3 * Copyright (C) 2011 Novell Inc.
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.
10 #include <uapi/linux/magic.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"
22 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
23 MODULE_DESCRIPTION("Overlay filesystem");
24 MODULE_LICENSE("GPL");
29 #define OVL_MAX_STACK 500
31 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
32 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
33 MODULE_PARM_DESC(ovl_redirect_dir_def,
34 "Default to on or off for the redirect_dir feature");
36 static bool ovl_redirect_always_follow =
37 IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
38 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
40 MODULE_PARM_DESC(ovl_redirect_always_follow,
41 "Follow redirects even if redirect_dir feature is turned off");
43 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
44 module_param_named(index, ovl_index_def, bool, 0644);
45 MODULE_PARM_DESC(ovl_index_def,
46 "Default to on or off for the inodes index feature");
48 static void ovl_entry_stack_free(struct ovl_entry *oe)
52 for (i = 0; i < oe->numlower; i++)
53 dput(oe->lowerstack[i].dentry);
56 static void ovl_dentry_release(struct dentry *dentry)
58 struct ovl_entry *oe = dentry->d_fsdata;
61 ovl_entry_stack_free(oe);
66 static int ovl_check_append_only(struct inode *inode, int flag)
69 * This test was moot in vfs may_open() because overlay inode does
70 * not have the S_APPEND flag, so re-check on real upper inode
72 if (IS_APPEND(inode)) {
73 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
82 static struct dentry *ovl_d_real(struct dentry *dentry,
83 const struct inode *inode,
84 unsigned int open_flags, unsigned int flags)
89 if (flags & D_REAL_UPPER)
90 return ovl_dentry_upper(dentry);
92 if (!d_is_reg(dentry)) {
93 if (!inode || inode == d_inode(dentry))
99 err = ovl_open_maybe_copy_up(dentry, open_flags);
104 real = ovl_dentry_upper(dentry);
105 if (real && (!inode || inode == d_inode(real))) {
107 err = ovl_check_append_only(d_inode(real), open_flags);
114 real = ovl_dentry_lower(dentry);
118 /* Handle recursion */
119 real = d_real(real, inode, open_flags, 0);
121 if (!inode || inode == d_inode(real))
124 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
125 inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
129 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
131 struct ovl_entry *oe = dentry->d_fsdata;
135 for (i = 0; i < oe->numlower; i++) {
136 struct dentry *d = oe->lowerstack[i].dentry;
138 if (d->d_flags & DCACHE_OP_REVALIDATE) {
139 ret = d->d_op->d_revalidate(d, flags);
143 if (!(flags & LOOKUP_RCU))
152 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
154 struct ovl_entry *oe = dentry->d_fsdata;
158 for (i = 0; i < oe->numlower; i++) {
159 struct dentry *d = oe->lowerstack[i].dentry;
161 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
162 ret = d->d_op->d_weak_revalidate(d, flags);
170 static const struct dentry_operations ovl_dentry_operations = {
171 .d_release = ovl_dentry_release,
172 .d_real = ovl_d_real,
175 static const struct dentry_operations ovl_reval_dentry_operations = {
176 .d_release = ovl_dentry_release,
177 .d_real = ovl_d_real,
178 .d_revalidate = ovl_dentry_revalidate,
179 .d_weak_revalidate = ovl_dentry_weak_revalidate,
182 static struct kmem_cache *ovl_inode_cachep;
184 static struct inode *ovl_alloc_inode(struct super_block *sb)
186 struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
195 oi->__upperdentry = NULL;
197 mutex_init(&oi->lock);
199 return &oi->vfs_inode;
202 static void ovl_i_callback(struct rcu_head *head)
204 struct inode *inode = container_of(head, struct inode, i_rcu);
206 kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
209 static void ovl_destroy_inode(struct inode *inode)
211 struct ovl_inode *oi = OVL_I(inode);
213 dput(oi->__upperdentry);
215 ovl_dir_cache_free(inode);
216 mutex_destroy(&oi->lock);
218 call_rcu(&inode->i_rcu, ovl_i_callback);
221 static void ovl_free_fs(struct ovl_fs *ofs)
227 if (ofs->workdir_locked)
228 ovl_inuse_unlock(ofs->workbasedir);
229 dput(ofs->workbasedir);
230 if (ofs->upperdir_locked)
231 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
232 mntput(ofs->upper_mnt);
233 for (i = 0; i < ofs->numlower; i++) {
234 mntput(ofs->lower_layers[i].mnt);
235 free_anon_bdev(ofs->lower_layers[i].pseudo_dev);
237 kfree(ofs->lower_layers);
239 kfree(ofs->config.lowerdir);
240 kfree(ofs->config.upperdir);
241 kfree(ofs->config.workdir);
242 kfree(ofs->config.redirect_mode);
243 if (ofs->creator_cred)
244 put_cred(ofs->creator_cred);
248 static void ovl_put_super(struct super_block *sb)
250 struct ovl_fs *ofs = sb->s_fs_info;
255 /* Sync real dirty inodes in upper filesystem (if it exists) */
256 static int ovl_sync_fs(struct super_block *sb, int wait)
258 struct ovl_fs *ofs = sb->s_fs_info;
259 struct super_block *upper_sb;
266 * If this is a sync(2) call or an emergency sync, all the super blocks
267 * will be iterated, including upper_sb, so no need to do anything.
