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perf/ring_buffer: Prevent concurent ring buffer access
[linux/fpc-iii.git] / fs / overlayfs / super.c
blob30adc9d408a0df84455b86811ee468faf439c0c1
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_i_callback(struct rcu_head *head)
194 {
195 struct inode *inode = container_of(head, struct inode, i_rcu);
196
197 kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
198 }
199
200 static void ovl_destroy_inode(struct inode *inode)
201 {
202 struct ovl_inode *oi = OVL_I(inode);
203
204 dput(oi->__upperdentry);
205 iput(oi->lower);
206 if (S_ISDIR(inode->i_mode))
207 ovl_dir_cache_free(inode);
208 else
209 iput(oi->lowerdata);
210 kfree(oi->redirect);
211 mutex_destroy(&oi->lock);
212
213 call_rcu(&inode->i_rcu, ovl_i_callback);
214 }
215
216 static void ovl_free_fs(struct ovl_fs *ofs)
217 {
218 unsigned i;
219
220 dput(ofs->indexdir);
221 dput(ofs->workdir);
222 if (ofs->workdir_locked)
223 ovl_inuse_unlock(ofs->workbasedir);
224 dput(ofs->workbasedir);
225 if (ofs->upperdir_locked)
226 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
227 mntput(ofs->upper_mnt);
228 for (i = 0; i < ofs->numlower; i++)
229 mntput(ofs->lower_layers[i].mnt);
230 for (i = 0; i < ofs->numlowerfs; i++)
231 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
232 kfree(ofs->lower_layers);
233 kfree(ofs->lower_fs);
234
235 kfree(ofs->config.lowerdir);
236 kfree(ofs->config.upperdir);
237 kfree(ofs->config.workdir);
238 kfree(ofs->config.redirect_mode);
239 if (ofs->creator_cred)
240 put_cred(ofs->creator_cred);
241 kfree(ofs);
242 }
243
244 static void ovl_put_super(struct super_block *sb)
245 {
246 struct ovl_fs *ofs = sb->s_fs_info;
247
248 ovl_free_fs(ofs);
249 }
250
251 /* Sync real dirty inodes in upper filesystem (if it exists) */
252 static int ovl_sync_fs(struct super_block *sb, int wait)
253 {
254 struct ovl_fs *ofs = sb->s_fs_info;
255 struct super_block *upper_sb;
256 int ret;
257
258 if (!ofs->upper_mnt)
259 return 0;
260
261 /*
262 * If this is a sync(2) call or an emergency sync, all the super blocks
263 * will be iterated, including upper_sb, so no need to do anything.
264 *
265 * If this is a syncfs(2) call, then we do need to call
266 * sync_filesystem() on upper_sb, but enough if we do it when being
267 * called with wait == 1.
268 */
269 if (!wait)
270 return 0;
271
272 upper_sb = ofs->upper_mnt->mnt_sb;
273
274 down_read(&upper_sb->s_umount);
275 ret = sync_filesystem(upper_sb);
276 up_read(&upper_sb->s_umount);
277
278 return ret;
279 }
280
281 /**
282 * ovl_statfs
283 * @sb: The overlayfs super block
284 * @buf: The struct kstatfs to fill in with stats
285 *
286 * Get the filesystem statistics. As writes always target the upper layer
287 * filesystem pass the statfs to the upper filesystem (if it exists)
288 */
289 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
290 {
291 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
292 struct dentry *root_dentry = dentry->d_sb->s_root;
293 struct path path;
294 int err;
295
296 ovl_path_real(root_dentry, &path);
297
298 err = vfs_statfs(&path, buf);
299 if (!err) {
300 buf->f_namelen = ofs->namelen;
301 buf->f_type = OVERLAYFS_SUPER_MAGIC;
302 }
303
304 return err;
305 }
306
307 /* Will this overlay be forced to mount/remount ro? */
308 static bool ovl_force_readonly(struct ovl_fs *ofs)
309 {
310 return (!ofs->upper_mnt || !ofs->workdir);
311 }
312
313 static const char *ovl_redirect_mode_def(void)
314 {
315 return ovl_redirect_dir_def ? "on" : "off";
316 }
317
318 enum {
319 OVL_XINO_OFF,
320 OVL_XINO_AUTO,
321 OVL_XINO_ON,
322 };
323
324 static const char * const ovl_xino_str[] = {
325 "off",
326 "auto",
327 "on",
328 };
329
330 static inline int ovl_xino_def(void)
331 {
332 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
333 }
334
335 /**
336 * ovl_show_options
337 *
338 * Prints the mount options for a given superblock.
339 * Returns zero; does not fail.
