1 // SPDX-License-Identifier: GPL-2.0-only
4 * Copyright (C) 2011 Novell Inc.
7 #include <uapi/linux/magic.h>
9 #include <linux/namei.h>
10 #include <linux/xattr.h>
11 #include <linux/mount.h>
12 #include <linux/parser.h>
13 #include <linux/module.h>
14 #include <linux/statfs.h>
15 #include <linux/seq_file.h>
16 #include <linux/posix_acl_xattr.h>
17 #include <linux/exportfs.h>
18 #include <linux/file.h>
19 #include <linux/fs_context.h>
20 #include <linux/fs_parser.h>
21 #include "overlayfs.h"
24 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
25 MODULE_DESCRIPTION("Overlay filesystem");
26 MODULE_LICENSE("GPL");
31 static struct dentry
*ovl_d_real(struct dentry
*dentry
,
32 const struct inode
*inode
)
34 struct dentry
*real
= NULL
, *lower
;
37 /* It's an overlay file */
38 if (inode
&& d_inode(dentry
) == inode
)
41 if (!d_is_reg(dentry
)) {
42 if (!inode
|| inode
== d_inode(dentry
))
47 real
= ovl_dentry_upper(dentry
);
48 if (real
&& (inode
== d_inode(real
)))
51 if (real
&& !inode
&& ovl_has_upperdata(d_inode(dentry
)))
55 * Best effort lazy lookup of lowerdata for !inode case to return
56 * the real lowerdata dentry. The only current caller of d_real() with
57 * NULL inode is d_real_inode() from trace_uprobe and this caller is
58 * likely going to be followed reading from the file, before placing
59 * uprobes on offset within the file, so lowerdata should be available
60 * when setting the uprobe.
62 err
= ovl_verify_lowerdata(dentry
);
65 lower
= ovl_dentry_lowerdata(dentry
);
70 /* Handle recursion */
71 real
= d_real(real
, inode
);
73 if (!inode
|| inode
== d_inode(real
))
76 WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
77 __func__
, dentry
, inode
? inode
->i_sb
->s_id
: "NULL",
78 inode
? inode
->i_ino
: 0, real
,
79 real
&& d_inode(real
) ? d_inode(real
)->i_ino
: 0);
83 static int ovl_revalidate_real(struct dentry
*d
, unsigned int flags
, bool weak
)
91 if (d
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)
92 ret
= d
->d_op
->d_weak_revalidate(d
, flags
);
93 } else if (d
->d_flags
& DCACHE_OP_REVALIDATE
) {
94 ret
= d
->d_op
->d_revalidate(d
, flags
);
96 if (!(flags
& LOOKUP_RCU
))
104 static int ovl_dentry_revalidate_common(struct dentry
*dentry
,
105 unsigned int flags
, bool weak
)
107 struct ovl_entry
*oe
= OVL_E(dentry
);
108 struct ovl_path
*lowerstack
= ovl_lowerstack(oe
);
109 struct inode
*inode
= d_inode_rcu(dentry
);
110 struct dentry
*upper
;
114 /* Careful in RCU mode */
118 upper
= ovl_i_dentry_upper(inode
);
120 ret
= ovl_revalidate_real(upper
, flags
, weak
);
122 for (i
= 0; ret
> 0 && i
< ovl_numlower(oe
); i
++)
123 ret
= ovl_revalidate_real(lowerstack
[i
].dentry
, flags
, weak
);
128 static int ovl_dentry_revalidate(struct dentry
*dentry
, unsigned int flags
)
130 return ovl_dentry_revalidate_common(dentry
, flags
, false);
133 static int ovl_dentry_weak_revalidate(struct dentry
*dentry
, unsigned int flags
)
135 return ovl_dentry_revalidate_common(dentry
, flags
, true);
138 static const struct dentry_operations ovl_dentry_operations
= {
139 .d_real
= ovl_d_real
,
140 .d_revalidate
= ovl_dentry_revalidate
,
141 .d_weak_revalidate
= ovl_dentry_weak_revalidate
,
144 static struct kmem_cache
*ovl_inode_cachep
;
146 static struct inode
*ovl_alloc_inode(struct super_block
*sb
)
148 struct ovl_inode
*oi
= alloc_inode_sb(sb
, ovl_inode_cachep
, GFP_KERNEL
);
157 oi
->__upperdentry
= NULL
;
158 oi
->lowerdata_redirect
= NULL
;
160 mutex_init(&oi
->lock
);
162 return &oi
->vfs_inode
;
165 static void ovl_free_inode(struct inode
*inode
)
167 struct ovl_inode
*oi
= OVL_I(inode
);
170 mutex_destroy(&oi
->lock
);
171 kmem_cache_free(ovl_inode_cachep
, oi
);
174 static void ovl_destroy_inode(struct inode
*inode
)
176 struct ovl_inode
*oi
= OVL_I(inode
);
178 dput(oi
->__upperdentry
);
179 ovl_free_entry(oi
->oe
);
180 if (S_ISDIR(inode
->i_mode
))
181 ovl_dir_cache_free(inode
);
183 kfree(oi
->lowerdata_redirect
);
186 static void ovl_put_super(struct super_block
*sb
)
188 struct ovl_fs
*ofs
= OVL_FS(sb
);
194 /* Sync real dirty inodes in upper filesystem (if it exists) */
195 static int ovl_sync_fs(struct super_block
*sb
, int wait
)
197 struct ovl_fs
*ofs
= OVL_FS(sb
);
198 struct super_block
*upper_sb
;
201 ret
= ovl_sync_status(ofs
);
203 * We have to always set the err, because the return value isn't
204 * checked in syncfs, and instead indirectly return an error via
205 * the sb's writeback errseq, which VFS inspects after this call.
