigned root_seq; | |
526 | int dfd; | |
527 | }; | |
528 | ||
529 | static void set_nameidata(struct nameidata *p, int dfd, struct filename *name) | |
530 | { | |
531 | struct nameidata *old = current->nameidata; | |
532 | p->stack = p->internal; | |
533 | p->dfd = dfd; | |
534 | p->name = name; | |
535 | p->total_link_count = old ? old->total_link_count : 0; | |
536 | p->saved = old; | |
537 | current->nameidata = p; | |
538 | } | |
539 | ||
540 | static void restore_nameidata(void) | |
541 | { | |
542 | struct nameidata *now = current->nameidata, *old = now->saved; | |
543 | ||
544 | current->nameidata = old; | |
545 | if (old) | |
546 | old->total_link_count = now->total_link_count; | |
547 | if (now->stack != now->internal) | |
548 | kfree(now->stack); | |
549 | } | |
550 | ||
551 | static int __nd_alloc_stack(struct nameidata *nd) | |
552 | { | |
553 | struct saved *p; | |
554 | ||
555 | if (nd->flags & LOOKUP_RCU) { | |
556 | p= kmalloc(MAXSYMLINKS * sizeof(struct saved), | |
557 | GFP_ATOMIC); | |
558 | if (unlikely(!p)) | |
559 | return -ECHILD; | |
560 | } else { | |
561 | p= kmalloc(MAXSYMLINKS * sizeof(struct saved), | |
562 | GFP_KERNEL); | |
563 | if (unlikely(!p)) | |
564 | return -ENOMEM; | |
565 | } | |
566 | memcpy(p, nd->internal, sizeof(nd->internal)); | |
567 | nd->stack = p; | |
568 | return 0; | |
569 | } | |
570 | ||
571 | /** | |
572 | * path_connected - Verify that a path->dentry is below path->mnt.mnt_root | |
573 | * @path: nameidate to verify | |
574 | * | |
575 | * Rename can sometimes move a file or directory outside of a bind | |
576 | * mount, path_connected allows those cases to be detected. | |
577 | */ | |
578 | static bool path_connected(const struct path *path) | |
579 | { | |
580 | struct vfsmount *mnt = path->mnt; | |
581 | ||
582 | /* Only bind mounts can have disconnected paths */ | |
583 | if (mnt->mnt_root == mnt->mnt_sb->s_root) | |
584 | return true; | |
585 | ||
586 | return is_subdir(path->dentry, mnt->mnt_root); | |
587 | } | |
588 | ||
589 | static inline int nd_alloc_stack(struct nameidata *nd) | |
590 | { | |
591 | if (likely(nd->depth != EMBEDDED_LEVELS)) | |
592 | return 0; | |
593 | if (likely(nd->stack != nd->internal)) | |
594 | return 0; | |
595 | return __nd_alloc_stack(nd); | |
596 | } | |
597 | ||
598 | static void drop_links(struct nameidata *nd) | |
599 | { | |
600 | int i = nd->depth; | |
601 | while (i--) { | |
602 | struct saved *last = nd->stack + i; | |
603 | do_delayed_call(&last->done); | |
604 | clear_delayed_call(&last->done); | |
605 | } | |
606 | } | |
607 | ||
608 | static void terminate_walk(struct nameidata *nd) | |
609 | { | |
610 | drop_links(nd); | |
611 | if (!(nd->flags & LOOKUP_RCU)) { | |
612 | int i; | |
613 | path_put(&nd->path); | |
614 | for (i = 0; i < nd->depth; i++) | |
615 | path_put(&nd->stack[i].link); | |
616 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { | |
617 | path_put(&nd->root); | |
618 | nd->root.mnt = NULL; | |
619 | } | |
620 | } else { | |
621 | nd->flags &= ~LOOKUP_RCU; | |
622 | if (!(nd->flags & LOOKUP_ROOT)) | |
623 | nd->root.mnt = NULL; | |
624 | rcu_read_unlock(); | |
625 | } | |
626 | nd->depth = 0; | |
627 | } | |
628 | ||
629 | /* path_put is needed afterwards regardless of success or failure */ | |
630 | static bool legitimize_path(struct nameidata *nd, | |
631 | struct path *path, unsigned seq) | |
632 | { | |
633 | int res = __legitimize_mnt(path->mnt, nd->m_seq); | |
634 | if (unlikely(res)) { | |
635 | if (res > 0) | |
636 | path->mnt = NULL; | |
637 | path->dentry = NULL; | |
638 | return false; | |
639 | } | |
640 | if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) { | |
641 | path->dentry = NULL; | |
642 | return false; | |
643 | } | |
644 | return !read_seqcount_retry(&path->dentry->d_seq, seq); | |
645 | } | |
646 | ||
647 | static bool legitimize_links(struct nameidata *nd) | |
648 | { | |
649 | int i; | |
650 | for (i = 0; i < nd->depth; i++) { | |
651 | struct saved *last = nd->stack + i; | |
652 | if (unlikely(!legitimize_path(nd, &last->link, last->seq))) { | |
653 | drop_links(nd); | |
654 | nd->depth = i + 1; | |
655 | return false; | |
656 | } | |
657 | } | |
658 | return true; | |
659 | } | |
660 | ||
661 | /* | |
662 | * Path walking has 2 modes, rcu-walk and ref-walk (see | |
663 | * Documentation/filesystems/path-lookup.txt). In situations when we can't | |
664 | * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab | |
665 | * normal reference counts on dentries and vfsmounts to transition to ref-walk | |
666 | * mode. Refcounts are grabbed at the last known good point before rcu-walk | |
667 | * got stuck, so ref-walk may continue from there. If this is not successful | |
668 | * (eg. a seqcount has changed), then failure is returned and it's up to caller | |
669 | * to restart the path walk from the beginning in ref-walk mode. | |
670 | */ | |
671 | ||
672 | /** | |
673 | * unlazy_walk - try to switch to ref-walk mode. | |
674 | * @nd: nameidata pathwalk data | |
675 | * @dentry: child of nd->path.dentry or NULL | |
676 | * @seq: seq number to check dentry against | |
677 | * Returns: 0 on success, -ECHILD on failure | |
678 | * | |
679 | * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry | |
680 | * for ref-walk mode. @dentry must be a path found by a do_lookup call on | |
681 | * @nd or NULL. Must be called from rcu-walk context. | |
682 | * Nothing should touch nameidata between unlazy_walk() failure and | |
683 | * terminate_walk(). | |
684 | */ | |
685 | static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq) | |
686 | { | |
687 | struct dentry *parent = nd->path.dentry; | |
688 | ||
689 | BUG_ON(!(nd->flags & LOOKUP_RCU)); | |
690 | ||
691 | nd->flags &= ~LOOKUP_RCU; | |
692 | if (unlikely(!legitimize_links(nd))) | |
693 | goto out2; | |
694 | if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq))) | |
695 | goto out2; | |
696 | if (unlikely(!lockref_get_not_dead(&parent->d_lockref))) | |
697 | goto out1; | |
698 | ||
699 | /* | |
700 | * For a negative lookup, the lookup sequence point is the parents | |
701 | * sequence point, and it only needs to revalidate the parent dentry. | |
702 | * | |
703 | * For a positive lookup, we need to move both the parent and the | |
704 | * dentry from the RCU domain to be properly refcounted. And the | |
705 | * sequence number in the dentry validates *both* dentry counters, | |
706 | * since we checked the sequence number of the parent after we got | |
707 | * the child sequence number. So we know the parent must still | |
708 | * be valid if the child sequence number is still valid. | |
709 | */ | |
710 | if (!dentry) { | |
711 | if (read_seqcount_retry(&parent->d_seq, nd->seq)) | |
712 | goto out; | |
713 | BUG_ON(nd->inode != parent->d_inode); | |
714 | } else { | |
715 | if (!lockref_get_not_dead(&dentry->d_lockref)) | |
716 | goto out; | |
717 | if (read_seqcount_retry(&dentry->d_seq, seq)) | |
718 | goto drop_dentry; | |
719 | } | |
720 | ||
721 | /* | |
722 | * Sequence counts matched. Now make sure that the root is | |
723 | * still valid and get it if required. | |
724 | */ | |
725 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { | |
726 | if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) { | |
727 | rcu_read_unlock(); | |
728 | dput(dentry); | |
729 | return -ECHILD; | |
730 | } | |
731 | } | |
732 | ||
733 | rcu_read_unlock(); | |
734 | return 0; | |
735 | ||
736 | drop_dentry: | |
737 | rcu_read_unlock(); | |
738 | dput(dentry); | |
739 | goto drop_root_mnt; | |
740 | out2: | |
741 | nd->path.mnt = NULL; | |
742 | out1: | |
743 | nd->path.dentry = NULL; | |
744 | out: | |
745 | rcu_read_unlock(); | |
746 | drop_root_mnt: | |
747 | if (!(nd->flags & LOOKUP_ROOT)) | |
748 | nd->root.mnt = NULL; | |
749 | return -ECHILD; | |
750 | } | |
751 | ||
752 | static int unlazy_link(struct nameidata *nd, struct path *link, unsigned seq) | |
753 | { | |
754 | if (unlikely(!legitimize_path(nd, link, seq))) { | |
755 | drop_links(nd); | |
756 | nd->depth = 0; | |
757 | nd->flags &= ~LOOKUP_RCU; | |
758 | nd->path.mnt = NULL; | |
759 | nd->path.dentry = NULL; | |
760 | if (!(nd->flags & LOOKUP_ROOT)) | |
761 | nd->root.mnt = NULL; | |
762 | rcu_read_unlock(); | |
763 | } else if (likely(unlazy_walk(nd, NULL, 0)) == 0) { | |
764 | return 0; | |
765 | } | |
766 | path_put(link); | |
767 | return -ECHILD; | |
768 | } | |
769 | ||
770 | static inline int d_revalidate(struct dentry *dentry, unsigned int flags) | |
771 | { | |
772 | return dentry->d_op->d_revalidate(dentry, flags); | |
773 | } | |
774 | ||
775 | /** | |
776 | * complete_walk - successful completion of path walk | |
777 | * @nd: pointer nameidata | |
778 | * | |
779 | * If we had been in RCU mode, drop out of it and legitimize nd->path. | |
780 | * Revalidate the final result, unless we'd already done that during | |
781 | * the path walk or the filesystem doesn't ask for it. Return 0 on | |
782 | * success, -error on failure. In case of failure caller does not | |
783 | * need to drop nd->path. | |
784 | */ | |
785 | static int complete_walk(struct nameidata *nd) | |
786 | { | |
787 | struct dentry *dentry = nd->path.dentry; | |
788 | int status; | |
789 | ||
790 | if (nd->flags & LOOKUP_RCU) { | |
791 | if (!(nd->flags & LOOKUP_ROOT)) | |
792 | nd->root.mnt = NULL; | |
793 | if (unlikely(unlazy_walk(nd, NULL, 0))) | |
794 | return -ECHILD; | |
795 | } | |
796 | ||
797 | if (likely(!(nd->flags & LOOKUP_JUMPED))) | |
798 | return 0; | |
799 | ||
800 | if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) | |
801 | return 0; | |
802 | ||
803 | status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); | |
804 | if (status > 0) | |
805 | return 0; | |
806 | ||
807 | if (!status) | |
808 | status = -ESTALE; | |
809 | ||
810 | return status; | |
811 | } | |
812 | ||
813 | static void set_root(struct nameidata *nd) | |
814 | { | |
815 | struct fs_struct *fs = current->fs; | |
816 | ||
817 | if (nd->flags & LOOKUP_RCU) { | |
818 | unsigned seq; | |
819 | ||
820 | do { | |
821 | seq = read_seqcount_begin(&fs->seq); | |
822 | nd->root = fs->root; | |
823 | nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq); | |
824 | } while (read_seqcount_retry(&fs->seq, seq)); | |
825 | } else { | |
826 | get_fs_root(fs, &nd->root); | |
827 | } | |
828 | } | |
829 | ||
830 | static void path_put_conditional(struct path *path, struct nameidata *nd) | |
831 | { | |
832 | dput(path->dentry); | |
833 | if (path->mnt != nd->path.mnt) | |
834 | mntput(path->mnt); | |
835 | } | |
836 | ||
837 | static inline void path_to_nameidata(const struct path *path, | |
838 | struct nameidata *nd) | |
839 | { | |
840 | if (!(nd->flags & LOOKUP_RCU)) { | |
841 | dput(nd->path.dentry); | |
842 | if (nd->path.mnt != path->mnt) | |
843 | mntput(nd->path.mnt); | |
844 | } | |
845 | nd->path.mnt = path->mnt; | |
846 | nd->path.dentry = path->dentry; | |
847 | } | |
848 | ||
849 | static int nd_jump_root(struct nameidata *nd) | |
850 | { | |
851 | if (nd->flags & LOOKUP_RCU) { | |
852 | struct dentry *d; | |
853 | nd->path = nd->root; | |
854 | d = nd->path.dentry; | |
855 | nd->inode = d->d_inode; | |
856 | nd->seq = nd->root_seq; | |
857 | if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq))) | |
858 | return -ECHILD; | |
859 | } else { | |
860 | path_put(&nd->path); | |
861 | nd->path = nd->root; | |
862 | path_get(&nd->path); | |
863 | nd->inode = nd->path.dentry->d_inode; | |
864 | } | |
865 | nd->flags |= LOOKUP_JUMPED; | |
866 | return 0; | |
867 | } | |
868 | ||
869 | /* | |
870 | * Helper to directly jump to a known parsed path from ->get_link, | |
871 | * caller must have taken a reference to path beforehand. | |
872 | */ | |
873 | void nd_jump_link(struct path *path) | |
874 | { | |
875 | struct nameidata *nd = current->nameidata; | |
876 | path_put(&nd->path); | |
877 | ||
878 | nd->path = *path; | |
879 | nd->inode = nd->path.dentry->d_inode; | |
880 | nd->flags |= LOOKUP_JUMPED; | |
881 | } | |
882 | ||
883 | static inline void put_link(struct nameidata *nd) | |
884 | { | |
885 | struct saved *last = nd->stack + --nd->depth; | |
886 | do_delayed_call(&last->done); | |
887 | if (!(nd->flags & LOOKUP_RCU)) | |
888 | path_put(&last->link); | |
889 | } | |
890 | ||
891 | int sysctl_protected_symlinks __read_mostly = 1; | |
892 | int sysctl_protected_hardlinks __read_mostly = 1; | |
893 | ||
894 | /** | |
895 | * may_follow_link - Check symlink following for unsafe situations | |
896 | * @nd: nameidata pathwalk data | |
897 | * | |
898 | * In the case of the sysctl_protected_symlinks sysctl being enabled, | |
899 | * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is | |
900 | * in a sticky world-writable directory. This is to protect privileged | |
901 | * processes from failing races against path names that may change out | |
902 | * from under them by way of other users creating malicious symlinks. | |
903 | * It will permit symlinks to be followed only when outside a sticky | |
904 | * world-writable directory, or when the uid of the symlink and follower | |
905 | * match, or when the directory owner matches the symlink's owner. | |
906 | * | |
907 | * Returns 0 if following the symlink is allowed, -ve on error. | |
908 | */ | |
909 | static inline int may_follow_link(struct nameidata *nd) | |
910 | { | |
911 | const struct inode *inode; | |
912 | const struct inode *parent; | |
913 | kuid_t puid; | |
914 | ||
915 | if (!sysctl_protected_symlinks) | |
916 | return 0; | |
917 | ||
918 | /* Allowed if owner and follower match. */ | |
919 | inode = nd->link_inode; | |
920 | if (uid_eq(current_cred()->fsuid, inode->i_uid)) | |
921 | return 0; | |
922 | ||
923 | /* Allowed if parent directory not sticky and world-writable. */ | |
924 | parent = nd->inode; | |
925 | if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) | |
926 | return 0; | |
927 | ||
928 | /* Allowed if parent directory and link owner match. */ | |
929 | puid = parent->i_uid; | |
930 | if (uid_valid(puid) && uid_eq(puid, inode->i_uid)) | |
931 | return 0; | |
932 | ||
933 | if (nd->flags & LOOKUP_RCU) | |
934 | return -ECHILD; | |
935 | ||
936 | audit_log_link_denied("follow_link", &nd->stack[0].link); | |
937 | return -EACCES; | |
938 | } | |
939 | ||
940 | /** | |
941 | * safe_hardlink_source - Check for safe hardlink conditions | |
942 | * @inode: the source inode to hardlink from | |
943 | * | |
944 | * Return false if at least one of the following conditions: | |
945 | * - inode is not a regular file | |
946 | * - inode is setuid | |
947 | * - inode is setgid and group-exec | |
948 | * - access failure for read and write | |
949 | * | |
950 | * Otherwise returns true. | |
951 | */ | |
952 | static bool safe_hardlink_source(struct inode *inode) | |
953 | { | |
954 | umode_t mode = inode->i_mode; | |
955 | ||
956 | /* Special files should not get pinned to the filesystem. */ | |
957 | if (!S_ISREG(mode)) | |
958 | return false; | |
959 | ||
960 | /* Setuid files should not get pinned to the filesystem. */ | |
961 | if (mode & S_ISUID) | |
962 | return false; | |
963 | ||
964 | /* Executable setgid files should not get pinned to the filesystem. */ | |
965 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) | |
966 | return false; | |
967 | ||
968 | /* Hardlinking to unreadable or unwritable sources is dangerous. */ | |
969 | if (inode_permission(inode, MAY_READ | MAY_WRITE)) | |
970 | return false; | |
971 | ||
972 | return true; | |
973 | } | |
974 | ||
975 | /** | |
976 | * may_linkat - Check permissions for creating a hardlink | |
977 | * @link: the source to hardlink from | |
978 | * | |
979 | * Block hardlink when all of: | |
980 | * - sysctl_protected_hardlinks enabled | |
981 | * - fsuid does not match inode | |
982 | * - hardlink source is unsafe (see safe_hardlink_source() above) | |
983 | * - not CAP_FOWNER in a namespace with the inode owner uid mapped | |
984 | * | |
985 | * Returns 0 if successful, -ve on error. | |
986 | */ | |
987 | static int may_linkat(struct path *link) | |
988 | { | |
989 | struct inode *inode; | |
990 | ||
991 | if (!sysctl_protected_hardlinks) | |
992 | return 0; | |
993 | ||
994 | inode = link->dentry->d_inode; | |
995 | ||
996 | /* Source inode owner (or CAP_FOWNER) can hardlink all they like, | |
997 | * otherwise, it must be a safe source. | |
998 | */ | |
999 | if (inode_owner_or_capable(inode) || safe_hardlink_source(inode)) | |
1000 | return 0; | |
1001 | ||
1002 | audit_log_link_denied("linkat", link); | |
1003 | return -EPERM; | |
1004 | } | |
1005 | ||
1006 | static __always_inline | |
1007 | const char *get_link(struct nameidata *nd) | |
1008 | { | |
1009 | struct saved *last = nd->stack + nd->depth - 1; | |
1010 | struct dentry *dentry = last->link.dentry; | |
1011 | struct inode *inode = nd->link_inode; | |
1012 | int error; | |
1013 | const char *res; | |
1014 | ||
1015 | if (!(nd->flags & LOOKUP_RCU)) { | |
1016 | touch_atime(&last->link); | |
1017 | cond_resched(); | |
1018 | } else if (atime_needs_update_rcu(&last->link, inode)) { | |
1019 | if (unlikely(unlazy_walk(nd, NULL, 0))) | |
1020 | return ERR_PTR(-ECHILD); | |
1021 | touch_atime(&last->link); | |
1022 | } | |
1023 | ||
1024 | error = security_inode_follow_link(dentry, inode, | |
1025 | nd->flags & LOOKUP_RCU); | |
1026 | if (unlikely(error)) | |
1027 | return ERR_PTR(error); | |
1028 | ||
1029 | nd->last_type = LAST_BIND; | |
1030 | res = inode->i_link; | |
1031 | if (!res) { | |
1032 | const char * (*get)(struct dentry *, struct inode *, | |
1033 | struct delayed_call *); | |
1034 | get = inode->i_op->get_link; | |
1035 | if (nd->flags & LOOKUP_RCU) { | |
1036 | res = get(NULL, inode, &last->done); | |
1037 | if (res == ERR_PTR(-ECHILD)) { | |
1038 | if (unlikely(unlazy_walk(nd, NULL, 0))) | |
1039 | return ERR_PTR(-ECHILD); | |
1040 | res = get(dentry, inode, &last->done); | |
1041 | } | |
1042 | } else { | |
1043 | res = get(dentry, inode, &last->done); | |
1044 | } | |
1045 | if (IS_ERR_OR_NULL(res)) | |
1046 | return res; | |
1047 | } | |
1048 | if (*res == '/') { | |
1049 | if (!nd->root.mnt) | |
1050 | set_root(nd); | |
1051 | if (unlikely(nd_jump_root(nd))) | |
1052 | return ERR_PTR(-ECHILD); | |
1053 | while (unlikely(*++res == '/')) | |
1054 | ; | |
1055 | } | |
