Merge tag 'locks-v4.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton...
[sfrench/cifs-2.6.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 "overlayfs.h"
21 #include "ovl_entry.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_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
38 module_param_named(index, ovl_index_def, bool, 0644);
39 MODULE_PARM_DESC(ovl_index_def,
40                  "Default to on or off for the inodes index feature");
41
42 static void ovl_dentry_release(struct dentry *dentry)
43 {
44         struct ovl_entry *oe = dentry->d_fsdata;
45
46         if (oe) {
47                 unsigned int i;
48
49                 for (i = 0; i < oe->numlower; i++)
50                         dput(oe->lowerstack[i].dentry);
51                 kfree_rcu(oe, rcu);
52         }
53 }
54
55 static int ovl_check_append_only(struct inode *inode, int flag)
56 {
57         /*
58          * This test was moot in vfs may_open() because overlay inode does
59          * not have the S_APPEND flag, so re-check on real upper inode
60          */
61         if (IS_APPEND(inode)) {
62                 if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
63                         return -EPERM;
64                 if (flag & O_TRUNC)
65                         return -EPERM;
66         }
67
68         return 0;
69 }
70
71 static struct dentry *ovl_d_real(struct dentry *dentry,
72                                  const struct inode *inode,
73                                  unsigned int open_flags, unsigned int flags)
74 {
75         struct dentry *real;
76         int err;
77
78         if (flags & D_REAL_UPPER)
79                 return ovl_dentry_upper(dentry);
80
81         if (!d_is_reg(dentry)) {
82                 if (!inode || inode == d_inode(dentry))
83                         return dentry;
84                 goto bug;
85         }
86
87         if (open_flags) {
88                 err = ovl_open_maybe_copy_up(dentry, open_flags);
89                 if (err)
90                         return ERR_PTR(err);
91         }
92
93         real = ovl_dentry_upper(dentry);
94         if (real && (!inode || inode == d_inode(real))) {
95                 if (!inode) {
96                         err = ovl_check_append_only(d_inode(real), open_flags);
97                         if (err)
98                                 return ERR_PTR(err);
99                 }
100                 return real;
101         }
102
103         real = ovl_dentry_lower(dentry);
104         if (!real)
105                 goto bug;
106
107         /* Handle recursion */
108         real = d_real(real, inode, open_flags, 0);
109
110         if (!inode || inode == d_inode(real))
111                 return real;
112 bug:
113         WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
114              inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
115         return dentry;
116 }
117
118 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
119 {
120         struct ovl_entry *oe = dentry->d_fsdata;
121         unsigned int i;
122         int ret = 1;
123
124         for (i = 0; i < oe->numlower; i++) {
125                 struct dentry *d = oe->lowerstack[i].dentry;
126
127                 if (d->d_flags & DCACHE_OP_REVALIDATE) {
128                         ret = d->d_op->d_revalidate(d, flags);
129                         if (ret < 0)
130                                 return ret;
131                         if (!ret) {
132                                 if (!(flags & LOOKUP_RCU))
133                                         d_invalidate(d);
134                                 return -ESTALE;
135                         }
136                 }
137         }
138         return 1;
139 }
140
141 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
142 {
143         struct ovl_entry *oe = dentry->d_fsdata;
144         unsigned int i;
145         int ret = 1;
146
147         for (i = 0; i < oe->numlower; i++) {
148                 struct dentry *d = oe->lowerstack[i].dentry;
149
150                 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
151                         ret = d->d_op->d_weak_revalidate(d, flags);
152                         if (ret <= 0)
153                                 break;
154                 }
155         }
156         return ret;
157 }
158
159 static const struct dentry_operations ovl_dentry_operations = {
160         .d_release = ovl_dentry_release,
161         .d_real = ovl_d_real,
162 };
163
164 static const struct dentry_operations ovl_reval_dentry_operations = {
165         .d_release = ovl_dentry_release,
166         .d_real = ovl_d_real,
167         .d_revalidate = ovl_dentry_revalidate,
168         .d_weak_revalidate = ovl_dentry_weak_revalidate,
169 };
170
171 static struct kmem_cache *ovl_inode_cachep;
172
173 static struct inode *ovl_alloc_inode(struct super_block *sb)
174 {
175         struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
176
177         if (!oi)
178                 return NULL;
179
180         oi->cache = NULL;
181         oi->redirect = NULL;
182         oi->version = 0;
183         oi->flags = 0;
184         oi->__upperdentry = NULL;
185         oi->lower = NULL;
186         mutex_init(&oi->lock);
187
188         return &oi->vfs_inode;
189 }
190
191 static void ovl_i_callback(struct rcu_head *head)
192 {
193         struct inode *inode = container_of(head, struct inode, i_rcu);
194
195         kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
196 }
197
198 static void ovl_destroy_inode(struct inode *inode)
199 {
