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