1056 | if (!*res) | |
1057 | res = NULL; | |
1058 | return res; | |
1059 | } | |
1060 | ||
1061 | /* | |
1062 | * follow_up - Find the mountpoint of path's vfsmount | |
1063 | * | |
1064 | * Given a path, find the mountpoint of its source file system. | |
1065 | * Replace @path with the path of the mountpoint in the parent mount. | |
1066 | * Up is towards /. | |
1067 | * | |
1068 | * Return 1 if we went up a level and 0 if we were already at the | |
1069 | * root. | |
1070 | */ | |
1071 | int follow_up(struct path *path) | |
1072 | { | |
1073 | struct mount *mnt = real_mount(path->mnt); | |
1074 | struct mount *parent; | |
1075 | struct dentry *mountpoint; | |
1076 | ||
1077 | read_seqlock_excl(&mount_lock); | |
1078 | parent = mnt->mnt_parent; | |
1079 | if (parent == mnt) { | |
1080 | read_sequnlock_excl(&mount_lock); | |
1081 | return 0; | |
1082 | } | |
1083 | mntget(&parent->mnt); | |
1084 | mountpoint = dget(mnt->mnt_mountpoint); | |
1085 | read_sequnlock_excl(&mount_lock); | |
1086 | dput(path->dentry); | |
1087 | path->dentry = mountpoint; | |
1088 | mntput(path->mnt); | |
1089 | path->mnt = &parent->mnt; | |
1090 | return 1; | |
1091 | } | |
1092 | EXPORT_SYMBOL(follow_up); | |
1093 | ||
1094 | /* | |
1095 | * Perform an automount | |
1096 | * - return -EISDIR to tell follow_managed() to stop and return the path we | |
1097 | * were called with. | |
1098 | */ | |
1099 | static int follow_automount(struct path *path, struct nameidata *nd, | |
1100 | bool *need_mntput) | |
1101 | { | |
1102 | struct vfsmount *mnt; | |
1103 | int err; | |
1104 | ||
1105 | if (!path->dentry->d_op || !path->dentry->d_op->d_automount) | |
1106 | return -EREMOTE; | |
1107 | ||
1108 | /* We don't want to mount if someone's just doing a stat - | |
1109 | * unless they're stat'ing a directory and appended a '/' to | |
1110 | * the name. | |
1111 | * | |
1112 | * We do, however, want to mount if someone wants to open or | |
1113 | * create a file of any type under the mountpoint, wants to | |
1114 | * traverse through the mountpoint or wants to open the | |
1115 | * mounted directory. Also, autofs may mark negative dentries | |
1116 | * as being automount points. These will need the attentions | |
1117 | * of the daemon to instantiate them before they can be used. | |
1118 | */ | |
1119 | if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | | |
1120 | LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && | |
1121 | path->dentry->d_inode) | |
1122 | return -EISDIR; | |
1123 | ||
1124 | if (path->dentry->d_sb->s_user_ns != &init_user_ns) | |
1125 | return -EACCES; | |
1126 | ||
1127 | nd->total_link_count++; | |
1128 | if (nd->total_link_count >= 40) | |
1129 | return -ELOOP; | |
1130 | ||
1131 | mnt = path->dentry->d_op->d_automount(path); | |
1132 | if (IS_ERR(mnt)) { | |
1133 | /* | |
1134 | * The filesystem is allowed to return -EISDIR here to indicate | |
1135 | * it doesn't want to automount. For instance, autofs would do | |
1136 | * this so that its userspace daemon can mount on this dentry. | |
1137 | * | |
1138 | * However, we can only permit this if it's a terminal point in | |
1139 | * the path being looked up; if it wasn't then the remainder of | |
1140 | * the path is inaccessible and we should say so. | |
1141 | */ | |
1142 | if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT)) | |
1143 | return -EREMOTE; | |
1144 | return PTR_ERR(mnt); | |
1145 | } | |
1146 | ||
1147 | if (!mnt) /* mount collision */ | |
1148 | return 0; | |
1149 | ||
1150 | if (!*need_mntput) { | |
1151 | /* lock_mount() may release path->mnt on error */ | |
1152 | mntget(path->mnt); | |
1153 | *need_mntput = true; | |
1154 | } | |
1155 | err = finish_automount(mnt, path); | |
1156 | ||
1157 | switch (err) { | |
1158 | case -EBUSY: | |
1159 | /* Someone else made a mount here whilst we were busy */ | |
1160 | return 0; | |
1161 | case 0: | |
1162 | path_put(path); | |
1163 | path->mnt = mnt; | |
1164 | path->dentry = dget(mnt->mnt_root); | |
1165 | return 0; | |
1166 | default: | |
1167 | return err; | |
1168 | } | |
1169 | ||
1170 | } | |
1171 | ||
1172 | /* | |
1173 | * Handle a dentry that is managed in some way. | |
1174 | * - Flagged for transit management (autofs) | |
1175 | * - Flagged as mountpoint | |
1176 | * - Flagged as automount point | |
1177 | * | |
1178 | * This may only be called in refwalk mode. | |
1179 | * | |
1180 | * Serialization is taken care of in namespace.c | |
1181 | */ | |
1182 | static int follow_managed(struct path *path, struct nameidata *nd) | |
1183 | { | |
1184 | struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ | |
1185 | unsigned managed; | |
1186 | bool need_mntput = false; | |
1187 | int ret = 0; | |
1188 | ||
1189 | /* Given that we're not holding a lock here, we retain the value in a | |
1190 | * local variable for each dentry as we look at it so that we don't see | |
1191 | * the components of that value change under us */ | |
1192 | while (managed = ACCESS_ONCE(path->dentry->d_flags), | |
1193 | managed &= DCACHE_MANAGED_DENTRY, | |
1194 | unlikely(managed != 0)) { | |
1195 | /* Allow the filesystem to manage the transit without i_mutex | |
1196 | * being held. */ | |
1197 | if (managed & DCACHE_MANAGE_TRANSIT) { | |
1198 | BUG_ON(!path->dentry->d_op); | |
1199 | BUG_ON(!path->dentry->d_op->d_manage); | |
1200 | ret = path->dentry->d_op->d_manage(path, false); | |
1201 | if (ret < 0) | |
1202 | break; | |
1203 | } | |
1204 | ||
1205 | /* Transit to a mounted filesystem. */ | |
1206 | if (managed & DCACHE_MOUNTED) { | |
1207 | struct vfsmount *mounted = lookup_mnt(path); | |
1208 | if (mounted) { | |
1209 | dput(path->dentry); | |
1210 | if (need_mntput) | |
1211 | mntput(path->mnt); | |
1212 | path->mnt = mounted; | |
1213 | path->dentry = dget(mounted->mnt_root); | |
1214 | need_mntput = true; | |
1215 | continue; | |
1216 | } | |
1217 | ||
1218 | /* Something is mounted on this dentry in another | |
1219 | * namespace and/or whatever was mounted there in this | |
1220 | * namespace got unmounted before lookup_mnt() could | |
1221 | * get it */ | |
1222 | } | |
1223 | ||
1224 | /* Handle an automount point */ | |
1225 | if (managed & DCACHE_NEED_AUTOMOUNT) { | |
1226 | ret = follow_automount(path, nd, &need_mntput); | |
1227 | if (ret < 0) | |
1228 | break; | |
1229 | continue; | |
1230 | } | |
1231 | ||
1232 | /* We didn't change the current path point */ | |
1233 | break; | |
1234 | } | |
1235 | ||
1236 | if (need_mntput && path->mnt == mnt) | |
1237 | mntput(path->mnt); | |
1238 | if (ret == -EISDIR || !ret) | |
1239 | ret = 1; | |
1240 | if (need_mntput) | |
1241 | nd->flags |= LOOKUP_JUMPED; | |
1242 | if (unlikely(ret < 0)) | |
1243 | path_put_conditional(path, nd); | |
1244 | return ret; | |
1245 | } | |
1246 | ||
1247 | int follow_down_one(struct path *path) | |
1248 | { | |
1249 | struct vfsmount *mounted; | |
1250 | ||
1251 | mounted = lookup_mnt(path); | |
1252 | if (mounted) { | |
1253 | dput(path->dentry); | |
1254 | mntput(path->mnt); | |
1255 | path->mnt = mounted; | |
1256 | path->dentry = dget(mounted->mnt_root); | |
1257 | return 1; | |
1258 | } | |
1259 | return 0; | |
1260 | } | |
1261 | EXPORT_SYMBOL(follow_down_one); | |
1262 | ||
1263 | static inline int managed_dentry_rcu(const struct path *path) | |
1264 | { | |
1265 | return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ? | |
1266 | path->dentry->d_op->d_manage(path, true) : 0; | |
1267 | } | |
1268 | ||
1269 | /* | |
1270 | * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if | |
1271 | * we meet a managed dentry that would need blocking. | |
1272 | */ | |
1273 | static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, | |
1274 | struct inode **inode, unsigned *seqp) | |
1275 | { | |
1276 | for (;;) { | |
1277 | struct mount *mounted; | |
1278 | /* | |
1279 | * Don't forget we might have a non-mountpoint managed dentry | |
1280 | * that wants to block transit. | |
1281 | */ | |
1282 | switch (managed_dentry_rcu(path)) { | |
1283 | case -ECHILD: | |
1284 | default: | |
1285 | return false; | |
1286 | case -EISDIR: | |
1287 | return true; | |
1288 | case 0: | |
1289 | break; | |
1290 | } | |
1291 | ||
1292 | if (!d_mountpoint(path->dentry)) | |
1293 | return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); | |
1294 | ||
1295 | mounted = __lookup_mnt(path->mnt, path->dentry); | |
1296 | if (!mounted) | |
1297 | break; | |
1298 | path->mnt = &mounted->mnt; | |
1299 | path->dentry = mounted->mnt.mnt_root; | |
1300 | nd->flags |= LOOKUP_JUMPED; | |
1301 | *seqp = read_seqcount_begin(&path->dentry->d_seq); | |
1302 | /* | |
1303 | * Update the inode too. We don't need to re-check the | |
1304 | * dentry sequence number here after this d_inode read, | |
1305 | * because a mount-point is always pinned. | |
1306 | */ | |
1307 | *inode = path->dentry->d_inode; | |
1308 | } | |
1309 | return !read_seqretry(&mount_lock, nd->m_seq) && | |
1310 | !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); | |
1311 | } | |
1312 | ||
1313 | static int follow_dotdot_rcu(struct nameidata *nd) | |
1314 | { | |
1315 | struct inode *inode = nd->inode; | |
1316 | ||
1317 | while (1) { | |
1318 | if (path_equal(&nd->path, &nd->root)) | |
1319 | break; | |
1320 | if (nd->path.dentry != nd->path.mnt->mnt_root) { | |
1321 | struct dentry *old = nd->path.dentry; | |
1322 | struct dentry *parent = old->d_parent; | |
1323 | unsigned seq; | |
1324 | ||
1325 | inode = parent->d_inode; | |
1326 | seq = read_seqcount_begin(&parent->d_seq); | |
1327 | if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq))) | |
1328 | return -ECHILD; | |
1329 | nd->path.dentry = parent; | |
1330 | nd->seq = seq; | |
1331 | if (unlikely(!path_connected(&nd->path))) | |
1332 | return -ENOENT; | |
1333 | break; | |
1334 | } else { | |
1335 | struct mount *mnt = real_mount(nd->path.mnt); | |
1336 | struct mount *mparent = mnt->mnt_parent; | |
1337 | struct dentry *mountpoint = mnt->mnt_mountpoint; | |
1338 | struct inode *inode2 = mountpoint->d_inode; | |
1339 | unsigned seq = read_seqcount_begin(&mountpoint->d_seq); | |
1340 | if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) | |
1341 | return -ECHILD; | |
1342 | if (&mparent->mnt == nd->path.mnt) | |
1343 | break; | |
1344 | /* we know that mountpoint was pinned */ | |
1345 | nd->path.dentry = mountpoint; | |
1346 | nd->path.mnt = &mparent->mnt; | |
1347 | inode = inode2; | |
1348 | nd->seq = seq; | |
1349 | } | |
1350 | } | |
1351 | while (unlikely(d_mountpoint(nd->path.dentry))) { | |
1352 | struct mount *mounted; | |
1353 | mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); | |
1354 | if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) | |
1355 | return -ECHILD; | |
1356 | if (!mounted) | |
1357 | break; | |
1358 | nd->path.mnt = &mounted->mnt; | |
1359 | nd->path.dentry = mounted->mnt.mnt_root; | |
1360 | inode = nd->path.dentry->d_inode; | |
1361 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); | |
1362 | } | |
1363 | nd->inode = inode; | |
1364 | return 0; | |
1365 | } | |
1366 | ||
1367 | /* | |
1368 | * Follow down to the covering mount currently visible to userspace. At each | |
1369 | * point, the filesystem owning that dentry may be queried as to whether the | |
1370 | * caller is permitted to proceed or not. | |
1371 | */ | |
1372 | int follow_down(struct path *path) | |
1373 | { | |
1374 | unsigned managed; | |
1375 | int ret; | |
1376 | ||
1377 | while (managed = ACCESS_ONCE(path->dentry->d_flags), | |
1378 | unlikely(managed & DCACHE_MANAGED_DENTRY)) { | |
1379 | /* Allow the filesystem to manage the transit without i_mutex | |
1380 | * being held. | |
1381 | * | |
1382 | * We indicate to the filesystem if someone is trying to mount | |
1383 | * something here. This gives autofs the chance to deny anyone | |
1384 | * other than its daemon the right to mount on its | |
1385 | * superstructure. | |
1386 | * | |
1387 | * The filesystem may sleep at this point. | |
1388 | */ | |
1389 | if (managed & DCACHE_MANAGE_TRANSIT) { | |
1390 | BUG_ON(!path->dentry->d_op); | |
1391 | BUG_ON(!path->dentry->d_op->d_manage); | |
1392 | ret = path->dentry->d_op->d_manage(path, false); | |
1393 | if (ret < 0) | |
1394 | return ret == -EISDIR ? 0 : ret; | |
1395 | } | |
1396 | ||
1397 | /* Transit to a mounted filesystem. */ | |
1398 | if (managed & DCACHE_MOUNTED) { | |
1399 | struct vfsmount *mounted = lookup_mnt(path); | |
1400 | if (!mounted) | |
1401 | break; | |
1402 | dput(path->dentry); | |
1403 | mntput(path->mnt); | |
1404 | path->mnt = mounted; | |
1405 | path->dentry = dget(mounted->mnt_root); | |
1406 | continue; | |
1407 | } | |
1408 | ||
1409 | /* Don't handle automount points here */ | |
1410 | break; | |
1411 | } | |
1412 | return 0; | |
1413 | } | |
1414 | EXPORT_SYMBOL(follow_down); | |
1415 | ||
1416 | /* | |
1417 | * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() | |
1418 | */ | |
1419 | static void follow_mount(struct path *path) | |
1420 | { | |
1421 | while (d_mountpoint(path->dentry)) { | |
1422 | struct vfsmount *mounted = lookup_mnt(path); | |
1423 | if (!mounted) | |
1424 | break; | |
1425 | dput(path->dentry); | |
1426 | mntput(path->mnt); | |
1427 | path->mnt = mounted; | |
1428 | path->dentry = dget(mounted->mnt_root); | |
1429 | } | |
1430 | } | |
1431 | ||
1432 | static int path_parent_directory(struct path *path) | |
1433 | { | |
1434 | struct dentry *old = path->dentry; | |
1435 | /* rare case of legitimate dget_parent()... */ | |
1436 | path->dentry = dget_parent(path->dentry); | |
1437 | dput(old); | |
1438 | if (unlikely(!path_connected(path))) | |
1439 | return -ENOENT; | |
1440 | return 0; | |
1441 | } | |
1442 | ||
1443 | static int follow_dotdot(struct nameidata *nd) | |
1444 | { | |
1445 | while(1) { | |
1446 | if (nd->path.dentry == nd->root.dentry && | |
1447 | nd->path.mnt == nd->root.mnt) { | |
1448 | break; | |
1449 | } | |
1450 | if (nd->path.dentry != nd->path.mnt->mnt_root) { | |
1451 | int ret = path_parent_directory(&nd->path); | |
1452 | if (ret) | |
1453 | return ret; | |
1454 | break; | |
1455 | } | |
1456 | if (!follow_up(&nd->path)) | |
1457 | break; | |
1458 | } | |
1459 | follow_mount(&nd->path); | |
1460 | nd->inode = nd->path.dentry->d_inode; | |
1461 | return 0; | |
1462 | } | |
1463 | ||
1464 | /* | |
1465 | * This looks up the name in dcache and possibly revalidates the found dentry. | |
1466 | * NULL is returned if the dentry does not exist in the cache. | |
1467 | */ | |
1468 | static struct dentry *lookup_dcache(const struct qstr *name, | |
1469 | struct dentry *dir, | |
1470 | unsigned int flags) | |
1471 | { | |
1472 | struct dentry *dentry; | |
1473 | int error; | |
1474 | ||
1475 | dentry = d_lookup(dir, name); | |
1476 | if (dentry) { | |
1477 | if (dentry->d_flags & DCACHE_OP_REVALIDATE) { | |
1478 | error = d_revalidate(dentry, flags); | |
1479 | if (unlikely(error <= 0)) { | |
1480 | if (!error) | |
1481 | d_invalidate(dentry); | |
1482 | dput(dentry); | |
1483 | return ERR_PTR(error); | |
1484 | } | |
1485 | } | |
1486 | } | |
1487 | return dentry; | |
1488 | } | |
1489 | ||
1490 | /* | |
1491 | * Call i_op->lookup on the dentry. The dentry must be negative and | |
1492 | * unhashed. | |
1493 | * | |
1494 | * dir->d_inode->i_mutex must be held | |
1495 | */ | |
1496 | static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, | |
1497 | unsigned int flags) | |
1498 | { | |
1499 | struct dentry *old; | |
1500 | ||
1501 | /* Don't create child dentry for a dead directory. */ | |
1502 | if (unlikely(IS_DEADDIR(dir))) { | |
1503 | dput(dentry); | |
1504 | return ERR_PTR(-ENOENT); | |
1505 | } | |
1506 | ||
1507 | old = dir->i_op->lookup(dir, dentry, flags); | |
1508 | if (unlikely(old)) { | |
1509 | dput(dentry); | |
1510 | dentry = old; | |
1511 | } | |
1512 | return dentry; | |
1513 | } | |
1514 | ||
1515 | static struct dentry *__lookup_hash(const struct qstr *name, | |
1516 | struct dentry *base, unsigned int flags) | |
1517 | { | |
1518 | struct dentry *dentry = lookup_dcache(name, base, flags); | |
1519 | ||
1520 | if (dentry) | |
1521 | return dentry; | |
1522 | ||
1523 | dentry = d_alloc(base, name); | |
1524 | if (unlikely(!dentry)) | |
1525 | return ERR_PTR(-ENOMEM); | |
1526 | ||
1527 | return lookup_real(base->d_inode, dentry, flags); | |
1528 | } | |
1529 | ||
1530 | static int lookup_fast(struct nameidata *nd, | |
1531 | struct path *path, struct inode **inode, | |
1532 | unsigned *seqp) | |
1533 | { | |
1534 | struct vfsmount *mnt = nd->path.mnt; | |
1535 | struct dentry *dentry, *parent = nd->path.dentry; | |
1536 | int status = 1; | |
1537 | int err; | |
1538 | ||
1539 | /* | |
1540 | * Rename seqlock is not required here because in the off chance | |
1541 | * of a false negative due to a concurrent rename, the caller is | |
1542 | * going to fall back to non-racy lookup. | |
1543 | */ | |
1544 | if (nd->flags & LOOKUP_RCU) { | |
1545 | unsigned seq; | |
1546 | bool negative; | |
1547 | dentry = __d_lookup_rcu(parent, &nd->last, &seq); | |
1548 | if (unlikely(!dentry)) { | |
1549 | if (unlazy_walk(nd, NULL, 0)) | |
1550 | return -ECHILD; | |
1551 | return 0; | |
1552 | } | |
1553 | ||
1554 | /* | |
1555 | * This sequence count validates that the inode matches | |
1556 | * the dentry name information from lookup. | |
1557 | */ | |
1558 | *inode = d_backing_inode(dentry); | |
1559 | negative = d_is_negative(dentry); | |
1560 | if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) | |
1561 | return -ECHILD; | |
1562 | ||
1563 | /* | |
1564 | * This sequence count validates that the parent had no | |
1565 | * changes while we did the lookup of the dentry above. | |
1566 | * | |
1567 | * The memory barrier in read_seqcount_begin of child is | |
1568 | * enough, we can use __read_seqcount_retry here. | |
1569 | */ | |
1570 | if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq))) | |
1571 | return -ECHILD; | |
1572 | ||
1573 | *seqp = seq; | |
1574 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) | |
1575 | status = d_revalidate(dentry, nd->flags); | |
1576 | if (unlikely(status <= 0)) { | |
1577 | if (unlazy_walk(nd, dentry, seq)) | |
1578 | return -ECHILD; | |
1579 | if (status == -ECHILD) | |
1580 | status = d_revalidate(dentry, nd->flags); | |
1581 | } else { | |
1582 | /* | |
