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 "overlayfs.h"
15 static int ovl_copy_up_truncate(struct dentry
*dentry
)
18 struct dentry
*parent
;
20 struct path lowerpath
;
22 parent
= dget_parent(dentry
);
23 err
= ovl_copy_up(parent
);
27 ovl_path_lower(dentry
, &lowerpath
);
28 err
= vfs_getattr(&lowerpath
, &stat
);
33 err
= ovl_copy_up_one(parent
, dentry
, &lowerpath
, &stat
);
40 int ovl_setattr(struct dentry
*dentry
, struct iattr
*attr
)
43 struct dentry
*upperdentry
;
44 const struct cred
*old_cred
;
47 * Check for permissions before trying to copy-up. This is redundant
48 * since it will be rechecked later by ->setattr() on upper dentry. But
49 * without this, copy-up can be triggered by just about anybody.
51 * We don't initialize inode->size, which just means that
52 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
53 * check for a swapfile (which this won't be anyway).
55 err
= inode_change_ok(dentry
->d_inode
, attr
);
59 err
= ovl_want_write(dentry
);
63 if (attr
->ia_valid
& ATTR_SIZE
) {
64 struct inode
*realinode
= d_inode(ovl_dentry_real(dentry
));
67 if (atomic_read(&realinode
->i_writecount
) < 0)
71 err
= ovl_copy_up(dentry
);
73 struct inode
*winode
= NULL
;
75 upperdentry
= ovl_dentry_upper(dentry
);
77 if (attr
->ia_valid
& ATTR_SIZE
) {
78 winode
= d_inode(upperdentry
);
79 err
= get_write_access(winode
);
84 if (attr
->ia_valid
& (ATTR_KILL_SUID
|ATTR_KILL_SGID
))
85 attr
->ia_valid
&= ~ATTR_MODE
;
87 inode_lock(upperdentry
->d_inode
);
88 old_cred
= ovl_override_creds(dentry
->d_sb
);
89 err
= notify_change(upperdentry
, attr
, NULL
);
90 revert_creds(old_cred
);
92 ovl_copyattr(upperdentry
->d_inode
, dentry
->d_inode
);
93 inode_unlock(upperdentry
->d_inode
);
96 put_write_access(winode
);
99 ovl_drop_write(dentry
);
104 static int ovl_getattr(struct vfsmount
*mnt
, struct dentry
*dentry
,
107 struct path realpath
;
108 const struct cred
*old_cred
;
111 ovl_path_real(dentry
, &realpath
);
112 old_cred
= ovl_override_creds(dentry
->d_sb
);
113 err
= vfs_getattr(&realpath
, stat
);
114 revert_creds(old_cred
);
118 int ovl_permission(struct inode
*inode
, int mask
)
120 struct ovl_entry
*oe
= inode
->i_private
;
122 struct dentry
*realdentry
= ovl_entry_real(oe
, &is_upper
);
123 struct inode
*realinode
;
124 const struct cred
*old_cred
;
127 if (ovl_is_default_permissions(inode
)) {
129 struct path realpath
= { .dentry
= realdentry
};
131 if (mask
& MAY_NOT_BLOCK
)
134 realpath
.mnt
= ovl_entry_mnt_real(oe
, inode
, is_upper
);
136 err
= vfs_getattr(&realpath
, &stat
);
140 if ((stat
.mode
^ inode
->i_mode
) & S_IFMT
)
143 inode
->i_mode
= stat
.mode
;
144 inode
->i_uid
= stat
.uid
;
145 inode
->i_gid
= stat
.gid
;
147 return generic_permission(inode
, mask
);
150 /* Careful in RCU walk mode */
151 realinode
= d_inode_rcu(realdentry
);
153 WARN_ON(!(mask
& MAY_NOT_BLOCK
));
157 if (mask
& MAY_WRITE
) {
158 umode_t mode
= realinode
->i_mode
;
161 * Writes will always be redirected to upper layer, so
162 * ignore lower layer being read-only.
164 * If the overlay itself is read-only then proceed
165 * with the permission check, don't return EROFS.
