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.
11 #include <linux/slab.h>
12 #include <linux/cred.h>
13 #include <linux/xattr.h>
14 #include <linux/posix_acl.h>
15 #include "overlayfs.h"
17 int ovl_setattr(struct dentry
*dentry
, struct iattr
*attr
)
20 struct dentry
*upperdentry
;
21 const struct cred
*old_cred
;
24 * Check for permissions before trying to copy-up. This is redundant
25 * since it will be rechecked later by ->setattr() on upper dentry. But
26 * without this, copy-up can be triggered by just about anybody.
28 * We don't initialize inode->size, which just means that
29 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
30 * check for a swapfile (which this won't be anyway).
32 err
= setattr_prepare(dentry
, attr
);
36 err
= ovl_want_write(dentry
);
40 err
= ovl_copy_up(dentry
);
42 upperdentry
= ovl_dentry_upper(dentry
);
44 if (attr
->ia_valid
& (ATTR_KILL_SUID
|ATTR_KILL_SGID
))
45 attr
->ia_valid
&= ~ATTR_MODE
;
47 inode_lock(upperdentry
->d_inode
);
48 old_cred
= ovl_override_creds(dentry
->d_sb
);
49 err
= notify_change(upperdentry
, attr
, NULL
);
50 revert_creds(old_cred
);
52 ovl_copyattr(upperdentry
->d_inode
, dentry
->d_inode
);
53 inode_unlock(upperdentry
->d_inode
);
55 ovl_drop_write(dentry
);
60 int ovl_getattr(const struct path
*path
, struct kstat
*stat
,
61 u32 request_mask
, unsigned int flags
)
63 struct dentry
*dentry
= path
->dentry
;
64 enum ovl_path_type type
;
66 const struct cred
*old_cred
;
67 bool is_dir
= S_ISDIR(dentry
->d_inode
->i_mode
);
70 type
= ovl_path_real(dentry
, &realpath
);
71 old_cred
= ovl_override_creds(dentry
->d_sb
);
72 err
= vfs_getattr(&realpath
, stat
, request_mask
, flags
);
77 * When all layers are on the same fs, all real inode number are
78 * unique, so we use the overlay st_dev, which is friendly to du -x.
80 * We also use st_ino of the copy up origin, if we know it.
81 * This guaranties constant st_dev/st_ino across copy up.
83 * If filesystem supports NFS export ops, this also guaranties
84 * persistent st_ino across mount cycle.
86 if (ovl_same_sb(dentry
->d_sb
)) {
87 if (OVL_TYPE_ORIGIN(type
)) {
88 struct kstat lowerstat
;
89 u32 lowermask
= STATX_INO
| (!is_dir
? STATX_NLINK
: 0);
91 ovl_path_lower(dentry
, &realpath
);
92 err
= vfs_getattr(&realpath
, &lowerstat
,
97 WARN_ON_ONCE(stat
->dev
!= lowerstat
.dev
);
99 * Lower hardlinks are broken on copy up to different
100 * upper files, so we cannot use the lower origin st_ino
101 * for those different files, even for the same fs case.
103 if (is_dir
|| lowerstat
.nlink
== 1)
104 stat
->ino
= lowerstat
.ino
;
106 stat
->dev
= dentry
->d_sb
->s_dev
;
109 * If not all layers are on the same fs the pair {real st_ino;
110 * overlay st_dev} is not unique, so use the non persistent
113 * Always use the overlay st_dev for directories, so 'find
114 * -xdev' will scan the entire overlay mount and won't cross the
115 * overlay mount boundaries.