1583 | * Note: do negative dentry check after revalidation in | |
1584 | * case that drops it. | |
1585 | */ | |
1586 | if (unlikely(negative)) | |
1587 | return -ENOENT; | |
1588 | path->mnt = mnt; | |
1589 | path->dentry = dentry; | |
1590 | if (likely(__follow_mount_rcu(nd, path, inode, seqp))) | |
1591 | return 1; | |
1592 | if (unlazy_walk(nd, dentry, seq)) | |
1593 | return -ECHILD; | |
1594 | } | |
1595 | } else { | |
1596 | dentry = __d_lookup(parent, &nd->last); | |
1597 | if (unlikely(!dentry)) | |
1598 | return 0; | |
1599 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) | |
1600 | status = d_revalidate(dentry, nd->flags); | |
1601 | } | |
1602 | if (unlikely(status <= 0)) { | |
1603 | if (!status) | |
1604 | d_invalidate(dentry); | |
1605 | dput(dentry); | |
1606 | return status; | |
1607 | } | |
1608 | if (unlikely(d_is_negative(dentry))) { | |
1609 | dput(dentry); | |
1610 | return -ENOENT; | |
1611 | } | |
1612 | ||
1613 | path->mnt = mnt; | |
1614 | path->dentry = dentry; | |
1615 | err = follow_managed(path, nd); | |
1616 | if (likely(err > 0)) | |
1617 | *inode = d_backing_inode(path->dentry); | |
1618 | return err; | |
1619 | } | |
1620 | ||
1621 | /* Fast lookup failed, do it the slow way */ | |
1622 | static struct dentry *lookup_slow(const struct qstr *name, | |
1623 | struct dentry *dir, | |
1624 | unsigned int flags) | |
1625 | { | |
1626 | struct dentry *dentry = ERR_PTR(-ENOENT), *old; | |
1627 | struct inode *inode = dir->d_inode; | |
1628 | DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); | |
1629 | ||
1630 | inode_lock_shared(inode); | |
1631 | /* Don't go there if it's already dead */ | |
1632 | if (unlikely(IS_DEADDIR(inode))) | |
1633 | goto out; | |
1634 | again: | |
1635 | dentry = d_alloc_parallel(dir, name, &wq); | |
1636 | if (IS_ERR(dentry)) | |
1637 | goto out; | |
1638 | if (unlikely(!d_in_lookup(dentry))) { | |
1639 | if ((dentry->d_flags & DCACHE_OP_REVALIDATE) && | |
1640 | !(flags & LOOKUP_NO_REVAL)) { | |
1641 | int error = d_revalidate(dentry, flags); | |
1642 | if (unlikely(error <= 0)) { | |
1643 | if (!error) { | |
1644 | d_invalidate(dentry); | |
1645 | dput(dentry); | |
1646 | goto again; | |
1647 | } | |
1648 | dput(dentry); | |
1649 | dentry = ERR_PTR(error); | |
1650 | } | |
1651 | } | |
1652 | } else { | |
1653 | old = inode->i_op->lookup(inode, dentry, flags); | |
1654 | d_lookup_done(dentry); | |
1655 | if (unlikely(old)) { | |
1656 | dput(dentry); | |
1657 | dentry = old; | |
1658 | } | |
1659 | } | |
1660 | out: | |
1661 | inode_unlock_shared(inode); | |
1662 | return dentry; | |
1663 | } | |
1664 | ||
1665 | static inline int may_lookup(struct nameidata *nd) | |
1666 | { | |
1667 | if (nd->flags & LOOKUP_RCU) { | |
1668 | int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); | |
1669 | if (err != -ECHILD) | |
1670 | return err; | |
1671 | if (unlazy_walk(nd, NULL, 0)) | |
1672 | return -ECHILD; | |
1673 | } | |
1674 | return inode_permission(nd->inode, MAY_EXEC); | |
1675 | } | |
1676 | ||
1677 | static inline int handle_dots(struct nameidata *nd, int type) | |
1678 | { | |
1679 | if (type == LAST_DOTDOT) { | |
1680 | if (!nd->root.mnt) | |
1681 | set_root(nd); | |
1682 | if (nd->flags & LOOKUP_RCU) { | |
1683 | return follow_dotdot_rcu(nd); | |
1684 | } else | |
1685 | return follow_dotdot(nd); | |
1686 | } | |
1687 | return 0; | |
1688 | } | |
1689 | ||
1690 | static int pick_link(struct nameidata *nd, struct path *link, | |
1691 | struct inode *inode, unsigned seq) | |
1692 | { | |
1693 | int error; | |
1694 | struct saved *last; | |
1695 | if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) { | |
1696 | path_to_nameidata(link, nd); | |
1697 | return -ELOOP; | |
1698 | } | |
1699 | if (!(nd->flags & LOOKUP_RCU)) { | |
1700 | if (link->mnt == nd->path.mnt) | |
1701 | mntget(link->mnt); | |
1702 | } | |
1703 | error = nd_alloc_stack(nd); | |
1704 | if (unlikely(error)) { | |
1705 | if (error == -ECHILD) { | |
1706 | if (unlikely(unlazy_link(nd, link, seq))) | |
1707 | return -ECHILD; | |
1708 | error = nd_alloc_stack(nd); | |
1709 | } | |
1710 | if (error) { | |
1711 | path_put(link); | |
1712 | return error; | |
1713 | } | |
1714 | } | |
1715 | ||
1716 | last = nd->stack + nd->depth++; | |
1717 | last->link = *link; | |
1718 | clear_delayed_call(&last->done); | |
1719 | nd->link_inode = inode; | |
1720 | last->seq = seq; | |
1721 | return 1; | |
1722 | } | |
1723 | ||
1724 | enum {WALK_FOLLOW = 1, WALK_MORE = 2}; | |
1725 | ||
1726 | /* | |
1727 | * Do we need to follow links? We _really_ want to be able | |
1728 | * to do this check without having to look at inode->i_op, | |
1729 | * so we keep a cache of "no, this doesn't need follow_link" | |
1730 | * for the common case. | |
1731 | */ | |
1732 | static inline int step_into(struct nameidata *nd, struct path *path, | |
1733 | int flags, struct inode *inode, unsigned seq) | |
1734 | { | |
1735 | if (!(flags & WALK_MORE) && nd->depth) | |
1736 | put_link(nd); | |
1737 | if (likely(!d_is_symlink(path->dentry)) || | |
1738 | !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) { | |
1739 | /* not a symlink or should not follow */ | |
1740 | path_to_nameidata(path, nd); | |
1741 | nd->inode = inode; | |
1742 | nd->seq = seq; | |
1743 | return 0; | |
1744 | } | |
1745 | /* make sure that d_is_symlink above matches inode */ | |
1746 | if (nd->flags & LOOKUP_RCU) { | |
1747 | if (read_seqcount_retry(&path->dentry->d_seq, seq)) | |
1748 | return -ECHILD; | |
1749 | } | |
1750 | return pick_link(nd, path, inode, seq); | |
1751 | } | |
1752 | ||
1753 | static int walk_component(struct nameidata *nd, int flags) | |
1754 | { | |
1755 | struct path path; | |
1756 | struct inode *inode; | |
1757 | unsigned seq; | |
1758 | int err; | |
1759 | /* | |
1760 | * "." and ".." are special - ".." especially so because it has | |
1761 | * to be able to know about the current root directory and | |
1762 | * parent relationships. | |
1763 | */ | |
1764 | if (unlikely(nd->last_type != LAST_NORM)) { | |
1765 | err = handle_dots(nd, nd->last_type); | |
1766 | if (!(flags & WALK_MORE) && nd->depth) | |
1767 | put_link(nd); | |
1768 | return err; | |
1769 | } | |
1770 | err = lookup_fast(nd, &path, &inode, &seq); | |
1771 | if (unlikely(err <= 0)) { | |
1772 | if (err < 0) | |
1773 | return err; | |
1774 | path.dentry = lookup_slow(&nd->last, nd->path.dentry, | |
1775 | nd->flags); | |
1776 | if (IS_ERR(path.dentry)) | |
1777 | return PTR_ERR(path.dentry); | |
1778 | ||
1779 | path.mnt = nd->path.mnt; | |
1780 | err = follow_managed(&path, nd); | |
1781 | if (unlikely(err < 0)) | |
1782 | return err; | |
1783 | ||
1784 | if (unlikely(d_is_negative(path.dentry))) { | |
1785 | path_to_nameidata(&path, nd); | |
1786 | return -ENOENT; | |
1787 | } | |
1788 | ||
1789 | seq = 0; /* we are already out of RCU mode */ | |
1790 | inode = d_backing_inode(path.dentry); | |
1791 | } | |
1792 | ||
1793 | return step_into(nd, &path, flags, inode, seq); | |
1794 | } | |
1795 | ||
1796 | /* | |
1797 | * We can do the critical dentry name comparison and hashing | |
1798 | * operations one word at a time, but we are limited to: | |
1799 | * | |
1800 | * - Architectures with fast unaligned word accesses. We could | |
1801 | * do a "get_unaligned()" if this helps and is sufficiently | |
1802 | * fast. | |
1803 | * | |
1804 | * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we | |
1805 | * do not trap on the (extremely unlikely) case of a page | |
1806 | * crossing operation. | |
1807 | * | |
1808 | * - Furthermore, we need an efficient 64-bit compile for the | |
1809 | * 64-bit case in order to generate the "number of bytes in | |
1810 | * the final mask". Again, that could be replaced with a | |
1811 | * efficient population count instruction or similar. | |
1812 | */ | |
1813 | #ifdef CONFIG_DCACHE_WORD_ACCESS | |
1814 | ||
1815 | #include <asm/word-at-a-time.h> | |
1816 | ||
1817 | #ifdef HASH_MIX | |
1818 | ||
1819 | /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */ | |
1820 | ||
1821 | #elif defined(CONFIG_64BIT) | |
1822 | /* | |
1823 | * Register pressure in the mixing function is an issue, particularly | |
1824 | * on 32-bit x86, but almost any function requires one state value and | |
1825 | * one temporary. Instead, use a function designed for two state values | |
1826 | * and no temporaries. | |
1827 | * | |
1828 | * This function cannot create a collision in only two iterations, so | |
1829 | * we have two iterations to achieve avalanche. In those two iterations, | |
1830 | * we have six layers of mixing, which is enough to spread one bit's | |
1831 | * influence out to 2^6 = 64 state bits. | |
1832 | * | |
1833 | * Rotate constants are scored by considering either 64 one-bit input | |
1834 | * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the | |
1835 | * probability of that delta causing a change to each of the 128 output | |
1836 | * bits, using a sample of random initial states. | |
1837 | * | |
1838 | * The Shannon entropy of the computed probabilities is then summed | |
1839 | * to produce a score. Ideally, any input change has a 50% chance of | |
1840 | * toggling any given output bit. | |
1841 | * | |
1842 | * Mixing scores (in bits) for (12,45): | |
1843 | * Input delta: 1-bit 2-bit | |
1844 | * 1 round: 713.3 42542.6 | |
1845 | * 2 rounds: 2753.7 140389.8 | |
1846 | * 3 rounds: 5954.1 233458.2 | |
1847 | * 4 rounds: 7862.6 256672.2 | |
1848 | * Perfect: 8192 258048 | |
1849 | * (64*128) (64*63/2 * 128) | |
1850 | */ | |
1851 | #define HASH_MIX(x, y, a) \ | |
1852 | ( x ^= (a), \ | |
1853 | y ^= x, x = rol64(x,12),\ | |
1854 | x += y, y = rol64(y,45),\ | |
1855 | y *= 9 ) | |
1856 | ||
1857 | /* | |
1858 | * Fold two longs into one 32-bit hash value. This must be fast, but | |
1859 | * latency isn't quite as critical, as there is a fair bit of additional | |
1860 | * work done before the hash value is used. | |
1861 | */ | |
1862 | static inline unsigned int fold_hash(unsigned long x, unsigned long y) | |
1863 | { | |
1864 | y ^= x * GOLDEN_RATIO_64; | |
1865 | y *= GOLDEN_RATIO_64; | |
1866 | return y >> 32; | |
1867 | } | |
1868 | ||
1869 | #else /* 32-bit case */ | |
1870 | ||
1871 | /* | |
1872 | * Mixing scores (in bits) for (7,20): | |
1873 | * Input delta: 1-bit 2-bit | |
1874 | * 1 round: 330.3 9201.6 | |
1875 | * 2 rounds: 1246.4 25475.4 | |
1876 | * 3 rounds: 1907.1 31295.1 | |
1877 | * 4 rounds: 2042.3 31718.6 | |
1878 | * Perfect: 2048 31744 | |
1879 | * (32*64) (32*31/2 * 64) | |
1880 | */ | |
1881 | #define HASH_MIX(x, y, a) \ | |
1882 | ( x ^= (a), \ | |
1883 | y ^= x, x = rol32(x, 7),\ | |
1884 | x += y, y = rol32(y,20),\ | |
1885 | y *= 9 ) | |
1886 | ||
1887 | static inline unsigned int fold_hash(unsigned long x, unsigned long y) | |
1888 | { | |
1889 | /* Use arch-optimized multiply if one exists */ | |
1890 | return __hash_32(y ^ __hash_32(x)); | |
1891 | } | |
1892 | ||
1893 | #endif | |
1894 | ||
1895 | /* | |
1896 | * Return the hash of a string of known length. This is carfully | |
1897 | * designed to match hash_name(), which is the more critical function. | |
1898 | * In particular, we must end by hashing a final word containing 0..7 | |
1899 | * payload bytes, to match the way that hash_name() iterates until it | |
1900 | * finds the delimiter after the name. | |
1901 | */ | |
1902 | unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) | |
1903 | { | |
1904 | unsigned long a, x = 0, y = (unsigned long)salt; | |
1905 | ||
1906 | for (;;) { | |
1907 | if (!len) | |
1908 | goto done; | |
1909 | a = load_unaligned_zeropad(name); | |
1910 | if (len < sizeof(unsigned long)) | |
1911 | break; | |
1912 | HASH_MIX(x, y, a); | |
1913 | name += sizeof(unsigned long); | |
1914 | len -= sizeof(unsigned long); | |
1915 | } | |
1916 | x ^= a & bytemask_from_count(len); | |
1917 | done: | |
1918 | return fold_hash(x, y); | |
1919 | } | |
1920 | EXPORT_SYMBOL(full_name_hash); | |
1921 | ||
1922 | /* Return the "hash_len" (hash and length) of a null-terminated string */ | |
1923 | u64 hashlen_string(const void *salt, const char *name) | |
1924 | { | |
1925 | unsigned long a = 0, x = 0, y = (unsigned long)salt; | |
1926 | unsigned long adata, mask, len; | |
1927 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; | |
1928 | ||
1929 | len = 0; | |
1930 | goto inside; | |
1931 | ||
1932 | do { | |
1933 | HASH_MIX(x, y, a); | |
1934 | len += sizeof(unsigned long); | |
1935 | inside: | |
1936 | a = load_unaligned_zeropad(name+len); | |
1937 | } while (!has_zero(a, &adata, &constants)); | |
1938 | ||
1939 | adata = prep_zero_mask(a, adata, &constants); | |
1940 | mask = create_zero_mask(adata); | |
1941 | x ^= a & zero_bytemask(mask); | |
1942 | ||
1943 | return hashlen_create(fold_hash(x, y), len + find_zero(mask)); | |
1944 | } | |
1945 | EXPORT_SYMBOL(hashlen_string); | |
1946 | ||
1947 | /* | |
1948 | * Calculate the length and hash of the path component, and | |
1949 | * return the "hash_len" as the result. | |
1950 | */ | |
1951 | static inline u64 hash_name(const void *salt, const char *name) | |
1952 | { | |
1953 | unsigned long a = 0, b, x = 0, y = (unsigned long)salt; | |
1954 | unsigned long adata, bdata, mask, len; | |
1955 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; | |
1956 | ||
1957 | len = 0; | |
1958 | goto inside; | |
1959 | ||
1960 | do { | |
1961 | HASH_MIX(x, y, a); | |
1962 | len += sizeof(unsigned long); | |
1963 | inside: | |
1964 | a = load_unaligned_zeropad(name+len); | |
1965 | b = a ^ REPEAT_BYTE('/'); | |
1966 | } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); | |
1967 | ||
1968 | adata = prep_zero_mask(a, adata, &constants); | |
1969 | bdata = prep_zero_mask(b, bdata, &constants); | |
1970 | mask = create_zero_mask(adata | bdata); | |
1971 | x ^= a & zero_bytemask(mask); | |
1972 | ||
1973 | return hashlen_create(fold_hash(x, y), len + find_zero(mask)); | |
1974 | } | |
1975 | ||
1976 | #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */ | |
1977 | ||
1978 | /* Return the hash of a string of known length */ | |
1979 | unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) | |
1980 | { | |
1981 | unsigned long hash = init_name_hash(salt); | |
1982 | while (len--) | |
1983 | hash = partial_name_hash((unsigned char)*name++, hash); | |
1984 | return end_name_hash(hash); | |
1985 | } | |
1986 | EXPORT_SYMBOL(full_name_hash); | |
1987 | ||
1988 | /* Return the "hash_len" (hash and length) of a null-terminated string */ | |
1989 | u64 hashlen_string(const void *salt, const char *name) | |
1990 | { | |
1991 | unsigned long hash = init_name_hash(salt); | |
1992 | unsigned long len = 0, c; | |
1993 | ||
1994 | c = (unsigned char)*name; | |
1995 | while (c) { | |
1996 | len++; | |
1997 | hash = partial_name_hash(c, hash); | |
1998 | c = (unsigned char)name[len]; | |
1999 | } | |
2000 | return hashlen_create(end_name_hash(hash), len); | |
2001 | } | |
2002 | EXPORT_SYMBOL(hashlen_string); | |
2003 | ||
2004 | /* | |
2005 | * We know there's a real path component here of at least | |
2006 | * one character. | |
2007 | */ | |
2008 | static inline u64 hash_name(const void *salt, const char *name) | |
2009 | { | |
2010 | unsigned long hash = init_name_hash(salt); | |
2011 | unsigned long len = 0, c; | |
2012 | ||
2013 | c = (unsigned char)*name; | |
2014 | do { | |
2015 | len++; | |
2016 | hash = partial_name_hash(c, hash); | |
2017 | c = (unsigned char)name[len]; | |
2018 | } while (c && c != '/'); | |
2019 | return hashlen_create(end_name_hash(hash), len); | |
2020 | } | |
2021 | ||
2022 | #endif | |
2023 | ||
2024 | /* | |
2025 | * Name resolution. | |
2026 | * This is the basic name resolution function, turning a pathname into | |
2027 | * the final dentry. We expect 'base' to be positive and a directory. | |
2028 | * | |
2029 | * Returns 0 and nd will have valid dentry and mnt on success. | |
2030 | * Returns error and drops reference to input namei data on failure. | |
2031 | */ | |
2032 | static int link_path_walk(const char *name, struct nameidata *nd) | |
2033 | { | |
2034 | int err; | |
2035 | ||
2036 | while (*name=='/') | |
2037 | name++; | |
2038 | if (!*name) | |
2039 | return 0; | |
2040 | ||
2041 | /* At this point we know we have a real path component. */ | |
2042 | for(;;) { | |
2043 | u64 hash_len; | |
2044 | int type; | |
2045 | ||
2046 | err = may_lookup(nd); | |
2047 | if (err) | |
2048 | return err; | |
2049 | ||
2050 | hash_len = hash_name(nd->path.dentry, name); | |
2051 | ||
2052 | type = LAST_NORM; | |
2053 | if (name[0] == '.') switch (hashlen_len(hash_len)) { | |
2054 | case 2: | |
2055 | if (name[1] == '.') { | |
2056 | type = LAST_DOTDOT; | |
2057 | nd->flags |= LOOKUP_JUMPED; | |
2058 | } | |
2059 | break; | |
2060 | case 1: | |
2061 | type = LAST_DOT; | |
2062 | } | |
2063 | if (likely(type == LAST_NORM)) { | |
2064 | struct dentry *parent = nd->path.dentry; | |
2065 | nd->flags &= ~LOOKUP_JUMPED; | |
2066 | if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { | |
2067 | struct qstr this = { { .hash_len = hash_len }, .name = name }; | |
2068 | err = parent->d_op->d_hash(parent, &this); | |
2069 | if (err < 0) | |
2070 | return err; | |
2071 | hash_len = this.hash_len; | |
2072 | name = this.name; | |
2073 | } | |
2074 | } | |
2075 | ||
2076 | nd->last.hash_len = hash_len; | |
2077 | nd->last.name = name; | |
2078 | nd->last_type = type; | |
2079 | ||
2080 | name += hashlen_len(hash_len); | |
2081 | if (!*name) | |
2082 | goto OK; | |
2083 | /* | |
2084 | * If it wasn't NUL, we know it was '/'. Skip that | |
2085 | * slash, and continue until no more slashes. | |
2086 | */ | |
2087 | do { | |
2088 | name++; | |
2089 | } while (unlikely(*name == '/')); | |
2090 | if (unlikely(!*name)) { | |
2091 | OK: | |
2092 | /* pathname body, done */ | |
2093 | if (!nd->depth) | |
2094 | return 0; | |
2095 | name = nd->stack[nd->depth - 1].name; | |
2096 | /* trailing symlink, done */ | |
2097 | if (!name) | |
2098 | return 0; | |
2099 | /* last component of nested symlink */ | |
2100 | err = walk_component(nd, WALK_FOLLOW); | |
2101 | } else { | |
2102 | /* not the last component */ | |
2103 | err = walk_component(nd, WALK_FOLLOW | WALK_MORE); | |
2104 | } | |
2105 | if (err < 0) | |
2106 | return err; | |
2107 | ||
