]> git.ipfire.org Git - thirdparty/kernel/linux.git/blob - fs/overlayfs/super.c
projects / thirdparty / kernel / linux.git / blob
? search:
summary | shortlog | log | commit | commitdiff | tree
blame | history | raw | HEAD
ovl: fix bogus -Wmaybe-unitialized warning
[thirdparty/kernel/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 <uapi/linux/magic.h>
11 #include <linux/fs.h>
12 #include <linux/namei.h>
13 #include <linux/xattr.h>
14 #include <linux/mount.h>
15 #include <linux/parser.h>
16 #include <linux/module.h>
17 #include <linux/statfs.h>
18 #include <linux/seq_file.h>
19 #include <linux/posix_acl_xattr.h>
20 #include <linux/exportfs.h>
21 #include "overlayfs.h"
22
23 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
24 MODULE_DESCRIPTION("Overlay filesystem");
25 MODULE_LICENSE("GPL");
26
27
28 struct ovl_dir_cache;
29
30 #define OVL_MAX_STACK 500
31
32 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
33 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
34 MODULE_PARM_DESC(ovl_redirect_dir_def,
35 "Default to on or off for the redirect_dir feature");
36
37 static bool ovl_redirect_always_follow =
38 IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
39 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
40 bool, 0644);
41 MODULE_PARM_DESC(ovl_redirect_always_follow,
42 "Follow redirects even if redirect_dir feature is turned off");
43
44 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
45 module_param_named(index, ovl_index_def, bool, 0644);
46 MODULE_PARM_DESC(ovl_index_def,
47 "Default to on or off for the inodes index feature");
48
49 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
50 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
51 MODULE_PARM_DESC(ovl_nfs_export_def,
52 "Default to on or off for the NFS export feature");
53
54 static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
55 module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
56 MODULE_PARM_DESC(ovl_xino_auto_def,
57 "Auto enable xino feature");
58
59 static void ovl_entry_stack_free(struct ovl_entry *oe)
60 {
61 unsigned int i;
62
63 for (i = 0; i < oe->numlower; i++)
64 dput(oe->lowerstack[i].dentry);
65 }
66
67 static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
68 module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
69 MODULE_PARM_DESC(ovl_metacopy_def,
70 "Default to on or off for the metadata only copy up feature");
71
72 static void ovl_dentry_release(struct dentry *dentry)
73 {
74 struct ovl_entry *oe = dentry->d_fsdata;
75
76 if (oe) {
77 ovl_entry_stack_free(oe);
78 kfree_rcu(oe, rcu);
79 }
80 }
81
82 static struct dentry *ovl_d_real(struct dentry *dentry,
83 const struct inode *inode)
84 {
85 struct dentry *real;
86
87 /* It's an overlay file */
88 if (inode && d_inode(dentry) == inode)
89 return dentry;
90
91 if (!d_is_reg(dentry)) {
92 if (!inode || inode == d_inode(dentry))
93 return dentry;
94 goto bug;
95 }
96
97 real = ovl_dentry_upper(dentry);
98 if (real && (inode == d_inode(real)))
99 return real;
100
101 if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
102 return real;
103
104 real = ovl_dentry_lowerdata(dentry);
105 if (!real)
106 goto bug;
107
108 /* Handle recursion */
109 real = d_real(real, inode);
110
111 if (!inode || inode == d_inode(real))
112 return real;
113 bug:
114 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
115 inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
116 return dentry;
117 }
118
119 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
120 {
121 struct ovl_entry *oe = dentry->d_fsdata;
122 unsigned int i;
123 int ret = 1;
124
125 for (i = 0; i < oe->numlower; i++) {
126 struct dentry *d = oe->lowerstack[i].dentry;
127
128 if (d->d_flags & DCACHE_OP_REVALIDATE) {
129 ret = d->d_op->d_revalidate(d, flags);
130 if (ret < 0)
131 return ret;
132 if (!ret) {
133 if (!(flags & LOOKUP_RCU))
134 d_invalidate(d);
135 return -ESTALE;
136 }
137 }
138 }
139 return 1;
140 }
141
142 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
143 {
144 struct ovl_entry *oe = dentry->d_fsdata;
145 unsigned int i;
146 int ret = 1;
147
148 for (i = 0; i < oe->numlower; i++) {
149 struct dentry *d = oe->lowerstack[i].dentry;
150
151 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
152 ret = d->d_op->d_weak_revalidate(d, flags);
153 if (ret <= 0)
154 break;
155 }
156 }
157 return ret;
158 }
159
160 static const struct dentry_operations ovl_dentry_operations = {
161 .d_release = ovl_dentry_release,
162 .d_real = ovl_d_real,
163 };
164
165 static const struct dentry_operations ovl_reval_dentry_operations = {
166 .d_release = ovl_dentry_release,
167 .d_real = ovl_d_real,
168 .d_revalidate = ovl_dentry_revalidate,
169 .d_weak_revalidate = ovl_dentry_weak_revalidate,
170 };
171
172 static struct kmem_cache *ovl_inode_cachep;
173
174 static struct inode *ovl_alloc_inode(struct super_block *sb)
175 {
176 struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
177
178 if (!oi)
179 return NULL;
180
181 oi->cache = NULL;
182 oi->redirect = NULL;
183 oi->version = 0;
184 oi->flags = 0;
185 oi->__upperdentry = NULL;
186 oi->lower = NULL;
187 oi->lowerdata = NULL;
188 mutex_init(&oi->lock);
189
190 return &oi->vfs_inode;
191 }
192
193 static void ovl_free_inode(struct inode *inode)
194 {
195 struct ovl_inode *oi = OVL_I(inode);
196
197 kfree(oi->redirect);
198 mutex_destroy(&oi->lock);
199 kmem_cache_free(ovl_inode_cachep, oi);
200 }
201
202 static void ovl_destroy_inode(struct inode *inode)
203 {
204 struct ovl_inode *oi = OVL_I(inode);
205
206 dput(oi->__upperdentry);
207 iput(oi->lower);
208 if (S_ISDIR(inode->i_mode))
209 ovl_dir_cache_free(inode);
210 else
211 iput(oi->lowerdata);
212 }
213
214 static void ovl_free_fs(struct ovl_fs *ofs)
215 {
216 unsigned i;
217
218 iput(ofs->indexdir_trap);
219 iput(ofs->workdir_trap);
220 iput(ofs->upperdir_trap);
221 dput(ofs->indexdir);
222 dput(ofs->workdir);
223 if (ofs->workdir_locked)
224 ovl_inuse_unlock(ofs->workbasedir);
225 dput(ofs->workbasedir);
226 if (ofs->upperdir_locked)
227 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
228 mntput(ofs->upper_mnt);
229 for (i = 0; i < ofs->numlower; i++) {
230 iput(ofs->lower_layers[i].trap);
231 mntput(ofs->lower_layers[i].mnt);
232 }
233 for (i = 0; i < ofs->numlowerfs; i++)
234 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
235 kfree(ofs->lower_layers);
236 kfree(ofs->lower_fs);
237
238 kfree(ofs->config.lowerdir);
239 kfree(ofs->config.upperdir);
240 kfree(ofs->config.workdir);
241 kfree(ofs->config.redirect_mode);
242 if (ofs->creator_cred)
243 put_cred(ofs->creator_cred);
244 kfree(ofs);
245 }
246
247 static void ovl_put_super(struct super_block *sb)
248 {
249 struct ovl_fs *ofs = sb->s_fs_info;
250
251 ovl_free_fs(ofs);
252 }
253
254 /* Sync real dirty inodes in upper filesystem (if it exists) */
255 static int ovl_sync_fs(struct super_block *sb, int wait)
256 {
257 struct ovl_fs *ofs = sb->s_fs_info;
258 struct super_block *upper_sb;
259 int ret;
260
261 if (!ofs->upper_mnt)
262 return 0;
263
264 /*
265 * If this is a sync(2) call or an emergency sync, all the super blocks
266 * will be iterated, including upper_sb, so no need to do anything.