166 * This will only happen if this is the lower layer of
169 * If upper fs becomes read-only after the overlay was
170 * constructed return EROFS to prevent modification of
173 if (is_upper
&& !IS_RDONLY(inode
) && IS_RDONLY(realinode
) &&
174 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
179 * Check overlay inode with the creds of task and underlying inode
180 * with creds of mounter
182 err
= generic_permission(inode
, mask
);
186 old_cred
= ovl_override_creds(inode
->i_sb
);
188 mask
&= ~(MAY_WRITE
| MAY_APPEND
);
189 err
= __inode_permission(realinode
, mask
);
190 revert_creds(old_cred
);
195 static const char *ovl_get_link(struct dentry
*dentry
,
197 struct delayed_call
*done
)
199 struct dentry
*realdentry
;
200 struct inode
*realinode
;
201 const struct cred
*old_cred
;
205 return ERR_PTR(-ECHILD
);
207 realdentry
= ovl_dentry_real(dentry
);
208 realinode
= realdentry
->d_inode
;
210 if (WARN_ON(!realinode
->i_op
->get_link
))
211 return ERR_PTR(-EPERM
);
213 old_cred
= ovl_override_creds(dentry
->d_sb
);
214 p
= realinode
->i_op
->get_link(realdentry
, realinode
, done
);
215 revert_creds(old_cred
);
219 static int ovl_readlink(struct dentry
*dentry
, char __user
*buf
, int bufsiz
)
221 struct path realpath
;
222 struct inode
*realinode
;
223 const struct cred
*old_cred
;
226 ovl_path_real(dentry
, &realpath
);
227 realinode
= realpath
.dentry
->d_inode
;
229 if (!realinode
->i_op
->readlink
)
232 touch_atime(&realpath
);
234 old_cred
= ovl_override_creds(dentry
->d_sb
);
235 err
= realinode
->i_op
->readlink(realpath
.dentry
, buf
, bufsiz
);
236 revert_creds(old_cred
);
240 static bool ovl_is_private_xattr(const char *name
)
242 return strncmp(name
, OVL_XATTR_PRE_NAME
, OVL_XATTR_PRE_LEN
) == 0;
245 int ovl_setxattr(struct dentry
*dentry
, struct inode
*inode
,
246 const char *name
, const void *value
,
247 size_t size
, int flags
)
250 struct dentry
*upperdentry
;
251 const struct cred
*old_cred
;
253 err
= ovl_want_write(dentry
);
258 if (ovl_is_private_xattr(name
))
261 err
= ovl_copy_up(dentry
);
265 upperdentry
= ovl_dentry_upper(dentry
);
266 old_cred
= ovl_override_creds(dentry
->d_sb
);
267 err
= vfs_setxattr(upperdentry
, name
, value
, size
, flags
);
268 revert_creds(old_cred
);
271 ovl_drop_write(dentry
);
276 ssize_t
ovl_getxattr(struct dentry
*dentry
, struct inode
*inode
,
277 const char *name
, void *value
, size_t size
)
279 struct dentry
*realdentry
= ovl_dentry_real(dentry
);
281 const struct cred
*old_cred
;
283 if (ovl_is_private_xattr(name
))
286 old_cred
= ovl_override_creds(dentry
->d_sb
);
287 res
= vfs_getxattr(realdentry
, name
, value
, size
);
288 revert_creds(old_cred
);
292 ssize_t
ovl_listxattr(struct dentry
*dentry
, char *list
, size_t size
)
294 struct dentry
*realdentry
= ovl_dentry_real(dentry
);
297 const struct cred
*old_cred
;
299 old_cred
= ovl_override_creds(dentry
->d_sb
);
300 res
= vfs_listxattr(realdentry
, list
, size
);
301 revert_creds(old_cred
);
302 if (res
<= 0 || size
== 0)
305 /* filter out private xattrs */