2108 | if (err) { | |
2109 | const char *s = get_link(nd); | |
2110 | ||
2111 | if (IS_ERR(s)) | |
2112 | return PTR_ERR(s); | |
2113 | err = 0; | |
2114 | if (unlikely(!s)) { | |
2115 | /* jumped */ | |
2116 | put_link(nd); | |
2117 | } else { | |
2118 | nd->stack[nd->depth - 1].name = name; | |
2119 | name = s; | |
2120 | continue; | |
2121 | } | |
2122 | } | |
2123 | if (unlikely(!d_can_lookup(nd->path.dentry))) { | |
2124 | if (nd->flags & LOOKUP_RCU) { | |
2125 | if (unlazy_walk(nd, NULL, 0)) | |
2126 | return -ECHILD; | |
2127 | } | |
2128 | return -ENOTDIR; | |
2129 | } | |
2130 | } | |
2131 | } | |
2132 | ||
2133 | static const char *path_init(struct nameidata *nd, unsigned flags) | |
2134 | { | |
2135 | int retval = 0; | |
2136 | const char *s = nd->name->name; | |
2137 | ||
2138 | nd->last_type = LAST_ROOT; /* if there are only slashes... */ | |
2139 | nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT; | |
2140 | nd->depth = 0; | |
2141 | if (flags & LOOKUP_ROOT) { | |
2142 | struct dentry *root = nd->root.dentry; | |
2143 | struct inode *inode = root->d_inode; | |
2144 | if (*s) { | |
2145 | if (!d_can_lookup(root)) | |
2146 | return ERR_PTR(-ENOTDIR); | |
2147 | retval = inode_permission(inode, MAY_EXEC); | |
2148 | if (retval) | |
2149 | return ERR_PTR(retval); | |
2150 | } | |
2151 | nd->path = nd->root; | |
2152 | nd->inode = inode; | |
2153 | if (flags & LOOKUP_RCU) { | |
2154 | rcu_read_lock(); | |
2155 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
2156 | nd->root_seq = nd->seq; | |
2157 | nd->m_seq = read_seqbegin(&mount_lock); | |
2158 | } else { | |
2159 | path_get(&nd->path); | |
2160 | } | |
2161 | return s; | |
2162 | } | |
2163 | ||
2164 | nd->root.mnt = NULL; | |
2165 | nd->path.mnt = NULL; | |
2166 | nd->path.dentry = NULL; | |
2167 | ||
2168 | nd->m_seq = read_seqbegin(&mount_lock); | |
2169 | if (*s == '/') { | |
2170 | if (flags & LOOKUP_RCU) | |
2171 | rcu_read_lock(); | |
2172 | set_root(nd); | |
2173 | if (likely(!nd_jump_root(nd))) | |
2174 | return s; | |
2175 | nd->root.mnt = NULL; | |
2176 | rcu_read_unlock(); | |
2177 | return ERR_PTR(-ECHILD); | |
2178 | } else if (nd->dfd == AT_FDCWD) { | |
2179 | if (flags & LOOKUP_RCU) { | |
2180 | struct fs_struct *fs = current->fs; | |
2181 | unsigned seq; | |
2182 | ||
2183 | rcu_read_lock(); | |
2184 | ||
2185 | do { | |
2186 | seq = read_seqcount_begin(&fs->seq); | |
2187 | nd->path = fs->pwd; | |
2188 | nd->inode = nd->path.dentry->d_inode; | |
2189 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
2190 | } while (read_seqcount_retry(&fs->seq, seq)); | |
2191 | } else { | |
2192 | get_fs_pwd(current->fs, &nd->path); | |
2193 | nd->inode = nd->path.dentry->d_inode; | |
2194 | } | |
2195 | return s; | |
2196 | } else { | |
2197 | /* Caller must check execute permissions on the starting path component */ | |
2198 | struct fd f = fdget_raw(nd->dfd); | |
2199 | struct dentry *dentry; | |
2200 | ||
2201 | if (!f.file) | |
2202 | return ERR_PTR(-EBADF); | |
2203 | ||
2204 | dentry = f.file->f_path.dentry; | |
2205 | ||
2206 | if (*s) { | |
2207 | if (!d_can_lookup(dentry)) { | |
2208 | fdput(f); | |
2209 | return ERR_PTR(-ENOTDIR); | |
2210 | } | |
2211 | } | |
2212 | ||
2213 | nd->path = f.file->f_path; | |
2214 | if (flags & LOOKUP_RCU) { | |
2215 | rcu_read_lock(); | |
2216 | nd->inode = nd->path.dentry->d_inode; | |
2217 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); | |
2218 | } else { | |
2219 | path_get(&nd->path); | |
2220 | nd->inode = nd->path.dentry->d_inode; | |
2221 | } | |
2222 | fdput(f); | |
2223 | return s; | |
2224 | } | |
2225 | } | |
2226 | ||
2227 | static const char *trailing_symlink(struct nameidata *nd) | |
2228 | { | |
2229 | const char *s; | |
2230 | int error = may_follow_link(nd); | |
2231 | if (unlikely(error)) | |
2232 | return ERR_PTR(error); | |
2233 | nd->flags |= LOOKUP_PARENT; | |
2234 | nd->stack[0].name = NULL; | |
2235 | s = get_link(nd); | |
2236 | return s ? s : ""; | |
2237 | } | |
2238 | ||
2239 | static inline int lookup_last(struct nameidata *nd) | |
2240 | { | |
2241 | if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) | |
2242 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; | |
2243 | ||
2244 | nd->flags &= ~LOOKUP_PARENT; | |
2245 | return walk_component(nd, 0); | |
2246 | } | |
2247 | ||
2248 | /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ | |
2249 | static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path) | |
2250 | { | |
2251 | const char *s = path_init(nd, flags); | |
2252 | int err; | |
2253 | ||
2254 | if (IS_ERR(s)) | |
2255 | return PTR_ERR(s); | |
2256 | while (!(err = link_path_walk(s, nd)) | |
2257 | && ((err = lookup_last(nd)) > 0)) { | |
2258 | s = trailing_symlink(nd); | |
2259 | if (IS_ERR(s)) { | |
2260 | err = PTR_ERR(s); | |
2261 | break; | |
2262 | } | |
2263 | } | |
2264 | if (!err) | |
2265 | err = complete_walk(nd); | |
2266 | ||
2267 | if (!err && nd->flags & LOOKUP_DIRECTORY) | |
2268 | if (!d_can_lookup(nd->path.dentry)) | |
2269 | err = -ENOTDIR; | |
2270 | if (!err) { | |
2271 | *path = nd->path; | |
2272 | nd->path.mnt = NULL; | |
2273 | nd->path.dentry = NULL; | |
2274 | } | |
2275 | terminate_walk(nd); | |
2276 | return err; | |
2277 | } | |
2278 | ||
2279 | static int filename_lookup(int dfd, struct filename *name, unsigned flags, | |
2280 | struct path *path, struct path *root) | |
2281 | { | |
2282 | int retval; | |
2283 | struct nameidata nd; | |
2284 | if (IS_ERR(name)) | |
2285 | return PTR_ERR(name); | |
2286 | if (unlikely(root)) { | |
2287 | nd.root = *root; | |
2288 | flags |= LOOKUP_ROOT; | |
2289 | } | |
2290 | set_nameidata(&nd, dfd, name); | |
2291 | retval = path_lookupat(&nd, flags | LOOKUP_RCU, path); | |
2292 | if (unlikely(retval == -ECHILD)) | |
2293 | retval = path_lookupat(&nd, flags, path); | |
2294 | if (unlikely(retval == -ESTALE)) | |
2295 | retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path); | |
2296 | ||
2297 | if (likely(!retval)) | |
2298 | audit_inode(name, path->dentry, flags & LOOKUP_PARENT); | |
2299 | restore_nameidata(); | |
2300 | putname(name); | |
2301 | return retval; | |
2302 | } | |
2303 | ||
2304 | /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ | |
2305 | static int path_parentat(struct nameidata *nd, unsigned flags, | |
2306 | struct path *parent) | |
2307 | { | |
2308 | const char *s = path_init(nd, flags); | |
2309 | int err; | |
2310 | if (IS_ERR(s)) | |
2311 | return PTR_ERR(s); | |
2312 | err = link_path_walk(s, nd); | |
2313 | if (!err) | |
2314 | err = complete_walk(nd); | |
2315 | if (!err) { | |
2316 | *parent = nd->path; | |
2317 | nd->path.mnt = NULL; | |
2318 | nd->path.dentry = NULL; | |
2319 | } | |
2320 | terminate_walk(nd); | |
2321 | return err; | |
2322 | } | |
2323 | ||
2324 | static struct filename *filename_parentat(int dfd, struct filename *name, | |
2325 | unsigned int flags, struct path *parent, | |
2326 | struct qstr *last, int *type) | |
2327 | { | |
2328 | int retval; | |
2329 | struct nameidata nd; | |
2330 | ||
2331 | if (IS_ERR(name)) | |
2332 | return name; | |
2333 | set_nameidata(&nd, dfd, name); | |
2334 | retval = path_parentat(&nd, flags | LOOKUP_RCU, parent); | |
2335 | if (unlikely(retval == -ECHILD)) | |
2336 | retval = path_parentat(&nd, flags, parent); | |
2337 | if (unlikely(retval == -ESTALE)) | |
2338 | retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent); | |
2339 | if (likely(!retval)) { | |
2340 | *last = nd.last; | |
2341 | *type = nd.last_type; | |
2342 | audit_inode(name, parent->dentry, LOOKUP_PARENT); | |
2343 | } else { | |
2344 | putname(name); | |
2345 | name = ERR_PTR(retval); | |
2346 | } | |
2347 | restore_nameidata(); | |
2348 | return name; | |
2349 | } | |
2350 | ||
2351 | /* does lookup, returns the object with parent locked */ | |
2352 | struct dentry *kern_path_locked(const char *name, struct path *path) | |
2353 | { | |
2354 | struct filename *filename; | |
2355 | struct dentry *d; | |
2356 | struct qstr last; | |
2357 | int type; | |
2358 | ||
2359 | filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path, | |
2360 | &last, &type); | |
2361 | if (IS_ERR(filename)) | |
2362 | return ERR_CAST(filename); | |
2363 | if (unlikely(type != LAST_NORM)) { | |
2364 | path_put(path); | |
2365 | putname(filename); | |
2366 | return ERR_PTR(-EINVAL); | |
2367 | } | |
2368 | inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); | |
2369 | d = __lookup_hash(&last, path->dentry, 0); | |
2370 | if (IS_ERR(d)) { | |
2371 | inode_unlock(path->dentry->d_inode); | |
2372 | path_put(path); | |
2373 | } | |
2374 | putname(filename); | |
2375 | return d; | |
2376 | } | |
2377 | ||
2378 | int kern_path(const char *name, unsigned int flags, struct path *path) | |
2379 | { | |
2380 | return filename_lookup(AT_FDCWD, getname_kernel(name), | |
2381 | flags, path, NULL); | |
2382 | } | |
2383 | EXPORT_SYMBOL(kern_path); | |
2384 | ||
2385 | /** | |
2386 | * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair | |
2387 | * @dentry: pointer to dentry of the base directory | |
2388 | * @mnt: pointer to vfs mount of the base directory | |
2389 | * @name: pointer to file name | |
2390 | * @flags: lookup flags | |
2391 | * @path: pointer to struct path to fill | |
2392 | */ | |
2393 | int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, | |
2394 | const char *name, unsigned int flags, | |
2395 | struct path *path) | |
2396 | { | |
2397 | struct path root = {.mnt = mnt, .dentry = dentry}; | |
2398 | /* the first argument of filename_lookup() is ignored with root */ | |
2399 | return filename_lookup(AT_FDCWD, getname_kernel(name), | |
2400 | flags , path, &root); | |
2401 | } | |
2402 | EXPORT_SYMBOL(vfs_path_lookup); | |
2403 | ||
2404 | /** | |
2405 | * lookup_one_len - filesystem helper to lookup single pathname component | |
2406 | * @name: pathname component to lookup | |
2407 | * @base: base directory to lookup from | |
2408 | * @len: maximum length @len should be interpreted to | |
2409 | * | |
2410 | * Note that this routine is purely a helper for filesystem usage and should | |
2411 | * not be called by generic code. | |
2412 | * | |
2413 | * The caller must hold base->i_mutex. | |
2414 | */ | |
2415 | struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) | |
2416 | { | |
2417 | struct qstr this; | |
2418 | unsigned int c; | |
2419 | int err; | |
2420 | ||
2421 | WARN_ON_ONCE(!inode_is_locked(base->d_inode)); | |
2422 | ||
2423 | this.name = name; | |
2424 | this.len = len; | |
2425 | this.hash = full_name_hash(base, name, len); | |
2426 | if (!len) | |
2427 | return ERR_PTR(-EACCES); | |
2428 | ||
2429 | if (unlikely(name[0] == '.')) { | |
2430 | if (len < 2 || (len == 2 && name[1] == '.')) | |
2431 | return ERR_PTR(-EACCES); | |
2432 | } | |
2433 | ||
2434 | while (len--) { | |
2435 | c = *(const unsigned char *)name++; | |
2436 | if (c == '/' || c == '\0') | |
2437 | return ERR_PTR(-EACCES); | |
2438 | } | |
2439 | /* | |
2440 | * See if the low-level filesystem might want | |
2441 | * to use its own hash.. | |
2442 | */ | |
2443 | if (base->d_flags & DCACHE_OP_HASH) { | |
2444 | int err = base->d_op->d_hash(base, &this); | |
2445 | if (err < 0) | |
2446 | return ERR_PTR(err); | |
2447 | } | |
2448 | ||
2449 | err = inode_permission(base->d_inode, MAY_EXEC); | |
2450 | if (err) | |
2451 | return ERR_PTR(err); | |
2452 | ||
2453 | return __lookup_hash(&this, base, 0); | |
2454 | } | |
2455 | EXPORT_SYMBOL(lookup_one_len); | |
2456 | ||
2457 | /** | |
2458 | * lookup_one_len_unlocked - filesystem helper to lookup single pathname component | |
2459 | * @name: pathname component to lookup | |
2460 | * @base: base directory to lookup from | |
2461 | * @len: maximum length @len should be interpreted to | |
2462 | * | |
2463 | * Note that this routine is purely a helper for filesystem usage and should | |
2464 | * not be called by generic code. | |
2465 | * | |
2466 | * Unlike lookup_one_len, it should be called without the parent | |
2467 | * i_mutex held, and will take the i_mutex itself if necessary. | |
2468 | */ | |
2469 | struct dentry *lookup_one_len_unlocked(const char *name, | |
2470 | struct dentry *base, int len) | |
2471 | { | |
2472 | struct qstr this; | |
2473 | unsigned int c; | |
2474 | int err; | |
2475 | struct dentry *ret; | |
2476 | ||
2477 | this.name = name; | |
2478 | this.len = len; | |
2479 | this.hash = full_name_hash(base, name, len); | |
2480 | if (!len) | |
2481 | return ERR_PTR(-EACCES); | |
2482 | ||
2483 | if (unlikely(name[0] == '.')) { | |
2484 | if (len < 2 || (len == 2 && name[1] == '.')) | |
2485 | return ERR_PTR(-EACCES); | |
2486 | } | |
2487 | ||
2488 | while (len--) { | |
2489 | c = *(const unsigned char *)name++; | |
2490 | if (c == '/' || c == '\0') | |
2491 | return ERR_PTR(-EACCES); | |
2492 | } | |
2493 | /* | |
2494 | * See if the low-level filesystem might want | |
2495 | * to use its own hash.. | |
2496 | */ | |
2497 | if (base->d_flags & DCACHE_OP_HASH) { | |
2498 | int err = base->d_op->d_hash(base, &this); | |
2499 | if (err < 0) | |
2500 | return ERR_PTR(err); | |
2501 | } | |
2502 | ||
2503 | err = inode_permission(base->d_inode, MAY_EXEC); | |
2504 | if (err) | |
2505 | return ERR_PTR(err); | |
2506 | ||
2507 | ret = lookup_dcache(&this, base, 0); | |
2508 | if (!ret) | |
2509 | ret = lookup_slow(&this, base, 0); | |
2510 | return ret; | |
2511 | } | |
2512 | EXPORT_SYMBOL(lookup_one_len_unlocked); | |
2513 | ||
2514 | #ifdef CONFIG_UNIX98_PTYS | |
2515 | int path_pts(struct path *path) | |
2516 | { | |
2517 | /* Find something mounted on "pts" in the same directory as | |
2518 | * the input path. | |
2519 | */ | |
2520 | struct dentry *child, *parent; | |
2521 | struct qstr this; | |
2522 | int ret; | |
2523 | ||
2524 | ret = path_parent_directory(path); | |
2525 | if (ret) | |
2526 | return ret; | |
2527 | ||
2528 | parent = path->dentry; | |
2529 | this.name = "pts"; | |
2530 | this.len = 3; | |
2531 | child = d_hash_and_lookup(parent, &this); | |
2532 | if (!child) | |
2533 | return -ENOENT; | |
2534 | ||
2535 | path->dentry = child; | |
2536 | dput(parent); | |
2537 | follow_mount(path); | |
2538 | return 0; | |
2539 | } | |
2540 | #endif | |
2541 | ||
2542 | int user_path_at_empty(int dfd, const char __user *name, unsigned flags, | |
2543 | struct path *path, int *empty) | |
2544 | { | |
2545 | return filename_lookup(dfd, getname_flags(name, flags, empty), | |
2546 | flags, path, NULL); | |
2547 | } | |
2548 | EXPORT_SYMBOL(user_path_at_empty); | |
2549 | ||
2550 | /** | |
2551 | * mountpoint_last - look up last component for umount | |
2552 | * @nd: pathwalk nameidata - currently pointing at parent directory of "last" | |
2553 | * | |
2554 | * This is a special lookup_last function just for umount. In this case, we | |
2555 | * need to resolve the path without doing any revalidation. | |
2556 | * | |
2557 | * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since | |
2558 | * mountpoints are always pinned in the dcache, their ancestors are too. Thus, | |
2559 | * in almost all cases, this lookup will be served out of the dcache. The only | |
2560 | * cases where it won't are if nd->last refers to a symlink or the path is | |
2561 | * bogus and it doesn't exist. | |
2562 | * | |
2563 | * Returns: | |
2564 | * -error: if there was an error during lookup. This includes -ENOENT if the | |
2565 | * lookup found a negative dentry. | |
2566 | * | |
2567 | * 0: if we successfully resolved nd->last and found it to not to be a | |
2568 | * symlink that needs to be followed. | |
2569 | * | |
2570 | * 1: if we successfully resolved nd->last and found it to be a symlink | |
2571 | * that needs to be followed. | |
2572 | */ | |
2573 | static int | |
2574 | mountpoint_last(struct nameidata *nd) | |
2575 | { | |
2576 | int error = 0; | |
2577 | struct dentry *dir = nd->path.dentry; | |
2578 | struct path path; | |
2579 | ||
2580 | /* If we're in rcuwalk, drop out of it to handle last component */ | |
2581 | if (nd->flags & LOOKUP_RCU) { | |
2582 | if (unlazy_walk(nd, NULL, 0)) | |
2583 | return -ECHILD; | |
2584 | } | |
2585 | ||
2586 | nd->flags &= ~LOOKUP_PARENT; | |
2587 | ||
2588 | if (unlikely(nd->last_type != LAST_NORM)) { | |
2589 | error = handle_dots(nd, nd->last_type); | |
2590 | if (error) | |
2591 | return error; | |
2592 | path.dentry = dget(nd->path.dentry); | |
2593 | } else { | |
2594 | path.dentry = d_lookup(dir, &nd->last); | |
2595 | if (!path.dentry) { | |
2596 | /* | |
2597 | * No cached dentry. Mounted dentries are pinned in the | |
2598 | * cache, so that means that this dentry is probably | |
2599 | * a symlink or the path doesn't actually point | |
2600 | * to a mounted dentry. | |
2601 | */ | |
2602 | path.dentry = lookup_slow(&nd->last, dir, | |
2603 | nd->flags | LOOKUP_NO_REVAL); | |
2604 | if (IS_ERR(path.dentry)) | |
2605 | return PTR_ERR(path.dentry); | |
2606 | } | |
2607 | } | |
2608 | if (d_is_negative(path.dentry)) { | |
2609 | dput(path.dentry); | |
2610 | return -ENOENT; | |
2611 | } | |
2612 | path.mnt = nd->path.mnt; | |
2613 | return step_into(nd, &path, 0, d_backing_inode(path.dentry), 0); | |
2614 | } | |
2615 | ||
2616 | /** | |
2617 | * path_mountpoint - look up a path to be umounted | |
2618 | * @nd: lookup context | |
2619 | * @flags: lookup flags | |
2620 | * @path: pointer to container for result | |
2621 | * | |
2622 | * Look up the given name, but don't attempt to revalidate the last component. | |
2623 | * Returns 0 and "path" will be valid on success; Returns error otherwise. | |
2624 | */ | |
2625 | static int | |
2626 | path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path) | |
2627 | { | |
2628 | const char *s = path_init(nd, flags); | |
2629 | int err; | |
2630 | if (IS_ERR(s)) | |
2631 | return PTR_ERR(s); | |
2632 | while (!(err = link_path_walk(s, nd)) && | |
2633 | (err = mountpoint_last(nd)) > 0) { | |
2634 | s = trailing_symlink(nd); | |
2635 | if (IS_ERR(s)) { | |
2636 | err = PTR_ERR(s); | |
2637 | break; | |
2638 | } | |
2639 | } | |
2640 | if (!err) { | |
2641 | *path = nd->path; | |
2642 | nd->path.mnt = NULL; | |
2643 | nd->path.dentry = NULL; | |
2644 | follow_mount(path); | |
2645 | } | |
2646 | terminate_walk(nd); | |
2647 | return err; | |
2648 | } | |
2649 | ||