208 errseq_set(&sb
->s_wb_err
, -EIO
);
216 * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
217 * All the super blocks will be iterated, including upper_sb.
219 * If this is a syncfs(2) call, then we do need to call
220 * sync_filesystem() on upper_sb, but enough if we do it when being
221 * called with wait == 1.
226 upper_sb
= ovl_upper_mnt(ofs
)->mnt_sb
;
228 down_read(&upper_sb
->s_umount
);
229 ret
= sync_filesystem(upper_sb
);
230 up_read(&upper_sb
->s_umount
);
237 * @dentry: The dentry to query
238 * @buf: The struct kstatfs to fill in with stats
240 * Get the filesystem statistics. As writes always target the upper layer
241 * filesystem pass the statfs to the upper filesystem (if it exists)
243 static int ovl_statfs(struct dentry
*dentry
, struct kstatfs
*buf
)
245 struct super_block
*sb
= dentry
->d_sb
;
246 struct ovl_fs
*ofs
= OVL_FS(sb
);
247 struct dentry
*root_dentry
= sb
->s_root
;
251 ovl_path_real(root_dentry
, &path
);
253 err
= vfs_statfs(&path
, buf
);
255 buf
->f_namelen
= ofs
->namelen
;
256 buf
->f_type
= OVERLAYFS_SUPER_MAGIC
;
257 if (ovl_has_fsid(ofs
))
258 buf
->f_fsid
= uuid_to_fsid(sb
->s_uuid
.b
);
264 static const struct super_operations ovl_super_operations
= {
265 .alloc_inode
= ovl_alloc_inode
,
266 .free_inode
= ovl_free_inode
,
267 .destroy_inode
= ovl_destroy_inode
,
268 .drop_inode
= generic_delete_inode
,
269 .put_super
= ovl_put_super
,
270 .sync_fs
= ovl_sync_fs
,
271 .statfs
= ovl_statfs
,
272 .show_options
= ovl_show_options
,
275 #define OVL_WORKDIR_NAME "work"
276 #define OVL_INDEXDIR_NAME "index"
278 static struct dentry
*ovl_workdir_create(struct ovl_fs
*ofs
,
279 const char *name
, bool persist
)
281 struct inode
*dir
= ofs
->workbasedir
->d_inode
;
282 struct vfsmount
*mnt
= ovl_upper_mnt(ofs
);
285 bool retried
= false;
287 inode_lock_nested(dir
, I_MUTEX_PARENT
);
289 work
= ovl_lookup_upper(ofs
, name
, ofs
->workbasedir
, strlen(name
));
292 struct iattr attr
= {
293 .ia_valid
= ATTR_MODE
,
294 .ia_mode
= S_IFDIR
| 0,
306 err
= ovl_workdir_cleanup(ofs
, dir
, mnt
, work
, 0);
308 if (err
== -EINVAL
) {
315 err
= ovl_mkdir_real(ofs
, dir
, &work
, attr
.ia_mode
);
319 /* Weird filesystem returning with hashed negative (kernfs)? */
321 if (d_really_is_negative(work
))
325 * Try to remove POSIX ACL xattrs from workdir. We are good if:
327 * a) success (there was a POSIX ACL xattr and was removed)
328 * b) -ENODATA (there was no POSIX ACL xattr)
329 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
331 * There are various other error values that could effectively
332 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
333 * if the xattr name is too long), but the set of filesystems
334 * allowed as upper are limited to "normal" ones, where checking
335 * for the above two errors is sufficient.
337 err
= ovl_do_remove_acl(ofs
, work
, XATTR_NAME_POSIX_ACL_DEFAULT
);
338 if (err
&& err
!= -ENODATA
&& err
!= -EOPNOTSUPP
)
341 err
= ovl_do_remove_acl(ofs
, work
, XATTR_NAME_POSIX_ACL_ACCESS
);
342 if (err
&& err
!= -ENODATA
&& err
!= -EOPNOTSUPP
)
345 /* Clear any inherited mode bits */
346 inode_lock(work
->d_inode
);
347 err
= ovl_do_notify_change(ofs
, work
, &attr
);
348 inode_unlock(work
->d_inode
);
362 pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
363 ofs
->config
.workdir
, name
, -err
);
368 static int ovl_check_namelen(const struct path
*path
, struct ovl_fs
*ofs
,
371 struct kstatfs statfs
;
372 int err
= vfs_statfs(path
, &statfs
);
375 pr_err("statfs failed on '%s'\n", name
);
377 ofs
->namelen
= max(ofs
->namelen
, statfs
.f_namelen
);
382 static int ovl_lower_dir(const char *name
, struct path
*path
,
383 struct ovl_fs
*ofs
, int *stack_depth
)
388 err
= ovl_check_namelen(path
, ofs
, name
);
392 *stack_depth
= max(*stack_depth
, path
->mnt
->mnt_sb
->s_stack_depth
);
395 * The inodes index feature and NFS export need to encode and decode
396 * file handles, so they require that all layers support them.
398 fh_type
= ovl_can_decode_fh(path
->dentry
->d_sb
);
399 if ((ofs
->config
.nfs_export
||
400 (ofs
->config
.index
&& ofs
->config
.upperdir
)) && !fh_type
) {
401 ofs
->config
.index
= false;
402 ofs
->config
.nfs_export
= false;
403 pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
406 ofs
->nofh
|= !fh_type
;
408 * Decoding origin file handle is required for persistent st_ino.
409 * Without persistent st_ino, xino=auto falls back to xino=off.