200         struct ovl_inode *oi = OVL_I(inode);
201
202         dput(oi->__upperdentry);
203         kfree(oi->redirect);
204         ovl_dir_cache_free(inode);
205         mutex_destroy(&oi->lock);
206
207         call_rcu(&inode->i_rcu, ovl_i_callback);
208 }
209
210 static void ovl_put_super(struct super_block *sb)
211 {
212         struct ovl_fs *ufs = sb->s_fs_info;
213         unsigned i;
214
215         dput(ufs->indexdir);
216         dput(ufs->workdir);
217         if (ufs->workdir_locked)
218                 ovl_inuse_unlock(ufs->workbasedir);
219         dput(ufs->workbasedir);
220         if (ufs->upper_mnt && ufs->upperdir_locked)
221                 ovl_inuse_unlock(ufs->upper_mnt->mnt_root);
222         mntput(ufs->upper_mnt);
223         for (i = 0; i < ufs->numlower; i++)
224                 mntput(ufs->lower_mnt[i]);
225         kfree(ufs->lower_mnt);
226
227         kfree(ufs->config.lowerdir);
228         kfree(ufs->config.upperdir);
229         kfree(ufs->config.workdir);
230         put_cred(ufs->creator_cred);
231         kfree(ufs);
232 }
233
234 static int ovl_sync_fs(struct super_block *sb, int wait)
235 {
236         struct ovl_fs *ufs = sb->s_fs_info;
237         struct super_block *upper_sb;
238         int ret;
239
240         if (!ufs->upper_mnt)
241                 return 0;
242         upper_sb = ufs->upper_mnt->mnt_sb;
243         if (!upper_sb->s_op->sync_fs)
244                 return 0;
245
246         /* real inodes have already been synced by sync_filesystem(ovl_sb) */
247         down_read(&upper_sb->s_umount);
248         ret = upper_sb->s_op->sync_fs(upper_sb, wait);
249         up_read(&upper_sb->s_umount);
250         return ret;
251 }
252
253 /**
254  * ovl_statfs
255  * @sb: The overlayfs super block
256  * @buf: The struct kstatfs to fill in with stats
257  *
258  * Get the filesystem statistics.  As writes always target the upper layer
259  * filesystem pass the statfs to the upper filesystem (if it exists)
260  */
261 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
262 {
263         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
264         struct dentry *root_dentry = dentry->d_sb->s_root;
265         struct path path;
266         int err;
267
268         ovl_path_real(root_dentry, &path);
269
270         err = vfs_statfs(&path, buf);
271         if (!err) {
272                 buf->f_namelen = ofs->namelen;
273                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
274         }
275
276         return err;
277 }
278
279 /* Will this overlay be forced to mount/remount ro? */
280 static bool ovl_force_readonly(struct ovl_fs *ufs)
281 {
282         return (!ufs->upper_mnt || !ufs->workdir);
283 }
284
285 /**
286  * ovl_show_options
287  *
288  * Prints the mount options for a given superblock.
289  * Returns zero; does not fail.
290  */
291 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
292 {
293         struct super_block *sb = dentry->d_sb;
294         struct ovl_fs *ufs = sb->s_fs_info;
295
296         seq_show_option(m, "lowerdir", ufs->config.lowerdir);
297         if (ufs->config.upperdir) {
298                 seq_show_option(m, "upperdir", ufs->config.upperdir);
299                 seq_show_option(m, "workdir", ufs->config.workdir);
300         }
301         if (ufs->config.default_permissions)
302                 seq_puts(m, ",default_permissions");
303         if (ufs->config.redirect_dir != ovl_redirect_dir_def)
304                 seq_printf(m, ",redirect_dir=%s",
305                            ufs->config.redirect_dir ? "on" : "off");
306         if (ufs->config.index != ovl_index_def)
307                 seq_printf(m, ",index=%s",
308                            ufs->config.index ? "on" : "off");
309         return 0;
310 }
311
312 static int ovl_remount(struct super_block *sb, int *flags, char *data)
313 {
314         struct ovl_fs *ufs = sb->s_fs_info;
315
316         if (!(*flags & MS_RDONLY) && ovl_force_readonly(ufs))
317                 return -EROFS;
318
319         return 0;
320 }
321
322 static const struct super_operations ovl_super_operations = {
323         .alloc_inode    = ovl_alloc_inode,
324         .destroy_inode  = ovl_destroy_inode,
325         .drop_inode     = generic_delete_inode,
326         .put_super      = ovl_put_super,
327         .sync_fs        = ovl_sync_fs,
328         .statfs         = ovl_statfs,
329         .show_options   = ovl_show_options,
330         .remount_fs     = ovl_remount,
331 };
332
333 enum {
334         OPT_LOWERDIR,
335         OPT_UPPERDIR,
336         OPT_WORKDIR,
337         OPT_DEFAULT_PERMISSIONS,
338         OPT_REDIRECT_DIR_ON,
339         OPT_REDIRECT_DIR_OFF,
340         OPT_INDEX_ON,
341         OPT_INDEX_OFF,
342         OPT_ERR,
343 };
344
345 static const match_table_t ovl_tokens = {
346         {OPT_LOWERDIR,                  "lowerdir=%s"},
347         {OPT_UPPERDIR,                  "upperdir=%s"},
348         {OPT_WORKDIR,                   "workdir=%s"},
349         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
350         {OPT_REDIRECT_DIR_ON,           "redirect_dir=on"},
351         {OPT_REDIRECT_DIR_OFF,          "redirect_dir=off"},
352         {OPT_INDEX_ON,                  "index=on"},
353         {OPT_INDEX_OFF,                 "index=off"},
354         {OPT_ERR,                       NULL}
355 };
356
357 static char *ovl_next_opt(char **s)
358 {
359         char *sbegin = *s;
360         char *p;
361
362         if (sbegin == NULL)
363                 return NULL;
364
365         for (p = sbegin; *p; p++) {