267 *
268 * If this is a syncfs(2) call, then we do need to call
269 * sync_filesystem() on upper_sb, but enough if we do it when being
270 * called with wait == 1.
271 */
272 if (!wait)
273 return 0;
274
275 upper_sb = ofs->upper_mnt->mnt_sb;
276
277 down_read(&upper_sb->s_umount);
278 ret = sync_filesystem(upper_sb);
279 up_read(&upper_sb->s_umount);
280
281 return ret;
282 }
283
284 /**
285 * ovl_statfs
286 * @sb: The overlayfs super block
287 * @buf: The struct kstatfs to fill in with stats
288 *
289 * Get the filesystem statistics. As writes always target the upper layer
290 * filesystem pass the statfs to the upper filesystem (if it exists)
291 */
292 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
293 {
294 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
295 struct dentry *root_dentry = dentry->d_sb->s_root;
296 struct path path;
297 int err;
298
299 ovl_path_real(root_dentry, &path);
300
301 err = vfs_statfs(&path, buf);
302 if (!err) {
303 buf->f_namelen = ofs->namelen;
304 buf->f_type = OVERLAYFS_SUPER_MAGIC;
305 }
306
307 return err;
308 }
309
310 /* Will this overlay be forced to mount/remount ro? */
311 static bool ovl_force_readonly(struct ovl_fs *ofs)
312 {
313 return (!ofs->upper_mnt || !ofs->workdir);
314 }
315
316 static const char *ovl_redirect_mode_def(void)
317 {
318 return ovl_redirect_dir_def ? "on" : "off";
319 }
320
321 enum {
322 OVL_XINO_OFF,
323 OVL_XINO_AUTO,
324 OVL_XINO_ON,
325 };
326
327 static const char * const ovl_xino_str[] = {
328 "off",
329 "auto",
330 "on",
331 };
332
333 static inline int ovl_xino_def(void)
334 {
335 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
336 }
337
338 /**
339 * ovl_show_options
340 *
341 * Prints the mount options for a given superblock.
342 * Returns zero; does not fail.
343 */
344 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
345 {
346 struct super_block *sb = dentry->d_sb;
347 struct ovl_fs *ofs = sb->s_fs_info;
348
349 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
350 if (ofs->config.upperdir) {
351 seq_show_option(m, "upperdir", ofs->config.upperdir);
352 seq_show_option(m, "workdir", ofs->config.workdir);
353 }
354 if (ofs->config.default_permissions)
355 seq_puts(m, ",default_permissions");
356 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
357 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
358 if (ofs->config.index != ovl_index_def)
359 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
360 if (ofs->config.nfs_export != ovl_nfs_export_def)
361 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
362 "on" : "off");
363 if (ofs->config.xino != ovl_xino_def())
364 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
365 if (ofs->config.metacopy != ovl_metacopy_def)
366 seq_printf(m, ",metacopy=%s",
367 ofs->config.metacopy ? "on" : "off");
368 return 0;
369 }
370
371 static int ovl_remount(struct super_block *sb, int *flags, char *data)
372 {
373 struct ovl_fs *ofs = sb->s_fs_info;
374
375 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
376 return -EROFS;
377
378 return 0;
379 }
380
381 static const struct super_operations ovl_super_operations = {
382 .alloc_inode = ovl_alloc_inode,
383 .free_inode = ovl_free_inode,
384 .destroy_inode = ovl_destroy_inode,
385 .drop_inode = generic_delete_inode,
386 .put_super = ovl_put_super,
387 .sync_fs = ovl_sync_fs,
388 .statfs = ovl_statfs,
389 .show_options = ovl_show_options,
390 .remount_fs = ovl_remount,
391 };
392
393 enum {
394 OPT_LOWERDIR,
395 OPT_UPPERDIR,
396 OPT_WORKDIR,
397 OPT_DEFAULT_PERMISSIONS,
398 OPT_REDIRECT_DIR,
399 OPT_INDEX_ON,
400 OPT_INDEX_OFF,
401 OPT_NFS_EXPORT_ON,
402 OPT_NFS_EXPORT_OFF,
403 OPT_XINO_ON,
404 OPT_XINO_OFF,
405 OPT_XINO_AUTO,
406 OPT_METACOPY_ON,
407 OPT_METACOPY_OFF,
408 OPT_ERR,
409 };
410
411 static const match_table_t ovl_tokens = {
412 {OPT_LOWERDIR, "lowerdir=%s"},
413 {OPT_UPPERDIR, "upperdir=%s"},
414 {OPT_WORKDIR, "workdir=%s"},
415 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
416 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
417 {OPT_INDEX_ON, "index=on"},
418 {OPT_INDEX_OFF, "index=off"},
419 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
420 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
421 {OPT_XINO_ON, "xino=on"},
422 {OPT_XINO_OFF, "xino=off"},
423 {OPT_XINO_AUTO, "xino=auto"},
424 {OPT_METACOPY_ON, "metacopy=on"},
425 {OPT_METACOPY_OFF, "metacopy=off"},
426 {OPT_ERR, NULL}
427 };
428
429 static char *ovl_next_opt(char **s)
430 {
431 char *sbegin = *s;
432 char *p;
433
434 if (sbegin == NULL)
435 return NULL;
436
437 for (p = sbegin; *p; p++) {
438 if (*p == '\\') {
439 p++;
440 if (!*p)
441 break;
442 } else if (*p == ',') {
443 *p = '\0';
444 *s = p + 1;
445 return sbegin;
446 }
447 }
448 *s = NULL;
449 return sbegin;
450 }
451
452 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
453 {
454 if (strcmp(mode, "on") == 0) {
455 config->redirect_dir = true;
456 /*
457 * Does not make sense to have redirect creation without
458 * redirect following.