411 if (ofs
->config
.xino
== OVL_XINO_AUTO
&&
412 ofs
->config
.upperdir
&& !fh_type
) {
413 ofs
->config
.xino
= OVL_XINO_OFF
;
414 pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n",
418 /* Check if lower fs has 32bit inode numbers */
419 if (fh_type
!= FILEID_INO32_GEN
)
425 /* Workdir should not be subdir of upperdir and vice versa */
426 static bool ovl_workdir_ok(struct dentry
*workdir
, struct dentry
*upperdir
)
430 if (workdir
!= upperdir
) {
431 ok
= (lock_rename(workdir
, upperdir
) == NULL
);
432 unlock_rename(workdir
, upperdir
);
437 static int ovl_own_xattr_get(const struct xattr_handler
*handler
,
438 struct dentry
*dentry
, struct inode
*inode
,
439 const char *name
, void *buffer
, size_t size
)
444 static int ovl_own_xattr_set(const struct xattr_handler
*handler
,
445 struct mnt_idmap
*idmap
,
446 struct dentry
*dentry
, struct inode
*inode
,
447 const char *name
, const void *value
,
448 size_t size
, int flags
)
453 static int ovl_other_xattr_get(const struct xattr_handler
*handler
,
454 struct dentry
*dentry
, struct inode
*inode
,
455 const char *name
, void *buffer
, size_t size
)
457 return ovl_xattr_get(dentry
, inode
, name
, buffer
, size
);
460 static int ovl_other_xattr_set(const struct xattr_handler
*handler
,
461 struct mnt_idmap
*idmap
,
462 struct dentry
*dentry
, struct inode
*inode
,
463 const char *name
, const void *value
,
464 size_t size
, int flags
)
466 return ovl_xattr_set(dentry
, inode
, name
, value
, size
, flags
);
469 static const struct xattr_handler ovl_own_trusted_xattr_handler
= {
470 .prefix
= OVL_XATTR_TRUSTED_PREFIX
,
471 .get
= ovl_own_xattr_get
,
472 .set
= ovl_own_xattr_set
,
475 static const struct xattr_handler ovl_own_user_xattr_handler
= {
476 .prefix
= OVL_XATTR_USER_PREFIX
,
477 .get
= ovl_own_xattr_get
,
478 .set
= ovl_own_xattr_set
,
481 static const struct xattr_handler ovl_other_xattr_handler
= {
482 .prefix
= "", /* catch all */
483 .get
= ovl_other_xattr_get
,
484 .set
= ovl_other_xattr_set
,
487 static const struct xattr_handler
*ovl_trusted_xattr_handlers
[] = {
488 &ovl_own_trusted_xattr_handler
,
489 &ovl_other_xattr_handler
,
493 static const struct xattr_handler
*ovl_user_xattr_handlers
[] = {
494 &ovl_own_user_xattr_handler
,
495 &ovl_other_xattr_handler
,
499 static int ovl_setup_trap(struct super_block
*sb
, struct dentry
*dir
,
500 struct inode
**ptrap
, const char *name
)
505 trap
= ovl_get_trap_inode(sb
, dir
);
506 err
= PTR_ERR_OR_ZERO(trap
);
509 pr_err("conflicting %s path\n", name
);
518 * Determine how we treat concurrent use of upperdir/workdir based on the
519 * index feature. This is papering over mount leaks of container runtimes,
520 * for example, an old overlay mount is leaked and now its upperdir is
521 * attempted to be used as a lower layer in a new overlay mount.
523 static int ovl_report_in_use(struct ovl_fs
*ofs
, const char *name
)
525 if (ofs
->config
.index
) {
526 pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
530 pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
536 static int ovl_get_upper(struct super_block
*sb
, struct ovl_fs
*ofs
,
537 struct ovl_layer
*upper_layer
,
538 const struct path
*upperpath
)
540 struct vfsmount
*upper_mnt
;
543 /* Upperdir path should not be r/o */
544 if (__mnt_is_readonly(upperpath
->mnt
)) {
545 pr_err("upper fs is r/o, try multi-lower layers mount\n");
550 err
= ovl_check_namelen(upperpath
, ofs
, ofs
->config
.upperdir
);
554 err
= ovl_setup_trap(sb
, upperpath
->dentry
, &upper_layer
->trap
,
559 upper_mnt
= clone_private_mount(upperpath
);
560 err
= PTR_ERR(upper_mnt
);
561 if (IS_ERR(upper_mnt
)) {
562 pr_err("failed to clone upperpath\n");
566 /* Don't inherit atime flags */
567 upper_mnt
->mnt_flags
&= ~(MNT_NOATIME
| MNT_NODIRATIME
| MNT_RELATIME
);
568 upper_layer
->mnt
= upper_mnt
;
569 upper_layer
->idx
= 0;
570 upper_layer
->fsid
= 0;
573 upper_layer
->name
= kstrdup(ofs
->config
.upperdir
, GFP_KERNEL
);
574 if (!upper_layer
->name
)
578 * Inherit SB_NOSEC flag from upperdir.
580 * This optimization changes behavior when a security related attribute
581 * (suid/sgid/security.*) is changed on an underlying layer. This is
582 * okay because we don't yet have guarantees in that case, but it will
583 * need careful treatment once we want to honour changes to underlying
586 if (upper_mnt
->mnt_sb
->s_flags
& SB_NOSEC
)
587 sb
->s_flags
|= SB_NOSEC
;
589 if (ovl_inuse_trylock(ovl_upper_mnt(ofs
)->mnt_root
)) {
590 ofs
->upperdir_locked
= true;
592 err
= ovl_report_in_use(ofs
, "upperdir");
603 * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
604 * negative values if error is encountered.