269 * If this is a syncfs(2) call, then we do need to call
270 * sync_filesystem() on upper_sb, but enough if we do it when being
271 * called with wait == 1.
276 upper_sb = ofs->upper_mnt->mnt_sb;
278 down_read(&upper_sb->s_umount);
279 ret = sync_filesystem(upper_sb);
280 up_read(&upper_sb->s_umount);
287 * @sb: The overlayfs super block
288 * @buf: The struct kstatfs to fill in with stats
290 * Get the filesystem statistics. As writes always target the upper layer
291 * filesystem pass the statfs to the upper filesystem (if it exists)
293 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
295 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
296 struct dentry *root_dentry = dentry->d_sb->s_root;
300 ovl_path_real(root_dentry, &path);
302 err = vfs_statfs(&path, buf);
304 buf->f_namelen = ofs->namelen;
305 buf->f_type = OVERLAYFS_SUPER_MAGIC;
311 /* Will this overlay be forced to mount/remount ro? */
312 static bool ovl_force_readonly(struct ovl_fs *ofs)
314 return (!ofs->upper_mnt || !ofs->workdir);
317 static const char *ovl_redirect_mode_def(void)
319 return ovl_redirect_dir_def ? "on" : "off";
325 * Prints the mount options for a given superblock.
326 * Returns zero; does not fail.
328 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
330 struct super_block *sb = dentry->d_sb;
331 struct ovl_fs *ofs = sb->s_fs_info;
333 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
334 if (ofs->config.upperdir) {
335 seq_show_option(m, "upperdir", ofs->config.upperdir);
336 seq_show_option(m, "workdir", ofs->config.workdir);
338 if (ofs->config.default_permissions)
339 seq_puts(m, ",default_permissions");
340 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
341 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
342 if (ofs->config.index != ovl_index_def)
343 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
347 static int ovl_remount(struct super_block *sb, int *flags, char *data)
349 struct ovl_fs *ofs = sb->s_fs_info;
351 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
357 static const struct super_operations ovl_super_operations = {
358 .alloc_inode = ovl_alloc_inode,
359 .destroy_inode = ovl_destroy_inode,
360 .drop_inode = generic_delete_inode,
361 .put_super = ovl_put_super,
362 .sync_fs = ovl_sync_fs,
363 .statfs = ovl_statfs,
364 .show_options = ovl_show_options,
365 .remount_fs = ovl_remount,
372 OPT_DEFAULT_PERMISSIONS,
379 static const match_table_t ovl_tokens = {
380 {OPT_LOWERDIR, "lowerdir=%s"},
381 {OPT_UPPERDIR, "upperdir=%s"},
382 {OPT_WORKDIR, "workdir=%s"},
383 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
384 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
385 {OPT_INDEX_ON, "index=on"},
386 {OPT_INDEX_OFF, "index=off"},
390 static char *ovl_next_opt(char **s)
398 for (p = sbegin; *p; p++) {
403 } else if (*p == ',') {
413 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
415 if (strcmp(mode, "on") == 0) {
416 config->redirect_dir = true;
418 * Does not make sense to have redirect creation without
419 * redirect following.