459 */
460 config->redirect_follow = true;
461 } else if (strcmp(mode, "follow") == 0) {
462 config->redirect_follow = true;
463 } else if (strcmp(mode, "off") == 0) {
464 if (ovl_redirect_always_follow)
465 config->redirect_follow = true;
466 } else if (strcmp(mode, "nofollow") != 0) {
467 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
468 mode);
469 return -EINVAL;
470 }
471
472 return 0;
473 }
474
475 static int ovl_parse_opt(char *opt, struct ovl_config *config)
476 {
477 char *p;
478 int err;
479 bool metacopy_opt = false, redirect_opt = false;
480
481 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
482 if (!config->redirect_mode)
483 return -ENOMEM;
484
485 while ((p = ovl_next_opt(&opt)) != NULL) {
486 int token;
487 substring_t args[MAX_OPT_ARGS];
488
489 if (!*p)
490 continue;
491
492 token = match_token(p, ovl_tokens, args);
493 switch (token) {
494 case OPT_UPPERDIR:
495 kfree(config->upperdir);
496 config->upperdir = match_strdup(&args[0]);
497 if (!config->upperdir)
498 return -ENOMEM;
499 break;
500
501 case OPT_LOWERDIR:
502 kfree(config->lowerdir);
503 config->lowerdir = match_strdup(&args[0]);
504 if (!config->lowerdir)
505 return -ENOMEM;
506 break;
507
508 case OPT_WORKDIR:
509 kfree(config->workdir);
510 config->workdir = match_strdup(&args[0]);
511 if (!config->workdir)
512 return -ENOMEM;
513 break;
514
515 case OPT_DEFAULT_PERMISSIONS:
516 config->default_permissions = true;
517 break;
518
519 case OPT_REDIRECT_DIR:
520 kfree(config->redirect_mode);
521 config->redirect_mode = match_strdup(&args[0]);
522 if (!config->redirect_mode)
523 return -ENOMEM;
524 redirect_opt = true;
525 break;
526
527 case OPT_INDEX_ON:
528 config->index = true;
529 break;
530
531 case OPT_INDEX_OFF:
532 config->index = false;
533 break;
534
535 case OPT_NFS_EXPORT_ON:
536 config->nfs_export = true;
537 break;
538
539 case OPT_NFS_EXPORT_OFF:
540 config->nfs_export = false;
541 break;
542
543 case OPT_XINO_ON:
544 config->xino = OVL_XINO_ON;
545 break;
546
547 case OPT_XINO_OFF:
548 config->xino = OVL_XINO_OFF;
549 break;
550
551 case OPT_XINO_AUTO:
552 config->xino = OVL_XINO_AUTO;
553 break;
554
555 case OPT_METACOPY_ON:
556 config->metacopy = true;
557 metacopy_opt = true;
558 break;
559
560 case OPT_METACOPY_OFF:
561 config->metacopy = false;
562 break;
563
564 default:
565 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
566 return -EINVAL;
567 }
568 }
569
570 /* Workdir is useless in non-upper mount */
571 if (!config->upperdir && config->workdir) {
572 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
573 config->workdir);
574 kfree(config->workdir);
575 config->workdir = NULL;
576 }
577
578 err = ovl_parse_redirect_mode(config, config->redirect_mode);
579 if (err)
580 return err;
581
582 /*
583 * This is to make the logic below simpler. It doesn't make any other
584 * difference, since config->redirect_dir is only used for upper.
585 */
586 if (!config->upperdir && config->redirect_follow)
587 config->redirect_dir = true;
588
589 /* Resolve metacopy -> redirect_dir dependency */
590 if (config->metacopy && !config->redirect_dir) {
591 if (metacopy_opt && redirect_opt) {
592 pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",
593 config->redirect_mode);
594 return -EINVAL;
595 }
596 if (redirect_opt) {
597 /*
598 * There was an explicit redirect_dir=... that resulted
599 * in this conflict.
600 */
601 pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",
602 config->redirect_mode);
603 config->metacopy = false;
604 } else {
605 /* Automatically enable redirect otherwise. */
606 config->redirect_follow = config->redirect_dir = true;
607 }
608 }
609
610 return 0;
611 }
612
613 #define OVL_WORKDIR_NAME "work"
614 #define OVL_INDEXDIR_NAME "index"
615
616 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
617 const char *name, bool persist)
618 {
619 struct inode *dir = ofs->workbasedir->d_inode;
620 struct vfsmount *mnt = ofs->upper_mnt;
621 struct dentry *work;
622 int err;
623 bool retried = false;
624 bool locked = false;
625
626 inode_lock_nested(dir, I_MUTEX_PARENT);
627 locked = true;
628
629 retry:
630 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
631
632 if (!IS_ERR(work)) {
633 struct iattr attr = {
634 .ia_valid = ATTR_MODE,
635 .ia_mode = S_IFDIR | 0,
636 };
637
638 if (work->d_inode) {
639 err = -EEXIST;
640 if (retried)
641 goto out_dput;
642
643 if (persist)
644 goto out_unlock;
645
646 retried = true;
647 ovl_workdir_cleanup(dir, mnt, work, 0);
648 dput(work);
649 goto retry;
650 }
651
652 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
653 err = PTR_ERR(work);
654 if (IS_ERR(work))
655 goto out_err;
656
657 /*
658 * Try to remove POSIX ACL xattrs from workdir. We are good if:
659 *
660 * a) success (there was a POSIX ACL xattr and was removed)
661 * b) -ENODATA (there was no POSIX ACL xattr)
662 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
663 *
664 * There are various other error values that could effectively
665 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
666 * if the xattr name is too long), but the set of filesystems
667 * allowed as upper are limited to "normal" ones, where checking
668 * for the above two errors is sufficient.