340 */
341 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
342 {
343 struct super_block *sb = dentry->d_sb;
344 struct ovl_fs *ofs = sb->s_fs_info;
345
346 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
347 if (ofs->config.upperdir) {
348 seq_show_option(m, "upperdir", ofs->config.upperdir);
349 seq_show_option(m, "workdir", ofs->config.workdir);
350 }
351 if (ofs->config.default_permissions)
352 seq_puts(m, ",default_permissions");
353 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
354 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
355 if (ofs->config.index != ovl_index_def)
356 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
357 if (ofs->config.nfs_export != ovl_nfs_export_def)
358 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
359 "on" : "off");
360 if (ofs->config.xino != ovl_xino_def())
361 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
362 if (ofs->config.metacopy != ovl_metacopy_def)
363 seq_printf(m, ",metacopy=%s",
364 ofs->config.metacopy ? "on" : "off");
365 return 0;
366 }
367
368 static int ovl_remount(struct super_block *sb, int *flags, char *data)
369 {
370 struct ovl_fs *ofs = sb->s_fs_info;
371
372 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
373 return -EROFS;
374
375 return 0;
376 }
377
378 static const struct super_operations ovl_super_operations = {
379 .alloc_inode = ovl_alloc_inode,
380 .destroy_inode = ovl_destroy_inode,
381 .drop_inode = generic_delete_inode,
382 .put_super = ovl_put_super,
383 .sync_fs = ovl_sync_fs,
384 .statfs = ovl_statfs,
385 .show_options = ovl_show_options,
386 .remount_fs = ovl_remount,
387 };
388
389 enum {
390 OPT_LOWERDIR,
391 OPT_UPPERDIR,
392 OPT_WORKDIR,
393 OPT_DEFAULT_PERMISSIONS,
394 OPT_REDIRECT_DIR,
395 OPT_INDEX_ON,
396 OPT_INDEX_OFF,
397 OPT_NFS_EXPORT_ON,
398 OPT_NFS_EXPORT_OFF,
399 OPT_XINO_ON,
400 OPT_XINO_OFF,
401 OPT_XINO_AUTO,
402 OPT_METACOPY_ON,
403 OPT_METACOPY_OFF,
404 OPT_ERR,
405 };
406
407 static const match_table_t ovl_tokens = {
408 {OPT_LOWERDIR, "lowerdir=%s"},
409 {OPT_UPPERDIR, "upperdir=%s"},
410 {OPT_WORKDIR, "workdir=%s"},
411 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
412 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
413 {OPT_INDEX_ON, "index=on"},
414 {OPT_INDEX_OFF, "index=off"},
415 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
416 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
417 {OPT_XINO_ON, "xino=on"},
418 {OPT_XINO_OFF, "xino=off"},
419 {OPT_XINO_AUTO, "xino=auto"},
420 {OPT_METACOPY_ON, "metacopy=on"},
421 {OPT_METACOPY_OFF, "metacopy=off"},
422 {OPT_ERR, NULL}
423 };
424
425 static char *ovl_next_opt(char **s)
426 {
427 char *sbegin = *s;
428 char *p;
429
430 if (sbegin == NULL)
431 return NULL;
432
433 for (p = sbegin; *p; p++) {
434 if (*p == '\\') {
435 p++;
436 if (!*p)
437 break;
438 } else if (*p == ',') {
439 *p = '\0';
440 *s = p + 1;
441 return sbegin;
442 }
443 }
444 *s = NULL;
445 return sbegin;
446 }
447
448 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
449 {
450 if (strcmp(mode, "on") == 0) {
451 config->redirect_dir = true;
452 /*
453 * Does not make sense to have redirect creation without
454 * redirect following.
455 */
456 config->redirect_follow = true;
457 } else if (strcmp(mode, "follow") == 0) {
458 config->redirect_follow = true;
459 } else if (strcmp(mode, "off") == 0) {
460 if (ovl_redirect_always_follow)
461 config->redirect_follow = true;
462 } else if (strcmp(mode, "nofollow") != 0) {
463 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
464 mode);
465 return -EINVAL;
466 }
467
468 return 0;
469 }
470
471 static int ovl_parse_opt(char *opt, struct ovl_config *config)
472 {
473 char *p;
474 int err;
475
476 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
477 if (!config->redirect_mode)
478 return -ENOMEM;
479
480 while ((p = ovl_next_opt(&opt)) != NULL) {
481 int token;
482 substring_t args[MAX_OPT_ARGS];
483
484 if (!*p)
485 continue;
486