421 config->redirect_follow = true;
422 } else if (strcmp(mode, "follow") == 0) {
423 config->redirect_follow = true;
424 } else if (strcmp(mode, "off") == 0) {
425 if (ovl_redirect_always_follow)
426 config->redirect_follow = true;
427 } else if (strcmp(mode, "nofollow") != 0) {
428 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
436 static int ovl_parse_opt(char *opt, struct ovl_config *config)
440 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
441 if (!config->redirect_mode)
444 while ((p = ovl_next_opt(&opt)) != NULL) {
446 substring_t args[MAX_OPT_ARGS];
451 token = match_token(p, ovl_tokens, args);
454 kfree(config->upperdir);
455 config->upperdir = match_strdup(&args[0]);
456 if (!config->upperdir)
461 kfree(config->lowerdir);
462 config->lowerdir = match_strdup(&args[0]);
463 if (!config->lowerdir)
468 kfree(config->workdir);
469 config->workdir = match_strdup(&args[0]);
470 if (!config->workdir)
474 case OPT_DEFAULT_PERMISSIONS:
475 config->default_permissions = true;
478 case OPT_REDIRECT_DIR:
479 kfree(config->redirect_mode);
480 config->redirect_mode = match_strdup(&args[0]);
481 if (!config->redirect_mode)
486 config->index = true;
490 config->index = false;
494 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
499 /* Workdir is useless in non-upper mount */
500 if (!config->upperdir && config->workdir) {
501 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
503 kfree(config->workdir);
504 config->workdir = NULL;
507 return ovl_parse_redirect_mode(config, config->redirect_mode);
510 #define OVL_WORKDIR_NAME "work"
511 #define OVL_INDEXDIR_NAME "index"
513 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
514 const char *name, bool persist)
516 struct inode *dir = ofs->workbasedir->d_inode;
517 struct vfsmount *mnt = ofs->upper_mnt;
520 bool retried = false;
523 err = mnt_want_write(mnt);
527 inode_lock_nested(dir, I_MUTEX_PARENT);
531 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
534 struct iattr attr = {
535 .ia_valid = ATTR_MODE,
536 .ia_mode = S_IFDIR | 0,
548 ovl_workdir_cleanup(dir, mnt, work, 0);
553 err = ovl_create_real(dir, work,
554 &(struct cattr){.mode = S_IFDIR | 0},
560 * Try to remove POSIX ACL xattrs from workdir. We are good if:
562 * a) success (there was a POSIX ACL xattr and was removed)
563 * b) -ENODATA (there was no POSIX ACL xattr)
564 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
566 * There are various other error values that could effectively
567 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
568 * if the xattr name is too long), but the set of filesystems
569 * allowed as upper are limited to "normal" ones, where checking
570 * for the above two errors is sufficient.
572 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
573 if (err && err != -ENODATA && err != -EOPNOTSUPP)
576 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
577 if (err && err != -ENODATA && err != -EOPNOTSUPP)
580 /* Clear any inherited mode bits */
581 inode_lock(work->d_inode);
582 err = notify_change(work, &attr, NULL);
583 inode_unlock(work->d_inode);
600 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
601 ofs->config.workdir, name, -err);
606 static void ovl_unescape(char *s)
619 static int ovl_mount_dir_noesc(const char *name, struct path *path)
624 pr_err("overlayfs: empty lowerdir\n");
627 err = kern_path(name, LOOKUP_FOLLOW, path);
629 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
633 if (ovl_dentry_weird(path->dentry)) {
634 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
637 if (!d_is_dir(path->dentry)) {
638 pr_err("overlayfs: '%s' not a directory\n", name);
649 static int ovl_mount_dir(const char *name, struct path *path)
652 char *tmp = kstrdup(name, GFP_KERNEL);
656 err = ovl_mount_dir_noesc(tmp, path);
659 if (ovl_dentry_remote(path->dentry)) {
660 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
670 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
673 struct kstatfs statfs;
674 int err = vfs_statfs(path, &statfs);
677 pr_err("overlayfs: statfs failed on '%s'\n", name);
679 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
684 static int ovl_lower_dir(const char *name, struct path *path,
685 struct ovl_fs *ofs, int *stack_depth, bool *remote)
689 err = ovl_mount_dir_noesc(name, path);
693 err = ovl_check_namelen(path, ofs, name);
697 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
699 if (ovl_dentry_remote(path->dentry))
703 * The inodes index feature needs to encode and decode file
704 * handles, so it requires that all layers support them.