669 */
670 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
671 if (err && err != -ENODATA && err != -EOPNOTSUPP)
672 goto out_dput;
673
674 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
675 if (err && err != -ENODATA && err != -EOPNOTSUPP)
676 goto out_dput;
677
678 /* Clear any inherited mode bits */
679 inode_lock(work->d_inode);
680 err = notify_change(work, &attr, NULL);
681 inode_unlock(work->d_inode);
682 if (err)
683 goto out_dput;
684 } else {
685 err = PTR_ERR(work);
686 goto out_err;
687 }
688 out_unlock:
689 if (locked)
690 inode_unlock(dir);
691
692 return work;
693
694 out_dput:
695 dput(work);
696 out_err:
697 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
698 ofs->config.workdir, name, -err);
699 work = NULL;
700 goto out_unlock;
701 }
702
703 static void ovl_unescape(char *s)
704 {
705 char *d = s;
706
707 for (;; s++, d++) {
708 if (*s == '\\')
709 s++;
710 *d = *s;
711 if (!*s)
712 break;
713 }
714 }
715
716 static int ovl_mount_dir_noesc(const char *name, struct path *path)
717 {
718 int err = -EINVAL;
719
720 if (!*name) {
721 pr_err("overlayfs: empty lowerdir\n");
722 goto out;
723 }
724 err = kern_path(name, LOOKUP_FOLLOW, path);
725 if (err) {
726 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
727 goto out;
728 }
729 err = -EINVAL;
730 if (ovl_dentry_weird(path->dentry)) {
731 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
732 goto out_put;
733 }
734 if (!d_is_dir(path->dentry)) {
735 pr_err("overlayfs: '%s' not a directory\n", name);
736 goto out_put;
737 }
738 return 0;
739
740 out_put:
741 path_put_init(path);
742 out:
743 return err;
744 }
745
746 static int ovl_mount_dir(const char *name, struct path *path)
747 {
748 int err = -ENOMEM;
749 char *tmp = kstrdup(name, GFP_KERNEL);
750
751 if (tmp) {
752 ovl_unescape(tmp);
753 err = ovl_mount_dir_noesc(tmp, path);
754
755 if (!err)
756 if (ovl_dentry_remote(path->dentry)) {
757 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
758 tmp);
759 path_put_init(path);
760 err = -EINVAL;
761 }
762 kfree(tmp);
763 }
764 return err;
765 }
766
767 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
768 const char *name)
769 {
770 struct kstatfs statfs;
771 int err = vfs_statfs(path, &statfs);
772
773 if (err)
774 pr_err("overlayfs: statfs failed on '%s'\n", name);
775 else
776 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
777
778 return err;
779 }
780
781 static int ovl_lower_dir(const char *name, struct path *path,
782 struct ovl_fs *ofs, int *stack_depth, bool *remote)
783 {
784 int fh_type;
785 int err;
786
787 err = ovl_mount_dir_noesc(name, path);
788 if (err)
789 goto out;
790
791 err = ovl_check_namelen(path, ofs, name);
792 if (err)
793 goto out_put;
794
795 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
796
797 if (ovl_dentry_remote(path->dentry))
798 *remote = true;
799
800 /*
801 * The inodes index feature and NFS export need to encode and decode
802 * file handles, so they require that all layers support them.
803 */
804 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
805 if ((ofs->config.nfs_export ||
806 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
807 ofs->config.index = false;
808 ofs->config.nfs_export = false;
809 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
810 name);
811 }
812
813 /* Check if lower fs has 32bit inode numbers */
814 if (fh_type != FILEID_INO32_GEN)
815 ofs->xino_bits = 0;
816
817 return 0;
818
819 out_put:
820 path_put_init(path);
821 out:
822 return err;
823 }
824
825 /* Workdir should not be subdir of upperdir and vice versa */
826 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
827 {
828 bool ok = false;
829
830 if (workdir != upperdir) {
831 ok = (lock_rename(workdir, upperdir) == NULL);
832 unlock_rename(workdir, upperdir);
833 }
834 return ok;
835 }
836
837 static unsigned int ovl_split_lowerdirs(char *str)
838 {
839 unsigned int ctr = 1;
840 char *s, *d;
841
842 for (s = d = str;; s++, d++) {
843 if (*s == '\\') {
844 s++;
845 } else if (*s == ':') {
846 *d = '\0';
847 ctr++;
848 continue;
849 }
850 *d = *s;
851 if (!*s)
852 break;
853 }
854 return ctr;
855 }
856
857 static int __maybe_unused
858 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
859 struct dentry *dentry, struct inode *inode,
860 const char *name, void *buffer, size_t size)
861 {
862 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
863 }
864
865 static int __maybe_unused
866 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
867 struct dentry *dentry, struct inode *inode,
868 const char *name, const void *value,
869 size_t size, int flags)
870 {
871 struct dentry *workdir = ovl_workdir(dentry);
872 struct inode *realinode = ovl_inode_real(inode);
873 struct posix_acl *acl = NULL;
874 int err;
875
876 /* Check that everything is OK before copy-up */
877 if (value) {
878 acl = posix_acl_from_xattr(&init_user_ns, value, size);
879 if (IS_ERR(acl))
880 return PTR_ERR(acl);
881 }
882 err = -EOPNOTSUPP;
883 if (!IS_POSIXACL(d_inode(workdir)))
884 goto out_acl_release;
885 if (!realinode->i_op->set_acl)
886 goto out_acl_release;
887 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
888 err = acl ? -EACCES : 0;
889 goto out_acl_release;
890 }
891 err = -EPERM;
892 if (!inode_owner_or_capable(inode))
893 goto out_acl_release;
894
895 posix_acl_release(acl);
896
897 /*
898 * Check if sgid bit needs to be cleared (actual setacl operation will
899 * be done with mounter's capabilities and so that won't do it for us).