487 token = match_token(p, ovl_tokens, args);
488 switch (token) {
489 case OPT_UPPERDIR:
490 kfree(config->upperdir);
491 config->upperdir = match_strdup(&args[0]);
492 if (!config->upperdir)
493 return -ENOMEM;
494 break;
495
496 case OPT_LOWERDIR:
497 kfree(config->lowerdir);
498 config->lowerdir = match_strdup(&args[0]);
499 if (!config->lowerdir)
500 return -ENOMEM;
501 break;
502
503 case OPT_WORKDIR:
504 kfree(config->workdir);
505 config->workdir = match_strdup(&args[0]);
506 if (!config->workdir)
507 return -ENOMEM;
508 break;
509
510 case OPT_DEFAULT_PERMISSIONS:
511 config->default_permissions = true;
512 break;
513
514 case OPT_REDIRECT_DIR:
515 kfree(config->redirect_mode);
516 config->redirect_mode = match_strdup(&args[0]);
517 if (!config->redirect_mode)
518 return -ENOMEM;
519 break;
520
521 case OPT_INDEX_ON:
522 config->index = true;
523 break;
524
525 case OPT_INDEX_OFF:
526 config->index = false;
527 break;
528
529 case OPT_NFS_EXPORT_ON:
530 config->nfs_export = true;
531 break;
532
533 case OPT_NFS_EXPORT_OFF:
534 config->nfs_export = false;
535 break;
536
537 case OPT_XINO_ON:
538 config->xino = OVL_XINO_ON;
539 break;
540
541 case OPT_XINO_OFF:
542 config->xino = OVL_XINO_OFF;
543 break;
544
545 case OPT_XINO_AUTO:
546 config->xino = OVL_XINO_AUTO;
547 break;
548
549 case OPT_METACOPY_ON:
550 config->metacopy = true;
551 break;
552
553 case OPT_METACOPY_OFF:
554 config->metacopy = false;
555 break;
556
557 default:
558 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
559 return -EINVAL;
560 }
561 }
562
563 /* Workdir is useless in non-upper mount */
564 if (!config->upperdir && config->workdir) {
565 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
566 config->workdir);
567 kfree(config->workdir);
568 config->workdir = NULL;
569 }
570
571 err = ovl_parse_redirect_mode(config, config->redirect_mode);
572 if (err)
573 return err;
574
575 /* metacopy feature with upper requires redirect_dir=on */
576 if (config->upperdir && config->metacopy && !config->redirect_dir) {
577 pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=on\", falling back to metacopy=off.\n");
578 config->metacopy = false;
579 } else if (config->metacopy && !config->redirect_follow) {
580 pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=follow\" on non-upper mount, falling back to metacopy=off.\n");
581 config->metacopy = false;
582 }
583
584 return 0;
585 }
586
587 #define OVL_WORKDIR_NAME "work"
588 #define OVL_INDEXDIR_NAME "index"
589
590 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
591 const char *name, bool persist)
592 {
593 struct inode *dir = ofs->workbasedir->d_inode;
594 struct vfsmount *mnt = ofs->upper_mnt;
595 struct dentry *work;
596 int err;
597 bool retried = false;
598 bool locked = false;
599
600 inode_lock_nested(dir, I_MUTEX_PARENT);
601 locked = true;
602
603 retry:
604 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
605
606 if (!IS_ERR(work)) {
607 struct iattr attr = {
608 .ia_valid = ATTR_MODE,
609 .ia_mode = S_IFDIR | 0,
610 };
611
612 if (work->d_inode) {
613 err = -EEXIST;
614 if (retried)
615 goto out_dput;
616
617 if (persist)
618 goto out_unlock;
619
620 retried = true;
621 ovl_workdir_cleanup(dir, mnt, work, 0);
622 dput(work);
623 goto retry;
624 }
625
626 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
627 err = PTR_ERR(work);
628 if (IS_ERR(work))
629 goto out_err;
630
631 /*
632 * Try to remove POSIX ACL xattrs from workdir. We are good if:
633 *
634 * a) success (there was a POSIX ACL xattr and was removed)
635 * b) -ENODATA (there was no POSIX ACL xattr)
636 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
637 *
638 * There are various other error values that could effectively
639 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
640 * if the xattr name is too long), but the set of filesystems
641 * allowed as upper are limited to "normal" ones, where checking
642 * for the above two errors is sufficient.
