Merge remote-tracking branch 'omap_dss2/for-next'
[deliverable/linux.git] / fs / overlayfs / super.c
1 /*
2 *
3 * Copyright (C) 2011 Novell Inc.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
8 */
9
10 #include <linux/fs.h>
11 #include <linux/namei.h>
12 #include <linux/pagemap.h>
13 #include <linux/xattr.h>
14 #include <linux/security.h>
15 #include <linux/mount.h>
16 #include <linux/slab.h>
17 #include <linux/parser.h>
18 #include <linux/module.h>
19 #include <linux/sched.h>
20 #include <linux/statfs.h>
21 #include <linux/seq_file.h>
22 #include <linux/posix_acl_xattr.h>
23 #include "overlayfs.h"
24
25 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
26 MODULE_DESCRIPTION("Overlay filesystem");
27 MODULE_LICENSE("GPL");
28
29 struct ovl_config {
30 char *lowerdir;
31 char *upperdir;
32 char *workdir;
33 bool default_permissions;
34 };
35
36 /* private information held for overlayfs's superblock */
37 struct ovl_fs {
38 struct vfsmount *upper_mnt;
39 unsigned numlower;
40 struct vfsmount **lower_mnt;
41 struct dentry *workdir;
42 long lower_namelen;
43 /* pathnames of lower and upper dirs, for show_options */
44 struct ovl_config config;
45 /* creds of process who forced instantiation of super block */
46 const struct cred *creator_cred;
47 };
48
49 struct ovl_dir_cache;
50
51 /* private information held for every overlayfs dentry */
52 struct ovl_entry {
53 struct dentry *__upperdentry;
54 struct ovl_dir_cache *cache;
55 union {
56 struct {
57 u64 version;
58 bool opaque;
59 };
60 struct rcu_head rcu;
61 };
62 unsigned numlower;
63 struct path lowerstack[];
64 };
65
66 #define OVL_MAX_STACK 500
67
68 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
69 {
70 return oe->numlower ? oe->lowerstack[0].dentry : NULL;
71 }
72
73 enum ovl_path_type ovl_path_type(struct dentry *dentry)
74 {
75 struct ovl_entry *oe = dentry->d_fsdata;
76 enum ovl_path_type type = 0;
77
78 if (oe->__upperdentry) {
79 type = __OVL_PATH_UPPER;
80
81 /*
82 * Non-dir dentry can hold lower dentry from previous
83 * location. Its purity depends only on opaque flag.
84 */
85 if (oe->numlower && S_ISDIR(dentry->d_inode->i_mode))
86 type |= __OVL_PATH_MERGE;
87 else if (!oe->opaque)
88 type |= __OVL_PATH_PURE;
89 } else {
90 if (oe->numlower > 1)
91 type |= __OVL_PATH_MERGE;
92 }
93 return type;
94 }
95
96 static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
97 {
98 return lockless_dereference(oe->__upperdentry);
99 }
100
101 void ovl_path_upper(struct dentry *dentry, struct path *path)
102 {
103 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
104 struct ovl_entry *oe = dentry->d_fsdata;
105
106 path->mnt = ofs->upper_mnt;
107 path->dentry = ovl_upperdentry_dereference(oe);
108 }
109
110 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
111 {
112 enum ovl_path_type type = ovl_path_type(dentry);
113
114 if (!OVL_TYPE_UPPER(type))
115 ovl_path_lower(dentry, path);
116 else
117 ovl_path_upper(dentry, path);
118
119 return type;
120 }
121
122 struct dentry *ovl_dentry_upper(struct dentry *dentry)
123 {
124 struct ovl_entry *oe = dentry->d_fsdata;
125
126 return ovl_upperdentry_dereference(oe);
127 }
128
129 struct dentry *ovl_dentry_lower(struct dentry *dentry)
130 {
131 struct ovl_entry *oe = dentry->d_fsdata;
132
133 return __ovl_dentry_lower(oe);
134 }
135
136 struct dentry *ovl_dentry_real(struct dentry *dentry)
137 {
138 struct ovl_entry *oe = dentry->d_fsdata;
139 struct dentry *realdentry;
140
141 realdentry = ovl_upperdentry_dereference(oe);
142 if (!realdentry)
143 realdentry = __ovl_dentry_lower(oe);
144
145 return realdentry;
146 }
147
148 static void ovl_inode_init(struct inode *inode, struct inode *realinode,
149 bool is_upper)
150 {
151 WRITE_ONCE(inode->i_private, (unsigned long) realinode |
152 (is_upper ? OVL_ISUPPER_MASK : 0));
153 }
154
155 struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
156 bool is_upper)
157 {
158 if (is_upper) {
159 struct ovl_fs *ofs = inode->i_sb->s_fs_info;
160
161 return ofs->upper_mnt;
162 } else {
163 return oe->numlower ? oe->lowerstack[0].mnt : NULL;
164 }
165 }
166
167 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
168 {
169 struct ovl_entry *oe = dentry->d_fsdata;
170
171 return oe->cache;
172 }
173
174 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
175 {
176 struct ovl_entry *oe = dentry->d_fsdata;
177
178 oe->cache = cache;
179 }
180
181 void ovl_path_lower(struct dentry *dentry, struct path *path)
182 {
183 struct ovl_entry *oe = dentry->d_fsdata;
184
185 *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
186 }
187
188 int ovl_want_write(struct dentry *dentry)
189 {
190 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
191 return mnt_want_write(ofs->upper_mnt);
192 }
193
194 void ovl_drop_write(struct dentry *dentry)
195 {
196 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
197 mnt_drop_write(ofs->upper_mnt);
198 }
199
200 struct dentry *ovl_workdir(struct dentry *dentry)
201 {
202 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
203 return ofs->workdir;
204 }
205
206 bool ovl_dentry_is_opaque(struct dentry *dentry)
207 {
208 struct ovl_entry *oe = dentry->d_fsdata;
209 return oe->opaque;
210 }
211
212 void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
213 {
214 struct ovl_entry *oe = dentry->d_fsdata;
215 oe->opaque = opaque;
216 }
217
218 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
219 {
220 struct ovl_entry *oe = dentry->d_fsdata;
221
222 WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
223 WARN_ON(oe->__upperdentry);
224 /*
225 * Make sure upperdentry is consistent before making it visible to
226 * ovl_upperdentry_dereference().
