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 <linux/exportfs.h>
21 #include "overlayfs.h"
23 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
24 MODULE_DESCRIPTION("Overlay filesystem");
25 MODULE_LICENSE("GPL");
30 #define OVL_MAX_STACK 500
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");
37 static bool ovl_redirect_always_follow
=
38 IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
);
39 module_param_named(redirect_always_follow
, ovl_redirect_always_follow
,
41 MODULE_PARM_DESC(ovl_redirect_always_follow
,
42 "Follow redirects even if redirect_dir feature is turned off");
44 static bool ovl_index_def
= IS_ENABLED(CONFIG_OVERLAY_FS_INDEX
);
45 module_param_named(index
, ovl_index_def
, bool, 0644);
46 MODULE_PARM_DESC(ovl_index_def
,
47 "Default to on or off for the inodes index feature");
49 static bool ovl_nfs_export_def
= IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT
);
50 module_param_named(nfs_export
, ovl_nfs_export_def
, bool, 0644);
51 MODULE_PARM_DESC(ovl_nfs_export_def
,
52 "Default to on or off for the NFS export feature");
54 static bool ovl_xino_auto_def
= IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO
);
55 module_param_named(xino_auto
, ovl_xino_auto_def
, bool, 0644);
56 MODULE_PARM_DESC(ovl_xino_auto_def
,
57 "Auto enable xino feature");
59 static void ovl_entry_stack_free(struct ovl_entry
*oe
)
63 for (i
= 0; i
< oe
->numlower
; i
++)
64 dput(oe
->lowerstack
[i
].dentry
);
67 static void ovl_dentry_release(struct dentry
*dentry
)
69 struct ovl_entry
*oe
= dentry
->d_fsdata
;
72 ovl_entry_stack_free(oe
);
77 static int ovl_check_append_only(struct inode
*inode
, int flag
)
80 * This test was moot in vfs may_open() because overlay inode does
81 * not have the S_APPEND flag, so re-check on real upper inode
83 if (IS_APPEND(inode
)) {
84 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
93 static struct dentry
*ovl_d_real(struct dentry
*dentry
,
94 const struct inode
*inode
,
95 unsigned int open_flags
, unsigned int flags
)
100 if (flags
& D_REAL_UPPER
)
101 return ovl_dentry_upper(dentry
);
103 if (!d_is_reg(dentry
)) {
104 if (!inode
|| inode
== d_inode(dentry
))
110 err
= ovl_open_maybe_copy_up(dentry
, open_flags
);
115 real
= ovl_dentry_upper(dentry
);
116 if (real
&& (!inode
|| inode
== d_inode(real
))) {
118 err
= ovl_check_append_only(d_inode(real
), open_flags
);
125 real
= ovl_dentry_lower(dentry
);
129 /* Handle recursion */
130 real
= d_real(real
, inode
, open_flags
, 0);
132 if (!inode
|| inode
== d_inode(real
))
135 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry
,
136 inode
? inode
->i_sb
->s_id
: "NULL", inode
? inode
->i_ino
: 0);
140 static int ovl_dentry_revalidate(struct dentry
*dentry
, unsigned int flags
)
142 struct ovl_entry
*oe
= dentry
->d_fsdata
;
146 for (i
= 0; i
< oe
->numlower
; i
++) {
147 struct dentry
*d
= oe
->lowerstack
[i
].dentry
;
149 if (d
->d_flags
& DCACHE_OP_REVALIDATE
) {
150 ret
= d
->d_op
->d_revalidate(d
, flags
);
154 if (!(flags
& LOOKUP_RCU
))
163 static int ovl_dentry_weak_revalidate(struct dentry
*dentry
, unsigned int flags
)
165 struct ovl_entry
*oe
= dentry
->d_fsdata
;
169 for (i
= 0; i
< oe
->numlower
; i
++) {
170 struct dentry
*d
= oe
->lowerstack
[i
].dentry
;
172 if (d
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
) {
173 ret
= d
->d_op
->d_weak_revalidate(d
, flags
);
181 static const struct dentry_operations ovl_dentry_operations
= {
182 .d_release
= ovl_dentry_release
,
183 .d_real
= ovl_d_real
,
186 static const struct dentry_operations ovl_reval_dentry_operations
= {
187 .d_release
= ovl_dentry_release
,
188 .d_real
= ovl_d_real
,
189 .d_revalidate
= ovl_dentry_revalidate
,
190 .d_weak_revalidate
= ovl_dentry_weak_revalidate
,
193 static struct kmem_cache
*ovl_inode_cachep
;
195 static struct inode
*ovl_alloc_inode(struct super_block
*sb
)
197 struct ovl_inode
*oi
= kmem_cache_alloc(ovl_inode_cachep
, GFP_KERNEL
);