900 */
901 if (unlikely(inode->i_mode & S_ISGID) &&
902 handler->flags == ACL_TYPE_ACCESS &&
903 !in_group_p(inode->i_gid) &&
904 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
905 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
906
907 err = ovl_setattr(dentry, &iattr);
908 if (err)
909 return err;
910 }
911
912 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
913 if (!err)
914 ovl_copyattr(ovl_inode_real(inode), inode);
915
916 return err;
917
918 out_acl_release:
919 posix_acl_release(acl);
920 return err;
921 }
922
923 static int ovl_own_xattr_get(const struct xattr_handler *handler,
924 struct dentry *dentry, struct inode *inode,
925 const char *name, void *buffer, size_t size)
926 {
927 return -EOPNOTSUPP;
928 }
929
930 static int ovl_own_xattr_set(const struct xattr_handler *handler,
931 struct dentry *dentry, struct inode *inode,
932 const char *name, const void *value,
933 size_t size, int flags)
934 {
935 return -EOPNOTSUPP;
936 }
937
938 static int ovl_other_xattr_get(const struct xattr_handler *handler,
939 struct dentry *dentry, struct inode *inode,
940 const char *name, void *buffer, size_t size)
941 {
942 return ovl_xattr_get(dentry, inode, name, buffer, size);
943 }
944
945 static int ovl_other_xattr_set(const struct xattr_handler *handler,
946 struct dentry *dentry, struct inode *inode,
947 const char *name, const void *value,
948 size_t size, int flags)
949 {
950 return ovl_xattr_set(dentry, inode, name, value, size, flags);
951 }
952
953 static const struct xattr_handler __maybe_unused
954 ovl_posix_acl_access_xattr_handler = {
955 .name = XATTR_NAME_POSIX_ACL_ACCESS,
956 .flags = ACL_TYPE_ACCESS,
957 .get = ovl_posix_acl_xattr_get,
958 .set = ovl_posix_acl_xattr_set,
959 };
960
961 static const struct xattr_handler __maybe_unused
962 ovl_posix_acl_default_xattr_handler = {
963 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
964 .flags = ACL_TYPE_DEFAULT,
965 .get = ovl_posix_acl_xattr_get,
966 .set = ovl_posix_acl_xattr_set,
967 };
968
969 static const struct xattr_handler ovl_own_xattr_handler = {
970 .prefix = OVL_XATTR_PREFIX,
971 .get = ovl_own_xattr_get,
972 .set = ovl_own_xattr_set,
973 };
974
975 static const struct xattr_handler ovl_other_xattr_handler = {
976 .prefix = "", /* catch all */
977 .get = ovl_other_xattr_get,
978 .set = ovl_other_xattr_set,
979 };
980
981 static const struct xattr_handler *ovl_xattr_handlers[] = {
982 #ifdef CONFIG_FS_POSIX_ACL
983 &ovl_posix_acl_access_xattr_handler,
984 &ovl_posix_acl_default_xattr_handler,
985 #endif
986 &ovl_own_xattr_handler,
987 &ovl_other_xattr_handler,
988 NULL
989 };
990
991 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
992 struct inode **ptrap, const char *name)
993 {
994 struct inode *trap;
995 int err;
996
997 trap = ovl_get_trap_inode(sb, dir);
998 err = PTR_ERR_OR_ZERO(trap);
999 if (err) {
1000 if (err == -ELOOP)
1001 pr_err("overlayfs: conflicting %s path\n", name);
1002 return err;
1003 }
1004
1005 *ptrap = trap;
1006 return 0;
1007 }
1008
1009 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
1010 struct path *upperpath)
1011 {
1012 struct vfsmount *upper_mnt;
1013 int err;
1014
1015 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
1016 if (err)
1017 goto out;
1018
1019 /* Upper fs should not be r/o */
1020 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
1021 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
1022 err = -EINVAL;
1023 goto out;
1024 }
1025
1026 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1027 if (err)
1028 goto out;
1029
1030 err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
1031 "upperdir");
1032 if (err)
1033 goto out;
1034
1035 upper_mnt = clone_private_mount(upperpath);
1036 err = PTR_ERR(upper_mnt);
1037 if (IS_ERR(upper_mnt)) {
1038 pr_err("overlayfs: failed to clone upperpath\n");
1039 goto out;
1040 }
1041
1042 /* Don't inherit atime flags */
1043 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1044 ofs->upper_mnt = upper_mnt;
1045
1046 err = -EBUSY;
1047 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
1048 ofs->upperdir_locked = true;
1049 } else if (ofs->config.index) {
1050 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
1051 goto out;
1052 } else {
1053 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1054 }
1055
1056 err = 0;
1057 out:
1058 return err;
1059 }
1060
1061 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
1062 struct path *workpath)
1063 {
1064 struct vfsmount *mnt = ofs->upper_mnt;
1065 struct dentry *temp;
1066 int fh_type;
1067 int err;
1068
1069 err = mnt_want_write(mnt);
1070 if (err)
1071 return err;
1072
1073 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1074 if (!ofs->workdir)
1075 goto out;
1076
1077 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
1078 if (err)
1079 goto out;
1080
1081 /*
1082 * Upper should support d_type, else whiteouts are visible. Given
1083 * workdir and upper are on same fs, we can do iterate_dir() on
1084 * workdir. This check requires successful creation of workdir in
1085 * previous step.
1086 */
1087 err = ovl_check_d_type_supported(workpath);
1088 if (err < 0)
1089 goto out;
1090
1091 /*
1092 * We allowed this configuration and don't want to break users over
1093 * kernel upgrade. So warn instead of erroring out.