643 */
644 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
645 if (err && err != -ENODATA && err != -EOPNOTSUPP)
646 goto out_dput;
647
648 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
649 if (err && err != -ENODATA && err != -EOPNOTSUPP)
650 goto out_dput;
651
652 /* Clear any inherited mode bits */
653 inode_lock(work->d_inode);
654 err = notify_change(work, &attr, NULL);
655 inode_unlock(work->d_inode);
656 if (err)
657 goto out_dput;
658 } else {
659 err = PTR_ERR(work);
660 goto out_err;
661 }
662 out_unlock:
663 if (locked)
664 inode_unlock(dir);
665
666 return work;
667
668 out_dput:
669 dput(work);
670 out_err:
671 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
672 ofs->config.workdir, name, -err);
673 work = NULL;
674 goto out_unlock;
675 }
676
677 static void ovl_unescape(char *s)
678 {
679 char *d = s;
680
681 for (;; s++, d++) {
682 if (*s == '\\')
683 s++;
684 *d = *s;
685 if (!*s)
686 break;
687 }
688 }
689
690 static int ovl_mount_dir_noesc(const char *name, struct path *path)
691 {
692 int err = -EINVAL;
693
694 if (!*name) {
695 pr_err("overlayfs: empty lowerdir\n");
696 goto out;
697 }
698 err = kern_path(name, LOOKUP_FOLLOW, path);
699 if (err) {
700 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
701 goto out;
702 }
703 err = -EINVAL;
704 if (ovl_dentry_weird(path->dentry)) {
705 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
706 goto out_put;
707 }
708 if (!d_is_dir(path->dentry)) {
709 pr_err("overlayfs: '%s' not a directory\n", name);
710 goto out_put;
711 }
712 return 0;
713
714 out_put:
715 path_put_init(path);
716 out:
717 return err;
718 }
719
720 static int ovl_mount_dir(const char *name, struct path *path)
721 {
722 int err = -ENOMEM;
723 char *tmp = kstrdup(name, GFP_KERNEL);
724
725 if (tmp) {
726 ovl_unescape(tmp);
727 err = ovl_mount_dir_noesc(tmp, path);
728
729 if (!err)
730 if (ovl_dentry_remote(path->dentry)) {
731 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
732 tmp);
733 path_put_init(path);
734 err = -EINVAL;
735 }
736 kfree(tmp);
737 }
738 return err;
739 }
740
741 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
742 const char *name)
743 {
744 struct kstatfs statfs;
745 int err = vfs_statfs(path, &statfs);
746
747 if (err)
748 pr_err("overlayfs: statfs failed on '%s'\n", name);
749 else
750 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
751
752 return err;
753 }
754
755 static int ovl_lower_dir(const char *name, struct path *path,
756 struct ovl_fs *ofs, int *stack_depth, bool *remote)
757 {
758 int fh_type;
759 int err;
760
761 err = ovl_mount_dir_noesc(name, path);
762 if (err)
763 goto out;
764
765 err = ovl_check_namelen(path, ofs, name);
766 if (err)
767 goto out_put;
768
769 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
770
771 if (ovl_dentry_remote(path->dentry))
772 *remote = true;
773
774 /*
775 * The inodes index feature and NFS export need to encode and decode
776 * file handles, so they require that all layers support them.
777 */
778 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
779 if ((ofs->config.nfs_export ||
780 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
781 ofs->config.index = false;
782 ofs->config.nfs_export = false;
783 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
784 name);
785 }
786
787 /* Check if lower fs has 32bit inode numbers */
788 if (fh_type != FILEID_INO32_GEN)
789 ofs->xino_bits = 0;
790
791 return 0;
792
793 out_put:
794 path_put_init(path);
795 out:
796 return err;
797 }
798
799 /* Workdir should not be subdir of upperdir and vice versa */
800 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
801 {
802 bool ok = false;
803
804 if (workdir != upperdir) {
805 ok = (lock_rename(workdir, upperdir) == NULL);
806 unlock_rename(workdir, upperdir);
807 }
808 return ok;
809 }
810
811 static unsigned int ovl_split_lowerdirs(char *str)
812 {
813 unsigned int ctr = 1;
814 char *s, *d;
815
816 for (s = d = str;; s++, d++) {
817 if (*s == '\\') {
818 s++;
819 } else if (*s == ':') {
820 *d = '\0';
821 ctr++;
822 continue;
823 }
824 *d = *s;
825 if (!*s)
826 break;
827 }
828 return ctr;
829 }
830
831 static int __maybe_unused
832 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
833 struct dentry *dentry, struct inode *inode,
834 const char *name, void *buffer, size_t size)
835 {
836 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
837 }
838
839 static int __maybe_unused
840 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
841 struct dentry *dentry, struct inode *inode,
842 const char *name, const void *value,
843 size_t size, int flags)
844 {
845 struct dentry *workdir = ovl_workdir(dentry);
846 struct inode *realinode = ovl_inode_real(inode);
847 struct posix_acl *acl = NULL;
848 int err;
849
850 /* Check that everything is OK before copy-up */
851 if (value) {
852 acl = posix_acl_from_xattr(&init_user_ns, value, size);
853 if (IS_ERR(acl))
854 return PTR_ERR(acl);
855 }
856 err = -EOPNOTSUPP;
857 if (!IS_POSIXACL(d_inode(workdir)))
858 goto out_acl_release;
859 if (!realinode->i_op->set_acl)
860 goto out_acl_release;
861 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
862 err = acl ? -EACCES : 0;
863 goto out_acl_release;
864 }
865 err = -EPERM;
866 if (!inode_owner_or_capable(inode))
867 goto out_acl_release;
868
869 posix_acl_release(acl);
870
871 /*
872 * Check if sgid bit needs to be cleared (actual setacl operation will
873 * be done with mounter's capabilities and so that won't do it for us).