606 static int ovl_check_rename_whiteout(struct ovl_fs
*ofs
)
608 struct dentry
*workdir
= ofs
->workdir
;
609 struct inode
*dir
= d_inode(workdir
);
612 struct dentry
*whiteout
;
613 struct name_snapshot name
;
616 inode_lock_nested(dir
, I_MUTEX_PARENT
);
618 temp
= ovl_create_temp(ofs
, workdir
, OVL_CATTR(S_IFREG
| 0));
623 dest
= ovl_lookup_temp(ofs
, workdir
);
630 /* Name is inline and stable - using snapshot as a copy helper */
631 take_dentry_name_snapshot(&name
, temp
);
632 err
= ovl_do_rename(ofs
, dir
, temp
, dir
, dest
, RENAME_WHITEOUT
);
639 whiteout
= ovl_lookup_upper(ofs
, name
.name
.name
, workdir
, name
.name
.len
);
640 err
= PTR_ERR(whiteout
);
641 if (IS_ERR(whiteout
))
644 err
= ovl_is_whiteout(whiteout
);
646 /* Best effort cleanup of whiteout and temp file */
648 ovl_cleanup(ofs
, dir
, whiteout
);
652 ovl_cleanup(ofs
, dir
, temp
);
653 release_dentry_name_snapshot(&name
);
663 static struct dentry
*ovl_lookup_or_create(struct ovl_fs
*ofs
,
664 struct dentry
*parent
,
665 const char *name
, umode_t mode
)
667 size_t len
= strlen(name
);
668 struct dentry
*child
;
670 inode_lock_nested(parent
->d_inode
, I_MUTEX_PARENT
);
671 child
= ovl_lookup_upper(ofs
, name
, parent
, len
);
672 if (!IS_ERR(child
) && !child
->d_inode
)
673 child
= ovl_create_real(ofs
, parent
->d_inode
, child
,
675 inode_unlock(parent
->d_inode
);
682 * Creates $workdir/work/incompat/volatile/dirty file if it is not already
685 static int ovl_create_volatile_dirty(struct ovl_fs
*ofs
)
688 struct dentry
*d
= dget(ofs
->workbasedir
);
689 static const char *const volatile_path
[] = {
690 OVL_WORKDIR_NAME
, "incompat", "volatile", "dirty"
692 const char *const *name
= volatile_path
;
694 for (ctr
= ARRAY_SIZE(volatile_path
); ctr
; ctr
--, name
++) {
695 d
= ovl_lookup_or_create(ofs
, d
, *name
, ctr
> 1 ? S_IFDIR
: S_IFREG
);
703 static int ovl_make_workdir(struct super_block
*sb
, struct ovl_fs
*ofs
,
704 const struct path
*workpath
)
706 struct vfsmount
*mnt
= ovl_upper_mnt(ofs
);
707 struct dentry
*workdir
;
708 struct file
*tmpfile
;
709 bool rename_whiteout
;
714 err
= mnt_want_write(mnt
);
718 workdir
= ovl_workdir_create(ofs
, OVL_WORKDIR_NAME
, false);
719 err
= PTR_ERR(workdir
);
720 if (IS_ERR_OR_NULL(workdir
))
723 ofs
->workdir
= workdir
;
725 err
= ovl_setup_trap(sb
, ofs
->workdir
, &ofs
->workdir_trap
, "workdir");
730 * Upper should support d_type, else whiteouts are visible. Given
731 * workdir and upper are on same fs, we can do iterate_dir() on
732 * workdir. This check requires successful creation of workdir in
735 err
= ovl_check_d_type_supported(workpath
);
741 pr_warn("upper fs needs to support d_type.\n");
743 /* Check if upper/work fs supports O_TMPFILE */
744 tmpfile
= ovl_do_tmpfile(ofs
, ofs
->workdir
, S_IFREG
| 0);
745 ofs
->tmpfile
= !IS_ERR(tmpfile
);
749 pr_warn("upper fs does not support tmpfile.\n");
752 /* Check if upper/work fs supports RENAME_WHITEOUT */
753 err
= ovl_check_rename_whiteout(ofs
);
757 rename_whiteout
= err
;
758 if (!rename_whiteout
)
759 pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
762 * Check if upper/work fs supports (trusted|user).overlay.* xattr
764 err
= ovl_setxattr(ofs
, ofs
->workdir
, OVL_XATTR_OPAQUE
, "0", 1);
766 pr_warn("failed to set xattr on upper\n");
768 if (ovl_redirect_follow(ofs
)) {
769 ofs
->config
.redirect_mode
= OVL_REDIRECT_NOFOLLOW
;
770 pr_warn("...falling back to redirect_dir=nofollow.\n");
772 if (ofs
->config
.metacopy
) {
773 ofs
->config
.metacopy
= false;
774 pr_warn("...falling back to metacopy=off.\n");
776 if (ofs
->config
.index
) {
777 ofs
->config
.index
= false;
778 pr_warn("...falling back to index=off.\n");
780 if (ovl_has_fsid(ofs
)) {
781 ofs
->config
.uuid
= OVL_UUID_NULL
;
782 pr_warn("...falling back to uuid=null.\n");
785 * xattr support is required for persistent st_ino.
786 * Without persistent st_ino, xino=auto falls back to xino=off.
788 if (ofs
->config
.xino
== OVL_XINO_AUTO
) {
789 ofs
->config
.xino
= OVL_XINO_OFF
;
790 pr_warn("...falling back to xino=off.\n");
792 if (err
== -EPERM
&& !ofs
->config
.userxattr
)
793 pr_info("try mounting with 'userxattr' option\n");
796 ovl_removexattr(ofs
, ofs
->workdir
, OVL_XATTR_OPAQUE
);
800 * We allowed sub-optimal upper fs configuration and don't want to break
801 * users over kernel upgrade, but we never allowed remote upper fs, so
802 * we can enforce strict requirements for remote upper fs.