227 */
228 smp_wmb();
229 oe->__upperdentry = upperdentry;
230 }
231
232 void ovl_inode_update(struct inode *inode, struct inode *upperinode)
233 {
234 WARN_ON(!upperinode);
235 WARN_ON(!inode_unhashed(inode));
236 WRITE_ONCE(inode->i_private,
237 (unsigned long) upperinode | OVL_ISUPPER_MASK);
238 if (!S_ISDIR(upperinode->i_mode))
239 __insert_inode_hash(inode, (unsigned long) upperinode);
240 }
241
242 void ovl_dentry_version_inc(struct dentry *dentry)
243 {
244 struct ovl_entry *oe = dentry->d_fsdata;
245
246 WARN_ON(!inode_is_locked(dentry->d_inode));
247 oe->version++;
248 }
249
250 u64 ovl_dentry_version_get(struct dentry *dentry)
251 {
252 struct ovl_entry *oe = dentry->d_fsdata;
253
254 WARN_ON(!inode_is_locked(dentry->d_inode));
255 return oe->version;
256 }
257
258 bool ovl_is_whiteout(struct dentry *dentry)
259 {
260 struct inode *inode = dentry->d_inode;
261
262 return inode && IS_WHITEOUT(inode);
263 }
264
265 const struct cred *ovl_override_creds(struct super_block *sb)
266 {
267 struct ovl_fs *ofs = sb->s_fs_info;
268
269 return override_creds(ofs->creator_cred);
270 }
271
272 static bool ovl_is_opaquedir(struct dentry *dentry)
273 {
274 int res;
275 char val;
276 struct inode *inode = dentry->d_inode;
277
278 if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
279 return false;
280
281 res = inode->i_op->getxattr(dentry, inode, OVL_XATTR_OPAQUE, &val, 1);
282 if (res == 1 && val == 'y')
283 return true;
284
285 return false;
286 }
287
288 static void ovl_dentry_release(struct dentry *dentry)
289 {
290 struct ovl_entry *oe = dentry->d_fsdata;
291
292 if (oe) {
293 unsigned int i;
294
295 dput(oe->__upperdentry);
296 for (i = 0; i < oe->numlower; i++)
297 dput(oe->lowerstack[i].dentry);
298 kfree_rcu(oe, rcu);
299 }
300 }
301
302 static struct dentry *ovl_d_real(struct dentry *dentry,
303 const struct inode *inode,
304 unsigned int open_flags)
305 {
306 struct dentry *real;
307
308 if (d_is_dir(dentry)) {
309 if (!inode || inode == d_inode(dentry))
310 return dentry;
311 goto bug;
312 }
313
314 if (d_is_negative(dentry))
315 return dentry;
316
317 if (open_flags) {
318 int err = ovl_open_maybe_copy_up(dentry, open_flags);
319
320 if (err)
321 return ERR_PTR(err);
322 }
323
324 real = ovl_dentry_upper(dentry);
325 if (real && (!inode || inode == d_inode(real)))
326 return real;
327
328 real = ovl_dentry_lower(dentry);
329 if (!real)
330 goto bug;
331
332 if (!inode || inode == d_inode(real))
333 return real;
334
335 /* Handle recursion */
336 return d_real(real, inode, open_flags);
337 bug:
338 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
339 inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
340 return dentry;
341 }
342
343 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
344 {
345 struct ovl_entry *oe = dentry->d_fsdata;
346 unsigned int i;
347 int ret = 1;
348
349 for (i = 0; i < oe->numlower; i++) {
350 struct dentry *d = oe->lowerstack[i].dentry;
351
352 if (d->d_flags & DCACHE_OP_REVALIDATE) {
353 ret = d->d_op->d_revalidate(d, flags);
354 if (ret < 0)
355 return ret;
356 if (!ret) {
357 if (!(flags & LOOKUP_RCU))
358 d_invalidate(d);
359 return -ESTALE;
360 }
361 }
362 }
363 return 1;
364 }
365
366 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
367 {
368 struct ovl_entry *oe = dentry->d_fsdata;
369 unsigned int i;
370 int ret = 1;
371
372 for (i = 0; i < oe->numlower; i++) {
373 struct dentry *d = oe->lowerstack[i].dentry;
374
375 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
376 ret = d->d_op->d_weak_revalidate(d, flags);
377 if (ret <= 0)
378 break;
379 }
380 }
381 return ret;
382 }
383
384 static const struct dentry_operations ovl_dentry_operations = {
385 .d_release = ovl_dentry_release,
386 .d_real = ovl_d_real,
387 };
388
389 static const struct dentry_operations ovl_reval_dentry_operations = {