2650 | static int | |
2651 | filename_mountpoint(int dfd, struct filename *name, struct path *path, | |
2652 | unsigned int flags) | |
2653 | { | |
2654 | struct nameidata nd; | |
2655 | int error; | |
2656 | if (IS_ERR(name)) | |
2657 | return PTR_ERR(name); | |
2658 | set_nameidata(&nd, dfd, name); | |
2659 | error = path_mountpoint(&nd, flags | LOOKUP_RCU, path); | |
2660 | if (unlikely(error == -ECHILD)) | |
2661 | error = path_mountpoint(&nd, flags, path); | |
2662 | if (unlikely(error == -ESTALE)) | |
2663 | error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path); | |
2664 | if (likely(!error)) | |
2665 | audit_inode(name, path->dentry, 0); | |
2666 | restore_nameidata(); | |
2667 | putname(name); | |
2668 | return error; | |
2669 | } | |
2670 | ||
2671 | /** | |
2672 | * user_path_mountpoint_at - lookup a path from userland in order to umount it | |
2673 | * @dfd: directory file descriptor | |
2674 | * @name: pathname from userland | |
2675 | * @flags: lookup flags | |
2676 | * @path: pointer to container to hold result | |
2677 | * | |
2678 | * A umount is a special case for path walking. We're not actually interested | |
2679 | * in the inode in this situation, and ESTALE errors can be a problem. We | |
2680 | * simply want track down the dentry and vfsmount attached at the mountpoint | |
2681 | * and avoid revalidating the last component. | |
2682 | * | |
2683 | * Returns 0 and populates "path" on success. | |
2684 | */ | |
2685 | int | |
2686 | user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags, | |
2687 | struct path *path) | |
2688 | { | |
2689 | return filename_mountpoint(dfd, getname(name), path, flags); | |
2690 | } | |
2691 | ||
2692 | int | |
2693 | kern_path_mountpoint(int dfd, const char *name, struct path *path, | |
2694 | unsigned int flags) | |
2695 | { | |
2696 | return filename_mountpoint(dfd, getname_kernel(name), path, flags); | |
2697 | } | |
2698 | EXPORT_SYMBOL(kern_path_mountpoint); | |
2699 | ||
2700 | int __check_sticky(struct inode *dir, struct inode *inode) | |
2701 | { | |
2702 | kuid_t fsuid = current_fsuid(); | |
2703 | ||
2704 | if (uid_eq(inode->i_uid, fsuid)) | |
2705 | return 0; | |
2706 | if (uid_eq(dir->i_uid, fsuid)) | |
2707 | return 0; | |
2708 | return !capable_wrt_inode_uidgid(inode, CAP_FOWNER); | |
2709 | } | |
2710 | EXPORT_SYMBOL(__check_sticky); | |
2711 | ||
2712 | /* | |
2713 | * Check whether we can remove a link victim from directory dir, check | |
2714 | * whether the type of victim is right. | |
2715 | * 1. We can't do it if dir is read-only (done in permission()) | |
2716 | * 2. We should have write and exec permissions on dir | |
2717 | * 3. We can't remove anything from append-only dir | |
2718 | * 4. We can't do anything with immutable dir (done in permission()) | |
2719 | * 5. If the sticky bit on dir is set we should either | |
2720 | * a. be owner of dir, or | |
2721 | * b. be owner of victim, or | |
2722 | * c. have CAP_FOWNER capability | |
2723 | * 6. If the victim is append-only or immutable we can't do antyhing with | |
2724 | * links pointing to it. | |
2725 | * 7. If the victim has an unknown uid or gid we can't change the inode. | |
2726 | * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR. | |
2727 | * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR. | |
2728 | * 10. We can't remove a root or mountpoint. | |
2729 | * 11. We don't allow removal of NFS sillyrenamed files; it's handled by | |
2730 | * nfs_async_unlink(). | |
2731 | */ | |
2732 | static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) | |
2733 | { | |
2734 | struct inode *inode = d_backing_inode(victim); | |
2735 | int error; | |
2736 | ||
2737 | if (d_is_negative(victim)) | |
2738 | return -ENOENT; | |
2739 | BUG_ON(!inode); | |
2740 | ||
2741 | BUG_ON(victim->d_parent->d_inode != dir); | |
2742 | audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); | |
2743 | ||
2744 | error = inode_permission(dir, MAY_WRITE | MAY_EXEC); | |
2745 | if (error) | |
2746 | return error; | |
2747 | if (IS_APPEND(dir)) | |
2748 | return -EPERM; | |
2749 | ||
2750 | if (check_sticky(dir, inode) || IS_APPEND(inode) || | |
2751 | IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode)) | |
2752 | return -EPERM; | |
2753 | if (isdir) { | |
2754 | if (!d_is_dir(victim)) | |
2755 | return -ENOTDIR; | |
2756 | if (IS_ROOT(victim)) | |
2757 | return -EBUSY; | |
2758 | } else if (d_is_dir(victim)) | |
2759 | return -EISDIR; | |
2760 | if (IS_DEADDIR(dir)) | |
2761 | return -ENOENT; | |
2762 | if (victim->d_flags & DCACHE_NFSFS_RENAMED) | |
2763 | return -EBUSY; | |
2764 | return 0; | |
2765 | } | |
2766 | ||
2767 | /* Check whether we can create an object with dentry child in directory | |
2768 | * dir. | |
2769 | * 1. We can't do it if child already exists (open has special treatment for | |
2770 | * this case, but since we are inlined it's OK) | |
2771 | * 2. We can't do it if dir is read-only (done in permission()) | |
2772 | * 3. We can't do it if the fs can't represent the fsuid or fsgid. | |
2773 | * 4. We should have write and exec permissions on dir | |
2774 | * 5. We can't do it if dir is immutable (done in permission()) | |
2775 | */ | |
2776 | static inline int may_create(struct inode *dir, struct dentry *child) | |
2777 | { | |
2778 | struct user_namespace *s_user_ns; | |
2779 | audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); | |
2780 | if (child->d_inode) | |
2781 | return -EEXIST; | |
2782 | if (IS_DEADDIR(dir)) | |
2783 | return -ENOENT; | |
2784 | s_user_ns = dir->i_sb->s_user_ns; | |
2785 | if (!kuid_has_mapping(s_user_ns, current_fsuid()) || | |
2786 | !kgid_has_mapping(s_user_ns, current_fsgid())) | |
2787 | return -EOVERFLOW; | |
2788 | return inode_permission(dir, MAY_WRITE | MAY_EXEC); | |
2789 | } | |
2790 | ||
2791 | /* | |
2792 | * p1 and p2 should be directories on the same fs. | |
2793 | */ | |
2794 | struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) | |
2795 | { | |
2796 | struct dentry *p; | |
2797 | ||
2798 | if (p1 == p2) { | |
2799 | inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); | |
2800 | return NULL; | |
2801 | } | |
2802 | ||
2803 | mutex_lock(&p1->d_sb->s_vfs_rename_mutex); | |
2804 | ||
2805 | p = d_ancestor(p2, p1); | |
2806 | if (p) { | |
2807 | inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); | |
2808 | inode_lock_nested(p1->d_inode, I_MUTEX_CHILD); | |
2809 | return p; | |
2810 | } | |
2811 | ||
2812 | p = d_ancestor(p1, p2); | |
2813 | if (p) { | |
2814 | inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); | |
2815 | inode_lock_nested(p2->d_inode, I_MUTEX_CHILD); | |
2816 | return p; | |
2817 | } | |
2818 | ||
2819 | inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); | |
2820 | inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2); | |
2821 | return NULL; | |
2822 | } | |
2823 | EXPORT_SYMBOL(lock_rename); | |
2824 | ||
2825 | void unlock_rename(struct dentry *p1, struct dentry *p2) | |
2826 | { | |
2827 | inode_unlock(p1->d_inode); | |
2828 | if (p1 != p2) { | |
2829 | inode_unlock(p2->d_inode); | |
2830 | mutex_unlock(&p1->d_sb->s_vfs_rename_mutex); | |
2831 | } | |
2832 | } | |
2833 | EXPORT_SYMBOL(unlock_rename); | |
2834 | ||
2835 | int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, | |
2836 | bool want_excl) | |
2837 | { | |
2838 | int error = may_create(dir, dentry); | |
2839 | if (error) | |
2840 | return error; | |
2841 | ||
2842 | if (!dir->i_op->create) | |
2843 | return -EACCES; /* shouldn't it be ENOSYS? */ | |
2844 | mode &= S_IALLUGO; | |
2845 | mode |= S_IFREG; | |
2846 | error = security_inode_create(dir, dentry, mode); | |
2847 | if (error) | |
2848 | return error; | |
2849 | error = dir->i_op->create(dir, dentry, mode, want_excl); | |
2850 | if (!error) | |
2851 | fsnotify_create(dir, dentry); | |
2852 | return error; | |
2853 | } | |
2854 | EXPORT_SYMBOL(vfs_create); | |
2855 | ||
2856 | bool may_open_dev(const struct path *path) | |
2857 | { | |
2858 | return !(path->mnt->mnt_flags & MNT_NODEV) && | |
2859 | !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV); | |
2860 | } | |
2861 | ||
2862 | static int may_open(const struct path *path, int acc_mode, int flag) | |
2863 | { | |
2864 | struct dentry *dentry = path->dentry; | |
2865 | struct inode *inode = dentry->d_inode; | |
2866 | int error; | |
2867 | ||
2868 | if (!inode) | |
2869 | return -ENOENT; | |
2870 | ||
2871 | switch (inode->i_mode & S_IFMT) { | |
2872 | case S_IFLNK: | |
2873 | return -ELOOP; | |
2874 | case S_IFDIR: | |
2875 | if (acc_mode & MAY_WRITE) | |
2876 | return -EISDIR; | |
2877 | break; | |
2878 | case S_IFBLK: | |
2879 | case S_IFCHR: | |
2880 | if (!may_open_dev(path)) | |
2881 | return -EACCES; | |
2882 | /*FALLTHRU*/ | |
2883 | case S_IFIFO: | |
2884 | case S_IFSOCK: | |
2885 | flag &= ~O_TRUNC; | |
2886 | break; | |
2887 | } | |
2888 | ||
2889 | error = inode_permission(inode, MAY_OPEN | acc_mode); | |
2890 | if (error) | |
2891 | return error; | |
2892 | ||
2893 | /* | |
2894 | * An append-only file must be opened in append mode for writing. | |
2895 | */ | |
2896 | if (IS_APPEND(inode)) { | |
2897 | if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) | |
2898 | return -EPERM; | |
2899 | if (flag & O_TRUNC) | |
2900 | return -EPERM; | |
2901 | } | |
2902 | ||
2903 | /* O_NOATIME can only be set by the owner or superuser */ | |
2904 | if (flag & O_NOATIME && !inode_owner_or_capable(inode)) | |
2905 | return -EPERM; | |
2906 | ||
2907 | return 0; | |
2908 | } | |
2909 | ||
2910 | static int handle_truncate(struct file *filp) | |
2911 | { | |
2912 | const struct path *path = &filp->f_path; | |
2913 | struct inode *inode = path->dentry->d_inode; | |
2914 | int error = get_write_access(inode); | |
2915 | if (error) | |
2916 | return error; | |
2917 | /* | |
2918 | * Refuse to truncate files with mandatory locks held on them. | |
2919 | */ | |
2920 | error = locks_verify_locked(filp); | |
2921 | if (!error) | |
2922 | error = security_path_truncate(path); | |
2923 | if (!error) { | |
2924 | error = do_truncate(path->dentry, 0, | |
2925 | ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, | |
2926 | filp); | |
2927 | } | |
2928 | put_write_access(inode); | |
2929 | return error; | |
2930 | } | |
2931 | ||
2932 | static inline int open_to_namei_flags(int flag) | |
2933 | { | |
2934 | if ((flag & O_ACCMODE) == 3) | |
2935 | flag--; | |
2936 | return flag; | |
2937 | } | |
2938 | ||
2939 | static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode) | |
2940 | { | |
2941 | int error = security_path_mknod(dir, dentry, mode, 0); | |
2942 | if (error) | |
2943 | return error; | |
2944 | ||
2945 | error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); | |
2946 | if (error) | |
2947 | return error; | |
2948 | ||
2949 | return security_inode_create(dir->dentry->d_inode, dentry, mode); | |
2950 | } | |
2951 | ||
2952 | /* | |
2953 | * Attempt to atomically look up, create and open a file from a negative | |
2954 | * dentry. | |
2955 | * | |
2956 | * Returns 0 if successful. The file will have been created and attached to | |
2957 | * @file by the filesystem calling finish_open(). | |
2958 | * | |
2959 | * Returns 1 if the file was looked up only or didn't need creating. The | |
2960 | * caller will need to perform the open themselves. @path will have been | |
2961 | * updated to point to the new dentry. This may be negative. | |
2962 | * | |
2963 | * Returns an error code otherwise. | |
2964 | */ | |
2965 | static int atomic_open(struct nameidata *nd, struct dentry *dentry, | |
2966 | struct path *path, struct file *file, | |
2967 | const struct open_flags *op, | |
2968 | int open_flag, umode_t mode, | |
2969 | int *opened) | |
2970 | { | |
2971 | struct dentry *const DENTRY_NOT_SET = (void *) -1UL; | |
2972 | struct inode *dir = nd->path.dentry->d_inode; | |
2973 | int error; | |
2974 | ||
2975 | if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */ | |
2976 | open_flag &= ~O_TRUNC; | |
2977 | ||
2978 | if (nd->flags & LOOKUP_DIRECTORY) | |
2979 | open_flag |= O_DIRECTORY; | |
2980 | ||
2981 | file->f_path.dentry = DENTRY_NOT_SET; | |
2982 | file->f_path.mnt = nd->path.mnt; | |
2983 | error = dir->i_op->atomic_open(dir, dentry, file, | |
2984 | open_to_namei_flags(open_flag), | |
2985 | mode, opened); | |
2986 | d_lookup_done(dentry); | |
2987 | if (!error) { | |
2988 | /* | |
2989 | * We didn't have the inode before the open, so check open | |
2990 | * permission here. | |
2991 | */ | |
2992 | int acc_mode = op->acc_mode; | |
2993 | if (*opened & FILE_CREATED) { | |
2994 | WARN_ON(!(open_flag & O_CREAT)); | |
2995 | fsnotify_create(dir, dentry); | |
2996 | acc_mode = 0; | |
2997 | } | |
2998 | error = may_open(&file->f_path, acc_mode, open_flag); | |
2999 | if (WARN_ON(error > 0)) | |
3000 | error = -EINVAL; | |
3001 | } else if (error > 0) { | |
3002 | if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { | |
3003 | error = -EIO; | |
3004 | } else { | |
3005 | if (file->f_path.dentry) { | |
3006 | dput(dentry); | |
3007 | dentry = file->f_path.dentry; | |
3008 | } | |
3009 | if (*opened & FILE_CREATED) | |
3010 | fsnotify_create(dir, dentry); | |
3011 | if (unlikely(d_is_negative(dentry))) { | |
3012 | error = -ENOENT; | |
3013 | } else { | |
3014 | path->dentry = dentry; | |
3015 | path->mnt = nd->path.mnt; | |
3016 | return 1; | |
3017 | } | |
3018 | } | |
3019 | } | |
3020 | dput(dentry); | |
3021 | return error; | |
3022 | } | |
3023 | ||
3024 | /* | |
3025 | * Look up and maybe create and open the last component. | |
3026 | * | |
3027 | * Must be called with i_mutex held on parent. | |
3028 | * | |
3029 | * Returns 0 if the file was successfully atomically created (if necessary) and | |
3030 | * opened. In this case the file will be returned attached to @file. | |
3031 | * | |
3032 | * Returns 1 if the file was not completely opened at this time, though lookups | |
3033 | * and creations will have been performed and the dentry returned in @path will | |
3034 | * be positive upon return if O_CREAT was specified. If O_CREAT wasn't | |
3035 | * specified then a negative dentry may be returned. | |
3036 | * | |
3037 | * An error code is returned otherwise. | |
3038 | * | |
3039 | * FILE_CREATE will be set in @*opened if the dentry was created and will be | |
3040 | * cleared otherwise prior to returning. | |
3041 | */ | |
3042 | static int lookup_open(struct nameidata *nd, struct path *path, | |
3043 | struct file *file, | |
3044 | const struct open_flags *op, | |
3045 | bool got_write, int *opened) | |
3046 | { | |
3047 | struct dentry *dir = nd->path.dentry; | |
3048 | struct inode *dir_inode = dir->d_inode; | |
3049 | int open_flag = op->open_flag; | |
3050 | struct dentry *dentry; | |
3051 | int error, create_error = 0; | |
3052 | umode_t mode = op->mode; | |
3053 | DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); | |
3054 | ||
3055 | if (unlikely(IS_DEADDIR(dir_inode))) | |
3056 | return -ENOENT; | |
3057 | ||
3058 | *opened &= ~FILE_CREATED; | |
3059 | dentry = d_lookup(dir, &nd->last); | |
3060 | for (;;) { | |
3061 | if (!dentry) { | |
3062 | dentry = d_alloc_parallel(dir, &nd->last, &wq); | |
3063 | if (IS_ERR(dentry)) | |
3064 | return PTR_ERR(dentry); | |
3065 | } | |
3066 | if (d_in_lookup(dentry)) | |
3067 | break; | |
3068 | ||
3069 | if (!(dentry->d_flags & DCACHE_OP_REVALIDATE)) | |
3070 | break; | |
3071 | ||
3072 | error = d_revalidate(dentry, nd->flags); | |
3073 | if (likely(error > 0)) | |
3074 | break; | |
3075 | if (error) | |
3076 | goto out_dput; | |
3077 | d_invalidate(dentry); | |
3078 | dput(dentry); | |
3079 | dentry = NULL; | |
3080 | } | |
3081 | if (dentry->d_inode) { | |
3082 | /* Cached positive dentry: will open in f_op->open */ | |
3083 | goto out_no_open; | |
3084 | } | |
3085 | ||
3086 | /* | |
3087 | * Checking write permission is tricky, bacuse we don't know if we are | |
3088 | * going to actually need it: O_CREAT opens should work as long as the | |
3089 | * file exists. But checking existence breaks atomicity. The trick is | |
3090 | * to check access and if not granted clear O_CREAT from the flags. | |
3091 | * | |
3092 | * Another problem is returing the "right" error value (e.g. for an | |
3093 | * O_EXCL open we want to return EEXIST not EROFS). | |
3094 | */ | |
3095 | if (open_flag & O_CREAT) { | |
3096 | if (!IS_POSIXACL(dir->d_inode)) | |
3097 | mode &= ~current_umask(); | |
3098 | if (unlikely(!got_write)) { | |
3099 | create_error = -EROFS; | |
3100 | open_flag &= ~O_CREAT; | |
3101 | if (open_flag & (O_EXCL | O_TRUNC)) | |
3102 | goto no_open; | |
3103 | /* No side effects, safe to clear O_CREAT */ | |
3104 | } else { | |
3105 | create_error = may_o_create(&nd->path, dentry, mode); | |
3106 | if (create_error) { | |
3107 | open_flag &= ~O_CREAT; | |
3108 | if (open_flag & O_EXCL) | |
3109 | goto no_open; | |
3110 | } | |
3111 | } | |
3112 | } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) && | |
3113 | unlikely(!got_write)) { | |
3114 | /* | |
3115 | * No O_CREATE -> atomicity not a requirement -> fall | |
3116 | * back to lookup + open | |
3117 | */ | |
3118 | goto no_open; | |
3119 | } | |
3120 | ||
3121 | if (dir_inode->i_op->atomic_open) { | |
3122 | error = atomic_open(nd, dentry, path, file, op, open_flag, | |
3123 | mode, opened); | |
3124 | if (unlikely(error == -ENOENT) && create_error) | |
3125 | error = create_error; | |
3126 | return error; | |
3127 | } | |
3128 | ||
3129 | no_open: | |
3130 | if (d_in_lookup(dentry)) { | |
3131 | struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry, | |
3132 | nd->flags); | |
3133 | d_lookup_done(dentry); | |
3134 | if (unlikely(res)) { | |
3135 | if (IS_ERR(res)) { | |
3136 | error = PTR_ERR(res); | |
3137 | goto out_dput; | |
3138 | } | |
3139 | dput(dentry); | |
3140 | dentry = res; | |
3141 | } | |
3142 | } | |
3143 | ||
3144 | /* Negative dentry, just create the file */ | |
3145 | if (!dentry->d_inode && (open_flag & O_CREAT)) { | |
3146 | *opened |= FILE_CREATED; | |
3147 | audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE); | |
3148 | if (!dir_inode->i_op->create) { | |
3149 | error = -EACCES; | |
3150 | goto out_dput; | |
3151 | } | |
3152 | error = dir_inode->i_op->create(dir_inode, dentry, mode, | |
3153 | open_flag & O_EXCL); | |