804 if (ovl_dentry_remote(ofs
->workdir
) &&
805 (!d_type
|| !rename_whiteout
|| ofs
->noxattr
)) {
806 pr_err("upper fs missing required features.\n");
812 * For volatile mount, create a incompat/volatile/dirty file to keep
815 if (ofs
->config
.ovl_volatile
) {
816 err
= ovl_create_volatile_dirty(ofs
);
818 pr_err("Failed to create volatile/dirty file.\n");
823 /* Check if upper/work fs supports file handles */
824 fh_type
= ovl_can_decode_fh(ofs
->workdir
->d_sb
);
825 if (ofs
->config
.index
&& !fh_type
) {
826 ofs
->config
.index
= false;
827 pr_warn("upper fs does not support file handles, falling back to index=off.\n");
829 ofs
->nofh
|= !fh_type
;
831 /* Check if upper fs has 32bit inode numbers */
832 if (fh_type
!= FILEID_INO32_GEN
)
835 /* NFS export of r/w mount depends on index */
836 if (ofs
->config
.nfs_export
&& !ofs
->config
.index
) {
837 pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
838 ofs
->config
.nfs_export
= false;
845 static int ovl_get_workdir(struct super_block
*sb
, struct ovl_fs
*ofs
,
846 const struct path
*upperpath
,
847 const struct path
*workpath
)
852 if (upperpath
->mnt
!= workpath
->mnt
) {
853 pr_err("workdir and upperdir must reside under the same mount\n");
856 if (!ovl_workdir_ok(workpath
->dentry
, upperpath
->dentry
)) {
857 pr_err("workdir and upperdir must be separate subtrees\n");
861 ofs
->workbasedir
= dget(workpath
->dentry
);
863 if (ovl_inuse_trylock(ofs
->workbasedir
)) {
864 ofs
->workdir_locked
= true;
866 err
= ovl_report_in_use(ofs
, "workdir");
871 err
= ovl_setup_trap(sb
, ofs
->workbasedir
, &ofs
->workbasedir_trap
,
876 return ovl_make_workdir(sb
, ofs
, workpath
);
879 static int ovl_get_indexdir(struct super_block
*sb
, struct ovl_fs
*ofs
,
880 struct ovl_entry
*oe
, const struct path
*upperpath
)
882 struct vfsmount
*mnt
= ovl_upper_mnt(ofs
);
883 struct dentry
*indexdir
;
886 err
= mnt_want_write(mnt
);
890 /* Verify lower root is upper root origin */
891 err
= ovl_verify_origin(ofs
, upperpath
->dentry
,
892 ovl_lowerstack(oe
)->dentry
, true);
894 pr_err("failed to verify upper root origin\n");
898 /* index dir will act also as workdir */
899 iput(ofs
->workdir_trap
);
900 ofs
->workdir_trap
= NULL
;
903 indexdir
= ovl_workdir_create(ofs
, OVL_INDEXDIR_NAME
, true);
904 if (IS_ERR(indexdir
)) {
905 err
= PTR_ERR(indexdir
);
906 } else if (indexdir
) {
907 ofs
->indexdir
= indexdir
;
908 ofs
->workdir
= dget(indexdir
);
910 err
= ovl_setup_trap(sb
, ofs
->indexdir
, &ofs
->indexdir_trap
,
916 * Verify upper root is exclusively associated with index dir.
917 * Older kernels stored upper fh in ".overlay.origin"
918 * xattr. If that xattr exists, verify that it is a match to
919 * upper dir file handle. In any case, verify or set xattr
920 * ".overlay.upper" to indicate that index may have
923 if (ovl_check_origin_xattr(ofs
, ofs
->indexdir
)) {
924 err
= ovl_verify_set_fh(ofs
, ofs
->indexdir
,
926 upperpath
->dentry
, true, false);
928 pr_err("failed to verify index dir 'origin' xattr\n");
930 err
= ovl_verify_upper(ofs
, ofs
->indexdir
, upperpath
->dentry
,
933 pr_err("failed to verify index dir 'upper' xattr\n");
935 /* Cleanup bad/stale/orphan index entries */
937 err
= ovl_indexdir_cleanup(ofs
);
939 if (err
|| !ofs
->indexdir
)
940 pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
947 static bool ovl_lower_uuid_ok(struct ovl_fs
*ofs
, const uuid_t
*uuid
)
951 if (!ofs
->config
.nfs_export
&& !ovl_upper_mnt(ofs
))
955 * We allow using single lower with null uuid for index and nfs_export
956 * for example to support those features with single lower squashfs.
957 * To avoid regressions in setups of overlay with re-formatted lower
958 * squashfs, do not allow decoding origin with lower null uuid unless
959 * user opted-in to one of the new features that require following the
960 * lower inode of non-dir upper.
962 if (ovl_allow_offline_changes(ofs
) && uuid_is_null(uuid
))
965 for (i
= 0; i
< ofs
->numfs
; i
++) {
967 * We use uuid to associate an overlay lower file handle with a
968 * lower layer, so we can accept lower fs with null uuid as long
969 * as all lower layers with null uuid are on the same fs.
970 * if we detect multiple lower fs with the same uuid, we
971 * disable lower file handle decoding on all of them.
973 if (ofs
->fs
[i
].is_lower
&&
974 uuid_equal(&ofs
->fs
[i
].sb
->s_uuid
, uuid
)) {
975 ofs
->fs
[i
].bad_uuid
= true;
982 /* Get a unique fsid for the layer */
983 static int ovl_get_fsid(struct ovl_fs
*ofs
, const struct path
*path
)
985 struct super_block
*sb
= path
->mnt
->mnt_sb
;
989 bool bad_uuid
= false;
992 for (i
= 0; i
< ofs
->numfs
; i
++) {
993 if (ofs
->fs
[i
].sb
== sb
)
997 if (!ovl_lower_uuid_ok(ofs
, &sb
->s_uuid
)) {
999 if (ofs
->config
.xino
== OVL_XINO_AUTO
) {
1000 ofs
->config
.xino
= OVL_XINO_OFF
;
1003 if (ofs
->config
.index
|| ofs
->config
.nfs_export
) {
1004 ofs
->config
.index
= false;
1005 ofs
->config
.nfs_export
= false;
1009 pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n",
1010 uuid_is_null(&sb
->s_uuid
) ? "null" :
1012 path
->dentry
, ovl_xino_mode(&ofs
->config
));
1016 err
= get_anon_bdev(&dev
);
1018 pr_err("failed to get anonymous bdev for lowerpath\n");
1022 ofs
->fs
[ofs
->numfs
].sb
= sb
;
1023 ofs
->fs
[ofs
->numfs
].pseudo_dev
= dev
;
1024 ofs
->fs
[ofs
->numfs
].bad_uuid
= bad_uuid
;
1026 return ofs
->numfs
++;
1030 * The fsid after the last lower fsid is used for the data layers.