874 */
875 if (unlikely(inode->i_mode & S_ISGID) &&
876 handler->flags == ACL_TYPE_ACCESS &&
877 !in_group_p(inode->i_gid) &&
878 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
879 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
880
881 err = ovl_setattr(dentry, &iattr);
882 if (err)
883 return err;
884 }
885
886 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
887 if (!err)
888 ovl_copyattr(ovl_inode_real(inode), inode);
889
890 return err;
891
892 out_acl_release:
893 posix_acl_release(acl);
894 return err;
895 }
896
897 static int ovl_own_xattr_get(const struct xattr_handler *handler,
898 struct dentry *dentry, struct inode *inode,
899 const char *name, void *buffer, size_t size)
900 {
901 return -EOPNOTSUPP;
902 }
903
904 static int ovl_own_xattr_set(const struct xattr_handler *handler,
905 struct dentry *dentry, struct inode *inode,
906 const char *name, const void *value,
907 size_t size, int flags)
908 {
909 return -EOPNOTSUPP;
910 }
911
912 static int ovl_other_xattr_get(const struct xattr_handler *handler,
913 struct dentry *dentry, struct inode *inode,
914 const char *name, void *buffer, size_t size)
915 {
916 return ovl_xattr_get(dentry, inode, name, buffer, size);
917 }
918
919 static int ovl_other_xattr_set(const struct xattr_handler *handler,
920 struct dentry *dentry, struct inode *inode,
921 const char *name, const void *value,
922 size_t size, int flags)
923 {
924 return ovl_xattr_set(dentry, inode, name, value, size, flags);
925 }
926
927 static const struct xattr_handler __maybe_unused
928 ovl_posix_acl_access_xattr_handler = {
929 .name = XATTR_NAME_POSIX_ACL_ACCESS,
930 .flags = ACL_TYPE_ACCESS,
931 .get = ovl_posix_acl_xattr_get,
932 .set = ovl_posix_acl_xattr_set,
933 };
934
935 static const struct xattr_handler __maybe_unused
936 ovl_posix_acl_default_xattr_handler = {
937 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
938 .flags = ACL_TYPE_DEFAULT,
939 .get = ovl_posix_acl_xattr_get,
940 .set = ovl_posix_acl_xattr_set,
941 };
942
943 static const struct xattr_handler ovl_own_xattr_handler = {
944 .prefix = OVL_XATTR_PREFIX,
945 .get = ovl_own_xattr_get,
946 .set = ovl_own_xattr_set,
947 };
948
949 static const struct xattr_handler ovl_other_xattr_handler = {
950 .prefix = "", /* catch all */
951 .get = ovl_other_xattr_get,
952 .set = ovl_other_xattr_set,
953 };
954
955 static const struct xattr_handler *ovl_xattr_handlers[] = {
956 #ifdef CONFIG_FS_POSIX_ACL
957 &ovl_posix_acl_access_xattr_handler,
958 &ovl_posix_acl_default_xattr_handler,
959 #endif
960 &ovl_own_xattr_handler,
961 &ovl_other_xattr_handler,
962 NULL
963 };
964
965 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
966 {
967 struct vfsmount *upper_mnt;
968 int err;
969
970 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
971 if (err)
972 goto out;
973
974 /* Upper fs should not be r/o */
975 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
976 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
977 err = -EINVAL;
978 goto out;
979 }
980
981 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
982 if (err)
983 goto out;
984
985 upper_mnt = clone_private_mount(upperpath);
986 err = PTR_ERR(upper_mnt);
987 if (IS_ERR(upper_mnt)) {
988 pr_err("overlayfs: failed to clone upperpath\n");
989 goto out;
990 }
991
992 /* Don't inherit atime flags */
993 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
994 ofs->upper_mnt = upper_mnt;
995
996 err = -EBUSY;
997 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
998 ofs->upperdir_locked = true;
999 } else if (ofs->config.index) {
1000 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
1001 goto out;
1002 } else {
1003 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1004 }
1005
1006 err = 0;
1007 out:
1008 return err;
1009 }
1010
1011 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
1012 {
1013 struct vfsmount *mnt = ofs->upper_mnt;
1014 struct dentry *temp;
1015 int fh_type;
1016 int err;
1017
1018 err = mnt_want_write(mnt);
1019 if (err)
1020 return err;
1021
1022 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1023 if (!ofs->workdir)
1024 goto out;
1025
1026 /*
1027 * Upper should support d_type, else whiteouts are visible. Given
1028 * workdir and upper are on same fs, we can do iterate_dir() on
1029 * workdir. This check requires successful creation of workdir in
1030 * previous step.
1031 */
1032 err = ovl_check_d_type_supported(workpath);
1033 if (err < 0)
1034 goto out;
1035
1036 /*
1037 * We allowed this configuration and don't want to break users over
1038 * kernel upgrade. So warn instead of erroring out.