3154 | if (error) | |
3155 | goto out_dput; | |
3156 | fsnotify_create(dir_inode, dentry); | |
3157 | } | |
3158 | if (unlikely(create_error) && !dentry->d_inode) { | |
3159 | error = create_error; | |
3160 | goto out_dput; | |
3161 | } | |
3162 | out_no_open: | |
3163 | path->dentry = dentry; | |
3164 | path->mnt = nd->path.mnt; | |
3165 | return 1; | |
3166 | ||
3167 | out_dput: | |
3168 | dput(dentry); | |
3169 | return error; | |
3170 | } | |
3171 | ||
3172 | /* | |
3173 | * Handle the last step of open() | |
3174 | */ | |
3175 | static int do_last(struct nameidata *nd, | |
3176 | struct file *file, const struct open_flags *op, | |
3177 | int *opened) | |
3178 | { | |
3179 | struct dentry *dir = nd->path.dentry; | |
3180 | int open_flag = op->open_flag; | |
3181 | bool will_truncate = (open_flag & O_TRUNC) != 0; | |
3182 | bool got_write = false; | |
3183 | int acc_mode = op->acc_mode; | |
3184 | unsigned seq; | |
3185 | struct inode *inode; | |
3186 | struct path path; | |
3187 | int error; | |
3188 | ||
3189 | nd->flags &= ~LOOKUP_PARENT; | |
3190 | nd->flags |= op->intent; | |
3191 | ||
3192 | if (nd->last_type != LAST_NORM) { | |
3193 | error = handle_dots(nd, nd->last_type); | |
3194 | if (unlikely(error)) | |
3195 | return error; | |
3196 | goto finish_open; | |
3197 | } | |
3198 | ||
3199 | if (!(open_flag & O_CREAT)) { | |
3200 | if (nd->last.name[nd->last.len]) | |
3201 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; | |
3202 | /* we _can_ be in RCU mode here */ | |
3203 | error = lookup_fast(nd, &path, &inode, &seq); | |
3204 | if (likely(error > 0)) | |
3205 | goto finish_lookup; | |
3206 | ||
3207 | if (error < 0) | |
3208 | return error; | |
3209 | ||
3210 | BUG_ON(nd->inode != dir->d_inode); | |
3211 | BUG_ON(nd->flags & LOOKUP_RCU); | |
3212 | } else { | |
3213 | /* create side of things */ | |
3214 | /* | |
3215 | * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED | |
3216 | * has been cleared when we got to the last component we are | |
3217 | * about to look up | |
3218 | */ | |
3219 | error = complete_walk(nd); | |
3220 | if (error) | |
3221 | return error; | |
3222 | ||
3223 | audit_inode(nd->name, dir, LOOKUP_PARENT); | |
3224 | /* trailing slashes? */ | |
3225 | if (unlikely(nd->last.name[nd->last.len])) | |
3226 | return -EISDIR; | |
3227 | } | |
3228 | ||
3229 | if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { | |
3230 | error = mnt_want_write(nd->path.mnt); | |
3231 | if (!error) | |
3232 | got_write = true; | |
3233 | /* | |
3234 | * do _not_ fail yet - we might not need that or fail with | |
3235 | * a different error; let lookup_open() decide; we'll be | |
3236 | * dropping this one anyway. | |
3237 | */ | |
3238 | } | |
3239 | if (open_flag & O_CREAT) | |
3240 | inode_lock(dir->d_inode); | |
3241 | else | |
3242 | inode_lock_shared(dir->d_inode); | |
3243 | error = lookup_open(nd, &path, file, op, got_write, opened); | |
3244 | if (open_flag & O_CREAT) | |
3245 | inode_unlock(dir->d_inode); | |
3246 | else | |
3247 | inode_unlock_shared(dir->d_inode); | |
3248 | ||
3249 | if (error <= 0) { | |
3250 | if (error) | |
3251 | goto out; | |
3252 | ||
3253 | if ((*opened & FILE_CREATED) || | |
3254 | !S_ISREG(file_inode(file)->i_mode)) | |
3255 | will_truncate = false; | |
3256 | ||
3257 | audit_inode(nd->name, file->f_path.dentry, 0); | |
3258 | goto opened; | |
3259 | } | |
3260 | ||
3261 | if (*opened & FILE_CREATED) { | |
3262 | /* Don't check for write permission, don't truncate */ | |
3263 | open_flag &= ~O_TRUNC; | |
3264 | will_truncate = false; | |
3265 | acc_mode = 0; | |
3266 | path_to_nameidata(&path, nd); | |
3267 | goto finish_open_created; | |
3268 | } | |
3269 | ||
3270 | /* | |
3271 | * If atomic_open() acquired write access it is dropped now due to | |
3272 | * possible mount and symlink following (this might be optimized away if | |
3273 | * necessary...) | |
3274 | */ | |
3275 | if (got_write) { | |
3276 | mnt_drop_write(nd->path.mnt); | |
3277 | got_write = false; | |
3278 | } | |
3279 | ||
3280 | error = follow_managed(&path, nd); | |
3281 | if (unlikely(error < 0)) | |
3282 | return error; | |
3283 | ||
3284 | if (unlikely(d_is_negative(path.dentry))) { | |
3285 | path_to_nameidata(&path, nd); | |
3286 | return -ENOENT; | |
3287 | } | |
3288 | ||
3289 | /* | |
3290 | * create/update audit record if it already exists. | |
3291 | */ | |
3292 | audit_inode(nd->name, path.dentry, 0); | |
3293 | ||
3294 | if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) { | |
3295 | path_to_nameidata(&path, nd); | |
3296 | return -EEXIST; | |
3297 | } | |
3298 | ||
3299 | seq = 0; /* out of RCU mode, so the value doesn't matter */ | |
3300 | inode = d_backing_inode(path.dentry); | |
3301 | finish_lookup: | |
3302 | error = step_into(nd, &path, 0, inode, seq); | |
3303 | if (unlikely(error)) | |
3304 | return error; | |
3305 | finish_open: | |
3306 | /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ | |
3307 | error = complete_walk(nd); | |
3308 | if (error) | |
3309 | return error; | |
3310 | audit_inode(nd->name, nd->path.dentry, 0); | |
3311 | error = -EISDIR; | |
3312 | if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry)) | |
3313 | goto out; | |
3314 | error = -ENOTDIR; | |
3315 | if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) | |
3316 | goto out; | |
3317 | if (!d_is_reg(nd->path.dentry)) | |
3318 | will_truncate = false; | |
3319 | ||
3320 | if (will_truncate) { | |
3321 | error = mnt_want_write(nd->path.mnt); | |
3322 | if (error) | |
3323 | goto out; | |
3324 | got_write = true; | |
3325 | } | |
3326 | finish_open_created: | |
3327 | error = may_open(&nd->path, acc_mode, open_flag); | |
3328 | if (error) | |
3329 | goto out; | |
3330 | BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */ | |
3331 | error = vfs_open(&nd->path, file, current_cred()); | |
3332 | if (error) | |
3333 | goto out; | |
3334 | *opened |= FILE_OPENED; | |
3335 | opened: | |
3336 | error = open_check_o_direct(file); | |
3337 | if (!error) | |
3338 | error = ima_file_check(file, op->acc_mode, *opened); | |
3339 | if (!error && will_truncate) | |
3340 | error = handle_truncate(file); | |
3341 | out: | |
3342 | if (unlikely(error) && (*opened & FILE_OPENED)) | |
3343 | fput(file); | |
3344 | if (unlikely(error > 0)) { | |
3345 | WARN_ON(1); | |
3346 | error = -EINVAL; | |
3347 | } | |
3348 | if (got_write) | |
3349 | mnt_drop_write(nd->path.mnt); | |
3350 | return error; | |
3351 | } | |
3352 | ||
3353 | static int do_tmpfile(struct nameidata *nd, unsigned flags, | |
3354 | const struct open_flags *op, | |
3355 | struct file *file, int *opened) | |
3356 | { | |
3357 | static const struct qstr name = QSTR_INIT("/", 1); | |
3358 | struct dentry *child; | |
3359 | struct inode *dir; | |
3360 | struct path path; | |
3361 | int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path); | |
3362 | if (unlikely(error)) | |
3363 | return error; | |
3364 | error = mnt_want_write(path.mnt); | |
3365 | if (unlikely(error)) | |
3366 | goto out; | |
3367 | dir = path.dentry->d_inode; | |
3368 | /* we want directory to be writable */ | |
3369 | error = inode_permission(dir, MAY_WRITE | MAY_EXEC); | |
3370 | if (error) | |
3371 | goto out2; | |
3372 | if (!dir->i_op->tmpfile) { | |
3373 | error = -EOPNOTSUPP; | |
3374 | goto out2; | |
3375 | } | |
3376 | child = d_alloc(path.dentry, &name); | |
3377 | if (unlikely(!child)) { | |
3378 | error = -ENOMEM; | |
3379 | goto out2; | |
3380 | } | |
3381 | dput(path.dentry); | |
3382 | path.dentry = child; | |
3383 | error = dir->i_op->tmpfile(dir, child, op->mode); | |
3384 | if (error) | |
3385 | goto out2; | |
3386 | audit_inode(nd->name, child, 0); | |
3387 | /* Don't check for other permissions, the inode was just created */ | |
3388 | error = may_open(&path, 0, op->open_flag); | |
3389 | if (error) | |
3390 | goto out2; | |
3391 | file->f_path.mnt = path.mnt; | |
3392 | error = finish_open(file, child, NULL, opened); | |
3393 | if (error) | |
3394 | goto out2; | |
3395 | error = open_check_o_direct(file); | |
3396 | if (error) { | |
3397 | fput(file); | |
3398 | } else if (!(op->open_flag & O_EXCL)) { | |
3399 | struct inode *inode = file_inode(file); | |
3400 | spin_lock(&inode->i_lock); | |
3401 | inode->i_state |= I_LINKABLE; | |
3402 | spin_unlock(&inode->i_lock); | |
3403 | } | |
3404 | out2: | |
3405 | mnt_drop_write(path.mnt); | |
3406 | out: | |
3407 | path_put(&path); | |
3408 | return error; | |
3409 | } | |
3410 | ||
3411 | static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file) | |
3412 | { | |
3413 | struct path path; | |
3414 | int error = path_lookupat(nd, flags, &path); | |
3415 | if (!error) { | |
3416 | audit_inode(nd->name, path.dentry, 0); | |
3417 | error = vfs_open(&path, file, current_cred()); | |
3418 | path_put(&path); | |
3419 | } | |
3420 | return error; | |
3421 | } | |
3422 | ||
3423 | static struct file *path_openat(struct nameidata *nd, | |
3424 | const struct open_flags *op, unsigned flags) | |
3425 | { | |
3426 | const char *s; | |
3427 | struct file *file; | |
3428 | int opened = 0; | |
3429 | int error; | |
3430 | ||
3431 | file = get_empty_filp(); | |
3432 | if (IS_ERR(file)) | |
3433 | return file; | |
3434 | ||
3435 | file->f_flags = op->open_flag; | |
3436 | ||
3437 | if (unlikely(file->f_flags & __O_TMPFILE)) { | |
3438 | error = do_tmpfile(nd, flags, op, file, &opened); | |
3439 | goto out2; | |
3440 | } | |
3441 | ||
3442 | if (unlikely(file->f_flags & O_PATH)) { | |
3443 | error = do_o_path(nd, flags, file); | |
3444 | if (!error) | |
3445 | opened |= FILE_OPENED; | |
3446 | goto out2; | |
3447 | } | |
3448 | ||
3449 | s = path_init(nd, flags); | |
3450 | if (IS_ERR(s)) { | |
3451 | put_filp(file); | |
3452 | return ERR_CAST(s); | |
3453 | } | |
3454 | while (!(error = link_path_walk(s, nd)) && | |
3455 | (error = do_last(nd, file, op, &opened)) > 0) { | |
3456 | nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); | |
3457 | s = trailing_symlink(nd); | |
3458 | if (IS_ERR(s)) { | |
3459 | error = PTR_ERR(s); | |
3460 | break; | |
3461 | } | |
3462 | } | |
3463 | terminate_walk(nd); | |
3464 | out2: | |
3465 | if (!(opened & FILE_OPENED)) { | |
3466 | BUG_ON(!error); | |
3467 | put_filp(file); | |
3468 | } | |
3469 | if (unlikely(error)) { | |
3470 | if (error == -EOPENSTALE) { | |
3471 | if (flags & LOOKUP_RCU) | |
3472 | error = -ECHILD; | |
3473 | else | |
3474 | error = -ESTALE; | |
3475 | } | |
3476 | file = ERR_PTR(error); | |
3477 | } | |
3478 | return file; | |
3479 | } | |
3480 | ||
3481 | struct file *do_filp_open(int dfd, struct filename *pathname, | |
3482 | const struct open_flags *op) | |
3483 | { | |
3484 | struct nameidata nd; | |
3485 | int flags = op->lookup_flags; | |
3486 | struct file *filp; | |
3487 | ||
3488 | set_nameidata(&nd, dfd, pathname); | |
3489 | filp = path_openat(&nd, op, flags | LOOKUP_RCU); | |
3490 | if (unlikely(filp == ERR_PTR(-ECHILD))) | |
3491 | filp = path_openat(&nd, op, flags); | |
3492 | if (unlikely(filp == ERR_PTR(-ESTALE))) | |
3493 | filp = path_openat(&nd, op, flags | LOOKUP_REVAL); | |
3494 | restore_nameidata(); | |
3495 | return filp; | |
3496 | } | |
3497 | ||
3498 | struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, | |
3499 | const char *name, const struct open_flags *op) | |
3500 | { | |
3501 | struct nameidata nd; | |
3502 | struct file *file; | |
3503 | struct filename *filename; | |
3504 | int flags = op->lookup_flags | LOOKUP_ROOT; | |
3505 | ||
3506 | nd.root.mnt = mnt; | |
3507 | nd.root.dentry = dentry; | |
3508 | ||
3509 | if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN) | |
3510 | return ERR_PTR(-ELOOP); | |
3511 | ||
3512 | filename = getname_kernel(name); | |
3513 | if (IS_ERR(filename)) | |
3514 | return ERR_CAST(filename); | |
3515 | ||
3516 | set_nameidata(&nd, -1, filename); | |
3517 | file = path_openat(&nd, op, flags | LOOKUP_RCU); | |
3518 | if (unlikely(file == ERR_PTR(-ECHILD))) | |
3519 | file = path_openat(&nd, op, flags); | |
3520 | if (unlikely(file == ERR_PTR(-ESTALE))) | |
3521 | file = path_openat(&nd, op, flags | LOOKUP_REVAL); | |
3522 | restore_nameidata(); | |
3523 | putname(filename); | |
3524 | return file; | |
3525 | } | |
3526 | ||
3527 | static struct dentry *filename_create(int dfd, struct filename *name, | |
3528 | struct path *path, unsigned int lookup_flags) | |
3529 | { | |
3530 | struct dentry *dentry = ERR_PTR(-EEXIST); | |
3531 | struct qstr last; | |
3532 | int type; | |
3533 | int err2; | |
3534 | int error; | |
3535 | bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); | |
3536 | ||
3537 | /* | |
3538 | * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any | |
3539 | * other flags passed in are ignored! | |
3540 | */ | |
3541 | lookup_flags &= LOOKUP_REVAL; | |
3542 | ||
3543 | name = filename_parentat(dfd, name, lookup_flags, path, &last, &type); | |
3544 | if (IS_ERR(name)) | |
3545 | return ERR_CAST(name); | |
3546 | ||
3547 | /* | |
3548 | * Yucky last component or no last component at all? | |
3549 | * (foo/., foo/.., /////) | |
3550 | */ | |
3551 | if (unlikely(type != LAST_NORM)) | |
3552 | goto out; | |
3553 | ||
3554 | /* don't fail immediately if it's r/o, at least try to report other errors */ | |
3555 | err2 = mnt_want_write(path->mnt); | |
3556 | /* | |
3557 | * Do the final lookup. | |
3558 | */ | |
3559 | lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL; | |
3560 | inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); | |
3561 | dentry = __lookup_hash(&last, path->dentry, lookup_flags); | |
3562 | if (IS_ERR(dentry)) | |
3563 | goto unlock; | |
3564 | ||
3565 | error = -EEXIST; | |
3566 | if (d_is_positive(dentry)) | |
3567 | goto fail; | |
3568 | ||
3569 | /* | |
3570 | * Special case - lookup gave negative, but... we had foo/bar/ | |
3571 | * From the vfs_mknod() POV we just have a negative dentry - | |
3572 | * all is fine. Let's be bastards - you had / on the end, you've | |
3573 | * been asking for (non-existent) directory. -ENOENT for you. | |
3574 | */ | |
3575 | if (unlikely(!is_dir && last.name[last.len])) { | |
3576 | error = -ENOENT; | |
3577 | goto fail; | |
3578 | } | |
3579 | if (unlikely(err2)) { | |
3580 | error = err2; | |
3581 | goto fail; | |
3582 | } | |
3583 | putname(name); | |
3584 | return dentry; | |
3585 | fail: | |
3586 | dput(dentry); | |
3587 | dentry = ERR_PTR(error); | |
3588 | unlock: | |
3589 | inode_unlock(path->dentry->d_inode); | |
3590 | if (!err2) | |
3591 | mnt_drop_write(path->mnt); | |
3592 | out: | |
3593 | path_put(path); | |
3594 | putname(name); | |
3595 | return dentry; | |
3596 | } | |
3597 | ||
3598 | struct dentry *kern_path_create(int dfd, const char *pathname, | |
3599 | struct path *path, unsigned int lookup_flags) | |
3600 | { | |
3601 | return filename_create(dfd, getname_kernel(pathname), | |
3602 | path, lookup_flags); | |
3603 | } | |
3604 | EXPORT_SYMBOL(kern_path_create); | |
3605 | ||
3606 | void done_path_create(struct path *path, struct dentry *dentry) | |
3607 | { | |
3608 | dput(dentry); | |
3609 | inode_unlock(path->dentry->d_inode); | |
3610 | mnt_drop_write(path->mnt); | |
3611 | path_put(path); | |
3612 | } | |
3613 | EXPORT_SYMBOL(done_path_create); | |
3614 | ||
3615 | inline struct dentry *user_path_create(int dfd, const char __user *pathname, | |
3616 | struct path *path, unsigned int lookup_flags) | |
3617 | { | |
3618 | return filename_create(dfd, getname(pathname), path, lookup_flags); | |
3619 | } | |
3620 | EXPORT_SYMBOL(user_path_create); | |
3621 | ||
3622 | int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) | |
3623 | { | |
3624 | int error = may_create(dir, dentry); | |
3625 | ||
3626 | if (error) | |
3627 | return error; | |
3628 | ||
3629 | if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) | |
3630 | return -EPERM; | |
3631 | ||
3632 | if (!dir->i_op->mknod) | |
3633 | return -EPERM; | |
3634 | ||
3635 | error = devcgroup_inode_mknod(mode, dev); | |
3636 | if (error) | |
3637 | return error; | |
3638 | ||
3639 | error = security_inode_mknod(dir, dentry, mode, dev); | |
3640 | if (error) | |
3641 | return error; | |
3642 | ||
3643 | error = dir->i_op->mknod(dir, dentry, mode, dev); | |
3644 | if (!error) | |
3645 | fsnotify_create(dir, dentry); | |
3646 | return error; | |
3647 | } | |
3648 | EXPORT_SYMBOL(vfs_mknod); | |
3649 | ||
3650 | static int may_mknod(umode_t mode) | |
3651 | { | |
3652 | switch (mode & S_IFMT) { | |
3653 | case S_IFREG: | |
3654 | case S_IFCHR: | |
3655 | case S_IFBLK: | |
3656 | case S_IFIFO: | |
3657 | case S_IFSOCK: | |
3658 | case 0: /* zero mode translates to S_IFREG */ | |
3659 | return 0; | |
3660 | case S_IFDIR: | |
3661 | return -EPERM; | |
3662 | default: | |
3663 | return -EINVAL; | |
3664 | } | |
3665 | } | |
3666 | ||
3667 | SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, | |
3668 | unsigned, dev) | |
3669 | { | |
3670 | struct dentry *dentry; | |
3671 | struct path path; | |
3672 | int error; | |
3673 | unsigned int lookup_flags = 0; | |
3674 | ||
3675 | error = may_mknod(mode); | |
3676 | if (error) | |
3677 | return error; | |
3678 | retry: | |
3679 | dentry = user_path_create(dfd, filename, &path, lookup_flags); | |
3680 | if (IS_ERR(dentry)) | |
3681 | return PTR_ERR(dentry); | |
3682 | ||
3683 | if (!IS_POSIXACL(path.dentry->d_inode)) | |
3684 | mode &= ~current_umask(); | |
3685 | error = security_path_mknod(&path, dentry, mode, dev); | |
3686 | if (error) | |
3687 | goto out; | |
3688 | switch (mode & S_IFMT) { | |
3689 | case 0: case S_IFREG: | |
3690 | error = vfs_create(path.dentry->d_inode,dentry,mode,true); | |
3691 | if (!error) | |
3692 | ima_post_path_mknod(dentry); | |
3693 | break; | |
3694 | case S_IFCHR: case S_IFBLK: | |
3695 | error = vfs_mknod(path.dentry->d_inode,dentry,mode, | |
3696 | new_decode_dev(dev)); | |
3697 | break; | |
3698 | case S_IFIFO: case S_IFSOCK: | |
3699 | error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); | |
3700 | break; | |
3701 | } | |
3702 | out: | |
3703 | done_path_create(&path, dentry); | |
3704 | if (retry_estale(error, lookup_flags)) { | |
3705 | lookup_flags |= LOOKUP_REVAL; | |
3706 | goto retry; | |
3707 | } | |
3708 | return error; | |
3709 | } | |
3710 | ||
3711 | SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) | |