1031 * It is a "null fs" with a null sb, null uuid, and no pseudo dev.
1033 static int ovl_get_data_fsid(struct ovl_fs
*ofs
)
1039 static int ovl_get_layers(struct super_block
*sb
, struct ovl_fs
*ofs
,
1040 struct ovl_fs_context
*ctx
, struct ovl_layer
*layers
)
1044 size_t nr_merged_lower
;
1046 ofs
->fs
= kcalloc(ctx
->nr
+ 2, sizeof(struct ovl_sb
), GFP_KERNEL
);
1047 if (ofs
->fs
== NULL
)
1051 * idx/fsid 0 are reserved for upper fs even with lower only overlay
1052 * and the last fsid is reserved for "null fs" of the data layers.
1057 * All lower layers that share the same fs as upper layer, use the same
1058 * pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower
1059 * only overlay to simplify ovl_fs_free().
1060 * is_lower will be set if upper fs is shared with a lower layer.
1062 err
= get_anon_bdev(&ofs
->fs
[0].pseudo_dev
);
1064 pr_err("failed to get anonymous bdev for upper fs\n");
1068 if (ovl_upper_mnt(ofs
)) {
1069 ofs
->fs
[0].sb
= ovl_upper_mnt(ofs
)->mnt_sb
;
1070 ofs
->fs
[0].is_lower
= false;
1073 nr_merged_lower
= ctx
->nr
- ctx
->nr_data
;
1074 for (i
= 0; i
< ctx
->nr
; i
++) {
1075 struct ovl_fs_context_layer
*l
= &ctx
->lower
[i
];
1076 struct vfsmount
*mnt
;
1080 if (i
< nr_merged_lower
)
1081 fsid
= ovl_get_fsid(ofs
, &l
->path
);
1083 fsid
= ovl_get_data_fsid(ofs
);
1088 * Check if lower root conflicts with this overlay layers before
1089 * checking if it is in-use as upperdir/workdir of "another"
1090 * mount, because we do not bother to check in ovl_is_inuse() if
1091 * the upperdir/workdir is in fact in-use by our
1094 err
= ovl_setup_trap(sb
, l
->path
.dentry
, &trap
, "lowerdir");
1098 if (ovl_is_inuse(l
->path
.dentry
)) {
1099 err
= ovl_report_in_use(ofs
, "lowerdir");
1106 mnt
= clone_private_mount(&l
->path
);
1109 pr_err("failed to clone lowerpath\n");
1115 * Make lower layers R/O. That way fchmod/fchown on lower file
1116 * will fail instead of modifying lower fs.
1118 mnt
->mnt_flags
|= MNT_READONLY
| MNT_NOATIME
;
1120 layers
[ofs
->numlayer
].trap
= trap
;
1121 layers
[ofs
->numlayer
].mnt
= mnt
;
1122 layers
[ofs
->numlayer
].idx
= ofs
->numlayer
;
1123 layers
[ofs
->numlayer
].fsid
= fsid
;
1124 layers
[ofs
->numlayer
].fs
= &ofs
->fs
[fsid
];
1125 layers
[ofs
->numlayer
].name
= l
->name
;
1128 ofs
->fs
[fsid
].is_lower
= true;
1132 * When all layers on same fs, overlay can use real inode numbers.
1133 * With mount option "xino=<on|auto>", mounter declares that there are
1134 * enough free high bits in underlying fs to hold the unique fsid.
1135 * If overlayfs does encounter underlying inodes using the high xino
1136 * bits reserved for fsid, it emits a warning and uses the original
1137 * inode number or a non persistent inode number allocated from a
1140 if (ofs
->numfs
- !ovl_upper_mnt(ofs
) == 1) {
1141 if (ofs
->config
.xino
== OVL_XINO_ON
)
1142 pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
1144 } else if (ofs
->config
.xino
== OVL_XINO_OFF
) {
1145 ofs
->xino_mode
= -1;
1146 } else if (ofs
->xino_mode
< 0) {
1148 * This is a roundup of number of bits needed for encoding
1149 * fsid, where fsid 0 is reserved for upper fs (even with
1150 * lower only overlay) +1 extra bit is reserved for the non
1151 * persistent inode number range that is used for resolving
1152 * xino lower bits overflow.