366                 if (*p == '\\') {
367                         p++;
368                         if (!*p)
369                                 break;
370                 } else if (*p == ',') {
371                         *p = '\0';
372                         *s = p + 1;
373                         return sbegin;
374                 }
375         }
376         *s = NULL;
377         return sbegin;
378 }
379
380 static int ovl_parse_opt(char *opt, struct ovl_config *config)
381 {
382         char *p;
383
384         while ((p = ovl_next_opt(&opt)) != NULL) {
385                 int token;
386                 substring_t args[MAX_OPT_ARGS];
387
388                 if (!*p)
389                         continue;
390
391                 token = match_token(p, ovl_tokens, args);
392                 switch (token) {
393                 case OPT_UPPERDIR:
394                         kfree(config->upperdir);
395                         config->upperdir = match_strdup(&args[0]);
396                         if (!config->upperdir)
397                                 return -ENOMEM;
398                         break;
399
400                 case OPT_LOWERDIR:
401                         kfree(config->lowerdir);
402                         config->lowerdir = match_strdup(&args[0]);
403                         if (!config->lowerdir)
404                                 return -ENOMEM;
405                         break;
406
407                 case OPT_WORKDIR:
408                         kfree(config->workdir);
409                         config->workdir = match_strdup(&args[0]);
410                         if (!config->workdir)
411                                 return -ENOMEM;
412                         break;
413
414                 case OPT_DEFAULT_PERMISSIONS:
415                         config->default_permissions = true;
416                         break;
417
418                 case OPT_REDIRECT_DIR_ON:
419                         config->redirect_dir = true;
420                         break;
421
422                 case OPT_REDIRECT_DIR_OFF:
423                         config->redirect_dir = false;
424                         break;
425
426                 case OPT_INDEX_ON:
427                         config->index = true;
428                         break;
429
430                 case OPT_INDEX_OFF:
431                         config->index = false;
432                         break;
433
434                 default:
435                         pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
436                         return -EINVAL;
437                 }
438         }
439
440         /* Workdir is useless in non-upper mount */
441         if (!config->upperdir && config->workdir) {
442                 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
443                         config->workdir);
444                 kfree(config->workdir);
445                 config->workdir = NULL;
446         }
447
448         return 0;
449 }
450
451 #define OVL_WORKDIR_NAME "work"
452 #define OVL_INDEXDIR_NAME "index"
453
454 static struct dentry *ovl_workdir_create(struct super_block *sb,
455                                          struct ovl_fs *ufs,
456                                          struct dentry *dentry,
457                                          const char *name, bool persist)
458 {
459         struct inode *dir = dentry->d_inode;
460         struct vfsmount *mnt = ufs->upper_mnt;
461         struct dentry *work;
462         int err;
463         bool retried = false;
464         bool locked = false;
465
466         err = mnt_want_write(mnt);
467         if (err)
468                 goto out_err;
469
470         inode_lock_nested(dir, I_MUTEX_PARENT);
471         locked = true;
472
473 retry:
474         work = lookup_one_len(name, dentry, strlen(name));
475
476         if (!IS_ERR(work)) {
477                 struct iattr attr = {
478                         .ia_valid = ATTR_MODE,
479                         .ia_mode = S_IFDIR | 0,
480                 };
481
482                 if (work->d_inode) {
483                         err = -EEXIST;
484                         if (retried)
485                                 goto out_dput;
486
487                         if (persist)
488                                 goto out_unlock;
489
490                         retried = true;
491                         ovl_workdir_cleanup(dir, mnt, work, 0);
492                         dput(work);
493                         goto retry;
494                 }
495
496                 err = ovl_create_real(dir, work,
497                                       &(struct cattr){.mode = S_IFDIR | 0},
498                                       NULL, true);
499                 if (err)
500                         goto out_dput;
501
502                 /*
503                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
504                  *
505                  * a) success (there was a POSIX ACL xattr and was removed)
506                  * b) -ENODATA (there was no POSIX ACL xattr)
507                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
508                  *
509                  * There are various other error values that could effectively
510                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
511                  * if the xattr name is too long), but the set of filesystems
512                  * allowed as upper are limited to "normal" ones, where checking
513                  * for the above two errors is sufficient.