706 if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
707 ofs->config.index = false;
708 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
719 /* Workdir should not be subdir of upperdir and vice versa */
720 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
724 if (workdir != upperdir) {
725 ok = (lock_rename(workdir, upperdir) == NULL);
726 unlock_rename(workdir, upperdir);
731 static unsigned int ovl_split_lowerdirs(char *str)
733 unsigned int ctr = 1;
736 for (s = d = str;; s++, d++) {
739 } else if (*s == ':') {
751 static int __maybe_unused
752 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
753 struct dentry *dentry, struct inode *inode,
754 const char *name, void *buffer, size_t size)
756 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
759 static int __maybe_unused
760 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
761 struct dentry *dentry, struct inode *inode,
762 const char *name, const void *value,
763 size_t size, int flags)
765 struct dentry *workdir = ovl_workdir(dentry);
766 struct inode *realinode = ovl_inode_real(inode);
767 struct posix_acl *acl = NULL;
770 /* Check that everything is OK before copy-up */
772 acl = posix_acl_from_xattr(&init_user_ns, value, size);
777 if (!IS_POSIXACL(d_inode(workdir)))
778 goto out_acl_release;
779 if (!realinode->i_op->set_acl)
780 goto out_acl_release;
781 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
782 err = acl ? -EACCES : 0;
783 goto out_acl_release;
786 if (!inode_owner_or_capable(inode))
787 goto out_acl_release;
789 posix_acl_release(acl);
792 * Check if sgid bit needs to be cleared (actual setacl operation will
793 * be done with mounter's capabilities and so that won't do it for us).
795 if (unlikely(inode->i_mode & S_ISGID) &&
796 handler->flags == ACL_TYPE_ACCESS &&
797 !in_group_p(inode->i_gid) &&
798 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
799 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
801 err = ovl_setattr(dentry, &iattr);
806 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
808 ovl_copyattr(ovl_inode_real(inode), inode);
813 posix_acl_release(acl);
817 static int ovl_own_xattr_get(const struct xattr_handler *handler,
818 struct dentry *dentry, struct inode *inode,
819 const char *name, void *buffer, size_t size)
824 static int ovl_own_xattr_set(const struct xattr_handler *handler,
825 struct dentry *dentry, struct inode *inode,
826 const char *name, const void *value,
827 size_t size, int flags)
832 static int ovl_other_xattr_get(const struct xattr_handler *handler,
833 struct dentry *dentry, struct inode *inode,
834 const char *name, void *buffer, size_t size)
836 return ovl_xattr_get(dentry, inode, name, buffer, size);
839 static int ovl_other_xattr_set(const struct xattr_handler *handler,
840 struct dentry *dentry, struct inode *inode,
841 const char *name, const void *value,
842 size_t size, int flags)
844 return ovl_xattr_set(dentry, inode, name, value, size, flags);
847 static const struct xattr_handler __maybe_unused
848 ovl_posix_acl_access_xattr_handler = {
849 .name = XATTR_NAME_POSIX_ACL_ACCESS,
850 .flags = ACL_TYPE_ACCESS,
851 .get = ovl_posix_acl_xattr_get,
852 .set = ovl_posix_acl_xattr_set,
855 static const struct xattr_handler __maybe_unused
856 ovl_posix_acl_default_xattr_handler = {
857 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
858 .flags = ACL_TYPE_DEFAULT,
859 .get = ovl_posix_acl_xattr_get,
860 .set = ovl_posix_acl_xattr_set,
863 static const struct xattr_handler ovl_own_xattr_handler = {
864 .prefix = OVL_XATTR_PREFIX,
865 .get = ovl_own_xattr_get,
866 .set = ovl_own_xattr_set,
869 static const struct xattr_handler ovl_other_xattr_handler = {
870 .prefix = "", /* catch all */
871 .get = ovl_other_xattr_get,
872 .set = ovl_other_xattr_set,
875 static const struct xattr_handler *ovl_xattr_handlers[] = {
876 #ifdef CONFIG_FS_POSIX_ACL
877 &ovl_posix_acl_access_xattr_handler,
878 &ovl_posix_acl_default_xattr_handler,
880 &ovl_own_xattr_handler,
881 &ovl_other_xattr_handler,
885 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
887 struct vfsmount *upper_mnt;
890 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
894 /* Upper fs should not be r/o */
895 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
896 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
901 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
906 if (ovl_inuse_trylock(upperpath->dentry)) {
907 ofs->upperdir_locked = true;
908 } else if (ofs->config.index) {
909 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
912 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
915 upper_mnt = clone_private_mount(upperpath);
916 err = PTR_ERR(upper_mnt);
917 if (IS_ERR(upper_mnt)) {
918 pr_err("overlayfs: failed to clone upperpath\n");
922 /* Don't inherit atime flags */
923 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
924 ofs->upper_mnt = upper_mnt;
930 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
935 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
940 * Upper should support d_type, else whiteouts are visible. Given
941 * workdir and upper are on same fs, we can do iterate_dir() on
942 * workdir. This check requires successful creation of workdir in
945 err = ovl_check_d_type_supported(workpath);
950 * We allowed this configuration and don't want to break users over
951 * kernel upgrade. So warn instead of erroring out.