206 oi
->__upperdentry
= NULL
;
208 mutex_init(&oi
->lock
);
210 return &oi
->vfs_inode
;
213 static void ovl_i_callback(struct rcu_head
*head
)
215 struct inode
*inode
= container_of(head
, struct inode
, i_rcu
);
217 kmem_cache_free(ovl_inode_cachep
, OVL_I(inode
));
220 static void ovl_destroy_inode(struct inode
*inode
)
222 struct ovl_inode
*oi
= OVL_I(inode
);
224 dput(oi
->__upperdentry
);
227 ovl_dir_cache_free(inode
);
228 mutex_destroy(&oi
->lock
);
230 call_rcu(&inode
->i_rcu
, ovl_i_callback
);
233 static void ovl_free_fs(struct ovl_fs
*ofs
)
239 if (ofs
->workdir_locked
)
240 ovl_inuse_unlock(ofs
->workbasedir
);
241 dput(ofs
->workbasedir
);
242 if (ofs
->upperdir_locked
)
243 ovl_inuse_unlock(ofs
->upper_mnt
->mnt_root
);
244 mntput(ofs
->upper_mnt
);
245 for (i
= 0; i
< ofs
->numlower
; i
++)
246 mntput(ofs
->lower_layers
[i
].mnt
);
247 for (i
= 0; i
< ofs
->numlowerfs
; i
++)
248 free_anon_bdev(ofs
->lower_fs
[i
].pseudo_dev
);
249 kfree(ofs
->lower_layers
);
250 kfree(ofs
->lower_fs
);
252 kfree(ofs
->config
.lowerdir
);
253 kfree(ofs
->config
.upperdir
);
254 kfree(ofs
->config
.workdir
);
255 kfree(ofs
->config
.redirect_mode
);
256 if (ofs
->creator_cred
)
257 put_cred(ofs
->creator_cred
);
261 static void ovl_put_super(struct super_block
*sb
)
263 struct ovl_fs
*ofs
= sb
->s_fs_info
;
268 /* Sync real dirty inodes in upper filesystem (if it exists) */
269 static int ovl_sync_fs(struct super_block
*sb
, int wait
)
271 struct ovl_fs
*ofs
= sb
->s_fs_info
;
272 struct super_block
*upper_sb
;
279 * If this is a sync(2) call or an emergency sync, all the super blocks
280 * will be iterated, including upper_sb, so no need to do anything.
282 * If this is a syncfs(2) call, then we do need to call
283 * sync_filesystem() on upper_sb, but enough if we do it when being
284 * called with wait == 1.
289 upper_sb
= ofs
->upper_mnt
->mnt_sb
;
291 down_read(&upper_sb
->s_umount
);
292 ret
= sync_filesystem(upper_sb
);
293 up_read(&upper_sb
->s_umount
);
300 * @sb: The overlayfs super block
301 * @buf: The struct kstatfs to fill in with stats
303 * Get the filesystem statistics. As writes always target the upper layer
304 * filesystem pass the statfs to the upper filesystem (if it exists)
306 static int ovl_statfs(struct dentry
*dentry
, struct kstatfs
*buf
)
308 struct ovl_fs
*ofs
= dentry
->d_sb
->s_fs_info
;
309 struct dentry
*root_dentry
= dentry
->d_sb
->s_root
;
313 ovl_path_real(root_dentry
, &path
);
315 err
= vfs_statfs(&path
, buf
);
317 buf
->f_namelen
= ofs
->namelen
;
318 buf
->f_type
= OVERLAYFS_SUPER_MAGIC
;
324 /* Will this overlay be forced to mount/remount ro? */
325 static bool ovl_force_readonly(struct ovl_fs
*ofs
)
327 return (!ofs
->upper_mnt
|| !ofs
->workdir
);
330 static const char *ovl_redirect_mode_def(void)
332 return ovl_redirect_dir_def
? "on" : "off";
341 static const char * const ovl_xino_str
[] = {
347 static inline int ovl_xino_def(void)
349 return ovl_xino_auto_def
? OVL_XINO_AUTO
: OVL_XINO_OFF
;
355 * Prints the mount options for a given superblock.
356 * Returns zero; does not fail.
358 static int ovl_show_options(struct seq_file
*m
, struct dentry
*dentry
)
360 struct super_block
*sb
= dentry
->d_sb
;
361 struct ovl_fs
*ofs
= sb
->s_fs_info
;
363 seq_show_option(m
, "lowerdir", ofs
->config
.lowerdir
);
364 if (ofs
->config
.upperdir
) {
365 seq_show_option(m
, "upperdir", ofs
->config
.upperdir
);
366 seq_show_option(m
, "workdir", ofs
->config
.workdir
);
368 if (ofs
->config
.default_permissions
)
369 seq_puts(m
, ",default_permissions");
370 if (strcmp(ofs
->config
.redirect_mode
, ovl_redirect_mode_def()) != 0)
371 seq_printf(m
, ",redirect_dir=%s", ofs
->config
.redirect_mode
);
372 if (ofs
->config
.index
!= ovl_index_def
)
373 seq_printf(m
, ",index=%s", ofs
->config
.index
? "on" : "off");
374 if (ofs
->config
.nfs_export
!= ovl_nfs_export_def
)
375 seq_printf(m
, ",nfs_export=%s", ofs
->config
.nfs_export
?