1094 */
1095 if (!err)
1096 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1097
1098 /* Check if upper/work fs supports O_TMPFILE */
1099 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1100 ofs->tmpfile = !IS_ERR(temp);
1101 if (ofs->tmpfile)
1102 dput(temp);
1103 else
1104 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1105
1106 /*
1107 * Check if upper/work fs supports trusted.overlay.* xattr
1108 */
1109 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1110 if (err) {
1111 ofs->noxattr = true;
1112 ofs->config.index = false;
1113 ofs->config.metacopy = false;
1114 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1115 err = 0;
1116 } else {
1117 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1118 }
1119
1120 /* Check if upper/work fs supports file handles */
1121 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1122 if (ofs->config.index && !fh_type) {
1123 ofs->config.index = false;
1124 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1125 }
1126
1127 /* Check if upper fs has 32bit inode numbers */
1128 if (fh_type != FILEID_INO32_GEN)
1129 ofs->xino_bits = 0;
1130
1131 /* NFS export of r/w mount depends on index */
1132 if (ofs->config.nfs_export && !ofs->config.index) {
1133 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1134 ofs->config.nfs_export = false;
1135 }
1136 out:
1137 mnt_drop_write(mnt);
1138 return err;
1139 }
1140
1141 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
1142 struct path *upperpath)
1143 {
1144 int err;
1145 struct path workpath = { };
1146
1147 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1148 if (err)
1149 goto out;
1150
1151 err = -EINVAL;
1152 if (upperpath->mnt != workpath.mnt) {
1153 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1154 goto out;
1155 }
1156 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1157 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1158 goto out;
1159 }
1160
1161 ofs->workbasedir = dget(workpath.dentry);
1162
1163 err = -EBUSY;
1164 if (ovl_inuse_trylock(ofs->workbasedir)) {
1165 ofs->workdir_locked = true;
1166 } else if (ofs->config.index) {
1167 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1168 goto out;
1169 } else {
1170 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1171 }
1172
1173 err = ovl_make_workdir(sb, ofs, &workpath);
1174
1175 out:
1176 path_put(&workpath);
1177
1178 return err;
1179 }
1180
1181 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
1182 struct ovl_entry *oe, struct path *upperpath)
1183 {
1184 struct vfsmount *mnt = ofs->upper_mnt;
1185 int err;
1186
1187 err = mnt_want_write(mnt);
1188 if (err)
1189 return err;
1190
1191 /* Verify lower root is upper root origin */
1192 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1193 true);
1194 if (err) {
1195 pr_err("overlayfs: failed to verify upper root origin\n");
1196 goto out;
1197 }
1198
1199 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1200 if (ofs->indexdir) {
1201 err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
1202 "indexdir");
1203 if (err)
1204 goto out;
1205
1206 /*
1207 * Verify upper root is exclusively associated with index dir.
1208 * Older kernels stored upper fh in "trusted.overlay.origin"
1209 * xattr. If that xattr exists, verify that it is a match to
1210 * upper dir file handle. In any case, verify or set xattr
1211 * "trusted.overlay.upper" to indicate that index may have
1212 * directory entries.
1213 */
1214 if (ovl_check_origin_xattr(ofs->indexdir)) {
1215 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1216 upperpath->dentry, true, false);
1217 if (err)
1218 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1219 }
1220 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1221 if (err)
1222 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1223
1224 /* Cleanup bad/stale/orphan index entries */
1225 if (!err)
1226 err = ovl_indexdir_cleanup(ofs);
1227 }
1228 if (err || !ofs->indexdir)
1229 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1230
1231 out:
1232 mnt_drop_write(mnt);
1233 return err;
1234 }
1235
1236 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
1237 {
1238 unsigned int i;
1239
1240 if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt))
1241 return true;
1242
1243 for (i = 0; i < ofs->numlowerfs; i++) {
1244 /*
1245 * We use uuid to associate an overlay lower file handle with a
1246 * lower layer, so we can accept lower fs with null uuid as long
1247 * as all lower layers with null uuid are on the same fs.
1248 */
1249 if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid))
1250 return false;
1251 }
1252 return true;
1253 }
1254
1255 /* Get a unique fsid for the layer */
1256 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
1257 {
1258 struct super_block *sb = path->mnt->mnt_sb;
1259 unsigned int i;
1260 dev_t dev;
1261 int err;
1262
1263 /* fsid 0 is reserved for upper fs even with non upper overlay */
1264 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1265 return 0;
1266
1267 for (i = 0; i < ofs->numlowerfs; i++) {
1268 if (ofs->lower_fs[i].sb == sb)
1269 return i + 1;
1270 }
1271
1272 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
1273 ofs->config.index = false;
1274 ofs->config.nfs_export = false;
1275 pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
1276 uuid_is_null(&sb->s_uuid) ? "null" : "conflicting",
1277 path->dentry);
1278 }
1279
1280 err = get_anon_bdev(&dev);
1281 if (err) {
1282 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1283 return err;
1284 }
1285
1286 ofs->lower_fs[ofs->numlowerfs].sb = sb;
1287 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1288 ofs->numlowerfs++;
1289
1290 return ofs->numlowerfs;
1291 }
1292
1293 static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
1294 struct path *stack, unsigned int numlower)
1295 {
1296 int err;
1297 unsigned int i;
1298
1299 err = -ENOMEM;
1300 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1301 GFP_KERNEL);
1302 if (ofs->lower_layers == NULL)
1303 goto out;
1304
1305 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1306 GFP_KERNEL);
1307 if (ofs->lower_fs == NULL)
1308 goto out;
1309
1310 for (i = 0; i < numlower; i++) {
1311 struct vfsmount *mnt;
1312 struct inode *trap;
1313 int fsid;
1314
1315 err = fsid = ovl_get_fsid(ofs, &stack[i]);
1316 if (err < 0)
1317 goto out;
1318
1319 err = -EBUSY;
1320 if (ovl_is_inuse(stack[i].dentry)) {
1321 pr_err("overlayfs: lowerdir is in-use as upperdir/workdir\n");
1322 goto out;
1323 }
1324
1325 err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
1326 if (err)
1327 goto out;
1328
1329 mnt = clone_private_mount(&stack[i]);
1330 err = PTR_ERR(mnt);
1331 if (IS_ERR(mnt)) {
1332 pr_err("overlayfs: failed to clone lowerpath\n");
1333 iput(trap);
1334 goto out;
1335 }
1336
1337 /*
1338 * Make lower layers R/O. That way fchmod/fchown on lower file
1339 * will fail instead of modifying lower fs.