514                  */
515                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
516                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
517                         goto out_dput;
518
519                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
520                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
521                         goto out_dput;
522
523                 /* Clear any inherited mode bits */
524                 inode_lock(work->d_inode);
525                 err = notify_change(work, &attr, NULL);
526                 inode_unlock(work->d_inode);
527                 if (err)
528                         goto out_dput;
529         } else {
530                 err = PTR_ERR(work);
531                 goto out_err;
532         }
533 out_unlock:
534         mnt_drop_write(mnt);
535         if (locked)
536                 inode_unlock(dir);
537
538         return work;
539
540 out_dput:
541         dput(work);
542 out_err:
543         pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
544                 ufs->config.workdir, name, -err);
545         sb->s_flags |= MS_RDONLY;
546         work = NULL;
547         goto out_unlock;
548 }
549
550 static void ovl_unescape(char *s)
551 {
552         char *d = s;
553
554         for (;; s++, d++) {
555                 if (*s == '\\')
556                         s++;
557                 *d = *s;
558                 if (!*s)
559                         break;
560         }
561 }
562
563 static int ovl_mount_dir_noesc(const char *name, struct path *path)
564 {
565         int err = -EINVAL;
566
567         if (!*name) {
568                 pr_err("overlayfs: empty lowerdir\n");
569                 goto out;
570         }
571         err = kern_path(name, LOOKUP_FOLLOW, path);
572         if (err) {
573                 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
574                 goto out;
575         }
576         err = -EINVAL;
577         if (ovl_dentry_weird(path->dentry)) {
578                 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
579                 goto out_put;
580         }
581         if (!d_is_dir(path->dentry)) {
582                 pr_err("overlayfs: '%s' not a directory\n", name);
583                 goto out_put;
584         }
585         return 0;
586
587 out_put:
588         path_put(path);
589 out:
590         return err;
591 }
592
593 static int ovl_mount_dir(const char *name, struct path *path)
594 {
595         int err = -ENOMEM;
596         char *tmp = kstrdup(name, GFP_KERNEL);
597
598         if (tmp) {
599                 ovl_unescape(tmp);
600                 err = ovl_mount_dir_noesc(tmp, path);
601
602                 if (!err)
603                         if (ovl_dentry_remote(path->dentry)) {
604                                 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
605                                        tmp);
606                                 path_put(path);
607                                 err = -EINVAL;
608                         }
609                 kfree(tmp);
610         }
611         return err;
612 }
613
614 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
615                              const char *name)
616 {
617         struct kstatfs statfs;
618         int err = vfs_statfs(path, &statfs);
619
620         if (err)
621                 pr_err("overlayfs: statfs failed on '%s'\n", name);
622         else
623                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
624
625         return err;
626 }
627
628 static int ovl_lower_dir(const char *name, struct path *path,
629                          struct ovl_fs *ofs, int *stack_depth, bool *remote)
630 {
631         int err;
632
633         err = ovl_mount_dir_noesc(name, path);
634         if (err)
635                 goto out;
636
637         err = ovl_check_namelen(path, ofs, name);
638         if (err)
639                 goto out_put;
640
641         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
642
643         if (ovl_dentry_remote(path->dentry))
644                 *remote = true;
645
646         /*
647          * The inodes index feature needs to encode and decode file
648          * handles, so it requires that all layers support them.