1154 BUILD_BUG_ON(ilog2(OVL_MAX_STACK
) > 30);
1155 ofs
->xino_mode
= ilog2(ofs
->numfs
- 1) + 2;
1158 if (ofs
->xino_mode
> 0) {
1159 pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
1166 static struct ovl_entry
*ovl_get_lowerstack(struct super_block
*sb
,
1167 struct ovl_fs_context
*ctx
,
1169 struct ovl_layer
*layers
)
1173 size_t nr_merged_lower
;
1174 struct ovl_entry
*oe
;
1175 struct ovl_path
*lowerstack
;
1177 struct ovl_fs_context_layer
*l
;
1179 if (!ofs
->config
.upperdir
&& ctx
->nr
== 1) {
1180 pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
1181 return ERR_PTR(-EINVAL
);
1185 for (i
= 0; i
< ctx
->nr
; i
++) {
1188 err
= ovl_lower_dir(l
->name
, &l
->path
, ofs
, &sb
->s_stack_depth
);
1190 return ERR_PTR(err
);
1194 sb
->s_stack_depth
++;
1195 if (sb
->s_stack_depth
> FILESYSTEM_MAX_STACK_DEPTH
) {
1196 pr_err("maximum fs stacking depth exceeded\n");
1197 return ERR_PTR(err
);
1200 err
= ovl_get_layers(sb
, ofs
, ctx
, layers
);
1202 return ERR_PTR(err
);
1205 /* Data-only layers are not merged in root directory */
1206 nr_merged_lower
= ctx
->nr
- ctx
->nr_data
;
1207 oe
= ovl_alloc_entry(nr_merged_lower
);
1209 return ERR_PTR(err
);
1211 lowerstack
= ovl_lowerstack(oe
);
1212 for (i
= 0; i
< nr_merged_lower
; i
++) {
1214 lowerstack
[i
].dentry
= dget(l
->path
.dentry
);
1215 lowerstack
[i
].layer
= &ofs
->layers
[i
+ 1];
1217 ofs
->numdatalayer
= ctx
->nr_data
;
1223 * Check if this layer root is a descendant of:
1224 * - another layer of this overlayfs instance
1225 * - upper/work dir of any overlayfs instance
1227 static int ovl_check_layer(struct super_block
*sb
, struct ovl_fs
*ofs
,
1228 struct dentry
*dentry
, const char *name
,
1231 struct dentry
*next
= dentry
, *parent
;
1237 parent
= dget_parent(next
);
1239 /* Walk back ancestors to root (inclusive) looking for traps */
1240 while (!err
&& parent
!= next
) {
1241 if (is_lower
&& ovl_lookup_trap_inode(sb
, parent
)) {
1243 pr_err("overlapping %s path\n", name
);
1244 } else if (ovl_is_inuse(parent
)) {
1245 err
= ovl_report_in_use(ofs
, name
);
1248 parent
= dget_parent(next
);
1258 * Check if any of the layers or work dirs overlap.
1260 static int ovl_check_overlapping_layers(struct super_block
*sb
,
1265 if (ovl_upper_mnt(ofs
)) {
1266 err
= ovl_check_layer(sb
, ofs
, ovl_upper_mnt(ofs
)->mnt_root
,
1272 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1273 * this instance and covers overlapping work and index dirs,
1274 * unless work or index dir have been moved since created inside
1275 * workbasedir. In that case, we already have their traps in
1276 * inode cache and we will catch that case on lookup.
1278 err
= ovl_check_layer(sb
, ofs
, ofs
->workbasedir
, "workdir",
1284 for (i
= 1; i
< ofs
->numlayer
; i
++) {
1285 err
= ovl_check_layer(sb
, ofs
,
1286 ofs
->layers
[i
].mnt
->mnt_root
,
1295 static struct dentry
*ovl_get_root(struct super_block
*sb
,
1296 struct dentry
*upperdentry
,
1297 struct ovl_entry
*oe
)
1299 struct dentry
*root
;
1300 struct ovl_path
*lowerpath
= ovl_lowerstack(oe
);
1301 unsigned long ino
= d_inode(lowerpath
->dentry
)->i_ino
;
1302 int fsid
= lowerpath
->layer
->fsid
;
1303 struct ovl_inode_params oip
= {
1304 .upperdentry
= upperdentry
,
1308 root
= d_make_root(ovl_new_inode(sb
, S_IFDIR
, 0));
1313 /* Root inode uses upper st_ino/i_ino */
1314 ino
= d_inode(upperdentry
)->i_ino
;
1316 ovl_dentry_set_upper_alias(root
);
1317 if (ovl_is_impuredir(sb
, upperdentry
))
1318 ovl_set_flag(OVL_IMPURE
, d_inode(root
));
1321 /* Root is always merge -> can have whiteouts */
1322 ovl_set_flag(OVL_WHITEOUTS
, d_inode(root
));
1323 ovl_dentry_set_flag(OVL_E_CONNECTED
, root
);
1324 ovl_set_upperdata(d_inode(root
));
1325 ovl_inode_init(d_inode(root
), &oip
, ino
, fsid
);
1326 ovl_dentry_init_flags(root
, upperdentry
, oe
, DCACHE_OP_WEAK_REVALIDATE
);
1327 /* root keeps a reference of upperdentry */
1333 int ovl_fill_super(struct super_block
*sb
, struct fs_context
*fc
)
1335 struct ovl_fs
*ofs
= sb
->s_fs_info
;
1336 struct ovl_fs_context
*ctx
= fc
->fs_private
;
1337 struct dentry
*root_dentry
;
1338 struct ovl_entry
*oe
;
1339 struct ovl_layer
*layers
;
1344 if (WARN_ON(fc
->user_ns
!= current_user_ns()))
1347 sb
->s_d_op
= &ovl_dentry_operations
;
1350 ofs
->creator_cred
= cred
= prepare_creds();
1354 err
= ovl_fs_params_verify(ctx
, &ofs
->config
);
1360 if (!(fc
->sb_flags
& SB_SILENT
))
1361 pr_err("missing 'lowerdir'\n");
1366 layers
= kcalloc(ctx
->nr
+ 1, sizeof(struct ovl_layer