954 pr_warn("overlayfs: upper fs needs to support d_type.\n");
956 /* Check if upper/work fs supports O_TMPFILE */
957 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
958 ofs->tmpfile = !IS_ERR(temp);
962 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
965 * Check if upper/work fs supports trusted.overlay.* xattr
967 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
970 pr_warn("overlayfs: upper fs does not support xattr.\n");
972 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
975 /* Check if upper/work fs supports file handles */
976 if (ofs->config.index &&
977 !ovl_can_decode_fh(ofs->workdir->d_sb)) {
978 ofs->config.index = false;
979 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
985 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
988 struct path workpath = { };
990 err = ovl_mount_dir(ofs->config.workdir, &workpath);
995 if (upperpath->mnt != workpath.mnt) {
996 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
999 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1000 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1005 if (ovl_inuse_trylock(workpath.dentry)) {
1006 ofs->workdir_locked = true;
1007 } else if (ofs->config.index) {
1008 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1011 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1014 ofs->workbasedir = dget(workpath.dentry);
1015 err = ovl_make_workdir(ofs, &workpath);
1021 path_put(&workpath);
1026 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
1027 struct path *upperpath)
1031 /* Verify lower root is upper root origin */
1032 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1035 pr_err("overlayfs: failed to verify upper root origin\n");
1039 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1040 if (ofs->indexdir) {
1041 /* Verify upper root is index dir origin */
1042 err = ovl_verify_origin(ofs->indexdir, upperpath->dentry,
1045 pr_err("overlayfs: failed to verify index dir origin\n");
1047 /* Cleanup bad/stale/orphan index entries */
1049 err = ovl_indexdir_cleanup(ofs->indexdir,
1054 if (err || !ofs->indexdir)
1055 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1061 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
1062 unsigned int numlower)
1068 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1070 if (ofs->lower_layers == NULL)
1072 for (i = 0; i < numlower; i++) {
1073 struct vfsmount *mnt;
1076 err = get_anon_bdev(&dev);
1078 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1082 mnt = clone_private_mount(&stack[i]);
1085 pr_err("overlayfs: failed to clone lowerpath\n");
1086 free_anon_bdev(dev);
1090 * Make lower layers R/O. That way fchmod/fchown on lower file
1091 * will fail instead of modifying lower fs.