1340 */
1341 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1342
1343 ofs->lower_layers[ofs->numlower].trap = trap;
1344 ofs->lower_layers[ofs->numlower].mnt = mnt;
1345 ofs->lower_layers[ofs->numlower].idx = i + 1;
1346 ofs->lower_layers[ofs->numlower].fsid = fsid;
1347 if (fsid) {
1348 ofs->lower_layers[ofs->numlower].fs =
1349 &ofs->lower_fs[fsid - 1];
1350 }
1351 ofs->numlower++;
1352 }
1353
1354 /*
1355 * When all layers on same fs, overlay can use real inode numbers.
1356 * With mount option "xino=on", mounter declares that there are enough
1357 * free high bits in underlying fs to hold the unique fsid.
1358 * If overlayfs does encounter underlying inodes using the high xino
1359 * bits reserved for fsid, it emits a warning and uses the original
1360 * inode number.
1361 */
1362 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1363 ofs->xino_bits = 0;
1364 ofs->config.xino = OVL_XINO_OFF;
1365 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1366 /*
1367 * This is a roundup of number of bits needed for numlowerfs+1
1368 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1369 * upper fs even with non upper overlay.
1370 */
1371 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1372 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1373 }
1374
1375 if (ofs->xino_bits) {
1376 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1377 ofs->xino_bits);
1378 }
1379
1380 err = 0;
1381 out:
1382 return err;
1383 }
1384
1385 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1386 struct ovl_fs *ofs)
1387 {
1388 int err;
1389 char *lowertmp, *lower;
1390 struct path *stack = NULL;
1391 unsigned int stacklen, numlower = 0, i;
1392 bool remote = false;
1393 struct ovl_entry *oe;
1394
1395 err = -ENOMEM;
1396 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1397 if (!lowertmp)
1398 goto out_err;
1399
1400 err = -EINVAL;
1401 stacklen = ovl_split_lowerdirs(lowertmp);
1402 if (stacklen > OVL_MAX_STACK) {
1403 pr_err("overlayfs: too many lower directories, limit is %d\n",
1404 OVL_MAX_STACK);
1405 goto out_err;
1406 } else if (!ofs->config.upperdir && stacklen == 1) {
1407 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1408 goto out_err;
1409 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1410 ofs->config.redirect_follow) {
1411 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1412 ofs->config.nfs_export = false;
1413 }
1414
1415 err = -ENOMEM;
1416 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1417 if (!stack)
1418 goto out_err;
1419
1420 err = -EINVAL;
1421 lower = lowertmp;
1422 for (numlower = 0; numlower < stacklen; numlower++) {
1423 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1424 &sb->s_stack_depth, &remote);
1425 if (err)
1426 goto out_err;
1427
1428 lower = strchr(lower, '\0') + 1;
1429 }
1430
1431 err = -EINVAL;
1432 sb->s_stack_depth++;
1433 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1434 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1435 goto out_err;
1436 }
1437
1438 err = ovl_get_lower_layers(sb, ofs, stack, numlower);
1439 if (err)
1440 goto out_err;
1441
1442 err = -ENOMEM;
1443 oe = ovl_alloc_entry(numlower);
1444 if (!oe)
1445 goto out_err;
1446
1447 for (i = 0; i < numlower; i++) {
1448 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1449 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1450 }
1451
1452 if (remote)
1453 sb->s_d_op = &ovl_reval_dentry_operations;
1454 else
1455 sb->s_d_op = &ovl_dentry_operations;
1456
1457 out:
1458 for (i = 0; i < numlower; i++)
1459 path_put(&stack[i]);
1460 kfree(stack);
1461 kfree(lowertmp);
1462
1463 return oe;
1464
1465 out_err:
1466 oe = ERR_PTR(err);
1467 goto out;
1468 }
1469
1470 /*
1471 * Check if this layer root is a descendant of:
1472 * - another layer of this overlayfs instance
1473 * - upper/work dir of any overlayfs instance
1474 */
1475 static int ovl_check_layer(struct super_block *sb, struct dentry *dentry,
1476 const char *name)
1477 {
1478 struct dentry *next = dentry, *parent;
1479 int err = 0;
1480
1481 if (!dentry)
1482 return 0;
1483
1484 parent = dget_parent(next);
1485
1486 /* Walk back ancestors to root (inclusive) looking for traps */
1487 while (!err && parent != next) {
1488 if (ovl_is_inuse(parent)) {
1489 err = -EBUSY;
1490 pr_err("overlayfs: %s path overlapping in-use upperdir/workdir\n",
1491 name);
1492 } else if (ovl_lookup_trap_inode(sb, parent)) {
1493 err = -ELOOP;
1494 pr_err("overlayfs: overlapping %s path\n", name);
1495 }
1496 next = parent;
1497 parent = dget_parent(next);
1498 dput(next);
1499 }
1500
1501 dput(parent);
1502
1503 return err;
1504 }
1505
1506 /*
1507 * Check if any of the layers or work dirs overlap.
1508 */
1509 static int ovl_check_overlapping_layers(struct super_block *sb,
1510 struct ovl_fs *ofs)
1511 {
1512 int i, err;
1513
1514 if (ofs->upper_mnt) {
1515 err = ovl_check_layer(sb, ofs->upper_mnt->mnt_root, "upperdir");
1516 if (err)
1517 return err;
1518
1519 /*
1520 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1521 * this instance and covers overlapping work and index dirs,
1522 * unless work or index dir have been moved since created inside
1523 * workbasedir. In that case, we already have their traps in
1524 * inode cache and we will catch that case on lookup.