377 if (ofs
->config
.xino
!= ovl_xino_def())
378 seq_printf(m
, ",xino=%s", ovl_xino_str
[ofs
->config
.xino
]);
382 static int ovl_remount(struct super_block
*sb
, int *flags
, char *data
)
384 struct ovl_fs
*ofs
= sb
->s_fs_info
;
386 if (!(*flags
& SB_RDONLY
) && ovl_force_readonly(ofs
))
392 static const struct super_operations ovl_super_operations
= {
393 .alloc_inode
= ovl_alloc_inode
,
394 .destroy_inode
= ovl_destroy_inode
,
395 .drop_inode
= generic_delete_inode
,
396 .put_super
= ovl_put_super
,
397 .sync_fs
= ovl_sync_fs
,
398 .statfs
= ovl_statfs
,
399 .show_options
= ovl_show_options
,
400 .remount_fs
= ovl_remount
,
407 OPT_DEFAULT_PERMISSIONS
,
419 static const match_table_t ovl_tokens
= {
420 {OPT_LOWERDIR
, "lowerdir=%s"},
421 {OPT_UPPERDIR
, "upperdir=%s"},
422 {OPT_WORKDIR
, "workdir=%s"},
423 {OPT_DEFAULT_PERMISSIONS
, "default_permissions"},
424 {OPT_REDIRECT_DIR
, "redirect_dir=%s"},
425 {OPT_INDEX_ON
, "index=on"},
426 {OPT_INDEX_OFF
, "index=off"},
427 {OPT_NFS_EXPORT_ON
, "nfs_export=on"},
428 {OPT_NFS_EXPORT_OFF
, "nfs_export=off"},
429 {OPT_XINO_ON
, "xino=on"},
430 {OPT_XINO_OFF
, "xino=off"},
431 {OPT_XINO_AUTO
, "xino=auto"},
435 static char *ovl_next_opt(char **s
)
443 for (p
= sbegin
; *p
; p
++) {
448 } else if (*p
== ',') {
458 static int ovl_parse_redirect_mode(struct ovl_config
*config
, const char *mode
)
460 if (strcmp(mode
, "on") == 0) {
461 config
->redirect_dir
= true;
463 * Does not make sense to have redirect creation without
464 * redirect following.
466 config
->redirect_follow
= true;
467 } else if (strcmp(mode
, "follow") == 0) {
468 config
->redirect_follow
= true;
469 } else if (strcmp(mode
, "off") == 0) {
470 if (ovl_redirect_always_follow
)
471 config
->redirect_follow
= true;
472 } else if (strcmp(mode
, "nofollow") != 0) {
473 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
481 static int ovl_parse_opt(char *opt
, struct ovl_config
*config
)
485 config
->redirect_mode
= kstrdup(ovl_redirect_mode_def(), GFP_KERNEL
);
486 if (!config
->redirect_mode
)
489 while ((p
= ovl_next_opt(&opt
)) != NULL
) {
491 substring_t args
[MAX_OPT_ARGS
];
496 token
= match_token(p
, ovl_tokens
, args
);
499 kfree(config
->upperdir
);
500 config
->upperdir
= match_strdup(&args
[0]);
501 if (!config
->upperdir
)
506 kfree(config
->lowerdir
);
507 config
->lowerdir
= match_strdup(&args
[0]);
508 if (!config
->lowerdir
)
513 kfree(config
->workdir
);
514 config
->workdir
= match_strdup(&args
[0]);
515 if (!config
->workdir
)
519 case OPT_DEFAULT_PERMISSIONS
:
520 config
->default_permissions
= true;
523 case OPT_REDIRECT_DIR
:
524 kfree(config
->redirect_mode
);
525 config
->redirect_mode
= match_strdup(&args
[0]);
526 if (!config
->redirect_mode
)
531 config
->index
= true;
535 config
->index
= false;
538 case OPT_NFS_EXPORT_ON
:
539 config
->nfs_export
= true;
542 case OPT_NFS_EXPORT_OFF
:
543 config
->nfs_export
= false;
547 config
->xino
= OVL_XINO_ON
;
551 config
->xino
= OVL_XINO_OFF
;
555 config
->xino
= OVL_XINO_AUTO
;
559 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p
);
564 /* Workdir is useless in non-upper mount */
565 if (!config
->upperdir
&& config
->workdir
) {
566 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
568 kfree(config
->workdir
);
569 config
->workdir
= NULL
;
572 return ovl_parse_redirect_mode(config
, config
->redirect_mode
);
575 #define OVL_WORKDIR_NAME "work"
576 #define OVL_INDEXDIR_NAME "index"
578 static struct dentry
*ovl_workdir_create(struct ovl_fs
*ofs
,
579 const char *name
, bool persist
)
581 struct inode
*dir
= ofs
->workbasedir
->d_inode
;
582 struct vfsmount
*mnt
= ofs
->upper_mnt
;
585 bool retried
= false;
588 inode_lock_nested(dir
, I_MUTEX_PARENT
);
592 work
= lookup_one_len(name
, ofs
->workbasedir
, strlen(name
));
595 struct iattr attr
= {
596 .ia_valid
= ATTR_MODE
,
597 .ia_mode
= S_IFDIR
| 0,
609 ovl_workdir_cleanup(dir
, mnt
, work
, 0);
614 work
= ovl_create_real(dir
, work
, OVL_CATTR(attr
.ia_mode
));
620 * Try to remove POSIX ACL xattrs from workdir. We are good if:
622 * a) success (there was a POSIX ACL xattr and was removed)
623 * b) -ENODATA (there was no POSIX ACL xattr)
624 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
626 * There are various other error values that could effectively
627 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
628 * if the xattr name is too long), but the set of filesystems
629 * allowed as upper are limited to "normal" ones, where checking
630 * for the above two errors is sufficient.