1039 */
1040 if (!err)
1041 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1042
1043 /* Check if upper/work fs supports O_TMPFILE */
1044 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1045 ofs->tmpfile = !IS_ERR(temp);
1046 if (ofs->tmpfile)
1047 dput(temp);
1048 else
1049 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1050
1051 /*
1052 * Check if upper/work fs supports trusted.overlay.* xattr
1053 */
1054 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1055 if (err) {
1056 ofs->noxattr = true;
1057 ofs->config.index = false;
1058 ofs->config.metacopy = false;
1059 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1060 err = 0;
1061 } else {
1062 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1063 }
1064
1065 /* Check if upper/work fs supports file handles */
1066 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1067 if (ofs->config.index && !fh_type) {
1068 ofs->config.index = false;
1069 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1070 }
1071
1072 /* Check if upper fs has 32bit inode numbers */
1073 if (fh_type != FILEID_INO32_GEN)
1074 ofs->xino_bits = 0;
1075
1076 /* NFS export of r/w mount depends on index */
1077 if (ofs->config.nfs_export && !ofs->config.index) {
1078 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1079 ofs->config.nfs_export = false;
1080 }
1081 out:
1082 mnt_drop_write(mnt);
1083 return err;
1084 }
1085
1086 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
1087 {
1088 int err;
1089 struct path workpath = { };
1090
1091 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1092 if (err)
1093 goto out;
1094
1095 err = -EINVAL;
1096 if (upperpath->mnt != workpath.mnt) {
1097 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1098 goto out;
1099 }
1100 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1101 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1102 goto out;
1103 }
1104
1105 ofs->workbasedir = dget(workpath.dentry);
1106
1107 err = -EBUSY;
1108 if (ovl_inuse_trylock(ofs->workbasedir)) {
1109 ofs->workdir_locked = true;
1110 } else if (ofs->config.index) {
1111 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1112 goto out;
1113 } else {
1114 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1115 }
1116
1117 err = ovl_make_workdir(ofs, &workpath);
1118 if (err)
1119 goto out;
1120
1121 err = 0;
1122 out:
1123 path_put(&workpath);
1124
1125 return err;
1126 }
1127
1128 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
1129 struct path *upperpath)
1130 {
1131 struct vfsmount *mnt = ofs->upper_mnt;
1132 int err;
1133
1134 err = mnt_want_write(mnt);
1135 if (err)
1136 return err;
1137
1138 /* Verify lower root is upper root origin */
1139 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1140 true);
1141 if (err) {
1142 pr_err("overlayfs: failed to verify upper root origin\n");
1143 goto out;
1144 }
1145
1146 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1147 if (ofs->indexdir) {
1148 /*
1149 * Verify upper root is exclusively associated with index dir.
1150 * Older kernels stored upper fh in "trusted.overlay.origin"
1151 * xattr. If that xattr exists, verify that it is a match to
1152 * upper dir file handle. In any case, verify or set xattr
1153 * "trusted.overlay.upper" to indicate that index may have
1154 * directory entries.
1155 */
1156 if (ovl_check_origin_xattr(ofs->indexdir)) {
1157 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1158 upperpath->dentry, true, false);
1159 if (err)
1160 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1161 }
1162 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1163 if (err)
1164 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1165
1166 /* Cleanup bad/stale/orphan index entries */
1167 if (!err)
1168 err = ovl_indexdir_cleanup(ofs);
1169 }
1170 if (err || !ofs->indexdir)
1171 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1172
1173 out:
1174 mnt_drop_write(mnt);
1175 return err;
1176 }
1177
1178 /* Get a unique fsid for the layer */
1179 static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb)
1180 {
1181 unsigned int i;
1182 dev_t dev;
1183 int err;
1184
1185 /* fsid 0 is reserved for upper fs even with non upper overlay */
1186 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1187 return 0;
1188
1189 for (i = 0; i < ofs->numlowerfs; i++) {
1190 if (ofs->lower_fs[i].sb == sb)
1191 return i + 1;
1192 }
1193
1194 err = get_anon_bdev(&dev);
1195 if (err) {
1196 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1197 return err;
1198 }
1199
1200 ofs->lower_fs[ofs->numlowerfs].sb = sb;
1201 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1202 ofs->numlowerfs++;
1203
1204 return ofs->numlowerfs;
1205 }
1206
1207 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
1208 unsigned int numlower)
1209 {
1210 int err;
1211 unsigned int i;
1212
1213 err = -ENOMEM;
1214 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1215 GFP_KERNEL);
1216 if (ofs->lower_layers == NULL)
1217 goto out;
1218
1219 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1220 GFP_KERNEL);
1221 if (ofs->lower_fs == NULL)
1222 goto out;
1223
1224 for (i = 0; i < numlower; i++) {
1225 struct vfsmount *mnt;
1226 int fsid;
1227
1228 err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb);
1229 if (err < 0)
1230 goto out;
1231
1232 mnt = clone_private_mount(&stack[i]);
1233 err = PTR_ERR(mnt);
1234 if (IS_ERR(mnt)) {
1235 pr_err("overlayfs: failed to clone lowerpath\n");
1236 goto out;
1237 }
1238
1239 /*
1240 * Make lower layers R/O. That way fchmod/fchown on lower file
1241 * will fail instead of modifying lower fs.