649          */
650         if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
651                 ofs->config.index = false;
652                 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
653         }
654
655         return 0;
656
657 out_put:
658         path_put(path);
659 out:
660         return err;
661 }
662
663 /* Workdir should not be subdir of upperdir and vice versa */
664 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
665 {
666         bool ok = false;
667
668         if (workdir != upperdir) {
669                 ok = (lock_rename(workdir, upperdir) == NULL);
670                 unlock_rename(workdir, upperdir);
671         }
672         return ok;
673 }
674
675 static unsigned int ovl_split_lowerdirs(char *str)
676 {
677         unsigned int ctr = 1;
678         char *s, *d;
679
680         for (s = d = str;; s++, d++) {
681                 if (*s == '\\') {
682                         s++;
683                 } else if (*s == ':') {
684                         *d = '\0';
685                         ctr++;
686                         continue;
687                 }
688                 *d = *s;
689                 if (!*s)
690                         break;
691         }
692         return ctr;
693 }
694
695 static int __maybe_unused
696 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
697                         struct dentry *dentry, struct inode *inode,
698                         const char *name, void *buffer, size_t size)
699 {
700         return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
701 }
702
703 static int __maybe_unused
704 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
705                         struct dentry *dentry, struct inode *inode,
706                         const char *name, const void *value,
707                         size_t size, int flags)
708 {
709         struct dentry *workdir = ovl_workdir(dentry);
710         struct inode *realinode = ovl_inode_real(inode);
711         struct posix_acl *acl = NULL;
712         int err;
713
714         /* Check that everything is OK before copy-up */
715         if (value) {
716                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
717                 if (IS_ERR(acl))
718                         return PTR_ERR(acl);
719         }
720         err = -EOPNOTSUPP;
721         if (!IS_POSIXACL(d_inode(workdir)))
722                 goto out_acl_release;
723         if (!realinode->i_op->set_acl)
724                 goto out_acl_release;
725         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
726                 err = acl ? -EACCES : 0;
727                 goto out_acl_release;
728         }
729         err = -EPERM;
730         if (!inode_owner_or_capable(inode))
731                 goto out_acl_release;
732
733         posix_acl_release(acl);
734
735         /*
736          * Check if sgid bit needs to be cleared (actual setacl operation will
737          * be done with mounter's capabilities and so that won't do it for us).
738          */
739         if (unlikely(inode->i_mode & S_ISGID) &&
740             handler->flags == ACL_TYPE_ACCESS &&
741             !in_group_p(inode->i_gid) &&
742             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
743                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
744
745                 err = ovl_setattr(dentry, &iattr);
746                 if (err)
747                         return err;
748         }
749
750         err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
751         if (!err)
752                 ovl_copyattr(ovl_inode_real(inode), inode);
753
754         return err;
755
756 out_acl_release:
757         posix_acl_release(acl);
758         return err;
759 }
760
761 static int ovl_own_xattr_get(const struct xattr_handler *handler,
762                              struct dentry *dentry, struct inode *inode,
763                              const char *name, void *buffer, size_t size)
764 {
765         return -EOPNOTSUPP;
766 }
767
768 static int ovl_own_xattr_set(const struct xattr_handler *handler,
769                              struct dentry *dentry, struct inode *inode,
770                              const char *name, const void *value,
771                              size_t size, int flags)
772 {
773         return -EOPNOTSUPP;
774 }
775
776 static int ovl_other_xattr_get(const struct xattr_handler *handler,
777                                struct dentry *dentry, struct inode *inode,
778                                const char *name, void *buffer, size_t size)
779 {
780         return ovl_xattr_get(dentry, inode, name, buffer, size);
781 }
782
783 static int ovl_other_xattr_set(const struct xattr_handler *handler,
784                                struct dentry *dentry, struct inode *inode,
785                                const char *name, const void *value,
786                                size_t size, int flags)
787 {
788         return ovl_xattr_set(dentry, inode, name, value, size, flags);
789 }
790
791 static const struct xattr_handler __maybe_unused
792 ovl_posix_acl_access_xattr_handler = {
793         .name = XATTR_NAME_POSIX_ACL_ACCESS,
794         .flags = ACL_TYPE_ACCESS,
795         .get = ovl_posix_acl_xattr_get,
796         .set = ovl_posix_acl_xattr_set,
797 };
798
799 static const struct xattr_handler __maybe_unused
800 ovl_posix_acl_default_xattr_handler = {
801         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
802         .flags = ACL_TYPE_DEFAULT,
803         .get = ovl_posix_acl_xattr_get,
804         .set = ovl_posix_acl_xattr_set,
805 };
806
807 static const struct xattr_handler ovl_own_xattr_handler = {
808         .prefix = OVL_XATTR_PREFIX,
809         .get = ovl_own_xattr_get,
810         .set = ovl_own_xattr_set,
811 };
812
813 static const struct xattr_handler ovl_other_xattr_handler = {
814         .prefix = "", /* catch all */
815         .get = ovl_other_xattr_get,
816         .set = ovl_other_xattr_set,
817 };
818
819 static const struct xattr_handler *ovl_xattr_handlers[] = {
820 #ifdef CONFIG_FS_POSIX_ACL
821         &ovl_posix_acl_access_xattr_handler,
822         &ovl_posix_acl_default_xattr_handler,
823 #endif
824         &ovl_own_xattr_handler,