390 .d_release = ovl_dentry_release,
391 .d_real = ovl_d_real,
392 .d_revalidate = ovl_dentry_revalidate,
393 .d_weak_revalidate = ovl_dentry_weak_revalidate,
394 };
395
396 static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
397 {
398 size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
399 struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
400
401 if (oe)
402 oe->numlower = numlower;
403
404 return oe;
405 }
406
407 static bool ovl_dentry_remote(struct dentry *dentry)
408 {
409 return dentry->d_flags &
410 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
411 DCACHE_OP_REAL);
412 }
413
414 static bool ovl_dentry_weird(struct dentry *dentry)
415 {
416 return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
417 DCACHE_MANAGE_TRANSIT |
418 DCACHE_OP_HASH |
419 DCACHE_OP_COMPARE);
420 }
421
422 static inline struct dentry *ovl_lookup_real(struct super_block *ovl_sb,
423 struct dentry *dir,
424 const struct qstr *name)
425 {
426 const struct cred *old_cred;
427 struct dentry *dentry;
428
429 old_cred = ovl_override_creds(ovl_sb);
430 dentry = lookup_one_len_unlocked(name->name, dir, name->len);
431 revert_creds(old_cred);
432
433 if (IS_ERR(dentry)) {
434 if (PTR_ERR(dentry) == -ENOENT)
435 dentry = NULL;
436 } else if (!dentry->d_inode) {
437 dput(dentry);
438 dentry = NULL;
439 } else if (ovl_dentry_weird(dentry)) {
440 dput(dentry);
441 /* Don't support traversing automounts and other weirdness */
442 dentry = ERR_PTR(-EREMOTE);
443 }
444 return dentry;
445 }
446
447 /*
448 * Returns next layer in stack starting from top.
449 * Returns -1 if this is the last layer.
450 */
451 int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
452 {
453 struct ovl_entry *oe = dentry->d_fsdata;
454
455 BUG_ON(idx < 0);
456 if (idx == 0) {
457 ovl_path_upper(dentry, path);
458 if (path->dentry)
459 return oe->numlower ? 1 : -1;
460 idx++;
461 }
462 BUG_ON(idx > oe->numlower);
463 *path = oe->lowerstack[idx - 1];
464
465 return (idx < oe->numlower) ? idx + 1 : -1;
466 }
467
468 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
469 unsigned int flags)
470 {
471 struct ovl_entry *oe;
472 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
473 struct path *stack = NULL;
474 struct dentry *upperdir, *upperdentry = NULL;
475 unsigned int ctr = 0;
476 struct inode *inode = NULL;
477 bool upperopaque = false;
478 struct dentry *this, *prev = NULL;
479 unsigned int i;
480 int err;
481
482 upperdir = ovl_upperdentry_dereference(poe);
483 if (upperdir) {
484 this = ovl_lookup_real(dentry->d_sb, upperdir, &dentry->d_name);
485 err = PTR_ERR(this);
486 if (IS_ERR(this))
487 goto out;
488
489 if (this) {
490 if (unlikely(ovl_dentry_remote(this))) {
491 dput(this);
492 err = -EREMOTE;
493 goto out;
494 }
495 if (ovl_is_whiteout(this)) {
496 dput(this);
497 this = NULL;
498 upperopaque = true;
499 } else if (poe->numlower && ovl_is_opaquedir(this)) {
500 upperopaque = true;
501 }
502 }
503 upperdentry = prev = this;
504 }
505
506 if (!upperopaque && poe->numlower) {
507 err = -ENOMEM;
508 stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
509 if (!stack)
510 goto out_put_upper;
511 }
512
513 for (i = 0; !upperopaque && i < poe->numlower; i++) {
514 bool opaque = false;
515 struct path lowerpath = poe->lowerstack[i];
516
517 this = ovl_lookup_real(dentry->d_sb,
518 lowerpath.dentry, &dentry->d_name);
519 err = PTR_ERR(this);
520 if (IS_ERR(this)) {
521 /*
522 * If it's positive, then treat ENAMETOOLONG as ENOENT.
523 */
524 if (err == -ENAMETOOLONG && (upperdentry || ctr))
525 continue;
526 goto out_put;
527 }
528 if (!this)
529 continue;
530 if (ovl_is_whiteout(this)) {
531 dput(this);
532 break;
533 }
534 /*
535 * Only makes sense to check opaque dir if this is not the
536 * lowermost layer.