632 err
= vfs_removexattr(work
, XATTR_NAME_POSIX_ACL_DEFAULT
);
633 if (err
&& err
!= -ENODATA
&& err
!= -EOPNOTSUPP
)
636 err
= vfs_removexattr(work
, XATTR_NAME_POSIX_ACL_ACCESS
);
637 if (err
&& err
!= -ENODATA
&& err
!= -EOPNOTSUPP
)
640 /* Clear any inherited mode bits */
641 inode_lock(work
->d_inode
);
642 err
= notify_change(work
, &attr
, NULL
);
643 inode_unlock(work
->d_inode
);
659 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
660 ofs
->config
.workdir
, name
, -err
);
665 static void ovl_unescape(char *s
)
678 static int ovl_mount_dir_noesc(const char *name
, struct path
*path
)
683 pr_err("overlayfs: empty lowerdir\n");
686 err
= kern_path(name
, LOOKUP_FOLLOW
, path
);
688 pr_err("overlayfs: failed to resolve '%s': %i\n", name
, err
);
692 if (ovl_dentry_weird(path
->dentry
)) {
693 pr_err("overlayfs: filesystem on '%s' not supported\n", name
);
696 if (!d_is_dir(path
->dentry
)) {
697 pr_err("overlayfs: '%s' not a directory\n", name
);
708 static int ovl_mount_dir(const char *name
, struct path
*path
)
711 char *tmp
= kstrdup(name
, GFP_KERNEL
);
715 err
= ovl_mount_dir_noesc(tmp
, path
);
718 if (ovl_dentry_remote(path
->dentry
)) {
719 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
729 static int ovl_check_namelen(struct path
*path
, struct ovl_fs
*ofs
,
732 struct kstatfs statfs
;
733 int err
= vfs_statfs(path
, &statfs
);
736 pr_err("overlayfs: statfs failed on '%s'\n", name
);
738 ofs
->namelen
= max(ofs
->namelen
, statfs
.f_namelen
);
743 static int ovl_lower_dir(const char *name
, struct path
*path
,
744 struct ovl_fs
*ofs
, int *stack_depth
, bool *remote
)
749 err
= ovl_mount_dir_noesc(name
, path
);
753 err
= ovl_check_namelen(path
, ofs
, name
);
757 *stack_depth
= max(*stack_depth
, path
->mnt
->mnt_sb
->s_stack_depth
);
759 if (ovl_dentry_remote(path
->dentry
))
763 * The inodes index feature and NFS export need to encode and decode
764 * file handles, so they require that all layers support them.
766 fh_type
= ovl_can_decode_fh(path
->dentry
->d_sb
);
767 if ((ofs
->config
.nfs_export
||
768 (ofs
->config
.index
&& ofs
->config
.upperdir
)) && !fh_type
) {
769 ofs
->config
.index
= false;
770 ofs
->config
.nfs_export
= false;
771 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
775 /* Check if lower fs has 32bit inode numbers */
776 if (fh_type
!= FILEID_INO32_GEN
)
787 /* Workdir should not be subdir of upperdir and vice versa */
788 static bool ovl_workdir_ok(struct dentry
*workdir
, struct dentry
*upperdir
)
792 if (workdir
!= upperdir
) {
793 ok
= (lock_rename(workdir
, upperdir
) == NULL
);
794 unlock_rename(workdir
, upperdir
);
799 static unsigned int ovl_split_lowerdirs(char *str
)
801 unsigned int ctr
= 1;
804 for (s
= d
= str
;; s
++, d
++) {
807 } else if (*s
== ':') {
819 static int __maybe_unused
820 ovl_posix_acl_xattr_get(const struct xattr_handler
*handler
,
821 struct dentry
*dentry
, struct inode
*inode
,
822 const char *name
, void *buffer
, size_t size
)
824 return ovl_xattr_get(dentry
, inode
, handler
->name
, buffer
, size
);
827 static int __maybe_unused
828 ovl_posix_acl_xattr_set(const struct xattr_handler
*handler
,
829 struct dentry
*dentry
, struct inode
*inode
,
830 const char *name
, const void *value
,
831 size_t size
, int flags
)
833 struct dentry
*workdir
= ovl_workdir(dentry
);
834 struct inode
*realinode
= ovl_inode_real(inode
);
835 struct posix_acl
*acl
= NULL
;
838 /* Check that everything is OK before copy-up */
840 acl
= posix_acl_from_xattr(&init_user_ns
, value
, size
);
845 if (!IS_POSIXACL(d_inode(workdir
)))
846 goto out_acl_release
;
847 if (!realinode
->i_op
->set_acl
)
848 goto out_acl_release
;
849 if (handler
->flags
== ACL_TYPE_DEFAULT
&& !S_ISDIR(inode
->i_mode
)) {
850 err
= acl
? -EACCES
: 0;
851 goto out_acl_release
;
854 if (!inode_owner_or_capable(inode
))
855 goto out_acl_release
;
857 posix_acl_release(acl
);
860 * Check if sgid bit needs to be cleared (actual setacl operation will
861 * be done with mounter's capabilities and so that won't do it for us).