825         &ovl_other_xattr_handler,
826         NULL
827 };
828
829 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
830 {
831         struct path upperpath = { };
832         struct path workpath = { };
833         struct dentry *root_dentry;
834         struct ovl_entry *oe;
835         struct ovl_fs *ufs;
836         struct path *stack = NULL;
837         char *lowertmp;
838         char *lower;
839         unsigned int numlower;
840         unsigned int stacklen = 0;
841         unsigned int i;
842         bool remote = false;
843         struct cred *cred;
844         int err;
845
846         err = -ENOMEM;
847         ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
848         if (!ufs)
849                 goto out;
850
851         ufs->config.redirect_dir = ovl_redirect_dir_def;
852         ufs->config.index = ovl_index_def;
853         err = ovl_parse_opt((char *) data, &ufs->config);
854         if (err)
855                 goto out_free_config;
856
857         err = -EINVAL;
858         if (!ufs->config.lowerdir) {
859                 if (!silent)
860                         pr_err("overlayfs: missing 'lowerdir'\n");
861                 goto out_free_config;
862         }
863
864         sb->s_stack_depth = 0;
865         sb->s_maxbytes = MAX_LFS_FILESIZE;
866         if (ufs->config.upperdir) {
867                 if (!ufs->config.workdir) {
868                         pr_err("overlayfs: missing 'workdir'\n");
869                         goto out_free_config;
870                 }
871
872                 err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
873                 if (err)
874                         goto out_free_config;
875
876                 /* Upper fs should not be r/o */
877                 if (sb_rdonly(upperpath.mnt->mnt_sb)) {
878                         pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
879                         err = -EINVAL;
880                         goto out_put_upperpath;
881                 }
882
883                 err = ovl_check_namelen(&upperpath, ufs, ufs->config.upperdir);
884                 if (err)
885                         goto out_put_upperpath;
886
887                 err = -EBUSY;
888                 if (ovl_inuse_trylock(upperpath.dentry)) {
889                         ufs->upperdir_locked = true;
890                 } else if (ufs->config.index) {
891                         pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
892                         goto out_put_upperpath;
893                 } else {
894                         pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
895                 }
896
897                 err = ovl_mount_dir(ufs->config.workdir, &workpath);
898                 if (err)
899                         goto out_unlock_upperdentry;
900
901                 err = -EINVAL;
902                 if (upperpath.mnt != workpath.mnt) {
903                         pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
904                         goto out_put_workpath;
905                 }
906                 if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
907                         pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
908                         goto out_put_workpath;
909                 }
910
911                 err = -EBUSY;
912                 if (ovl_inuse_trylock(workpath.dentry)) {
913                         ufs->workdir_locked = true;
914                 } else if (ufs->config.index) {
915                         pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
916                         goto out_put_workpath;
917                 } else {
918                         pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
919                 }
920
921                 ufs->workbasedir = workpath.dentry;
922                 sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
923         }
924         err = -ENOMEM;
925         lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
926         if (!lowertmp)
927                 goto out_unlock_workdentry;
928
929         err = -EINVAL;
930         stacklen = ovl_split_lowerdirs(lowertmp);
931         if (stacklen > OVL_MAX_STACK) {
932                 pr_err("overlayfs: too many lower directories, limit is %d\n",
933                        OVL_MAX_STACK);
934                 goto out_free_lowertmp;
935         } else if (!ufs->config.upperdir && stacklen == 1) {
936                 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
937                 goto out_free_lowertmp;
938         }
939
940         err = -ENOMEM;
941         stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
942         if (!stack)
943                 goto out_free_lowertmp;
944
945         err = -EINVAL;
946         lower = lowertmp;
947         for (numlower = 0; numlower < stacklen; numlower++) {
948                 err = ovl_lower_dir(lower, &stack[numlower], ufs,
949                                     &sb->s_stack_depth, &remote);
950                 if (err)
951                         goto out_put_lowerpath;
952
953                 lower = strchr(lower, '\0') + 1;
954         }
955
956         err = -EINVAL;
957         sb->s_stack_depth++;
958         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
959                 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
960                 goto out_put_lowerpath;
961         }
962
963         if (ufs->config.upperdir) {
964                 ufs->upper_mnt = clone_private_mount(&upperpath);
965                 err = PTR_ERR(ufs->upper_mnt);
966                 if (IS_ERR(ufs->upper_mnt)) {
967                         pr_err("overlayfs: failed to clone upperpath\n");
968                         goto out_put_lowerpath;
969                 }
970
971                 /* Don't inherit atime flags */
972                 ufs->upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
973
974                 sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
975
976                 ufs->workdir = ovl_workdir_create(sb, ufs, workpath.dentry,
977                                                   OVL_WORKDIR_NAME, false);
978                 /*
979                  * Upper should support d_type, else whiteouts are visible.