537 */
538 if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
539 opaque = true;
540
541 if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
542 !S_ISDIR(this->d_inode->i_mode))) {
543 /*
544 * FIXME: check for upper-opaqueness maybe better done
545 * in remove code.
546 */
547 if (prev == upperdentry)
548 upperopaque = true;
549 dput(this);
550 break;
551 }
552 /*
553 * If this is a non-directory then stop here.
554 */
555 if (!S_ISDIR(this->d_inode->i_mode))
556 opaque = true;
557
558 stack[ctr].dentry = this;
559 stack[ctr].mnt = lowerpath.mnt;
560 ctr++;
561 prev = this;
562 if (opaque)
563 break;
564 }
565
566 oe = ovl_alloc_entry(ctr);
567 err = -ENOMEM;
568 if (!oe)
569 goto out_put;
570
571 if (upperdentry || ctr) {
572 struct dentry *realdentry;
573 struct inode *realinode;
574
575 realdentry = upperdentry ? upperdentry : stack[0].dentry;
576 realinode = d_inode(realdentry);
577
578 err = -ENOMEM;
579 if (upperdentry && !d_is_dir(upperdentry)) {
580 inode = ovl_get_inode(dentry->d_sb, realinode);
581 } else {
582 inode = ovl_new_inode(dentry->d_sb, realinode->i_mode);
583 if (inode)
584 ovl_inode_init(inode, realinode, !!upperdentry);
585 }
586 if (!inode)
587 goto out_free_oe;
588 ovl_copyattr(realdentry->d_inode, inode);
589 }
590
591 oe->opaque = upperopaque;
592 oe->__upperdentry = upperdentry;
593 memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
594 kfree(stack);
595 dentry->d_fsdata = oe;
596 d_add(dentry, inode);
597
598 return NULL;
599
600 out_free_oe:
601 kfree(oe);
602 out_put:
603 for (i = 0; i < ctr; i++)
604 dput(stack[i].dentry);
605 kfree(stack);
606 out_put_upper:
607 dput(upperdentry);
608 out:
609 return ERR_PTR(err);
610 }
611
612 struct file *ovl_path_open(struct path *path, int flags)
613 {
614 return dentry_open(path, flags | O_NOATIME, current_cred());
615 }
616
617 static void ovl_put_super(struct super_block *sb)
618 {
619 struct ovl_fs *ufs = sb->s_fs_info;
620 unsigned i;
621
622 dput(ufs->workdir);
623 mntput(ufs->upper_mnt);
624 for (i = 0; i < ufs->numlower; i++)
625 mntput(ufs->lower_mnt[i]);
626 kfree(ufs->lower_mnt);
627
628 kfree(ufs->config.lowerdir);
629 kfree(ufs->config.upperdir);
630 kfree(ufs->config.workdir);
631 put_cred(ufs->creator_cred);
632 kfree(ufs);
633 }
634
635 /**
636 * ovl_statfs
637 * @sb: The overlayfs super block
638 * @buf: The struct kstatfs to fill in with stats
639 *
640 * Get the filesystem statistics. As writes always target the upper layer
641 * filesystem pass the statfs to the upper filesystem (if it exists)
642 */
643 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
644 {
645 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
646 struct dentry *root_dentry = dentry->d_sb->s_root;
647 struct path path;
648 int err;
649
650 ovl_path_real(root_dentry, &path);
651
652 err = vfs_statfs(&path, buf);
653 if (!err) {
654 buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
655 buf->f_type = OVERLAYFS_SUPER_MAGIC;
656 }
657
658 return err;
659 }
660
661 /**
662 * ovl_show_options
663 *
664 * Prints the mount options for a given superblock.
665 * Returns zero; does not fail.