3712 | { | |
3713 | return sys_mknodat(AT_FDCWD, filename, mode, dev); | |
3714 | } | |
3715 | ||
3716 | int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) | |
3717 | { | |
3718 | int error = may_create(dir, dentry); | |
3719 | unsigned max_links = dir->i_sb->s_max_links; | |
3720 | ||
3721 | if (error) | |
3722 | return error; | |
3723 | ||
3724 | if (!dir->i_op->mkdir) | |
3725 | return -EPERM; | |
3726 | ||
3727 | mode &= (S_IRWXUGO|S_ISVTX); | |
3728 | error = security_inode_mkdir(dir, dentry, mode); | |
3729 | if (error) | |
3730 | return error; | |
3731 | ||
3732 | if (max_links && dir->i_nlink >= max_links) | |
3733 | return -EMLINK; | |
3734 | ||
3735 | error = dir->i_op->mkdir(dir, dentry, mode); | |
3736 | if (!error) | |
3737 | fsnotify_mkdir(dir, dentry); | |
3738 | return error; | |
3739 | } | |
3740 | EXPORT_SYMBOL(vfs_mkdir); | |
3741 | ||
3742 | SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) | |
3743 | { | |
3744 | struct dentry *dentry; | |
3745 | struct path path; | |
3746 | int error; | |
3747 | unsigned int lookup_flags = LOOKUP_DIRECTORY; | |
3748 | ||
3749 | retry: | |
3750 | dentry = user_path_create(dfd, pathname, &path, lookup_flags); | |
3751 | if (IS_ERR(dentry)) | |
3752 | return PTR_ERR(dentry); | |
3753 | ||
3754 | if (!IS_POSIXACL(path.dentry->d_inode)) | |
3755 | mode &= ~current_umask(); | |
3756 | error = security_path_mkdir(&path, dentry, mode); | |
3757 | if (!error) | |
3758 | error = vfs_mkdir(path.dentry->d_inode, dentry, mode); | |
3759 | done_path_create(&path, dentry); | |
3760 | if (retry_estale(error, lookup_flags)) { | |
3761 | lookup_flags |= LOOKUP_REVAL; | |
3762 | goto retry; | |
3763 | } | |
3764 | return error; | |
3765 | } | |
3766 | ||
3767 | SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) | |
3768 | { | |
3769 | return sys_mkdirat(AT_FDCWD, pathname, mode); | |
3770 | } | |
3771 | ||
3772 | int vfs_rmdir(struct inode *dir, struct dentry *dentry) | |
3773 | { | |
3774 | int error = may_delete(dir, dentry, 1); | |
3775 | ||
3776 | if (error) | |
3777 | return error; | |
3778 | ||
3779 | if (!dir->i_op->rmdir) | |
3780 | return -EPERM; | |
3781 | ||
3782 | dget(dentry); | |
3783 | inode_lock(dentry->d_inode); | |
3784 | ||
3785 | error = -EBUSY; | |
3786 | if (is_local_mountpoint(dentry)) | |
3787 | goto out; | |
3788 | ||
3789 | error = security_inode_rmdir(dir, dentry); | |
3790 | if (error) | |
3791 | goto out; | |
3792 | ||
3793 | shrink_dcache_parent(dentry); | |
3794 | error = dir->i_op->rmdir(dir, dentry); | |
3795 | if (error) | |
3796 | goto out; | |
3797 | ||
3798 | dentry->d_inode->i_flags |= S_DEAD; | |
3799 | dont_mount(dentry); | |
3800 | detach_mounts(dentry); | |
3801 | ||
3802 | out: | |
3803 | inode_unlock(dentry->d_inode); | |
3804 | dput(dentry); | |
3805 | if (!error) | |
3806 | d_delete(dentry); | |
3807 | return error; | |
3808 | } | |
3809 | EXPORT_SYMBOL(vfs_rmdir); | |
3810 | ||
3811 | static long do_rmdir(int dfd, const char __user *pathname) | |
3812 | { | |
3813 | int error = 0; | |
3814 | struct filename *name; | |
3815 | struct dentry *dentry; | |
3816 | struct path path; | |
3817 | struct qstr last; | |
3818 | int type; | |
3819 | unsigned int lookup_flags = 0; | |
3820 | retry: | |
3821 | name = filename_parentat(dfd, getname(pathname), lookup_flags, | |
3822 | &path, &last, &type); | |
3823 | if (IS_ERR(name)) | |
3824 | return PTR_ERR(name); | |
3825 | ||
3826 | switch (type) { | |
3827 | case LAST_DOTDOT: | |
3828 | error = -ENOTEMPTY; | |
3829 | goto exit1; | |
3830 | case LAST_DOT: | |
3831 | error = -EINVAL; | |
3832 | goto exit1; | |
3833 | case LAST_ROOT: | |
3834 | error = -EBUSY; | |
3835 | goto exit1; | |
3836 | } | |
3837 | ||
3838 | error = mnt_want_write(path.mnt); | |
3839 | if (error) | |
3840 | goto exit1; | |
3841 | ||
3842 | inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); | |
3843 | dentry = __lookup_hash(&last, path.dentry, lookup_flags); | |
3844 | error = PTR_ERR(dentry); | |
3845 | if (IS_ERR(dentry)) | |
3846 | goto exit2; | |
3847 | if (!dentry->d_inode) { | |
3848 | error = -ENOENT; | |
3849 | goto exit3; | |
3850 | } | |
3851 | error = security_path_rmdir(&path, dentry); | |
3852 | if (error) | |
3853 | goto exit3; | |
3854 | error = vfs_rmdir(path.dentry->d_inode, dentry); | |
3855 | exit3: | |
3856 | dput(dentry); | |
3857 | exit2: | |
3858 | inode_unlock(path.dentry->d_inode); | |
3859 | mnt_drop_write(path.mnt); | |
3860 | exit1: | |
3861 | path_put(&path); | |
3862 | putname(name); | |
3863 | if (retry_estale(error, lookup_flags)) { | |
3864 | lookup_flags |= LOOKUP_REVAL; | |
3865 | goto retry; | |
3866 | } | |
3867 | return error; | |
3868 | } | |
3869 | ||
3870 | SYSCALL_DEFINE1(rmdir, const char __user *, pathname) | |
3871 | { | |
3872 | return do_rmdir(AT_FDCWD, pathname); | |
3873 | } | |
3874 | ||
3875 | /** | |
3876 | * vfs_unlink - unlink a filesystem object | |
3877 | * @dir: parent directory | |
3878 | * @dentry: victim | |
3879 | * @delegated_inode: returns victim inode, if the inode is delegated. | |
3880 | * | |
3881 | * The caller must hold dir->i_mutex. | |
3882 | * | |
3883 | * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and | |
3884 | * return a reference to the inode in delegated_inode. The caller | |
3885 | * should then break the delegation on that inode and retry. Because | |
3886 | * breaking a delegation may take a long time, the caller should drop | |
3887 | * dir->i_mutex before doing so. | |
3888 | * | |
3889 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
3890 | * be appropriate for callers that expect the underlying filesystem not | |
3891 | * to be NFS exported. | |
3892 | */ | |
3893 | int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode) | |
3894 | { | |
3895 | struct inode *target = dentry->d_inode; | |
3896 | int error = may_delete(dir, dentry, 0); | |
3897 | ||
3898 | if (error) | |
3899 | return error; | |
3900 | ||
3901 | if (!dir->i_op->unlink) | |
3902 | return -EPERM; | |
3903 | ||
3904 | inode_lock(target); | |
3905 | if (is_local_mountpoint(dentry)) | |
3906 | error = -EBUSY; | |
3907 | else { | |
3908 | error = security_inode_unlink(dir, dentry); | |
3909 | if (!error) { | |
3910 | error = try_break_deleg(target, delegated_inode); | |
3911 | if (error) | |
3912 | goto out; | |
3913 | error = dir->i_op->unlink(dir, dentry); | |
3914 | if (!error) { | |
3915 | dont_mount(dentry); | |
3916 | detach_mounts(dentry); | |
3917 | } | |
3918 | } | |
3919 | } | |
3920 | out: | |
3921 | inode_unlock(target); | |
3922 | ||
3923 | /* We don't d_delete() NFS sillyrenamed files--they still exist. */ | |
3924 | if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { | |
3925 | fsnotify_link_count(target); | |
3926 | d_delete(dentry); | |
3927 | } | |
3928 | ||
3929 | return error; | |
3930 | } | |
3931 | EXPORT_SYMBOL(vfs_unlink); | |
3932 | ||
3933 | /* | |
3934 | * Make sure that the actual truncation of the file will occur outside its | |
3935 | * directory's i_mutex. Truncate can take a long time if there is a lot of | |
3936 | * writeout happening, and we don't want to prevent access to the directory | |
3937 | * while waiting on the I/O. | |
3938 | */ | |
3939 | static long do_unlinkat(int dfd, const char __user *pathname) | |
3940 | { | |
3941 | int error; | |
3942 | struct filename *name; | |
3943 | struct dentry *dentry; | |
3944 | struct path path; | |
3945 | struct qstr last; | |
3946 | int type; | |
3947 | struct inode *inode = NULL; | |
3948 | struct inode *delegated_inode = NULL; | |
3949 | unsigned int lookup_flags = 0; | |
3950 | retry: | |
3951 | name = filename_parentat(dfd, getname(pathname), lookup_flags, | |
3952 | &path, &last, &type); | |
3953 | if (IS_ERR(name)) | |
3954 | return PTR_ERR(name); | |
3955 | ||
3956 | error = -EISDIR; | |
3957 | if (type != LAST_NORM) | |
3958 | goto exit1; | |
3959 | ||
3960 | error = mnt_want_write(path.mnt); | |
3961 | if (error) | |
3962 | goto exit1; | |
3963 | retry_deleg: | |
3964 | inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); | |
3965 | dentry = __lookup_hash(&last, path.dentry, lookup_flags); | |
3966 | error = PTR_ERR(dentry); | |
3967 | if (!IS_ERR(dentry)) { | |
3968 | /* Why not before? Because we want correct error value */ | |
3969 | if (last.name[last.len]) | |
3970 | goto slashes; | |
3971 | inode = dentry->d_inode; | |
3972 | if (d_is_negative(dentry)) | |
3973 | goto slashes; | |
3974 | ihold(inode); | |
3975 | error = security_path_unlink(&path, dentry); | |
3976 | if (error) | |
3977 | goto exit2; | |
3978 | error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode); | |
3979 | exit2: | |
3980 | dput(dentry); | |
3981 | } | |
3982 | inode_unlock(path.dentry->d_inode); | |
3983 | if (inode) | |
3984 | iput(inode); /* truncate the inode here */ | |
3985 | inode = NULL; | |
3986 | if (delegated_inode) { | |
3987 | error = break_deleg_wait(&delegated_inode); | |
3988 | if (!error) | |
3989 | goto retry_deleg; | |
3990 | } | |
3991 | mnt_drop_write(path.mnt); | |
3992 | exit1: | |
3993 | path_put(&path); | |
3994 | putname(name); | |
3995 | if (retry_estale(error, lookup_flags)) { | |
3996 | lookup_flags |= LOOKUP_REVAL; | |
3997 | inode = NULL; | |
3998 | goto retry; | |
3999 | } | |
4000 | return error; | |
4001 | ||
4002 | slashes: | |
4003 | if (d_is_negative(dentry)) | |
4004 | error = -ENOENT; | |
4005 | else if (d_is_dir(dentry)) | |
4006 | error = -EISDIR; | |
4007 | else | |
4008 | error = -ENOTDIR; | |
4009 | goto exit2; | |
4010 | } | |
4011 | ||
4012 | SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) | |
4013 | { | |
4014 | if ((flag & ~AT_REMOVEDIR) != 0) | |
4015 | return -EINVAL; | |
4016 | ||
4017 | if (flag & AT_REMOVEDIR) | |
4018 | return do_rmdir(dfd, pathname); | |
4019 | ||
4020 | return do_unlinkat(dfd, pathname); | |
4021 | } | |
4022 | ||
4023 | SYSCALL_DEFINE1(unlink, const char __user *, pathname) | |
4024 | { | |
4025 | return do_unlinkat(AT_FDCWD, pathname); | |
4026 | } | |
4027 | ||
4028 | int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) | |
4029 | { | |
4030 | int error = may_create(dir, dentry); | |
4031 | ||
4032 | if (error) | |
4033 | return error; | |
4034 | ||
4035 | if (!dir->i_op->symlink) | |
4036 | return -EPERM; | |
4037 | ||
4038 | error = security_inode_symlink(dir, dentry, oldname); | |
4039 | if (error) | |
4040 | return error; | |
4041 | ||
4042 | error = dir->i_op->symlink(dir, dentry, oldname); | |
4043 | if (!error) | |
4044 | fsnotify_create(dir, dentry); | |
4045 | return error; | |
4046 | } | |
4047 | EXPORT_SYMBOL(vfs_symlink); | |
4048 | ||
4049 | SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, | |
4050 | int, newdfd, const char __user *, newname) | |
4051 | { | |
4052 | int error; | |
4053 | struct filename *from; | |
4054 | struct dentry *dentry; | |
4055 | struct path path; | |
4056 | unsigned int lookup_flags = 0; | |
4057 | ||
4058 | from = getname(oldname); | |
4059 | if (IS_ERR(from)) | |
4060 | return PTR_ERR(from); | |
4061 | retry: | |
4062 | dentry = user_path_create(newdfd, newname, &path, lookup_flags); | |
4063 | error = PTR_ERR(dentry); | |
4064 | if (IS_ERR(dentry)) | |
4065 | goto out_putname; | |
4066 | ||
4067 | error = security_path_symlink(&path, dentry, from->name); | |
4068 | if (!error) | |
4069 | error = vfs_symlink(path.dentry->d_inode, dentry, from->name); | |
4070 | done_path_create(&path, dentry); | |
4071 | if (retry_estale(error, lookup_flags)) { | |
4072 | lookup_flags |= LOOKUP_REVAL; | |
4073 | goto retry; | |
4074 | } | |
4075 | out_putname: | |
4076 | putname(from); | |
4077 | return error; | |
4078 | } | |
4079 | ||
4080 | SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) | |
4081 | { | |
4082 | return sys_symlinkat(oldname, AT_FDCWD, newname); | |
4083 | } | |
4084 | ||
4085 | /** | |
4086 | * vfs_link - create a new link | |
4087 | * @old_dentry: object to be linked | |
4088 | * @dir: new parent | |
4089 | * @new_dentry: where to create the new link | |
4090 | * @delegated_inode: returns inode needing a delegation break | |
4091 | * | |
4092 | * The caller must hold dir->i_mutex | |
4093 | * | |
4094 | * If vfs_link discovers a delegation on the to-be-linked file in need | |
4095 | * of breaking, it will return -EWOULDBLOCK and return a reference to the | |
4096 | * inode in delegated_inode. The caller should then break the delegation | |
4097 | * and retry. Because breaking a delegation may take a long time, the | |
4098 | * caller should drop the i_mutex before doing so. | |
4099 | * | |
4100 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
4101 | * be appropriate for callers that expect the underlying filesystem not | |
4102 | * to be NFS exported. | |
4103 | */ | |
4104 | int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode) | |
4105 | { | |
4106 | struct inode *inode = old_dentry->d_inode; | |
4107 | unsigned max_links = dir->i_sb->s_max_links; | |
4108 | int error; | |
4109 | ||
4110 | if (!inode) | |
4111 | return -ENOENT; | |
4112 | ||
4113 | error = may_create(dir, new_dentry); | |
4114 | if (error) | |
4115 | return error; | |
4116 | ||
4117 | if (dir->i_sb != inode->i_sb) | |
4118 | return -EXDEV; | |
4119 | ||
4120 | /* | |
4121 | * A link to an append-only or immutable file cannot be created. | |
4122 | */ | |
4123 | if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) | |
4124 | return -EPERM; | |
4125 | /* | |
4126 | * Updating the link count will likely cause i_uid and i_gid to | |
4127 | * be writen back improperly if their true value is unknown to | |
4128 | * the vfs. | |
4129 | */ | |
4130 | if (HAS_UNMAPPED_ID(inode)) | |
4131 | return -EPERM; | |
4132 | if (!dir->i_op->link) | |
4133 | return -EPERM; | |
4134 | if (S_ISDIR(inode->i_mode)) | |
4135 | return -EPERM; | |
4136 | ||
4137 | error = security_inode_link(old_dentry, dir, new_dentry); | |
4138 | if (error) | |
4139 | return error; | |
4140 | ||
4141 | inode_lock(inode); | |
4142 | /* Make sure we don't allow creating hardlink to an unlinked file */ | |
4143 | if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE)) | |
4144 | error = -ENOENT; | |
4145 | else if (max_links && inode->i_nlink >= max_links) | |
4146 | error = -EMLINK; | |
4147 | else { | |
4148 | error = try_break_deleg(inode, delegated_inode); | |
4149 | if (!error) | |
4150 | error = dir->i_op->link(old_dentry, dir, new_dentry); | |
4151 | } | |
4152 | ||
4153 | if (!error && (inode->i_state & I_LINKABLE)) { | |
4154 | spin_lock(&inode->i_lock); | |
4155 | inode->i_state &= ~I_LINKABLE; | |
4156 | spin_unlock(&inode->i_lock); | |
4157 | } | |
4158 | inode_unlock(inode); | |
4159 | if (!error) | |
4160 | fsnotify_link(dir, inode, new_dentry); | |
4161 | return error; | |
4162 | } | |
4163 | EXPORT_SYMBOL(vfs_link); | |
4164 | ||
4165 | /* | |
4166 | * Hardlinks are often used in delicate situations. We avoid | |
4167 | * security-related surprises by not following symlinks on the | |
4168 | * newname. --KAB | |
4169 | * | |
4170 | * We don't follow them on the oldname either to be compatible | |
4171 | * with linux 2.0, and to avoid hard-linking to directories | |
4172 | * and other special files. --ADM | |
4173 | */ | |
4174 | SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, | |
4175 | int, newdfd, const char __user *, newname, int, flags) | |
4176 | { | |
4177 | struct dentry *new_dentry; | |
4178 | struct path old_path, new_path; | |
4179 | struct inode *delegated_inode = NULL; | |
4180 | int how = 0; | |
4181 | int error; | |
4182 | ||
4183 | if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) | |
4184 | return -EINVAL; | |
4185 | /* | |
4186 | * To use null names we require CAP_DAC_READ_SEARCH | |
4187 | * This ensures that not everyone will be able to create | |
4188 | * handlink using the passed filedescriptor. | |
4189 | */ | |
4190 | if (flags & AT_EMPTY_PATH) { | |
4191 | if (!capable(CAP_DAC_READ_SEARCH)) | |
4192 | return -ENOENT; | |
4193 | how = LOOKUP_EMPTY; | |
4194 | } | |
4195 | ||
4196 | if (flags & AT_SYMLINK_FOLLOW) | |
4197 | how |= LOOKUP_FOLLOW; | |
4198 | retry: | |
4199 | error = user_path_at(olddfd, oldname, how, &old_path); | |
4200 | if (error) | |
4201 | return error; | |
4202 | ||
4203 | new_dentry = user_path_create(newdfd, newname, &new_path, | |
4204 | (how & LOOKUP_REVAL)); | |
4205 | error = PTR_ERR(new_dentry); | |
4206 | if (IS_ERR(new_dentry)) | |
4207 | goto out; | |
4208 | ||
4209 | error = -EXDEV; | |
4210 | if (old_path.mnt != new_path.mnt) | |
4211 | goto out_dput; | |
4212 | error = may_linkat(&old_path); | |
4213 | if (unlikely(error)) | |
4214 | goto out_dput; | |
4215 | error = security_path_link(old_path.dentry, &new_path, new_dentry); | |
4216 | if (error) | |
4217 | goto out_dput; | |
4218 | error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode); | |
4219 | out_dput: | |
4220 | done_path_create(&new_path, new_dentry); | |
4221 | if (delegated_inode) { | |
4222 | error = break_deleg_wait(&delegated_inode); | |
4223 | if (!error) { | |
4224 | path_put(&old_path); | |
4225 | goto retry; | |
4226 | } | |
4227 | } | |
4228 | if (retry_estale(error, how)) { | |
4229 | path_put(&old_path); | |
4230 | how |= LOOKUP_REVAL; | |
4231 | goto retry; | |
4232 | } | |
4233 | out: | |
4234 | path_put(&old_path); | |
4235 | ||
4236 | return error; | |
4237 | } | |
4238 | ||
4239 | SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) | |
4240 | { | |
4241 | return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); | |
4242 | } | |
4243 | ||
4244 | /** | |
4245 | * vfs_rename - rename a filesystem object | |
4246 | * @old_dir: parent of source | |
4247 | * @old_dentry: source | |
4248 | * @new_dir: parent of destination | |
4249 | * @new_dentry: destination | |
4250 | * @delegated_inode: returns an inode needing a delegation break | |
4251 | * @flags: rename flags | |
4252 | * | |
4253 | * The caller must hold multiple mutexes--see lock_rename()). | |
4254 | * | |
4255 | * If vfs_rename discovers a delegation in need of breaking at either | |
4256 | * the source or destination, it will return -EWOULDBLOCK and return a | |
4257 | * reference to the inode in delegated_inode. The caller should then | |
4258 | * break the delegation and retry. Because breaking a delegation may | |
