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/xattr.h>
13 #include <linux/posix_acl.h>
14 #include "overlayfs.h"
16 static int ovl_copy_up_truncate(struct dentry
*dentry
)
19 struct dentry
*parent
;
21 struct path lowerpath
;
23 parent
= dget_parent(dentry
);
24 err
= ovl_copy_up(parent
);
28 ovl_path_lower(dentry
, &lowerpath
);
29 err
= vfs_getattr(&lowerpath
, &stat
);
34 err
= ovl_copy_up_one(parent
, dentry
, &lowerpath
, &stat
);
41 int ovl_setattr(struct dentry
*dentry
, struct iattr
*attr
)
44 struct dentry
*upperdentry
;
45 const struct cred
*old_cred
;
48 * Check for permissions before trying to copy-up. This is redundant
49 * since it will be rechecked later by ->setattr() on upper dentry. But
50 * without this, copy-up can be triggered by just about anybody.
52 * We don't initialize inode->size, which just means that
53 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
54 * check for a swapfile (which this won't be anyway).
56 err
= inode_change_ok(dentry
->d_inode
, attr
);
60 err
= ovl_want_write(dentry
);
64 err
= ovl_copy_up(dentry
);
66 upperdentry
= ovl_dentry_upper(dentry
);
68 if (attr
->ia_valid
& (ATTR_KILL_SUID
|ATTR_KILL_SGID
))
69 attr
->ia_valid
&= ~ATTR_MODE
;
71 inode_lock(upperdentry
->d_inode
);
72 old_cred
= ovl_override_creds(dentry
->d_sb
);
73 err
= notify_change(upperdentry
, attr
, NULL
);
74 revert_creds(old_cred
);
76 ovl_copyattr(upperdentry
->d_inode
, dentry
->d_inode
);
77 inode_unlock(upperdentry
->d_inode
);
79 ovl_drop_write(dentry
);
84 static int ovl_getattr(struct vfsmount
*mnt
, struct dentry
*dentry
,
88 const struct cred
*old_cred
;
91 ovl_path_real(dentry
, &realpath
);
92 old_cred
= ovl_override_creds(dentry
->d_sb
);
93 err
= vfs_getattr(&realpath
, stat
);
94 revert_creds(old_cred
);
98 int ovl_permission(struct inode
*inode
, int mask
)
101 struct inode
*realinode
= ovl_inode_real(inode
, &is_upper
);
102 const struct cred
*old_cred
;
105 /* Careful in RCU walk mode */
107 WARN_ON(!(mask
& MAY_NOT_BLOCK
));
112 * Check overlay inode with the creds of task and underlying inode
113 * with creds of mounter
115 err
= generic_permission(inode
, mask
);
119 old_cred
= ovl_override_creds(inode
->i_sb
);
120 if (!is_upper
&& !special_file(realinode
->i_mode
) && mask
& MAY_WRITE
) {
121 mask
&= ~(MAY_WRITE
| MAY_APPEND
);
122 /* Make sure mounter can read file for copy up later */
125 err
= inode_permission(realinode
, mask
);
126 revert_creds(old_cred
);
131 static const char *ovl_get_link(struct dentry
*dentry
,
133 struct delayed_call
*done
)
135 struct dentry
*realdentry
;
136 struct inode
*realinode
;
137 const struct cred
*old_cred
;
141 return ERR_PTR(-ECHILD
);
143 realdentry
= ovl_dentry_real(dentry
);
144 realinode
= realdentry
->d_inode
;
146 if (WARN_ON(!realinode
->i_op
->get_link
))
147 return ERR_PTR(-EPERM
);
149 old_cred
= ovl_override_creds(dentry
->d_sb
);
150 p
= realinode
->i_op
->get_link(realdentry
, realinode
, done
);
151 revert_creds(old_cred
);
155 static int ovl_readlink(struct dentry
*dentry
, char __user
*buf
, int bufsiz
)
157 struct path realpath
;
158 struct inode
*realinode
;
159 const struct cred
*old_cred
;
162 ovl_path_real(dentry
, &realpath
);
163 realinode
= realpath
.dentry
->d_inode
;
165 if (!realinode
->i_op
->readlink
)
168 old_cred
= ovl_override_creds(dentry
->d_sb
);
169 err
= realinode
->i_op
->readlink(realpath
.dentry
, buf
, bufsiz
);
170 revert_creds(old_cred
);
174 bool ovl_is_private_xattr(const char *name
)
176 return strncmp(name
, OVL_XATTR_PREFIX
,
177 sizeof(OVL_XATTR_PREFIX
) - 1) == 0;
180 int ovl_xattr_set(struct dentry
*dentry
, const char *name
, const void *value
,
181 size_t size
, int flags
)
184 struct path realpath
;
185 enum ovl_path_type type
= ovl_path_real(dentry
, &realpath
);
186 const struct cred
*old_cred
;
188 err
= ovl_want_write(dentry
);
192 if (!value
&& !OVL_TYPE_UPPER(type
)) {
193 err
= vfs_getxattr(realpath
.dentry
, name
, NULL
, 0);
198 err
= ovl_copy_up(dentry
);
202 if (!OVL_TYPE_UPPER(type
))
203 ovl_path_upper(dentry
, &realpath
);
205 old_cred
= ovl_override_creds(dentry
->d_sb
);
207 err
= vfs_setxattr(realpath
.dentry
, name
, value
, size
, flags
);
209 WARN_ON(flags
!= XATTR_REPLACE
);
210 err
= vfs_removexattr(realpath
.dentry
, name
);
212 revert_creds(old_cred
);
215 ovl_drop_write(dentry
);
220 int ovl_xattr_get(struct dentry
*dentry