863 if (unlikely(inode
->i_mode
& S_ISGID
) &&
864 handler
->flags
== ACL_TYPE_ACCESS
&&
865 !in_group_p(inode
->i_gid
) &&
866 !capable_wrt_inode_uidgid(inode
, CAP_FSETID
)) {
867 struct iattr iattr
= { .ia_valid
= ATTR_KILL_SGID
};
869 err
= ovl_setattr(dentry
, &iattr
);
874 err
= ovl_xattr_set(dentry
, inode
, handler
->name
, value
, size
, flags
);
876 ovl_copyattr(ovl_inode_real(inode
), inode
);
881 posix_acl_release(acl
);
885 static int ovl_own_xattr_get(const struct xattr_handler
*handler
,
886 struct dentry
*dentry
, struct inode
*inode
,
887 const char *name
, void *buffer
, size_t size
)
892 static int ovl_own_xattr_set(const struct xattr_handler
*handler
,
893 struct dentry
*dentry
, struct inode
*inode
,
894 const char *name
, const void *value
,
895 size_t size
, int flags
)
900 static int ovl_other_xattr_get(const struct xattr_handler
*handler
,
901 struct dentry
*dentry
, struct inode
*inode
,
902 const char *name
, void *buffer
, size_t size
)
904 return ovl_xattr_get(dentry
, inode
, name
, buffer
, size
);
907 static int ovl_other_xattr_set(const struct xattr_handler
*handler
,
908 struct dentry
*dentry
, struct inode
*inode
,
909 const char *name
, const void *value
,
910 size_t size
, int flags
)
912 return ovl_xattr_set(dentry
, inode
, name
, value
, size
, flags
);
915 static const struct xattr_handler __maybe_unused
916 ovl_posix_acl_access_xattr_handler
= {
917 .name
= XATTR_NAME_POSIX_ACL_ACCESS
,
918 .flags
= ACL_TYPE_ACCESS
,
919 .get
= ovl_posix_acl_xattr_get
,
920 .set
= ovl_posix_acl_xattr_set
,
923 static const struct xattr_handler __maybe_unused
924 ovl_posix_acl_default_xattr_handler
= {
925 .name
= XATTR_NAME_POSIX_ACL_DEFAULT
,
926 .flags
= ACL_TYPE_DEFAULT
,
927 .get
= ovl_posix_acl_xattr_get
,
928 .set
= ovl_posix_acl_xattr_set
,
931 static const struct xattr_handler ovl_own_xattr_handler
= {
932 .prefix
= OVL_XATTR_PREFIX
,
933 .get
= ovl_own_xattr_get
,
934 .set
= ovl_own_xattr_set
,
937 static const struct xattr_handler ovl_other_xattr_handler
= {
938 .prefix
= "", /* catch all */
939 .get
= ovl_other_xattr_get
,
940 .set
= ovl_other_xattr_set
,
943 static const struct xattr_handler
*ovl_xattr_handlers
[] = {
944 #ifdef CONFIG_FS_POSIX_ACL
945 &ovl_posix_acl_access_xattr_handler
,
946 &ovl_posix_acl_default_xattr_handler
,
948 &ovl_own_xattr_handler
,
949 &ovl_other_xattr_handler
,
953 static int ovl_get_upper(struct ovl_fs
*ofs
, struct path
*upperpath
)
955 struct vfsmount
*upper_mnt
;
958 err
= ovl_mount_dir(ofs
->config
.upperdir
, upperpath
);
962 /* Upper fs should not be r/o */
963 if (sb_rdonly(upperpath
->mnt
->mnt_sb
)) {
964 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
969 err
= ovl_check_namelen(upperpath
, ofs
, ofs
->config
.upperdir
);
974 if (ovl_inuse_trylock(upperpath
->dentry
)) {
975 ofs
->upperdir_locked
= true;
976 } else if (ofs
->config
.index
) {
977 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
980 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
983 upper_mnt
= clone_private_mount(upperpath
);
984 err
= PTR_ERR(upper_mnt
);
985 if (IS_ERR(upper_mnt
)) {
986 pr_err("overlayfs: failed to clone upperpath\n");
990 /* Don't inherit atime flags */
991 upper_mnt
->mnt_flags
&= ~(MNT_NOATIME
| MNT_NODIRATIME
| MNT_RELATIME
);
992 ofs
->upper_mnt
= upper_mnt
;
998 static int ovl_make_workdir(struct ovl_fs
*ofs
, struct path
*workpath
)
1000 struct vfsmount
*mnt
= ofs
->upper_mnt
;
1001 struct dentry
*temp
;
1005 err
= mnt_want_write(mnt
);
1009 ofs
->workdir
= ovl_workdir_create(ofs
, OVL_WORKDIR_NAME
, false);
1014 * Upper should support d_type, else whiteouts are visible. Given
1015 * workdir and upper are on same fs, we can do iterate_dir() on
1016 * workdir. This check requires successful creation of workdir in
1019 err
= ovl_check_d_type_supported(workpath
);
1024 * We allowed this configuration and don't want to break users over
1025 * kernel upgrade. So warn instead of erroring out.