), GFP_KERNEL
);
1370 ofs
->layers
= layers
;
1371 /* Layer 0 is reserved for upper even if there's no upper */
1374 sb
->s_stack_depth
= 0;
1375 sb
->s_maxbytes
= MAX_LFS_FILESIZE
;
1376 atomic_long_set(&ofs
->last_ino
, 1);
1377 /* Assume underlying fs uses 32bit inodes unless proven otherwise */
1378 if (ofs
->config
.xino
!= OVL_XINO_OFF
) {
1379 ofs
->xino_mode
= BITS_PER_LONG
- 32;
1380 if (!ofs
->xino_mode
) {
1381 pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
1382 ofs
->config
.xino
= OVL_XINO_OFF
;
1386 /* alloc/destroy_inode needed for setting up traps in inode cache */
1387 sb
->s_op
= &ovl_super_operations
;
1389 if (ofs
->config
.upperdir
) {
1390 struct super_block
*upper_sb
;
1393 if (!ofs
->config
.workdir
) {
1394 pr_err("missing 'workdir'\n");
1398 err
= ovl_get_upper(sb
, ofs
, &layers
[0], &ctx
->upper
);
1402 upper_sb
= ovl_upper_mnt(ofs
)->mnt_sb
;
1403 if (!ovl_should_sync(ofs
)) {
1404 ofs
->errseq
= errseq_sample(&upper_sb
->s_wb_err
);
1405 if (errseq_check(&upper_sb
->s_wb_err
, ofs
->errseq
)) {
1407 pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n");
1412 err
= ovl_get_workdir(sb
, ofs
, &ctx
->upper
, &ctx
->work
);
1417 sb
->s_flags
|= SB_RDONLY
;
1419 sb
->s_stack_depth
= upper_sb
->s_stack_depth
;
1420 sb
->s_time_gran
= upper_sb
->s_time_gran
;
1422 oe
= ovl_get_lowerstack(sb
, ctx
, ofs
, layers
);
1427 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1428 if (!ovl_upper_mnt(ofs
))
1429 sb
->s_flags
|= SB_RDONLY
;
1431 if (!ovl_origin_uuid(ofs
) && ofs
->numfs
> 1) {
1432 pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n");
1433 ofs
->config
.uuid
= OVL_UUID_NULL
;
1434 } else if (ovl_has_fsid(ofs
) && ovl_upper_mnt(ofs
)) {
1435 /* Use per instance persistent uuid/fsid */
1436 ovl_init_uuid_xattr(sb
, ofs
, &ctx
->upper
);
1439 if (!ovl_force_readonly(ofs
) && ofs
->config
.index
) {
1440 err
= ovl_get_indexdir(sb
, ofs
, oe
, &ctx
->upper
);
1444 /* Force r/o mount with no index dir */
1446 sb
->s_flags
|= SB_RDONLY
;
1449 err
= ovl_check_overlapping_layers(sb
, ofs
);
1453 /* Show index=off in /proc/mounts for forced r/o mount */
1454 if (!ofs
->indexdir
) {
1455 ofs
->config
.index
= false;
1456 if (ovl_upper_mnt(ofs
) && ofs
->config
.nfs_export
) {
1457 pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
1458 ofs
->config
.nfs_export
= false;
1462 if (ofs
->config
.metacopy
&& ofs
->config
.nfs_export
) {
1463 pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1464 ofs
->config
.nfs_export
= false;
1468 * Support encoding decodable file handles with nfs_export=on
1469 * and encoding non-decodable file handles with nfs_export=off
1470 * if all layers support file handles.
1472 if (ofs
->config
.nfs_export
)
1473 sb
->s_export_op
= &ovl_export_operations
;
1474 else if (!ofs
->nofh
)
1475 sb
->s_export_op
= &ovl_export_fid_operations
;
1477 /* Never override disk quota limits or use reserved space */
1478 cap_lower(cred
->cap_effective
, CAP_SYS_RESOURCE
);
1480 sb
->s_magic
= OVERLAYFS_SUPER_MAGIC
;
1481 sb
->s_xattr
= ofs
->config
.userxattr
? ovl_user_xattr_handlers
:
1482 ovl_trusted_xattr_handlers
;
1483 sb
->s_fs_info
= ofs
;
1484 sb
->s_flags
|= SB_POSIXACL
;
1485 sb
->s_iflags
|= SB_I_SKIP_SYNC
| SB_I_IMA_UNVERIFIABLE_SIGNATURE
;
1488 root_dentry
= ovl_get_root(sb
, ctx
->upper
.dentry
, oe
);
1492 sb
->s_root
= root_dentry
;
1500 sb
->s_fs_info
= NULL
;
1504 struct file_system_type ovl_fs_type
= {
1505 .owner
= THIS_MODULE
,
1507 .init_fs_context
= ovl_init_fs_context
,
1508 .parameters
= ovl_parameter_spec
,
1509 .fs_flags
= FS_USERNS_MOUNT
,
1510 .kill_sb
= kill_anon_super
,
1512 MODULE_ALIAS_FS("overlay");
1514 static void ovl_inode_init_once(void *foo
)
1516 struct ovl_inode
*oi
= foo
;
1518 inode_init_once(&oi
->vfs_inode
);
1521 static int __init
ovl_init(void)
1525 ovl_inode_cachep
= kmem_cache_create("ovl_inode",
1526 sizeof(struct ovl_inode
), 0,
1527 (SLAB_RECLAIM_ACCOUNT
|
1528 SLAB_MEM_SPREAD
|SLAB_ACCOUNT
),
1529 ovl_inode_init_once
);
1530 if (ovl_inode_cachep
== NULL
)
1533 err
= ovl_aio_request_cache_init();
1535 err
= register_filesystem(&ovl_fs_type
);
1539 ovl_aio_request_cache_destroy();
1541 kmem_cache_destroy(ovl_inode_cachep
);
1546 static void __exit
ovl_exit(void)
1548 unregister_filesystem(&ovl_fs_type
);
1551 * Make sure all delayed rcu free inodes are flushed before we
1555 kmem_cache_destroy(ovl_inode_cachep
);
1556 ovl_aio_request_cache_destroy();
1559 module_init(ovl_init
);
1560 module_exit(ovl_exit
);