1242 */
1243 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1244
1245 ofs->lower_layers[ofs->numlower].mnt = mnt;
1246 ofs->lower_layers[ofs->numlower].idx = i + 1;
1247 ofs->lower_layers[ofs->numlower].fsid = fsid;
1248 if (fsid) {
1249 ofs->lower_layers[ofs->numlower].fs =
1250 &ofs->lower_fs[fsid - 1];
1251 }
1252 ofs->numlower++;
1253 }
1254
1255 /*
1256 * When all layers on same fs, overlay can use real inode numbers.
1257 * With mount option "xino=on", mounter declares that there are enough
1258 * free high bits in underlying fs to hold the unique fsid.
1259 * If overlayfs does encounter underlying inodes using the high xino
1260 * bits reserved for fsid, it emits a warning and uses the original
1261 * inode number.
1262 */
1263 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1264 ofs->xino_bits = 0;
1265 ofs->config.xino = OVL_XINO_OFF;
1266 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1267 /*
1268 * This is a roundup of number of bits needed for numlowerfs+1
1269 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1270 * upper fs even with non upper overlay.
1271 */
1272 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1273 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1274 }
1275
1276 if (ofs->xino_bits) {
1277 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1278 ofs->xino_bits);
1279 }
1280
1281 err = 0;
1282 out:
1283 return err;
1284 }
1285
1286 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1287 struct ovl_fs *ofs)
1288 {
1289 int err;
1290 char *lowertmp, *lower;
1291 struct path *stack = NULL;
1292 unsigned int stacklen, numlower = 0, i;
1293 bool remote = false;
1294 struct ovl_entry *oe;
1295
1296 err = -ENOMEM;
1297 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1298 if (!lowertmp)
1299 goto out_err;
1300
1301 err = -EINVAL;
1302 stacklen = ovl_split_lowerdirs(lowertmp);
1303 if (stacklen > OVL_MAX_STACK) {
1304 pr_err("overlayfs: too many lower directories, limit is %d\n",
1305 OVL_MAX_STACK);
1306 goto out_err;
1307 } else if (!ofs->config.upperdir && stacklen == 1) {
1308 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1309 goto out_err;
1310 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1311 ofs->config.redirect_follow) {
1312 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1313 ofs->config.nfs_export = false;
1314 }
1315
1316 err = -ENOMEM;
1317 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1318 if (!stack)
1319 goto out_err;
1320
1321 err = -EINVAL;
1322 lower = lowertmp;
1323 for (numlower = 0; numlower < stacklen; numlower++) {
1324 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1325 &sb->s_stack_depth, &remote);
1326 if (err)
1327 goto out_err;
1328
1329 lower = strchr(lower, '\0') + 1;
1330 }
1331
1332 err = -EINVAL;
1333 sb->s_stack_depth++;
1334 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1335 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1336 goto out_err;
1337 }
1338
1339 err = ovl_get_lower_layers(ofs, stack, numlower);
1340 if (err)
1341 goto out_err;
1342
1343 err = -ENOMEM;
1344 oe = ovl_alloc_entry(numlower);
1345 if (!oe)
1346 goto out_err;
1347
1348 for (i = 0; i < numlower; i++) {
1349 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1350 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1351 }
1352
1353 if (remote)
1354 sb->s_d_op = &ovl_reval_dentry_operations;
1355 else
1356 sb->s_d_op = &ovl_dentry_operations;
1357
1358 out:
1359 for (i = 0; i < numlower; i++)
1360 path_put(&stack[i]);
1361 kfree(stack);
1362 kfree(lowertmp);
1363
1364 return oe;
1365
1366 out_err:
1367 oe = ERR_PTR(err);
1368 goto out;
1369 }
1370
1371 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1372 {
1373 struct path upperpath = { };
1374 struct dentry *root_dentry;
1375 struct ovl_entry *oe;
1376 struct ovl_fs *ofs;
1377 struct cred *cred;
1378 int err;
1379
1380 err = -ENOMEM;
1381 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1382 if (!ofs)
1383 goto out;
1384
1385 ofs->creator_cred = cred = prepare_creds();
1386 if (!cred)
1387 goto out_err;
1388
1389 ofs->config.index = ovl_index_def;
1390 ofs->config.nfs_export = ovl_nfs_export_def;
1391 ofs->config.xino = ovl_xino_def();
1392 ofs->config.metacopy = ovl_metacopy_def;
1393 err = ovl_parse_opt((char *) data, &ofs->config);
1394 if (err)
1395 goto out_err;
1396
1397 err = -EINVAL;
1398 if (!ofs->config.lowerdir) {
1399 if (!silent)
1400 pr_err("overlayfs: missing 'lowerdir'\n");