1028 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1030 /* Check if upper/work fs supports O_TMPFILE */
1031 temp
= ovl_do_tmpfile(ofs
->workdir
, S_IFREG
| 0);
1032 ofs
->tmpfile
= !IS_ERR(temp
);
1036 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1039 * Check if upper/work fs supports trusted.overlay.* xattr
1041 err
= ovl_do_setxattr(ofs
->workdir
, OVL_XATTR_OPAQUE
, "0", 1, 0);
1043 ofs
->noxattr
= true;
1044 ofs
->config
.index
= false;
1045 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off.\n");
1048 vfs_removexattr(ofs
->workdir
, OVL_XATTR_OPAQUE
);
1051 /* Check if upper/work fs supports file handles */
1052 fh_type
= ovl_can_decode_fh(ofs
->workdir
->d_sb
);
1053 if (ofs
->config
.index
&& !fh_type
) {
1054 ofs
->config
.index
= false;
1055 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1058 /* Check if upper fs has 32bit inode numbers */
1059 if (fh_type
!= FILEID_INO32_GEN
)
1062 /* NFS export of r/w mount depends on index */
1063 if (ofs
->config
.nfs_export
&& !ofs
->config
.index
) {
1064 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1065 ofs
->config
.nfs_export
= false;
1069 mnt_drop_write(mnt
);
1073 static int ovl_get_workdir(struct ovl_fs
*ofs
, struct path
*upperpath
)
1076 struct path workpath
= { };
1078 err
= ovl_mount_dir(ofs
->config
.workdir
, &workpath
);
1083 if (upperpath
->mnt
!= workpath
.mnt
) {
1084 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1087 if (!ovl_workdir_ok(workpath
.dentry
, upperpath
->dentry
)) {
1088 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1093 if (ovl_inuse_trylock(workpath
.dentry
)) {
1094 ofs
->workdir_locked
= true;
1095 } else if (ofs
->config
.index
) {
1096 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1099 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1102 ofs
->workbasedir
= dget(workpath
.dentry
);
1103 err
= ovl_make_workdir(ofs
, &workpath
);
1109 path_put(&workpath
);
1114 static int ovl_get_indexdir(struct ovl_fs
*ofs
, struct ovl_entry
*oe
,
1115 struct path
*upperpath
)
1117 struct vfsmount
*mnt
= ofs
->upper_mnt
;
1120 err
= mnt_want_write(mnt
);
1124 /* Verify lower root is upper root origin */
1125 err
= ovl_verify_origin(upperpath
->dentry
, oe
->lowerstack
[0].dentry
,
1128 pr_err("overlayfs: failed to verify upper root origin\n");
1132 ofs
->indexdir
= ovl_workdir_create(ofs
, OVL_INDEXDIR_NAME
, true);
1133 if (ofs
->indexdir
) {
1135 * Verify upper root is exclusively associated with index dir.
1136 * Older kernels stored upper fh in "trusted.overlay.origin"
1137 * xattr. If that xattr exists, verify that it is a match to
1138 * upper dir file handle. In any case, verify or set xattr
1139 * "trusted.overlay.upper" to indicate that index may have
1140 * directory entries.
1142 if (ovl_check_origin_xattr(ofs
->indexdir
)) {
1143 err
= ovl_verify_set_fh(ofs
->indexdir
, OVL_XATTR_ORIGIN
,
1144 upperpath
->dentry
, true, false);
1146 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1148 err
= ovl_verify_upper(ofs
->indexdir
, upperpath
->dentry
, true);
1150 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1152 /* Cleanup bad/stale/orphan index entries */
1154 err
= ovl_indexdir_cleanup(ofs
);
1156 if (err
|| !ofs
->indexdir
)
1157 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1160 mnt_drop_write(mnt
);
1164 /* Get a unique fsid for the layer */
1165 static int ovl_get_fsid(struct ovl_fs
*ofs
, struct super_block
*sb
)
1171 /* fsid 0 is reserved for upper fs even with non upper overlay */
1172 if (ofs
->upper_mnt
&& ofs
->upper_mnt
->mnt_sb
== sb
)
1175 for (i
= 0; i
< ofs
->numlowerfs
; i
++) {
1176 if (ofs
->lower_fs
[i
].sb
== sb
)
1180 err
= get_anon_bdev(&dev
);
1182 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1186 ofs
->lower_fs
[ofs
->numlowerfs
].sb
= sb
;
1187 ofs
->lower_fs
[ofs
->numlowerfs
].pseudo_dev
= dev
;
1190 return ofs
->numlowerfs
;
1193 static int ovl_get_lower_layers(struct ovl_fs
*ofs
, struct path
*stack
,
1194 unsigned int numlower
)
1200 ofs
->lower_layers
= kcalloc(numlower
, sizeof(struct ovl_layer
),
1202 if (ofs
->lower_layers
== NULL
)
1205 ofs
->lower_fs
= kcalloc(numlower
, sizeof(struct ovl_sb
),
1207 if (ofs
->lower_fs
== NULL
)
1210 for (i
= 0; i
< numlower
; i
++) {
1211 struct vfsmount
*mnt
;
1214 err
= fsid
= ovl_get_fsid(ofs
, stack
[i
].mnt
->mnt_sb
);
1218 mnt
= clone_private_mount(&stack
[i
]);
1221 pr_err("overlayfs: failed to clone lowerpath\n");
1226 * Make lower layers R/O. That way fchmod/fchown on lower file
1227 * will fail instead of modifying lower fs.