980                  * Given workdir and upper are on same fs, we can do
981                  * iterate_dir() on workdir. This check requires successful
982                  * creation of workdir in previous step.
983                  */
984                 if (ufs->workdir) {
985                         struct dentry *temp;
986
987                         err = ovl_check_d_type_supported(&workpath);
988                         if (err < 0)
989                                 goto out_put_workdir;
990
991                         /*
992                          * We allowed this configuration and don't want to
993                          * break users over kernel upgrade. So warn instead
994                          * of erroring out.
995                          */
996                         if (!err)
997                                 pr_warn("overlayfs: upper fs needs to support d_type.\n");
998
999                         /* Check if upper/work fs supports O_TMPFILE */
1000                         temp = ovl_do_tmpfile(ufs->workdir, S_IFREG | 0);
1001                         ufs->tmpfile = !IS_ERR(temp);
1002                         if (ufs->tmpfile)
1003                                 dput(temp);
1004                         else
1005                                 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1006
1007                         /*
1008                          * Check if upper/work fs supports trusted.overlay.*
1009                          * xattr
1010                          */
1011                         err = ovl_do_setxattr(ufs->workdir, OVL_XATTR_OPAQUE,
1012                                               "0", 1, 0);
1013                         if (err) {
1014                                 ufs->noxattr = true;
1015                                 pr_warn("overlayfs: upper fs does not support xattr.\n");
1016                         } else {
1017                                 vfs_removexattr(ufs->workdir, OVL_XATTR_OPAQUE);
1018                         }
1019
1020                         /* Check if upper/work fs supports file handles */
1021                         if (ufs->config.index &&
1022                             !ovl_can_decode_fh(ufs->workdir->d_sb)) {
1023                                 ufs->config.index = false;
1024                                 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1025                         }
1026                 }
1027         }
1028
1029         err = -ENOMEM;
1030         ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1031         if (ufs->lower_mnt == NULL)
1032                 goto out_put_workdir;
1033         for (i = 0; i < numlower; i++) {
1034                 struct vfsmount *mnt = clone_private_mount(&stack[i]);
1035
1036                 err = PTR_ERR(mnt);
1037                 if (IS_ERR(mnt)) {
1038                         pr_err("overlayfs: failed to clone lowerpath\n");
1039                         goto out_put_lower_mnt;
1040                 }
1041                 /*
1042                  * Make lower_mnt R/O.  That way fchmod/fchown on lower file
1043                  * will fail instead of modifying lower fs.
1044                  */
1045                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1046
1047                 ufs->lower_mnt[ufs->numlower] = mnt;
1048                 ufs->numlower++;
1049
1050                 /* Check if all lower layers are on same sb */
1051                 if (i == 0)
1052                         ufs->same_sb = mnt->mnt_sb;
1053                 else if (ufs->same_sb != mnt->mnt_sb)
1054                         ufs->same_sb = NULL;
1055         }
1056
1057         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1058         if (!ufs->upper_mnt)
1059                 sb->s_flags |= MS_RDONLY;
1060         else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
1061                 ufs->same_sb = NULL;
1062
1063         if (!(ovl_force_readonly(ufs)) && ufs->config.index) {
1064                 /* Verify lower root is upper root origin */
1065                 err = ovl_verify_origin(upperpath.dentry, ufs->lower_mnt[0],
1066                                         stack[0].dentry, false, true);
1067                 if (err) {
1068                         pr_err("overlayfs: failed to verify upper root origin\n");
1069                         goto out_put_lower_mnt;
1070                 }
1071
1072                 ufs->indexdir = ovl_workdir_create(sb, ufs, workpath.dentry,
1073                                                    OVL_INDEXDIR_NAME, true);
1074                 if (ufs->indexdir) {
1075                         /* Verify upper root is index dir origin */
1076                         err = ovl_verify_origin(ufs->indexdir, ufs->upper_mnt,
1077                                                 upperpath.dentry, true, true);
1078                         if (err)
1079                                 pr_err("overlayfs: failed to verify index dir origin\n");
1080
1081                         /* Cleanup bad/stale/orphan index entries */
1082                         if (!err)
1083                                 err = ovl_indexdir_cleanup(ufs->indexdir,
1084                                                            ufs->upper_mnt,
1085                                                            stack, numlower);