1401 goto out_err;
1402 }
1403
1404 sb->s_stack_depth = 0;
1405 sb->s_maxbytes = MAX_LFS_FILESIZE;
1406 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1407 if (ofs->config.xino != OVL_XINO_OFF)
1408 ofs->xino_bits = BITS_PER_LONG - 32;
1409
1410 if (ofs->config.upperdir) {
1411 if (!ofs->config.workdir) {
1412 pr_err("overlayfs: missing 'workdir'\n");
1413 goto out_err;
1414 }
1415
1416 err = ovl_get_upper(ofs, &upperpath);
1417 if (err)
1418 goto out_err;
1419
1420 err = ovl_get_workdir(ofs, &upperpath);
1421 if (err)
1422 goto out_err;
1423
1424 if (!ofs->workdir)
1425 sb->s_flags |= SB_RDONLY;
1426
1427 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1428 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1429
1430 }
1431 oe = ovl_get_lowerstack(sb, ofs);
1432 err = PTR_ERR(oe);
1433 if (IS_ERR(oe))
1434 goto out_err;
1435
1436 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1437 if (!ofs->upper_mnt)
1438 sb->s_flags |= SB_RDONLY;
1439
1440 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1441 err = ovl_get_indexdir(ofs, oe, &upperpath);
1442 if (err)
1443 goto out_free_oe;
1444
1445 /* Force r/o mount with no index dir */
1446 if (!ofs->indexdir) {
1447 dput(ofs->workdir);
1448 ofs->workdir = NULL;
1449 sb->s_flags |= SB_RDONLY;
1450 }
1451
1452 }
1453
1454 /* Show index=off in /proc/mounts for forced r/o mount */
1455 if (!ofs->indexdir) {
1456 ofs->config.index = false;
1457 if (ofs->upper_mnt && ofs->config.nfs_export) {
1458 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1459 ofs->config.nfs_export = false;
1460 }
1461 }
1462
1463 if (ofs->config.metacopy && ofs->config.nfs_export) {
1464 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1465 ofs->config.nfs_export = false;
1466 }
1467
1468 if (ofs->config.nfs_export)
1469 sb->s_export_op = &ovl_export_operations;
1470
1471 /* Never override disk quota limits or use reserved space */
1472 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1473
1474 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1475 sb->s_op = &ovl_super_operations;
1476 sb->s_xattr = ovl_xattr_handlers;
1477 sb->s_fs_info = ofs;
1478 sb->s_flags |= SB_POSIXACL;
1479
1480 err = -ENOMEM;
1481 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1482 if (!root_dentry)
1483 goto out_free_oe;
1484
1485 root_dentry->d_fsdata = oe;
1486
1487 mntput(upperpath.mnt);
1488 if (upperpath.dentry) {
1489 ovl_dentry_set_upper_alias(root_dentry);
1490 if (ovl_is_impuredir(upperpath.dentry))
1491 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1492 }
1493
1494 /* Root is always merge -> can have whiteouts */
1495 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1496 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1497 ovl_set_upperdata(d_inode(root_dentry));
1498 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1499 ovl_dentry_lower(root_dentry), NULL);
1500
1501 sb->s_root = root_dentry;
1502
1503 return 0;
1504
1505 out_free_oe:
1506 ovl_entry_stack_free(oe);
1507 kfree(oe);
1508 out_err:
1509 path_put(&upperpath);
1510 ovl_free_fs(ofs);
1511 out:
1512 return err;
1513 }
1514
1515 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1516 const char *dev_name, void *raw_data)
1517 {
1518 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1519 }
1520
1521 static struct file_system_type ovl_fs_type = {
1522 .owner = THIS_MODULE,
1523 .name = "overlay",
1524 .mount = ovl_mount,
1525 .kill_sb = kill_anon_super,
1526 };
1527 MODULE_ALIAS_FS("overlay");
1528
1529 static void ovl_inode_init_once(void *foo)
1530 {
1531 struct ovl_inode *oi = foo;
1532
1533 inode_init_once(&oi->vfs_inode);
1534 }
1535
1536 static int __init ovl_init(void)
1537 {
1538 int err;
1539
1540 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1541 sizeof(struct ovl_inode), 0,
1542 (SLAB_RECLAIM_ACCOUNT|
1543 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1544 ovl_inode_init_once);
1545 if (ovl_inode_cachep == NULL)
1546 return -ENOMEM;
1547
1548 err = register_filesystem(&ovl_fs_type);
1549 if (err)
1550 kmem_cache_destroy(ovl_inode_cachep);
1551
1552 return err;
1553 }
1554
1555 static void __exit ovl_exit(void)
1556 {
1557 unregister_filesystem(&ovl_fs_type);
1558
1559 /*
1560 * Make sure all delayed rcu free inodes are flushed before we
1561 * destroy cache.
1562 */
1563 rcu_barrier();
1564 kmem_cache_destroy(ovl_inode_cachep);
1565
1566 }
1567
1568 module_init(ovl_init);
1569 module_exit(ovl_exit);
Linux with added FPC-III support