666 */
667 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
668 {
669 struct super_block *sb = dentry->d_sb;
670 struct ovl_fs *ufs = sb->s_fs_info;
671
672 seq_show_option(m, "lowerdir", ufs->config.lowerdir);
673 if (ufs->config.upperdir) {
674 seq_show_option(m, "upperdir", ufs->config.upperdir);
675 seq_show_option(m, "workdir", ufs->config.workdir);
676 }
677 if (ufs->config.default_permissions)
678 seq_puts(m, ",default_permissions");
679 return 0;
680 }
681
682 static int ovl_remount(struct super_block *sb, int *flags, char *data)
683 {
684 struct ovl_fs *ufs = sb->s_fs_info;
685
686 if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
687 return -EROFS;
688
689 return 0;
690 }
691
692 static const struct super_operations ovl_super_operations = {
693 .put_super = ovl_put_super,
694 .statfs = ovl_statfs,
695 .show_options = ovl_show_options,
696 .remount_fs = ovl_remount,
697 .drop_inode = generic_delete_inode,
698 };
699
700 enum {
701 OPT_LOWERDIR,
702 OPT_UPPERDIR,
703 OPT_WORKDIR,
704 OPT_DEFAULT_PERMISSIONS,
705 OPT_ERR,
706 };
707
708 static const match_table_t ovl_tokens = {
709 {OPT_LOWERDIR, "lowerdir=%s"},
710 {OPT_UPPERDIR, "upperdir=%s"},
711 {OPT_WORKDIR, "workdir=%s"},
712 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
713 {OPT_ERR, NULL}
714 };
715
716 static char *ovl_next_opt(char **s)
717 {
718 char *sbegin = *s;
719 char *p;
720
721 if (sbegin == NULL)
722 return NULL;
723
724 for (p = sbegin; *p; p++) {
725 if (*p == '\\') {
726 p++;
727 if (!*p)
728 break;
729 } else if (*p == ',') {
730 *p = '\0';
731 *s = p + 1;
732 return sbegin;
733 }
734 }
735 *s = NULL;
736 return sbegin;
737 }
738
739 static int ovl_parse_opt(char *opt, struct ovl_config *config)
740 {
741 char *p;
742
743 while ((p = ovl_next_opt(&opt)) != NULL) {
744 int token;
745 substring_t args[MAX_OPT_ARGS];
746
747 if (!*p)
748 continue;
749
750 token = match_token(p, ovl_tokens, args);
751 switch (token) {
752 case OPT_UPPERDIR:
753 kfree(config->upperdir);
754 config->upperdir = match_strdup(&args[0]);
755 if (!config->upperdir)
756 return -ENOMEM;
757 break;
758
759 case OPT_LOWERDIR:
760 kfree(config->lowerdir);
761 config->lowerdir = match_strdup(&args[0]);
762 if (!config->lowerdir)
763 return -ENOMEM;
764 break;
765
766 case OPT_WORKDIR:
767 kfree(config->workdir);
768 config->workdir = match_strdup(&args[0]);
769 if (!config->workdir)
770 return -ENOMEM;
771 break;
772
773 case OPT_DEFAULT_PERMISSIONS:
774 config->default_permissions = true;
775 break;
776
777 default:
778 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
779 return -EINVAL;
780 }
781 }
782
783 /* Workdir is useless in non-upper mount */
784 if (!config->upperdir && config->workdir) {
785 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
786 config->workdir);
787 kfree(config->workdir);
788 config->workdir = NULL;
789 }
790
791 return 0;
792 }
793
794 #define OVL_WORKDIR_NAME "work"
795
796 static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
797 struct dentry *dentry)
798 {
799 struct inode *dir = dentry->d_inode;
800 struct dentry *work;
801 int err;
802 bool retried = false;
803
804 err = mnt_want_write(mnt);
805 if (err)
806 return ERR_PTR(err);
807
808 inode_lock_nested(dir, I_MUTEX_PARENT);
809 retry:
810 work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
811 strlen(OVL_WORKDIR_NAME));
812
813 if (!IS_ERR(work)) {
814 struct kstat stat = {
815 .mode = S_IFDIR | 0,
816 };
817 struct iattr attr = {
818 .ia_valid = ATTR_MODE,
819 .ia_mode = stat.mode,
820 };
821
822 if (work->d_inode) {
823 err = -EEXIST;
824 if (retried)
825 goto out_dput;
826
827 retried = true;
828 ovl_workdir_cleanup(dir, mnt, work, 0);
829 dput(work);
830 goto retry;
831 }
832
833 err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
834 if (err)
835 goto out_dput;
836
837 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
838 if (err && err != -ENODATA && err != -EOPNOTSUPP)
839 goto out_dput;
840
841 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
842 if (err && err != -ENODATA && err != -EOPNOTSUPP)
843 goto out_dput;
844
845 /* Clear any inherited mode bits */
846 inode_lock(work->d_inode);
847 err = notify_change(work, &attr, NULL);
848 inode_unlock(work->d_inode);
849 if (err)
850 goto out_dput;
851 }
852 out_unlock:
853 inode_unlock(dir);
854 mnt_drop_write(mnt);
855
856 return work;
857
858 out_dput:
859 dput(work);
860 work = ERR_PTR(err);
861 goto out_unlock;
862 }
863
864 static void ovl_unescape(char *s)
865 {
866 char *d = s;
867
868 for (;; s++, d++) {
869 if (*s == '\\')
870 s++;
871 *d = *s;
872 if (!*s)
873 break;
874 }
875 }
876
877 static int ovl_mount_dir_noesc(const char *name, struct path *path)
878 {
879 int err = -EINVAL;
880
881 if (!*name) {
882 pr_err("overlayfs: empty lowerdir\n");