1093 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1095 ofs->lower_layers[ofs->numlower].mnt = mnt;
1096 ofs->lower_layers[ofs->numlower].pseudo_dev = dev;
1099 /* Check if all lower layers are on same sb */
1101 ofs->same_sb = mnt->mnt_sb;
1102 else if (ofs->same_sb != mnt->mnt_sb)
1103 ofs->same_sb = NULL;
1110 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1114 char *lowertmp, *lower;
1115 struct path *stack = NULL;
1116 unsigned int stacklen, numlower = 0, i;
1117 bool remote = false;
1118 struct ovl_entry *oe;
1121 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1126 stacklen = ovl_split_lowerdirs(lowertmp);
1127 if (stacklen > OVL_MAX_STACK) {
1128 pr_err("overlayfs: too many lower directories, limit is %d\n",
1131 } else if (!ofs->config.upperdir && stacklen == 1) {
1132 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1137 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1143 for (numlower = 0; numlower < stacklen; numlower++) {
1144 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1145 &sb->s_stack_depth, &remote);
1149 lower = strchr(lower, '\0') + 1;
1153 sb->s_stack_depth++;
1154 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1155 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1159 err = ovl_get_lower_layers(ofs, stack, numlower);
1164 oe = ovl_alloc_entry(numlower);
1168 for (i = 0; i < numlower; i++) {
1169 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1170 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1174 sb->s_d_op = &ovl_reval_dentry_operations;
1176 sb->s_d_op = &ovl_dentry_operations;
1179 for (i = 0; i < numlower; i++)
1180 path_put(&stack[i]);
1191 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1193 struct path upperpath = { };
1194 struct dentry *root_dentry;
1195 struct ovl_entry *oe;
1201 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1205 ofs->creator_cred = cred = prepare_creds();
1209 ofs->config.index = ovl_index_def;
1210 err = ovl_parse_opt((char *) data, &ofs->config);
1215 if (!ofs->config.lowerdir) {
1217 pr_err("overlayfs: missing 'lowerdir'\n");
1221 sb->s_stack_depth = 0;
1222 sb->s_maxbytes = MAX_LFS_FILESIZE;
1223 if (ofs->config.upperdir) {
1224 if (!ofs->config.workdir) {
1225 pr_err("overlayfs: missing 'workdir'\n");
1229 err = ovl_get_upper(ofs, &upperpath);
1233 err = ovl_get_workdir(ofs, &upperpath);
1238 sb->s_flags |= SB_RDONLY;
1240 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1241 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1244 oe = ovl_get_lowerstack(sb, ofs);
1249 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1250 if (!ofs->upper_mnt)
1251 sb->s_flags |= SB_RDONLY;
1252 else if (ofs->upper_mnt->mnt_sb != ofs->same_sb)
1253 ofs->same_sb = NULL;
1255 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1256 err = ovl_get_indexdir(ofs, oe, &upperpath);
1261 sb->s_flags |= SB_RDONLY;
1264 /* Show index=off/on in /proc/mounts for any of the reasons above */
1266 ofs->config.index = false;
1268 /* Never override disk quota limits or use reserved space */
1269 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1271 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1272 sb->s_op = &ovl_super_operations;
1273 sb->s_xattr = ovl_xattr_handlers;
1274 sb->s_fs_info = ofs;
1275 sb->s_flags |= SB_POSIXACL | SB_NOREMOTELOCK;
1278 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1282 mntput(upperpath.mnt);
1283 if (upperpath.dentry) {
1284 oe->has_upper = true;
1285 if (ovl_is_impuredir(upperpath.dentry))
1286 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1289 root_dentry->d_fsdata = oe;
1291 /* Root is always merge -> can have whiteouts */
1292 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1293 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1294 ovl_dentry_lower(root_dentry));
1296 sb->s_root = root_dentry;
1301 ovl_entry_stack_free(oe);
1304 path_put(&upperpath);
1310 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1311 const char *dev_name, void *raw_data)
1313 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1316 static struct file_system_type ovl_fs_type = {
1317 .owner = THIS_MODULE,
1320 .kill_sb = kill_anon_super,
1322 MODULE_ALIAS_FS("overlay");
1324 static void ovl_inode_init_once(void *foo)
1326 struct ovl_inode *oi = foo;
1328 inode_init_once(&oi->vfs_inode);
1331 static int __init ovl_init(void)
1335 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1336 sizeof(struct ovl_inode), 0,
1337 (SLAB_RECLAIM_ACCOUNT|
1338 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1339 ovl_inode_init_once);
1340 if (ovl_inode_cachep == NULL)
1343 err = register_filesystem(&ovl_fs_type);
1345 kmem_cache_destroy(ovl_inode_cachep);
1350 static void __exit ovl_exit(void)
1352 unregister_filesystem(&ovl_fs_type);
1355 * Make sure all delayed rcu free inodes are flushed before we
1359 kmem_cache_destroy(ovl_inode_cachep);
1363 module_init(ovl_init);
1364 module_exit(ovl_exit);