4259 | * take a long time, the caller should drop all locks before doing | |
4260 | * so. | |
4261 | * | |
4262 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
4263 | * be appropriate for callers that expect the underlying filesystem not | |
4264 | * to be NFS exported. | |
4265 | * | |
4266 | * The worst of all namespace operations - renaming directory. "Perverted" | |
4267 | * doesn't even start to describe it. Somebody in UCB had a heck of a trip... | |
4268 | * Problems: | |
4269 | * a) we can get into loop creation. | |
4270 | * b) race potential - two innocent renames can create a loop together. | |
4271 | * That's where 4.4 screws up. Current fix: serialization on | |
4272 | * sb->s_vfs_rename_mutex. We might be more accurate, but that's another | |
4273 | * story. | |
4274 | * c) we have to lock _four_ objects - parents and victim (if it exists), | |
4275 | * and source (if it is not a directory). | |
4276 | * And that - after we got ->i_mutex on parents (until then we don't know | |
4277 | * whether the target exists). Solution: try to be smart with locking | |
4278 | * order for inodes. We rely on the fact that tree topology may change | |
4279 | * only under ->s_vfs_rename_mutex _and_ that parent of the object we | |
4280 | * move will be locked. Thus we can rank directories by the tree | |
4281 | * (ancestors first) and rank all non-directories after them. | |
4282 | * That works since everybody except rename does "lock parent, lookup, | |
4283 | * lock child" and rename is under ->s_vfs_rename_mutex. | |
4284 | * HOWEVER, it relies on the assumption that any object with ->lookup() | |
4285 | * has no more than 1 dentry. If "hybrid" objects will ever appear, | |
4286 | * we'd better make sure that there's no link(2) for them. | |
4287 | * d) conversion from fhandle to dentry may come in the wrong moment - when | |
4288 | * we are removing the target. Solution: we will have to grab ->i_mutex | |
4289 | * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on | |
4290 | * ->i_mutex on parents, which works but leads to some truly excessive | |
4291 | * locking]. | |
4292 | */ | |
4293 | int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, | |
4294 | struct inode *new_dir, struct dentry *new_dentry, | |
4295 | struct inode **delegated_inode, unsigned int flags) | |
4296 | { | |
4297 | int error; | |
4298 | bool is_dir = d_is_dir(old_dentry); | |
4299 | const unsigned char *old_name; | |
4300 | struct inode *source = old_dentry->d_inode; | |
4301 | struct inode *target = new_dentry->d_inode; | |
4302 | bool new_is_dir = false; | |
4303 | unsigned max_links = new_dir->i_sb->s_max_links; | |
4304 | ||
4305 | if (source == target) | |
4306 | return 0; | |
4307 | ||
4308 | error = may_delete(old_dir, old_dentry, is_dir); | |
4309 | if (error) | |
4310 | return error; | |
4311 | ||
4312 | if (!target) { | |
4313 | error = may_create(new_dir, new_dentry); | |
4314 | } else { | |
4315 | new_is_dir = d_is_dir(new_dentry); | |
4316 | ||
4317 | if (!(flags & RENAME_EXCHANGE)) | |
4318 | error = may_delete(new_dir, new_dentry, is_dir); | |
4319 | else | |
4320 | error = may_delete(new_dir, new_dentry, new_is_dir); | |
4321 | } | |
4322 | if (error) | |
4323 | return error; | |
4324 | ||
4325 | if (!old_dir->i_op->rename) | |
4326 | return -EPERM; | |
4327 | ||
4328 | /* | |
4329 | * If we are going to change the parent - check write permissions, | |
4330 | * we'll need to flip '..'. | |
4331 | */ | |
4332 | if (new_dir != old_dir) { | |
4333 | if (is_dir) { | |
4334 | error = inode_permission(source, MAY_WRITE); | |
4335 | if (error) | |
4336 | return error; | |
4337 | } | |
4338 | if ((flags & RENAME_EXCHANGE) && new_is_dir) { | |
4339 | error = inode_permission(target, MAY_WRITE); | |
4340 | if (error) | |
4341 | return error; | |
4342 | } | |
4343 | } | |
4344 | ||
4345 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry, | |
4346 | flags); | |
4347 | if (error) | |
4348 | return error; | |
4349 | ||
4350 | old_name = fsnotify_oldname_init(old_dentry->d_name.name); | |
4351 | dget(new_dentry); | |
4352 | if (!is_dir || (flags & RENAME_EXCHANGE)) | |
4353 | lock_two_nondirectories(source, target); | |
4354 | else if (target) | |
4355 | inode_lock(target); | |
4356 | ||
4357 | error = -EBUSY; | |
4358 | if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry)) | |
4359 | goto out; | |
4360 | ||
4361 | if (max_links && new_dir != old_dir) { | |
4362 | error = -EMLINK; | |
4363 | if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links) | |
4364 | goto out; | |
4365 | if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir && | |
4366 | old_dir->i_nlink >= max_links) | |
4367 | goto out; | |
4368 | } | |
4369 | if (is_dir && !(flags & RENAME_EXCHANGE) && target) | |
4370 | shrink_dcache_parent(new_dentry); | |
4371 | if (!is_dir) { | |
4372 | error = try_break_deleg(source, delegated_inode); | |
4373 | if (error) | |
4374 | goto out; | |
4375 | } | |
4376 | if (target && !new_is_dir) { | |
4377 | error = try_break_deleg(target, delegated_inode); | |
4378 | if (error) | |
4379 | goto out; | |
4380 | } | |
4381 | error = old_dir->i_op->rename(old_dir, old_dentry, | |
4382 | new_dir, new_dentry, flags); | |
4383 | if (error) | |
4384 | goto out; | |
4385 | ||
4386 | if (!(flags & RENAME_EXCHANGE) && target) { | |
4387 | if (is_dir) | |
4388 | target->i_flags |= S_DEAD; | |
4389 | dont_mount(new_dentry); | |
4390 | detach_mounts(new_dentry); | |
4391 | } | |
4392 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) { | |
4393 | if (!(flags & RENAME_EXCHANGE)) | |
4394 | d_move(old_dentry, new_dentry); | |
4395 | else | |
4396 | d_exchange(old_dentry, new_dentry); | |
4397 | } | |
4398 | out: | |
4399 | if (!is_dir || (flags & RENAME_EXCHANGE)) | |
4400 | unlock_two_nondirectories(source, target); | |
4401 | else if (target) | |
4402 | inode_unlock(target); | |
4403 | dput(new_dentry); | |
4404 | if (!error) { | |
4405 | fsnotify_move(old_dir, new_dir, old_name, is_dir, | |
4406 | !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); | |
4407 | if (flags & RENAME_EXCHANGE) { | |
4408 | fsnotify_move(new_dir, old_dir, old_dentry->d_name.name, | |
4409 | new_is_dir, NULL, new_dentry); | |
4410 | } | |
4411 | } | |
4412 | fsnotify_oldname_free(old_name); | |
4413 | ||
4414 | return error; | |
4415 | } | |
4416 | EXPORT_SYMBOL(vfs_rename); | |
4417 | ||
4418 | SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname, | |
4419 | int, newdfd, const char __user *, newname, unsigned int, flags) | |
4420 | { | |
4421 | struct dentry *old_dentry, *new_dentry; | |
4422 | struct dentry *trap; | |
4423 | struct path old_path, new_path; | |
4424 | struct qstr old_last, new_last; | |
4425 | int old_type, new_type; | |
4426 | struct inode *delegated_inode = NULL; | |
4427 | struct filename *from; | |
4428 | struct filename *to; | |
4429 | unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET; | |
4430 | bool should_retry = false; | |
4431 | int error; | |
4432 | ||
4433 | if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) | |
4434 | return -EINVAL; | |
4435 | ||
4436 | if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) && | |
4437 | (flags & RENAME_EXCHANGE)) | |
4438 | return -EINVAL; | |
4439 | ||
4440 | if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD)) | |
4441 | return -EPERM; | |
4442 | ||
4443 | if (flags & RENAME_EXCHANGE) | |
4444 | target_flags = 0; | |
4445 | ||
4446 | retry: | |
4447 | from = filename_parentat(olddfd, getname(oldname), lookup_flags, | |
4448 | &old_path, &old_last, &old_type); | |
4449 | if (IS_ERR(from)) { | |
4450 | error = PTR_ERR(from); | |
4451 | goto exit; | |
4452 | } | |
4453 | ||
4454 | to = filename_parentat(newdfd, getname(newname), lookup_flags, | |
4455 | &new_path, &new_last, &new_type); | |
4456 | if (IS_ERR(to)) { | |
4457 | error = PTR_ERR(to); | |
4458 | goto exit1; | |
4459 | } | |
4460 | ||
4461 | error = -EXDEV; | |
4462 | if (old_path.mnt != new_path.mnt) | |
4463 | goto exit2; | |
4464 | ||
4465 | error = -EBUSY; | |
4466 | if (old_type != LAST_NORM) | |
4467 | goto exit2; | |
4468 | ||
4469 | if (flags & RENAME_NOREPLACE) | |
4470 | error = -EEXIST; | |
4471 | if (new_type != LAST_NORM) | |
4472 | goto exit2; | |
4473 | ||
4474 | error = mnt_want_write(old_path.mnt); | |
4475 | if (error) | |
4476 | goto exit2; | |
4477 | ||
4478 | retry_deleg: | |
4479 | trap = lock_rename(new_path.dentry, old_path.dentry); | |
4480 | ||
4481 | old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags); | |
4482 | error = PTR_ERR(old_dentry); | |
4483 | if (IS_ERR(old_dentry)) | |
4484 | goto exit3; | |
4485 | /* source must exist */ | |
4486 | error = -ENOENT; | |
4487 | if (d_is_negative(old_dentry)) | |
4488 | goto exit4; | |
4489 | new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags); | |
4490 | error = PTR_ERR(new_dentry); | |
4491 | if (IS_ERR(new_dentry)) | |
4492 | goto exit4; | |
4493 | error = -EEXIST; | |
4494 | if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) | |
4495 | goto exit5; | |
4496 | if (flags & RENAME_EXCHANGE) { | |
4497 | error = -ENOENT; | |
4498 | if (d_is_negative(new_dentry)) | |
4499 | goto exit5; | |
4500 | ||
4501 | if (!d_is_dir(new_dentry)) { | |
4502 | error = -ENOTDIR; | |
4503 | if (new_last.name[new_last.len]) | |
4504 | goto exit5; | |
4505 | } | |
4506 | } | |
4507 | /* unless the source is a directory trailing slashes give -ENOTDIR */ | |
4508 | if (!d_is_dir(old_dentry)) { | |
4509 | error = -ENOTDIR; | |
4510 | if (old_last.name[old_last.len]) | |
4511 | goto exit5; | |
4512 | if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len]) | |
4513 | goto exit5; | |
4514 | } | |
4515 | /* source should not be ancestor of target */ | |
4516 | error = -EINVAL; | |
4517 | if (old_dentry == trap) | |
4518 | goto exit5; | |
4519 | /* target should not be an ancestor of source */ | |
4520 | if (!(flags & RENAME_EXCHANGE)) | |
4521 | error = -ENOTEMPTY; | |
4522 | if (new_dentry == trap) | |
4523 | goto exit5; | |
4524 | ||
4525 | error = security_path_rename(&old_path, old_dentry, | |
4526 | &new_path, new_dentry, flags); | |
4527 | if (error) | |
4528 | goto exit5; | |
4529 | error = vfs_rename(old_path.dentry->d_inode, old_dentry, | |
4530 | new_path.dentry->d_inode, new_dentry, | |
4531 | &delegated_inode, flags); | |
4532 | exit5: | |
4533 | dput(new_dentry); | |
4534 | exit4: | |
4535 | dput(old_dentry); | |
4536 | exit3: | |
4537 | unlock_rename(new_path.dentry, old_path.dentry); | |
4538 | if (delegated_inode) { | |
4539 | error = break_deleg_wait(&delegated_inode); | |
4540 | if (!error) | |
4541 | goto retry_deleg; | |
4542 | } | |
4543 | mnt_drop_write(old_path.mnt); | |
4544 | exit2: | |
4545 | if (retry_estale(error, lookup_flags)) | |
4546 | should_retry = true; | |
4547 | path_put(&new_path); | |
4548 | putname(to); | |
4549 | exit1: | |
4550 | path_put(&old_path); | |
4551 | putname(from); | |
4552 | if (should_retry) { | |
4553 | should_retry = false; | |
4554 | lookup_flags |= LOOKUP_REVAL; | |
4555 | goto retry; | |
4556 | } | |
4557 | exit: | |
4558 | return error; | |
4559 | } | |
4560 | ||
4561 | SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, | |
4562 | int, newdfd, const char __user *, newname) | |
4563 | { | |
4564 | return sys_renameat2(olddfd, oldname, newdfd, newname, 0); | |
4565 | } | |
4566 | ||
4567 | SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) | |
4568 | { | |
4569 | return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0); | |
4570 | } | |
4571 | ||
4572 | int vfs_whiteout(struct inode *dir, struct dentry *dentry) | |
4573 | { | |
4574 | int error = may_create(dir, dentry); | |
4575 | if (error) | |
4576 | return error; | |
4577 | ||
4578 | if (!dir->i_op->mknod) | |
4579 | return -EPERM; | |
4580 | ||
4581 | return dir->i_op->mknod(dir, dentry, | |
4582 | S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV); | |
4583 | } | |
4584 | EXPORT_SYMBOL(vfs_whiteout); | |
4585 | ||
4586 | int readlink_copy(char __user *buffer, int buflen, const char *link) | |
4587 | { | |
4588 | int len = PTR_ERR(link); | |
4589 | if (IS_ERR(link)) | |
4590 | goto out; | |
4591 | ||
4592 | len = strlen(link); | |
4593 | if (len > (unsigned) buflen) | |
4594 | len = buflen; | |
4595 | if (copy_to_user(buffer, link, len)) | |
4596 | len = -EFAULT; | |
4597 | out: | |
4598 | return len; | |
4599 | } | |
4600 | ||
4601 | /* | |
4602 | * A helper for ->readlink(). This should be used *ONLY* for symlinks that | |
4603 | * have ->get_link() not calling nd_jump_link(). Using (or not using) it | |
4604 | * for any given inode is up to filesystem. | |
4605 | */ | |
4606 | static int generic_readlink(struct dentry *dentry, char __user *buffer, | |
4607 | int buflen) | |
4608 | { | |
4609 | DEFINE_DELAYED_CALL(done); | |
4610 | struct inode *inode = d_inode(dentry); | |
4611 | const char *link = inode->i_link; | |
4612 | int res; | |
4613 | ||
4614 | if (!link) { | |
4615 | link = inode->i_op->get_link(dentry, inode, &done); | |
4616 | if (IS_ERR(link)) | |
4617 | return PTR_ERR(link); | |
4618 | } | |
4619 | res = readlink_copy(buffer, buflen, link); | |
4620 | do_delayed_call(&done); | |
4621 | return res; | |
4622 | } | |
4623 | ||
4624 | /** | |
4625 | * vfs_readlink - copy symlink body into userspace buffer | |
4626 | * @dentry: dentry on which to get symbolic link | |
4627 | * @buffer: user memory pointer | |
4628 | * @buflen: size of buffer | |
4629 | * | |
4630 | * Does not touch atime. That's up to the caller if necessary | |
4631 | * | |
4632 | * Does not call security hook. | |
4633 | */ | |
4634 | int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen) | |
4635 | { | |
4636 | struct inode *inode = d_inode(dentry); | |
4637 | ||
4638 | if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) { | |
4639 | if (unlikely(inode->i_op->readlink)) | |
4640 | return inode->i_op->readlink(dentry, buffer, buflen); | |
4641 | ||
4642 | if (!d_is_symlink(dentry)) | |
4643 | return -EINVAL; | |
4644 | ||
4645 | spin_lock(&inode->i_lock); | |
4646 | inode->i_opflags |= IOP_DEFAULT_READLINK; | |
4647 | spin_unlock(&inode->i_lock); | |
4648 | } | |
4649 | ||
4650 | return generic_readlink(dentry, buffer, buflen); | |
4651 | } | |
4652 | EXPORT_SYMBOL(vfs_readlink); | |
4653 | ||
4654 | /** | |
4655 | * vfs_get_link - get symlink body | |
4656 | * @dentry: dentry on which to get symbolic link | |
4657 | * @done: caller needs to free returned data with this | |
4658 | * | |
4659 | * Calls security hook and i_op->get_link() on the supplied inode. | |
4660 | * | |
4661 | * It does not touch atime. That's up to the caller if necessary. | |
4662 | * | |
4663 | * Does not work on "special" symlinks like /proc/$$/fd/N | |
4664 | */ | |
4665 | const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done) | |
4666 | { | |
4667 | const char *res = ERR_PTR(-EINVAL); | |
4668 | struct inode *inode = d_inode(dentry); | |
4669 | ||
4670 | if (d_is_symlink(dentry)) { | |
4671 | res = ERR_PTR(security_inode_readlink(dentry)); | |
4672 | if (!res) | |
4673 | res = inode->i_op->get_link(dentry, inode, done); | |
4674 | } | |
4675 | return res; | |
4676 | } | |
4677 | EXPORT_SYMBOL(vfs_get_link); | |
4678 | ||
4679 | /* get the link contents into pagecache */ | |
4680 | const char *page_get_link(struct dentry *dentry, struct inode *inode, | |
4681 | struct delayed_call *callback) | |
4682 | { | |
4683 | char *kaddr; | |
4684 | struct page *page; | |
4685 | struct address_space *mapping = inode->i_mapping; | |
4686 | ||
4687 | if (!dentry) { | |
4688 | page = find_get_page(mapping, 0); | |
4689 | if (!page) | |
4690 | return ERR_PTR(-ECHILD); | |
4691 | if (!PageUptodate(page)) { | |
4692 | put_page(page); | |
4693 | return ERR_PTR(-ECHILD); | |
4694 | } | |
4695 | } else { | |
4696 | page = read_mapping_page(mapping, 0, NULL); | |
4697 | if (IS_ERR(page)) | |
4698 | return (char*)page; | |
4699 | } | |
4700 | set_delayed_call(callback, page_put_link, page); | |
4701 | BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM); | |
4702 | kaddr = page_address(page); | |
4703 | nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1); | |
4704 | return kaddr; | |
4705 | } | |
4706 | ||
4707 | EXPORT_SYMBOL(page_get_link); | |
4708 | ||
4709 | void page_put_link(void *arg) | |
4710 | { | |
4711 | put_page(arg); | |
4712 | } | |
4713 | EXPORT_SYMBOL(page_put_link); | |
4714 | ||
4715 | int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) | |
4716 | { | |
4717 | DEFINE_DELAYED_CALL(done); | |
4718 | int res = readlink_copy(buffer, buflen, | |
4719 | page_get_link(dentry, d_inode(dentry), | |
4720 | &done)); | |
4721 | do_delayed_call(&done); | |
4722 | return res; | |
4723 | } | |
4724 | EXPORT_SYMBOL(page_readlink); | |
4725 | ||
4726 | /* | |
4727 | * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS | |
4728 | */ | |
4729 | int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) | |
4730 | { | |
4731 | struct address_space *mapping = inode->i_mapping; | |
4732 | struct page *page; | |
4733 | void *fsdata; | |
4734 | int err; | |
4735 | unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; | |
4736 | if (nofs) | |
4737 | flags |= AOP_FLAG_NOFS; | |
4738 | ||
4739 | retry: | |
4740 | err = pagecache_write_begin(NULL, mapping, 0, len-1, | |
4741 | flags, &page, &fsdata); | |
4742 | if (err) | |
4743 | goto fail; | |
4744 | ||
4745 | memcpy(page_address(page), symname, len-1); | |
4746 | ||
4747 | err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, | |
4748 | page, fsdata); | |
4749 | if (err < 0) | |
4750 | goto fail; | |
4751 | if (err < len-1) | |
4752 | goto retry; | |
4753 | ||
4754 | mark_inode_dirty(inode); | |
4755 | return 0; | |
4756 | fail: | |
4757 | return err; | |
4758 | } | |
4759 | EXPORT_SYMBOL(__page_symlink); | |
4760 | ||
4761 | int page_symlink(struct inode *inode, const char *symname, int len) | |
4762 | { | |
4763 | return __page_symlink(inode, symname, len, | |
4764 | !mapping_gfp_constraint(inode->i_mapping, __GFP_FS)); | |
4765 | } | |
4766 | EXPORT_SYMBOL(page_symlink); | |
4767 | ||
4768 | const struct inode_operations page_symlink_inode_operations = { | |
4769 | .get_link = page_get_link, | |
4770 | }; | |
4771 | EXPORT_SYMBOL(page_symlink_inode_operations); |