, const char *name
,
221 void *value
, size_t size
)
223 struct dentry
*realdentry
= ovl_dentry_real(dentry
);
225 const struct cred
*old_cred
;
227 old_cred
= ovl_override_creds(dentry
->d_sb
);
228 res
= vfs_getxattr(realdentry
, name
, value
, size
);
229 revert_creds(old_cred
);
233 ssize_t
ovl_listxattr(struct dentry
*dentry
, char *list
, size_t size
)
235 struct dentry
*realdentry
= ovl_dentry_real(dentry
);
239 const struct cred
*old_cred
;
241 old_cred
= ovl_override_creds(dentry
->d_sb
);
242 res
= vfs_listxattr(realdentry
, list
, size
);
243 revert_creds(old_cred
);
244 if (res
<= 0 || size
== 0)
247 /* filter out private xattrs */
248 for (s
= list
, len
= res
; len
;) {
249 size_t slen
= strnlen(s
, len
) + 1;
251 /* underlying fs providing us with an broken xattr list? */
252 if (WARN_ON(slen
> len
))
256 if (ovl_is_private_xattr(s
)) {
258 memmove(s
, s
+ slen
, len
);
267 struct posix_acl
*ovl_get_acl(struct inode
*inode
, int type
)
269 struct inode
*realinode
= ovl_inode_real(inode
, NULL
);
270 const struct cred
*old_cred
;
271 struct posix_acl
*acl
;
273 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL
) || !IS_POSIXACL(realinode
))
276 if (!realinode
->i_op
->get_acl
)
279 old_cred
= ovl_override_creds(inode
->i_sb
);
280 acl
= get_acl(realinode
, type
);
281 revert_creds(old_cred
);
286 static bool ovl_open_need_copy_up(int flags
, enum ovl_path_type type
,
287 struct dentry
*realdentry
)
289 if (OVL_TYPE_UPPER(type
))
292 if (special_file(realdentry
->d_inode
->i_mode
))
295 if (!(OPEN_FMODE(flags
) & FMODE_WRITE
) && !(flags
& O_TRUNC
))
301 int ovl_open_maybe_copy_up(struct dentry
*dentry
, unsigned int file_flags
)
304 struct path realpath
;
305 enum ovl_path_type type
;
307 type
= ovl_path_real(dentry
, &realpath
);
308 if (ovl_open_need_copy_up(file_flags
, type
, realpath
.dentry
)) {
309 err
= ovl_want_write(dentry
);
311 if (file_flags
& O_TRUNC
)
312 err
= ovl_copy_up_truncate(dentry
);
314 err
= ovl_copy_up(dentry
);
315 ovl_drop_write(dentry
);
322 int ovl_update_time(struct inode
*inode
, struct timespec
*ts
, int flags
)
324 struct dentry
*alias
;
325 struct path upperpath
;
327 if (!(flags
& S_ATIME
))
330 alias
= d_find_any_alias(inode
);
334 ovl_path_upper(alias
, &upperpath
);
335 if (upperpath
.dentry
) {
336 touch_atime(&upperpath
);
337 inode
->i_atime
= d_inode(upperpath
.dentry
)->i_atime
;
345 static const struct inode_operations ovl_file_inode_operations
= {
346 .setattr
= ovl_setattr
,
347 .permission
= ovl_permission
,
348 .getattr
= ovl_getattr
,
349 .setxattr
= generic_setxattr
,
350 .getxattr
= generic_getxattr
,
351 .listxattr
= ovl_listxattr
,
352 .removexattr
= generic_removexattr
,
353 .get_acl
= ovl_get_acl
,
354 .update_time
= ovl_update_time
,
357 static const struct inode_operations ovl_symlink_inode_operations
= {
358 .setattr
= ovl_setattr
,
359 .get_link
= ovl_get_link
,
360 .readlink
= ovl_readlink
,
361 .getattr
= ovl_getattr
,
362 .setxattr
= generic_setxattr
,
363 .getxattr
= generic_getxattr
,
364 .listxattr
= ovl_listxattr
,
365 .removexattr
= generic_removexattr
,
366 .update_time
= ovl_update_time
,
369 static void ovl_fill_inode(struct inode
*inode
, umode_t mode
)
371 inode
->i_ino
= get_next_ino();
372 inode
->i_mode
= mode
;
373 inode
->i_flags
|= S_NOCMTIME
;
374 #ifdef CONFIG_FS_POSIX_ACL
375 inode
->i_acl
= inode
->i_default_acl
= ACL_DONT_CACHE
;
381 inode
->i_op
= &ovl_dir_inode_operations
;
382 inode
->i_fop
= &ovl_dir_operations
;
386 inode
->i_op
= &ovl_symlink_inode_operations
;
390 WARN(1, "illegal file type: %i\n", mode
);
398 inode
->i_op
= &ovl_file_inode_operations
;
403 struct inode
*ovl_new_inode(struct super_block
*sb
, umode_t mode
)
407 inode
= new_inode(sb
);
409 ovl_fill_inode(inode
, mode
);
414 static int ovl_inode_test(struct inode
*inode
, void *data
)
416 return ovl_inode_real(inode
, NULL
) == data
;
419 static int ovl_inode_set(struct inode
*inode
, void *data
)
421 inode
->i_private
= (void *) (((unsigned long) data
) | OVL_ISUPPER_MASK
);
425 struct inode
*ovl_get_inode(struct super_block
*sb
, struct inode
*realinode
)
430 inode
= iget5_locked(sb
, (unsigned long) realinode
,
431 ovl_inode_test
, ovl_inode_set
, realinode
);
432 if (inode
&& inode
->i_state
& I_NEW
) {
433 ovl_fill_inode(inode
, realinode
->i_mode
);
434 set_nlink(inode
, realinode
->i_nlink
);
435 unlock_new_inode(inode
);