883 goto out;
884 }
885 err = kern_path(name, LOOKUP_FOLLOW, path);
886 if (err) {
887 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
888 goto out;
889 }
890 err = -EINVAL;
891 if (ovl_dentry_weird(path->dentry)) {
892 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
893 goto out_put;
894 }
895 if (!S_ISDIR(path->dentry->d_inode->i_mode)) {
896 pr_err("overlayfs: '%s' not a directory\n", name);
897 goto out_put;
898 }
899 return 0;
900
901 out_put:
902 path_put(path);
903 out:
904 return err;
905 }
906
907 static int ovl_mount_dir(const char *name, struct path *path)
908 {
909 int err = -ENOMEM;
910 char *tmp = kstrdup(name, GFP_KERNEL);
911
912 if (tmp) {
913 ovl_unescape(tmp);
914 err = ovl_mount_dir_noesc(tmp, path);
915
916 if (!err)
917 if (ovl_dentry_remote(path->dentry)) {
918 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
919 tmp);
920 path_put(path);
921 err = -EINVAL;
922 }
923 kfree(tmp);
924 }
925 return err;
926 }
927
928 static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
929 int *stack_depth, bool *remote)
930 {
931 int err;
932 struct kstatfs statfs;
933
934 err = ovl_mount_dir_noesc(name, path);
935 if (err)
936 goto out;
937
938 err = vfs_statfs(path, &statfs);
939 if (err) {
940 pr_err("overlayfs: statfs failed on '%s'\n", name);
941 goto out_put;
942 }
943 *namelen = max(*namelen, statfs.f_namelen);
944 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
945
946 if (ovl_dentry_remote(path->dentry))
947 *remote = true;
948
949 return 0;
950
951 out_put:
952 path_put(path);
953 out:
954 return err;
955 }
956
957 /* Workdir should not be subdir of upperdir and vice versa */
958 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
959 {
960 bool ok = false;
961
962 if (workdir != upperdir) {
963 ok = (lock_rename(workdir, upperdir) == NULL);
964 unlock_rename(workdir, upperdir);
965 }
966 return ok;
967 }
968
969 static unsigned int ovl_split_lowerdirs(char *str)
970 {
971 unsigned int ctr = 1;
972 char *s, *d;
973
974 for (s = d = str;; s++, d++) {
975 if (*s == '\\') {
976 s++;
977 } else if (*s == ':') {
978 *d = '\0';
979 ctr++;
980 continue;
981 }
982 *d = *s;
983 if (!*s)
984 break;
985 }
986 return ctr;
987 }
988
989 static int __maybe_unused
990 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
991 struct dentry *dentry, struct inode *inode,
992 const char *name, void *buffer, size_t size)
993 {
994 return ovl_xattr_get(dentry, handler->name, buffer, size);
995 }
996
997 static int __maybe_unused
998 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
999 struct dentry *dentry, struct inode *inode,
1000 const char *name, const void *value,
1001 size_t size, int flags)
1002 {
1003 struct dentry *workdir = ovl_workdir(dentry);
1004 struct inode *realinode = ovl_inode_real(inode, NULL);
1005 struct posix_acl *acl = NULL;
1006 int err;
1007
1008 /* Check that everything is OK before copy-up */
1009 if (value) {
1010 acl = posix_acl_from_xattr(&init_user_ns, value, size);
1011 if (IS_ERR(acl))
1012 return PTR_ERR(acl);
1013 }
1014 err = -EOPNOTSUPP;
1015 if (!IS_POSIXACL(d_inode(workdir)))
1016 goto out_acl_release;
1017 if (!realinode->i_op->set_acl)
1018 goto out_acl_release;
1019 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
1020 err = acl ? -EACCES : 0;
1021 goto out_acl_release;
1022 }
1023 err = -EPERM;
1024 if (!inode_owner_or_capable(inode))
1025 goto out_acl_release;
1026
1027 posix_acl_release(acl);
1028
1029 err = ovl_xattr_set(dentry, handler->name, value, size, flags);
1030 if (!err)
1031 ovl_copyattr(ovl_inode_real(inode, NULL), inode);
1032
1033 return err;
1034
1035 out_acl_release:
1036 posix_acl_release(acl);
1037 return err;
1038 }
1039
1040 static int ovl_own_xattr_get(const struct xattr_handler *handler,
1041 struct dentry *dentry, struct inode *inode,
1042 const char *name, void *buffer, size_t size)
1043 {
1044 return -EPERM;
1045 }
1046
1047 static int ovl_own_xattr_set(const struct xattr_handler *handler,
1048 struct dentry *dentry, struct inode *inode,
1049 const char *name, const void *value,
1050 size_t size, int flags)
1051 {
1052 return -EPERM;
1053 }
1054
1055 static int ovl_other_xattr_get(const struct xattr_handler *handler,
1056 struct dentry *dentry, struct inode *inode,
1057 const char *name, void *buffer, size_t size)
1058 {
1059 return ovl_xattr_get(dentry, name, buffer, size);
1060 }
1061
1062 static int ovl_other_xattr_set(const struct xattr_handler *handler,
1063 struct dentry *dentry, struct inode *inode,
1064 const char *name, const void *value,
1065 size_t size, int flags)
1066 {
1067 return ovl_xattr_set(dentry, name, value, size, flags);
1068 }
1069
1070 static const struct xattr_handler __maybe_unused
1071 ovl_posix_acl_access_xattr_handler = {
1072 .name = XATTR_NAME_POSIX_ACL_ACCESS,