117 stat
->dev
= dentry
->d_sb
->s_dev
;
118 stat
->ino
= dentry
->d_inode
->i_ino
;
122 * It's probably not worth it to count subdirs to get the
123 * correct link count. nlink=1 seems to pacify 'find' and
126 if (is_dir
&& OVL_TYPE_MERGE(type
))
130 revert_creds(old_cred
);
135 int ovl_permission(struct inode
*inode
, int mask
)
138 struct inode
*realinode
= ovl_inode_real(inode
, &is_upper
);
139 const struct cred
*old_cred
;
142 /* Careful in RCU walk mode */
144 WARN_ON(!(mask
& MAY_NOT_BLOCK
));
149 * Check overlay inode with the creds of task and underlying inode
150 * with creds of mounter
152 err
= generic_permission(inode
, mask
);
156 old_cred
= ovl_override_creds(inode
->i_sb
);
157 if (!is_upper
&& !special_file(realinode
->i_mode
) && mask
& MAY_WRITE
) {
158 mask
&= ~(MAY_WRITE
| MAY_APPEND
);
159 /* Make sure mounter can read file for copy up later */
162 err
= inode_permission(realinode
, mask
);
163 revert_creds(old_cred
);
168 static const char *ovl_get_link(struct dentry
*dentry
,
170 struct delayed_call
*done
)
172 const struct cred
*old_cred
;
176 return ERR_PTR(-ECHILD
);
178 old_cred
= ovl_override_creds(dentry
->d_sb
);
179 p
= vfs_get_link(ovl_dentry_real(dentry
), done
);
180 revert_creds(old_cred
);
184 bool ovl_is_private_xattr(const char *name
)
186 return strncmp(name
, OVL_XATTR_PREFIX
,
187 sizeof(OVL_XATTR_PREFIX
) - 1) == 0;
190 int ovl_xattr_set(struct dentry
*dentry
, const char *name
, const void *value
,
191 size_t size
, int flags
)
194 struct path realpath
;
195 enum ovl_path_type type
= ovl_path_real(dentry
, &realpath
);
196 const struct cred
*old_cred
;
198 err
= ovl_want_write(dentry
);
202 if (!value
&& !OVL_TYPE_UPPER(type
)) {
203 err
= vfs_getxattr(realpath
.dentry
, name
, NULL
, 0);
208 err
= ovl_copy_up(dentry
);
212 if (!OVL_TYPE_UPPER(type
))
213 ovl_path_upper(dentry
, &realpath
);
215 old_cred
= ovl_override_creds(dentry
->d_sb
);
217 err
= vfs_setxattr(realpath
.dentry
, name
, value
, size
, flags
);
219 WARN_ON(flags
!= XATTR_REPLACE
);
220 err
= vfs_removexattr(realpath
.dentry
, name
);
222 revert_creds(old_cred
);
225 ovl_drop_write(dentry
);
230 int ovl_xattr_get(struct dentry
*dentry
, const char *name
,
231 void *value
, size_t size
)
233 struct dentry
*realdentry
= ovl_dentry_real(dentry
);
235 const struct cred
*old_cred
;
237 old_cred
= ovl_override_creds(dentry
->d_sb
);
238 res
= vfs_getxattr(realdentry
, name
, value
, size
);
239 revert_creds(old_cred
);
243 static bool ovl_can_list(const char *s
)
245 /* List all non-trusted xatts */
246 if (strncmp(s
, XATTR_TRUSTED_PREFIX
, XATTR_TRUSTED_PREFIX_LEN
) != 0)
249 /* Never list trusted.overlay, list other trusted for superuser only */
250 return !ovl_is_private_xattr(s
) && capable(CAP_SYS_ADMIN
);
253 ssize_t
ovl_listxattr(struct dentry
*dentry
, char *list
, size_t size
)
255 struct dentry
*realdentry
= ovl_dentry_real(dentry
);
259 const struct cred
*old_cred
;
261 old_cred
= ovl_override_creds(dentry
->d_sb
);
262 res
= vfs_listxattr(realdentry
, list
, size
);
263 revert_creds(old_cred
);
264 if (res
<= 0 || size
== 0)
267 /* filter out private xattrs */
268 for (s
= list
, len
= res
; len
;) {
269 size_t slen
= strnlen(s
, len
) + 1;
271 /* underlying fs providing us with an broken xattr list? */
272 if (WARN_ON(slen
> len
))
276 if (!ovl_can_list(s
)) {
278 memmove(s
, s
+ slen
, len
);
287 struct posix_acl
*ovl_get_acl(struct inode
*inode
, int type
)
289 struct inode
*realinode
= ovl_inode_real(inode
, NULL
);
290 const struct cred
*old_cred
;
291 struct posix_acl
*acl
;
293 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL
) || !IS_POSIXACL(realinode
))
296 old_cred
= ovl_override_creds(inode
->i_sb
);
297 acl
= get_acl(realinode
, type
);
298 revert_creds(old_cred
);
303 static bool ovl_open_need_copy_up(int flags
, enum ovl_path_type type
,
304 struct dentry
*realdentry
)
306 if (OVL_TYPE_UPPER(type
))
309 if (special_file(realdentry
->d_inode
->i_mode
))
312 if (!(OPEN_FMODE(flags