1229 mnt
->mnt_flags
|= MNT_READONLY
| MNT_NOATIME
;
1231 ofs
->lower_layers
[ofs
->numlower
].mnt
= mnt
;
1232 ofs
->lower_layers
[ofs
->numlower
].idx
= i
+ 1;
1233 ofs
->lower_layers
[ofs
->numlower
].fsid
= fsid
;
1235 ofs
->lower_layers
[ofs
->numlower
].fs
=
1236 &ofs
->lower_fs
[fsid
- 1];
1242 * When all layers on same fs, overlay can use real inode numbers.
1243 * With mount option "xino=on", mounter declares that there are enough
1244 * free high bits in underlying fs to hold the unique fsid.
1245 * If overlayfs does encounter underlying inodes using the high xino
1246 * bits reserved for fsid, it emits a warning and uses the original
1249 if (!ofs
->numlowerfs
|| (ofs
->numlowerfs
== 1 && !ofs
->upper_mnt
)) {
1251 ofs
->config
.xino
= OVL_XINO_OFF
;
1252 } else if (ofs
->config
.xino
== OVL_XINO_ON
&& !ofs
->xino_bits
) {
1254 * This is a roundup of number of bits needed for numlowerfs+1
1255 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1256 * upper fs even with non upper overlay.
1258 BUILD_BUG_ON(ilog2(OVL_MAX_STACK
) > 31);
1259 ofs
->xino_bits
= ilog2(ofs
->numlowerfs
) + 1;
1262 if (ofs
->xino_bits
) {
1263 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1272 static struct ovl_entry
*ovl_get_lowerstack(struct super_block
*sb
,
1276 char *lowertmp
, *lower
;
1277 struct path
*stack
= NULL
;
1278 unsigned int stacklen
, numlower
= 0, i
;
1279 bool remote
= false;
1280 struct ovl_entry
*oe
;
1283 lowertmp
= kstrdup(ofs
->config
.lowerdir
, GFP_KERNEL
);
1288 stacklen
= ovl_split_lowerdirs(lowertmp
);
1289 if (stacklen
> OVL_MAX_STACK
) {
1290 pr_err("overlayfs: too many lower directories, limit is %d\n",
1293 } else if (!ofs
->config
.upperdir
&& stacklen
== 1) {
1294 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1296 } else if (!ofs
->config
.upperdir
&& ofs
->config
.nfs_export
&&
1297 ofs
->config
.redirect_follow
) {
1298 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1299 ofs
->config
.nfs_export
= false;
1303 stack
= kcalloc(stacklen
, sizeof(struct path
), GFP_KERNEL
);
1309 for (numlower
= 0; numlower
< stacklen
; numlower
++) {
1310 err
= ovl_lower_dir(lower
, &stack
[numlower
], ofs
,
1311 &sb
->s_stack_depth
, &remote
);
1315 lower
= strchr(lower
, '\0') + 1;
1319 sb
->s_stack_depth
++;
1320 if (sb
->s_stack_depth
> FILESYSTEM_MAX_STACK_DEPTH
) {
1321 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1325 err
= ovl_get_lower_layers(ofs
, stack
, numlower
);
1330 oe
= ovl_alloc_entry(numlower
);
1334 for (i
= 0; i
< numlower
; i
++) {
1335 oe
->lowerstack
[i
].dentry
= dget(stack
[i
].dentry
);
1336 oe
->lowerstack
[i
].layer
= &ofs
->lower_layers
[i
];
1340 sb
->s_d_op
= &ovl_reval_dentry_operations
;
1342 sb
->s_d_op
= &ovl_dentry_operations
;
1345 for (i
= 0; i
< numlower
; i
++)
1346 path_put(&stack
[i
]);
1357 static int ovl_fill_super(struct super_block
*sb
, void *data
, int silent
)
1359 struct path upperpath
= { };
1360 struct dentry
*root_dentry
;
1361 struct ovl_entry
*oe
;
1367 ofs
= kzalloc(sizeof(struct ovl_fs
), GFP_KERNEL
);
1371 ofs
->creator_cred
= cred
= prepare_creds();
1375 ofs
->config
.index
= ovl_index_def
;
1376 ofs
->config
.nfs_export
= ovl_nfs_export_def
;
1377 ofs
->config
.xino
= ovl_xino_def();
1378 err
= ovl_parse_opt((char *) data
, &ofs
->config
);
1383 if (!ofs
->config
.lowerdir
) {
1385 pr_err("overlayfs: missing 'lowerdir'\n");
1389 sb
->s_stack_depth
= 0;
1390 sb