306 for (off
= 0; off
< res
;) {
307 char *s
= list
+ off
;
308 size_t slen
= strlen(s
) + 1;
310 BUG_ON(off
+ slen
> res
);
312 if (ovl_is_private_xattr(s
)) {
314 memmove(s
, s
+ slen
, res
- off
);
323 int ovl_removexattr(struct dentry
*dentry
, const char *name
)
326 struct path realpath
;
327 enum ovl_path_type type
= ovl_path_real(dentry
, &realpath
);
328 const struct cred
*old_cred
;
330 err
= ovl_want_write(dentry
);
335 if (ovl_is_private_xattr(name
))
338 if (!OVL_TYPE_UPPER(type
)) {
339 err
= vfs_getxattr(realpath
.dentry
, name
, NULL
, 0);
343 err
= ovl_copy_up(dentry
);
347 ovl_path_upper(dentry
, &realpath
);
350 old_cred
= ovl_override_creds(dentry
->d_sb
);
351 err
= vfs_removexattr(realpath
.dentry
, name
);
352 revert_creds(old_cred
);
354 ovl_drop_write(dentry
);
359 struct posix_acl
*ovl_get_acl(struct inode
*inode
, int type
)
361 struct inode
*realinode
= ovl_inode_real(inode
);
362 const struct cred
*old_cred
;
363 struct posix_acl
*acl
;
365 if (!IS_POSIXACL(realinode
))
368 if (!realinode
->i_op
->get_acl
)
371 old_cred
= ovl_override_creds(inode
->i_sb
);
372 acl
= realinode
->i_op
->get_acl(realinode
, type
);
373 revert_creds(old_cred
);
378 static bool ovl_open_need_copy_up(int flags
, enum ovl_path_type type
,
379 struct dentry
*realdentry
)
381 if (OVL_TYPE_UPPER(type
))
384 if (special_file(realdentry
->d_inode
->i_mode
))
387 if (!(OPEN_FMODE(flags
) & FMODE_WRITE
) && !(flags
& O_TRUNC
))
393 int ovl_open_maybe_copy_up(struct dentry
*dentry
, unsigned int file_flags
)
396 struct path realpath
;
397 enum ovl_path_type type
;
399 type
= ovl_path_real(dentry
, &realpath
);
400 if (ovl_open_need_copy_up(file_flags
, type
, realpath
.dentry
)) {
401 err
= ovl_want_write(dentry
);
403 if (file_flags
& O_TRUNC
)
404 err
= ovl_copy_up_truncate(dentry
);
406 err
= ovl_copy_up(dentry
);
407 ovl_drop_write(dentry
);
414 static const struct inode_operations ovl_file_inode_operations
= {
415 .setattr
= ovl_setattr
,
416 .permission
= ovl_permission
,
417 .getattr
= ovl_getattr
,
418 .setxattr
= ovl_setxattr
,
419 .getxattr
= ovl_getxattr
,
420 .listxattr
= ovl_listxattr
,
421 .removexattr
= ovl_removexattr
,
422 .get_acl
= ovl_get_acl
,
425 static const struct inode_operations ovl_symlink_inode_operations
= {
426 .setattr
= ovl_setattr
,
427 .get_link
= ovl_get_link
,
428 .readlink
= ovl_readlink
,
429 .getattr
= ovl_getattr
,
430 .setxattr
= ovl_setxattr
,
431 .getxattr
= ovl_getxattr
,
432 .listxattr
= ovl_listxattr
,
433 .removexattr
= ovl_removexattr
,
436 struct inode
*ovl_new_inode(struct super_block
*sb
, umode_t mode
,
437 struct ovl_entry
*oe
)
441 inode
= new_inode(sb
);
445 inode
->i_ino
= get_next_ino();
446 inode
->i_mode
= mode
;
447 inode
->i_flags
|= S_NOATIME
| S_NOCMTIME
;
448 inode
->i_private
= oe
;
453 inode
->i_op
= &ovl_dir_inode_operations
;
454 inode
->i_fop
= &ovl_dir_operations
;
458 inode
->i_op
= &ovl_symlink_inode_operations
;
466 inode
->i_op
= &ovl_file_inode_operations
;
470 WARN(1, "illegal file type: %i\n", mode
);