1525 */
1526 err = ovl_check_layer(sb, ofs->workbasedir, "workdir");
1527 if (err)
1528 return err;
1529 }
1530
1531 for (i = 0; i < ofs->numlower; i++) {
1532 err = ovl_check_layer(sb, ofs->lower_layers[i].mnt->mnt_root,
1533 "lowerdir");
1534 if (err)
1535 return err;
1536 }
1537
1538 return 0;
1539 }
1540
1541 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1542 {
1543 struct path upperpath = { };
1544 struct dentry *root_dentry;
1545 struct ovl_entry *oe;
1546 struct ovl_fs *ofs;
1547 struct cred *cred;
1548 int err;
1549
1550 err = -ENOMEM;
1551 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1552 if (!ofs)
1553 goto out;
1554
1555 ofs->creator_cred = cred = prepare_creds();
1556 if (!cred)
1557 goto out_err;
1558
1559 ofs->config.index = ovl_index_def;
1560 ofs->config.nfs_export = ovl_nfs_export_def;
1561 ofs->config.xino = ovl_xino_def();
1562 ofs->config.metacopy = ovl_metacopy_def;
1563 err = ovl_parse_opt((char *) data, &ofs->config);
1564 if (err)
1565 goto out_err;
1566
1567 err = -EINVAL;
1568 if (!ofs->config.lowerdir) {
1569 if (!silent)
1570 pr_err("overlayfs: missing 'lowerdir'\n");
1571 goto out_err;
1572 }
1573
1574 sb->s_stack_depth = 0;
1575 sb->s_maxbytes = MAX_LFS_FILESIZE;
1576 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1577 if (ofs->config.xino != OVL_XINO_OFF)
1578 ofs->xino_bits = BITS_PER_LONG - 32;
1579
1580 /* alloc/destroy_inode needed for setting up traps in inode cache */
1581 sb->s_op = &ovl_super_operations;
1582
1583 if (ofs->config.upperdir) {
1584 if (!ofs->config.workdir) {
1585 pr_err("overlayfs: missing 'workdir'\n");
1586 goto out_err;
1587 }
1588
1589 err = ovl_get_upper(sb, ofs, &upperpath);
1590 if (err)
1591 goto out_err;
1592
1593 err = ovl_get_workdir(sb, ofs, &upperpath);
1594 if (err)
1595 goto out_err;
1596
1597 if (!ofs->workdir)
1598 sb->s_flags |= SB_RDONLY;
1599
1600 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1601 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1602
1603 }
1604 oe = ovl_get_lowerstack(sb, ofs);
1605 err = PTR_ERR(oe);
1606 if (IS_ERR(oe))
1607 goto out_err;
1608
1609 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1610 if (!ofs->upper_mnt)
1611 sb->s_flags |= SB_RDONLY;
1612
1613 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1614 err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
1615 if (err)
1616 goto out_free_oe;
1617
1618 /* Force r/o mount with no index dir */
1619 if (!ofs->indexdir) {
1620 dput(ofs->workdir);
1621 ofs->workdir = NULL;
1622 sb->s_flags |= SB_RDONLY;
1623 }
1624
1625 }
1626
1627 err = ovl_check_overlapping_layers(sb, ofs);
1628 if (err)
1629 goto out_free_oe;
1630
1631 /* Show index=off in /proc/mounts for forced r/o mount */
1632 if (!ofs->indexdir) {
1633 ofs->config.index = false;
1634 if (ofs->upper_mnt && ofs->config.nfs_export) {
1635 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1636 ofs->config.nfs_export = false;
1637 }
1638 }
1639
1640 if (ofs->config.metacopy && ofs->config.nfs_export) {
1641 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1642 ofs->config.nfs_export = false;
1643 }
1644
1645 if (ofs->config.nfs_export)
1646 sb->s_export_op = &ovl_export_operations;
1647
1648 /* Never override disk quota limits or use reserved space */
1649 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1650
1651 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1652 sb->s_xattr = ovl_xattr_handlers;
1653 sb->s_fs_info = ofs;
1654 sb->s_flags |= SB_POSIXACL;
1655
1656 err = -ENOMEM;
1657 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1658 if (!root_dentry)
1659 goto out_free_oe;
1660
1661 root_dentry->d_fsdata = oe;
1662
1663 mntput(upperpath.mnt);
1664 if (upperpath.dentry) {
1665 ovl_dentry_set_upper_alias(root_dentry);
1666 if (ovl_is_impuredir(upperpath.dentry))
1667 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1668 }
1669
1670 /* Root is always merge -> can have whiteouts */
1671 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1672 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1673 ovl_set_upperdata(d_inode(root_dentry));
1674 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1675 ovl_dentry_lower(root_dentry), NULL);
1676
1677 sb->s_root = root_dentry;
1678
1679 return 0;
1680
1681 out_free_oe:
1682 ovl_entry_stack_free(oe);
1683 kfree(oe);
1684 out_err:
1685 path_put(&upperpath);
1686 ovl_free_fs(ofs);
1687 out:
1688 return err;
1689 }
1690
1691 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1692 const char *dev_name, void *raw_data)
1693 {
1694 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1695 }
1696
1697 static struct file_system_type ovl_fs_type = {
1698 .owner = THIS_MODULE,
1699 .name = "overlay",
1700 .mount = ovl_mount,
1701 .kill_sb = kill_anon_super,
1702 };
1703 MODULE_ALIAS_FS("overlay");
1704
1705 static void ovl_inode_init_once(void *foo)
1706 {
1707 struct ovl_inode *oi = foo;
1708
1709 inode_init_once(&oi->vfs_inode);
1710 }
1711
1712 static int __init ovl_init(void)
1713 {
1714 int err;
1715
1716 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1717 sizeof(struct ovl_inode), 0,
1718 (SLAB_RECLAIM_ACCOUNT|
1719 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1720 ovl_inode_init_once);
1721 if (ovl_inode_cachep == NULL)
1722 return -ENOMEM;
1723
1724 err = register_filesystem(&ovl_fs_type);
1725 if (err)
1726 kmem_cache_destroy(ovl_inode_cachep);
1727
1728 return err;
1729 }
1730
1731 static void __exit ovl_exit(void)
1732 {
1733 unregister_filesystem(&ovl_fs_type);
1734
1735 /*
1736 * Make sure all delayed rcu free inodes are flushed before we
1737 * destroy cache.
1738 */
1739 rcu_barrier();
1740 kmem_cache_destroy(ovl_inode_cachep);
1741
1742 }
1743
1744 module_init(ovl_init);
1745 module_exit(ovl_exit);
A mirror of Linus' kernel repository