->s_maxbytes
= MAX_LFS_FILESIZE
;
1391 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1392 if (ofs
->config
.xino
!= OVL_XINO_OFF
)
1393 ofs
->xino_bits
= BITS_PER_LONG
- 32;
1395 if (ofs
->config
.upperdir
) {
1396 if (!ofs
->config
.workdir
) {
1397 pr_err("overlayfs: missing 'workdir'\n");
1401 err
= ovl_get_upper(ofs
, &upperpath
);
1405 err
= ovl_get_workdir(ofs
, &upperpath
);
1410 sb
->s_flags
|= SB_RDONLY
;
1412 sb
->s_stack_depth
= ofs
->upper_mnt
->mnt_sb
->s_stack_depth
;
1413 sb
->s_time_gran
= ofs
->upper_mnt
->mnt_sb
->s_time_gran
;
1416 oe
= ovl_get_lowerstack(sb
, ofs
);
1421 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1422 if (!ofs
->upper_mnt
)
1423 sb
->s_flags
|= SB_RDONLY
;
1425 if (!(ovl_force_readonly(ofs
)) && ofs
->config
.index
) {
1426 err
= ovl_get_indexdir(ofs
, oe
, &upperpath
);
1430 /* Force r/o mount with no index dir */
1431 if (!ofs
->indexdir
) {
1433 ofs
->workdir
= NULL
;
1434 sb
->s_flags
|= SB_RDONLY
;
1439 /* Show index=off in /proc/mounts for forced r/o mount */
1440 if (!ofs
->indexdir
) {
1441 ofs
->config
.index
= false;
1442 if (ofs
->upper_mnt
&& ofs
->config
.nfs_export
) {
1443 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1444 ofs
->config
.nfs_export
= false;
1448 if (ofs
->config
.nfs_export
)
1449 sb
->s_export_op
= &ovl_export_operations
;
1451 /* Never override disk quota limits or use reserved space */
1452 cap_lower(cred
->cap_effective
, CAP_SYS_RESOURCE
);
1454 sb
->s_magic
= OVERLAYFS_SUPER_MAGIC
;
1455 sb
->s_op
= &ovl_super_operations
;
1456 sb
->s_xattr
= ovl_xattr_handlers
;
1457 sb
->s_fs_info
= ofs
;
1458 sb
->s_flags
|= SB_POSIXACL
| SB_NOREMOTELOCK
;
1461 root_dentry
= d_make_root(ovl_new_inode(sb
, S_IFDIR
, 0));
1465 root_dentry
->d_fsdata
= oe
;
1467 mntput(upperpath
.mnt
);
1468 if (upperpath
.dentry
) {
1469 ovl_dentry_set_upper_alias(root_dentry
);
1470 if (ovl_is_impuredir(upperpath
.dentry
))
1471 ovl_set_flag(OVL_IMPURE
, d_inode(root_dentry
));
1474 /* Root is always merge -> can have whiteouts */
1475 ovl_set_flag(OVL_WHITEOUTS
, d_inode(root_dentry
));
1476 ovl_dentry_set_flag(OVL_E_CONNECTED
, root_dentry
);
1477 ovl_inode_init(d_inode(root_dentry
), upperpath
.dentry
,
1478 ovl_dentry_lower(root_dentry
));
1480 sb
->s_root
= root_dentry
;
1485 ovl_entry_stack_free(oe
);
1488 path_put(&upperpath
);
1494 static struct dentry
*ovl_mount(struct file_system_type
*fs_type
, int flags
,
1495 const char *dev_name
, void *raw_data
)
1497 return mount_nodev(fs_type
, flags
, raw_data
, ovl_fill_super
);
1500 static struct file_system_type ovl_fs_type
= {
1501 .owner
= THIS_MODULE
,
1504 .kill_sb
= kill_anon_super
,
1506 MODULE_ALIAS_FS("overlay");
1508 static void ovl_inode_init_once(void *foo
)
1510 struct ovl_inode
*oi
= foo
;
1512 inode_init_once(&oi
->vfs_inode
);
1515 static int __init
ovl_init(void)
1519 ovl_inode_cachep
= kmem_cache_create("ovl_inode",
1520 sizeof(struct ovl_inode
), 0,
1521 (SLAB_RECLAIM_ACCOUNT
|
1522 SLAB_MEM_SPREAD
|SLAB_ACCOUNT
),
1523 ovl_inode_init_once
);
1524 if (ovl_inode_cachep
== NULL
)
1527 err
= register_filesystem(&ovl_fs_type
);
1529 kmem_cache_destroy(ovl_inode_cachep
);
1534 static void __exit
ovl_exit(void)
1536 unregister_filesystem(&ovl_fs_type
);
1539 * Make sure all delayed rcu free inodes are flushed before we
1543 kmem_cache_destroy(ovl_inode_cachep
);
1547 module_init(ovl_init
);
1548 module_exit(ovl_exit
);