) & FMODE_WRITE
) && !(flags
& O_TRUNC
))
318 int ovl_open_maybe_copy_up(struct dentry
*dentry
, unsigned int file_flags
)
321 struct path realpath
;
322 enum ovl_path_type type
;
324 type
= ovl_path_real(dentry
, &realpath
);
325 if (ovl_open_need_copy_up(file_flags
, type
, realpath
.dentry
)) {
326 err
= ovl_want_write(dentry
);
328 err
= ovl_copy_up_flags(dentry
, file_flags
);
329 ovl_drop_write(dentry
);
336 int ovl_update_time(struct inode
*inode
, struct timespec
*ts
, int flags
)
338 struct dentry
*alias
;
339 struct path upperpath
;
341 if (!(flags
& S_ATIME
))
344 alias
= d_find_any_alias(inode
);
348 ovl_path_upper(alias
, &upperpath
);
349 if (upperpath
.dentry
) {
350 touch_atime(&upperpath
);
351 inode
->i_atime
= d_inode(upperpath
.dentry
)->i_atime
;
359 static const struct inode_operations ovl_file_inode_operations
= {
360 .setattr
= ovl_setattr
,
361 .permission
= ovl_permission
,
362 .getattr
= ovl_getattr
,
363 .listxattr
= ovl_listxattr
,
364 .get_acl
= ovl_get_acl
,
365 .update_time
= ovl_update_time
,
368 static const struct inode_operations ovl_symlink_inode_operations
= {
369 .setattr
= ovl_setattr
,
370 .get_link
= ovl_get_link
,
371 .getattr
= ovl_getattr
,
372 .listxattr
= ovl_listxattr
,
373 .update_time
= ovl_update_time
,
377 * It is possible to stack overlayfs instance on top of another
378 * overlayfs instance as lower layer. We need to annonate the
379 * stackable i_mutex locks according to stack level of the super
380 * block instance. An overlayfs instance can never be in stack
381 * depth 0 (there is always a real fs below it). An overlayfs
382 * inode lock will use the lockdep annotaion ovl_i_mutex_key[depth].
384 * For example, here is a snip from /proc/lockdep_chains after
385 * dir_iterate of nested overlayfs:
387 * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2)
388 * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
389 * [...] &type->i_mutex_dir_key (stack_depth=0)
391 #define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
393 static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode
*inode
)
395 #ifdef CONFIG_LOCKDEP
396 static struct lock_class_key ovl_i_mutex_key
[OVL_MAX_NESTING
];
397 static struct lock_class_key ovl_i_mutex_dir_key
[OVL_MAX_NESTING
];
399 int depth
= inode
->i_sb
->s_stack_depth
- 1;
401 if (WARN_ON_ONCE(depth
< 0 || depth
>= OVL_MAX_NESTING
))
404 if (S_ISDIR(inode
->i_mode
))
405 lockdep_set_class(&inode
->i_rwsem
, &ovl_i_mutex_dir_key
[depth
]);
407 lockdep_set_class(&inode
->i_rwsem
, &ovl_i_mutex_key
[depth
]);
411 static void ovl_fill_inode(struct inode
*inode
, umode_t mode
, dev_t rdev
)
413 inode
->i_ino
= get_next_ino();
414 inode
->i_mode
= mode
;
415 inode
->i_flags
|= S_NOCMTIME
;
416 #ifdef CONFIG_FS_POSIX_ACL
417 inode
->i_acl
= inode
->i_default_acl
= ACL_DONT_CACHE
;
420 ovl_lockdep_annotate_inode_mutex_key(inode
);
422 switch (mode
& S_IFMT
) {
424 inode
->i_op
= &ovl_file_inode_operations
;
428 inode
->i_op
= &ovl_dir_inode_operations
;
429 inode
->i_fop
= &ovl_dir_operations
;
433 inode
->i_op
= &ovl_symlink_inode_operations
;
437 inode
->i_op
= &ovl_file_inode_operations
;
438 init_special_inode(inode
, mode
, rdev
);
443 struct inode
*ovl_new_inode(struct super_block
*sb
, umode_t mode
, dev_t rdev
)
447 inode
= new_inode(sb
);
449 ovl_fill_inode(inode
, mode
, rdev
);
454 static int ovl_inode_test(struct inode
*inode
, void *data
)
456 return ovl_inode_real(inode
, NULL
) == data
;
459 static int ovl_inode_set(struct inode
*inode
, void *data
)
461 inode
->i_private
= (void *) (((unsigned long) data
) | OVL_ISUPPER_MASK
);
465 struct inode
*ovl_get_inode(struct super_block
*sb
, struct inode
*realinode
)
470 inode
= iget5_locked(sb
, (unsigned long) realinode
,
471 ovl_inode_test
, ovl_inode_set
, realinode
);
472 if (inode
&& inode
->i_state
& I_NEW
) {
473 ovl_fill_inode(inode
, realinode
->i_mode
, realinode
->i_rdev
);
474 set_nlink(inode
, realinode
->i_nlink
);
475 unlock_new_inode(inode
);