1073 .flags = ACL_TYPE_ACCESS,
1074 .get = ovl_posix_acl_xattr_get,
1075 .set = ovl_posix_acl_xattr_set,
1076 };
1077
1078 static const struct xattr_handler __maybe_unused
1079 ovl_posix_acl_default_xattr_handler = {
1080 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
1081 .flags = ACL_TYPE_DEFAULT,
1082 .get = ovl_posix_acl_xattr_get,
1083 .set = ovl_posix_acl_xattr_set,
1084 };
1085
1086 static const struct xattr_handler ovl_own_xattr_handler = {
1087 .prefix = OVL_XATTR_PREFIX,
1088 .get = ovl_own_xattr_get,
1089 .set = ovl_own_xattr_set,
1090 };
1091
1092 static const struct xattr_handler ovl_other_xattr_handler = {
1093 .prefix = "", /* catch all */
1094 .get = ovl_other_xattr_get,
1095 .set = ovl_other_xattr_set,
1096 };
1097
1098 static const struct xattr_handler *ovl_xattr_handlers[] = {
1099 #ifdef CONFIG_FS_POSIX_ACL
1100 &ovl_posix_acl_access_xattr_handler,
1101 &ovl_posix_acl_default_xattr_handler,
1102 #endif
1103 &ovl_own_xattr_handler,
1104 &ovl_other_xattr_handler,
1105 NULL
1106 };
1107
1108 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1109 {
1110 struct path upperpath = { NULL, NULL };
1111 struct path workpath = { NULL, NULL };
1112 struct dentry *root_dentry;
1113 struct inode *realinode;
1114 struct ovl_entry *oe;
1115 struct ovl_fs *ufs;
1116 struct path *stack = NULL;
1117 char *lowertmp;
1118 char *lower;
1119 unsigned int numlower;
1120 unsigned int stacklen = 0;
1121 unsigned int i;
1122 bool remote = false;
1123 int err;
1124
1125 err = -ENOMEM;
1126 ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1127 if (!ufs)
1128 goto out;
1129
1130 err = ovl_parse_opt((char *) data, &ufs->config);
1131 if (err)
1132 goto out_free_config;
1133
1134 err = -EINVAL;
1135 if (!ufs->config.lowerdir) {
1136 if (!silent)
1137 pr_err("overlayfs: missing 'lowerdir'\n");
1138 goto out_free_config;
1139 }
1140
1141 sb->s_stack_depth = 0;
1142 sb->s_maxbytes = MAX_LFS_FILESIZE;
1143 if (ufs->config.upperdir) {
1144 if (!ufs->config.workdir) {
1145 pr_err("overlayfs: missing 'workdir'\n");
1146 goto out_free_config;
1147 }
1148
1149 err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
1150 if (err)
1151 goto out_free_config;
1152
1153 /* Upper fs should not be r/o */
1154 if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
1155 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
1156 err = -EINVAL;
1157 goto out_put_upperpath;
1158 }
1159
1160 err = ovl_mount_dir(ufs->config.workdir, &workpath);
1161 if (err)
1162 goto out_put_upperpath;
1163
1164 err = -EINVAL;
1165 if (upperpath.mnt != workpath.mnt) {
1166 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1167 goto out_put_workpath;
1168 }
1169 if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
1170 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1171 goto out_put_workpath;
1172 }
1173 sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
1174 }
1175 err = -ENOMEM;
1176 lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
1177 if (!lowertmp)
1178 goto out_put_workpath;
1179
1180 err = -EINVAL;
1181 stacklen = ovl_split_lowerdirs(lowertmp);
1182 if (stacklen > OVL_MAX_STACK) {
1183 pr_err("overlayfs: too many lower directories, limit is %d\n",
1184 OVL_MAX_STACK);
1185 goto out_free_lowertmp;
1186 } else if (!ufs->config.upperdir && stacklen == 1) {
1187 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1188 goto out_free_lowertmp;
1189 }
1190
1191 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1192 if (!stack)
1193 goto out_free_lowertmp;
1194
1195 lower = lowertmp;
1196 for (numlower = 0; numlower < stacklen; numlower++) {
1197 err = ovl_lower_dir(lower, &stack[numlower],
1198 &ufs->lower_namelen, &sb->s_stack_depth,
1199 &remote);
1200 if (err)
1201 goto out_put_lowerpath;
1202
1203 lower = strchr(lower, '\0') + 1;
1204 }
1205
1206 err = -EINVAL;
1207 sb->s_stack_depth++;
1208 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1209 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1210 goto out_put_lowerpath;
1211 }
1212
1213 if (ufs->config.upperdir) {
1214 ufs->upper_mnt = clone_private_mount(&upperpath);
1215 err = PTR_ERR(ufs->upper_mnt);
1216 if (IS_ERR(ufs->upper_mnt)) {
1217 pr_err("overlayfs: failed to clone upperpath\n");
1218 goto out_put_lowerpath;
1219 }
1220 /* Don't inherit atime flags */
1221 ufs->upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1222
1223 sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
1224
1225 ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
1226 err = PTR_ERR(ufs->workdir);
1227 if (IS_ERR(ufs->workdir)) {
1228 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
1229 ufs->config.workdir, OVL_WORKDIR_NAME, -err);
1230 sb->s_flags |= MS_RDONLY;
1231 ufs->workdir = NULL;
1232 }
1233
1234 /*
1235 * Upper should support d_type, else whiteouts are visible.