1086                 }
1087                 if (err || !ufs->indexdir)
1088                         pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1089                 if (err)
1090                         goto out_put_indexdir;
1091         }
1092
1093         /* Show index=off/on in /proc/mounts for any of the reasons above */
1094         if (!ufs->indexdir)
1095                 ufs->config.index = false;
1096
1097         if (remote)
1098                 sb->s_d_op = &ovl_reval_dentry_operations;
1099         else
1100                 sb->s_d_op = &ovl_dentry_operations;
1101
1102         err = -ENOMEM;
1103         ufs->creator_cred = cred = prepare_creds();
1104         if (!cred)
1105                 goto out_put_indexdir;
1106
1107         /* Never override disk quota limits or use reserved space */
1108         cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1109
1110         err = -ENOMEM;
1111         oe = ovl_alloc_entry(numlower);
1112         if (!oe)
1113                 goto out_put_cred;
1114
1115         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1116         sb->s_op = &ovl_super_operations;
1117         sb->s_xattr = ovl_xattr_handlers;
1118         sb->s_fs_info = ufs;
1119         sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;
1120
1121         root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1122         if (!root_dentry)
1123                 goto out_free_oe;
1124
1125         mntput(upperpath.mnt);
1126         for (i = 0; i < numlower; i++)
1127                 mntput(stack[i].mnt);
1128         mntput(workpath.mnt);
1129         kfree(lowertmp);
1130
1131         if (upperpath.dentry) {
1132                 oe->has_upper = true;
1133                 if (ovl_is_impuredir(upperpath.dentry))
1134                         ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1135         }
1136         for (i = 0; i < numlower; i++) {
1137                 oe->lowerstack[i].dentry = stack[i].dentry;
1138                 oe->lowerstack[i].mnt = ufs->lower_mnt[i];
1139         }
1140         kfree(stack);
1141
1142         root_dentry->d_fsdata = oe;
1143
1144         ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1145                        ovl_dentry_lower(root_dentry));
1146
1147         sb->s_root = root_dentry;
1148
1149         return 0;
1150
1151 out_free_oe:
1152         kfree(oe);
1153 out_put_cred:
1154         put_cred(ufs->creator_cred);
1155 out_put_indexdir:
1156         dput(ufs->indexdir);
1157 out_put_lower_mnt:
1158         for (i = 0; i < ufs->numlower; i++)
1159                 mntput(ufs->lower_mnt[i]);
1160         kfree(ufs->lower_mnt);
1161 out_put_workdir:
1162         dput(ufs->workdir);
1163         mntput(ufs->upper_mnt);
1164 out_put_lowerpath:
1165         for (i = 0; i < numlower; i++)
1166                 path_put(&stack[i]);
1167         kfree(stack);
1168 out_free_lowertmp:
1169         kfree(lowertmp);
1170 out_unlock_workdentry:
1171         if (ufs->workdir_locked)
1172                 ovl_inuse_unlock(workpath.dentry);
1173 out_put_workpath:
1174         path_put(&workpath);
1175 out_unlock_upperdentry:
1176         if (ufs->upperdir_locked)
1177                 ovl_inuse_unlock(upperpath.dentry);
1178 out_put_upperpath:
1179         path_put(&upperpath);
1180 out_free_config:
1181         kfree(ufs->config.lowerdir);
1182         kfree(ufs->config.upperdir);
1183         kfree(ufs->config.workdir);
1184         kfree(ufs);
1185 out:
1186         return err;
1187 }
1188
1189 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1190                                 const char *dev_name, void *raw_data)
1191 {
1192         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1193 }
1194
1195 static struct file_system_type ovl_fs_type = {
1196         .owner          = THIS_MODULE,
1197         .name           = "overlay",
1198         .mount          = ovl_mount,
1199         .kill_sb        = kill_anon_super,
1200 };
1201 MODULE_ALIAS_FS("overlay");
1202
1203 static void ovl_inode_init_once(void *foo)
1204 {
1205         struct ovl_inode *oi = foo;
1206
1207         inode_init_once(&oi->vfs_inode);
1208 }
1209
1210 static int __init ovl_init(void)
1211 {
1212         int err;
1213
1214         ovl_inode_cachep = kmem_cache_create("ovl_inode",
1215                                              sizeof(struct ovl_inode), 0,
1216                                              (SLAB_RECLAIM_ACCOUNT|
1217                                               SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1218                                              ovl_inode_init_once);
1219         if (ovl_inode_cachep == NULL)
1220                 return -ENOMEM;
1221
1222         err = register_filesystem(&ovl_fs_type);
1223         if (err)
1224                 kmem_cache_destroy(ovl_inode_cachep);
1225
1226         return err;
1227 }
1228
1229 static void __exit ovl_exit(void)
1230 {
1231         unregister_filesystem(&ovl_fs_type);
1232
1233         /*
1234          * Make sure all delayed rcu free inodes are flushed before we
1235          * destroy cache.
1236          */
1237         rcu_barrier();
1238         kmem_cache_destroy(ovl_inode_cachep);
1239
1240 }
1241
1242 module_init(ovl_init);
1243 module_exit(ovl_exit);