1236 * Given workdir and upper are on same fs, we can do
1237 * iterate_dir() on workdir. This check requires successful
1238 * creation of workdir in previous step.
1239 */
1240 if (ufs->workdir) {
1241 err = ovl_check_d_type_supported(&workpath);
1242 if (err < 0)
1243 goto out_put_workdir;
1244
1245 /*
1246 * We allowed this configuration and don't want to
1247 * break users over kernel upgrade. So warn instead
1248 * of erroring out.
1249 */
1250 if (!err)
1251 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1252 }
1253 }
1254
1255 err = -ENOMEM;
1256 ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1257 if (ufs->lower_mnt == NULL)
1258 goto out_put_workdir;
1259 for (i = 0; i < numlower; i++) {
1260 struct vfsmount *mnt = clone_private_mount(&stack[i]);
1261
1262 err = PTR_ERR(mnt);
1263 if (IS_ERR(mnt)) {
1264 pr_err("overlayfs: failed to clone lowerpath\n");
1265 goto out_put_lower_mnt;
1266 }
1267 /*
1268 * Make lower_mnt R/O. That way fchmod/fchown on lower file
1269 * will fail instead of modifying lower fs.
1270 */
1271 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1272
1273 ufs->lower_mnt[ufs->numlower] = mnt;
1274 ufs->numlower++;
1275 }
1276
1277 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1278 if (!ufs->upper_mnt)
1279 sb->s_flags |= MS_RDONLY;
1280
1281 if (remote)
1282 sb->s_d_op = &ovl_reval_dentry_operations;
1283 else
1284 sb->s_d_op = &ovl_dentry_operations;
1285
1286 ufs->creator_cred = prepare_creds();
1287 if (!ufs->creator_cred)
1288 goto out_put_lower_mnt;
1289
1290 err = -ENOMEM;
1291 oe = ovl_alloc_entry(numlower);
1292 if (!oe)
1293 goto out_put_cred;
1294
1295 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR));
1296 if (!root_dentry)
1297 goto out_free_oe;
1298
1299 mntput(upperpath.mnt);
1300 for (i = 0; i < numlower; i++)
1301 mntput(stack[i].mnt);
1302 path_put(&workpath);
1303 kfree(lowertmp);
1304
1305 oe->__upperdentry = upperpath.dentry;
1306 for (i = 0; i < numlower; i++) {
1307 oe->lowerstack[i].dentry = stack[i].dentry;
1308 oe->lowerstack[i].mnt = ufs->lower_mnt[i];
1309 }
1310 kfree(stack);
1311
1312 root_dentry->d_fsdata = oe;
1313
1314 realinode = d_inode(ovl_dentry_real(root_dentry));
1315 ovl_inode_init(d_inode(root_dentry), realinode, !!upperpath.dentry);
1316 ovl_copyattr(realinode, d_inode(root_dentry));
1317
1318 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1319 sb->s_op = &ovl_super_operations;
1320 sb->s_xattr = ovl_xattr_handlers;
1321 sb->s_root = root_dentry;
1322 sb->s_fs_info = ufs;
1323 sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;
1324
1325 return 0;
1326
1327 out_free_oe:
1328 kfree(oe);
1329 out_put_cred:
1330 put_cred(ufs->creator_cred);
1331 out_put_lower_mnt:
1332 for (i = 0; i < ufs->numlower; i++)
1333 mntput(ufs->lower_mnt[i]);
1334 kfree(ufs->lower_mnt);
1335 out_put_workdir:
1336 dput(ufs->workdir);
1337 mntput(ufs->upper_mnt);
1338 out_put_lowerpath:
1339 for (i = 0; i < numlower; i++)
1340 path_put(&stack[i]);
1341 kfree(stack);
1342 out_free_lowertmp:
1343 kfree(lowertmp);
1344 out_put_workpath:
1345 path_put(&workpath);
1346 out_put_upperpath:
1347 path_put(&upperpath);
1348 out_free_config:
1349 kfree(ufs->config.lowerdir);
1350 kfree(ufs->config.upperdir);
1351 kfree(ufs->config.workdir);
1352 kfree(ufs);
1353 out:
1354 return err;
1355 }
1356
1357 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1358 const char *dev_name, void *raw_data)
1359 {
1360 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1361 }
1362
1363 static struct file_system_type ovl_fs_type = {
1364 .owner = THIS_MODULE,
1365 .name = "overlay",
1366 .mount = ovl_mount,
1367 .kill_sb = kill_anon_super,
1368 };
1369 MODULE_ALIAS_FS("overlay");
1370
1371 static int __init ovl_init(void)
1372 {
1373 return register_filesystem(&ovl_fs_type);
1374 }
1375
1376 static void __exit ovl_exit(void)
1377 {
1378 unregister_filesystem(&ovl_fs_type);
1379 }
1380
1381 module_init(ovl_init);
1382 module_exit(ovl_exit);
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