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Commit | Line | Data |
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e9be9d5e MS |
1 | /* |
2 | * | |
3 | * Copyright (C) 2011 Novell Inc. | |
4 | * | |
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. | |
8 | */ | |
9 | ||
10 | #include <linux/fs.h> | |
11 | #include <linux/slab.h> | |
12 | #include <linux/xattr.h> | |
13 | #include "overlayfs.h" | |
14 | ||
0f7ff2da | 15 | static int ovl_copy_up_truncate(struct dentry *dentry) |
e9be9d5e MS |
16 | { |
17 | int err; | |
18 | struct dentry *parent; | |
19 | struct kstat stat; | |
20 | struct path lowerpath; | |
21 | ||
22 | parent = dget_parent(dentry); | |
23 | err = ovl_copy_up(parent); | |
24 | if (err) | |
25 | goto out_dput_parent; | |
26 | ||
27 | ovl_path_lower(dentry, &lowerpath); | |
28 | err = vfs_getattr(&lowerpath, &stat); | |
29 | if (err) | |
30 | goto out_dput_parent; | |
31 | ||
0f7ff2da AV |
32 | stat.size = 0; |
33 | err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat); | |
e9be9d5e MS |
34 | |
35 | out_dput_parent: | |
36 | dput(parent); | |
37 | return err; | |
38 | } | |
39 | ||
40 | int ovl_setattr(struct dentry *dentry, struct iattr *attr) | |
41 | { | |
42 | int err; | |
43 | struct dentry *upperdentry; | |
44 | ||
cf9a6784 MS |
45 | /* |
46 | * Check for permissions before trying to copy-up. This is redundant | |
47 | * since it will be rechecked later by ->setattr() on upper dentry. But | |
48 | * without this, copy-up can be triggered by just about anybody. | |
49 | * | |
50 | * We don't initialize inode->size, which just means that | |
51 | * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not | |
52 | * check for a swapfile (which this won't be anyway). | |
53 | */ | |
54 | err = inode_change_ok(dentry->d_inode, attr); | |
55 | if (err) | |
56 | return err; | |
57 | ||
e9be9d5e MS |
58 | err = ovl_want_write(dentry); |
59 | if (err) | |
60 | goto out; | |
61 | ||
acff81ec MS |
62 | err = ovl_copy_up(dentry); |
63 | if (!err) { | |
64 | upperdentry = ovl_dentry_upper(dentry); | |
65 | ||
5955102c | 66 | inode_lock(upperdentry->d_inode); |
e9be9d5e | 67 | err = notify_change(upperdentry, attr, NULL); |
5955102c | 68 | inode_unlock(upperdentry->d_inode); |
e9be9d5e MS |
69 | } |
70 | ovl_drop_write(dentry); | |
71 | out: | |
72 | return err; | |
73 | } | |
74 | ||
75 | static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, | |
76 | struct kstat *stat) | |
77 | { | |
78 | struct path realpath; | |
79 | ||
80 | ovl_path_real(dentry, &realpath); | |
81 | return vfs_getattr(&realpath, stat); | |
82 | } | |
83 | ||
84 | int ovl_permission(struct inode *inode, int mask) | |
85 | { | |
86 | struct ovl_entry *oe; | |
87 | struct dentry *alias = NULL; | |
88 | struct inode *realinode; | |
89 | struct dentry *realdentry; | |
90 | bool is_upper; | |
91 | int err; | |
92 | ||
93 | if (S_ISDIR(inode->i_mode)) { | |
94 | oe = inode->i_private; | |
95 | } else if (mask & MAY_NOT_BLOCK) { | |
96 | return -ECHILD; | |
97 | } else { | |
98 | /* | |
99 | * For non-directories find an alias and get the info | |
100 | * from there. | |
101 | */ | |
102 | alias = d_find_any_alias(inode); | |
103 | if (WARN_ON(!alias)) | |
104 | return -ENOENT; | |
105 | ||
106 | oe = alias->d_fsdata; | |
107 | } | |
108 | ||
109 | realdentry = ovl_entry_real(oe, &is_upper); | |
110 | ||
8d3095f4 MS |
111 | if (ovl_is_default_permissions(inode)) { |
112 | struct kstat stat; | |
113 | struct path realpath = { .dentry = realdentry }; | |
114 | ||
115 | if (mask & MAY_NOT_BLOCK) | |
116 | return -ECHILD; | |
117 | ||
118 | realpath.mnt = ovl_entry_mnt_real(oe, inode, is_upper); | |
119 | ||
120 | err = vfs_getattr(&realpath, &stat); | |
121 | if (err) | |
122 | return err; | |
123 | ||
124 | if ((stat.mode ^ inode->i_mode) & S_IFMT) | |
125 | return -ESTALE; | |
126 | ||
127 | inode->i_mode = stat.mode; | |
128 | inode->i_uid = stat.uid; | |
129 | inode->i_gid = stat.gid; | |
130 | ||
131 | return generic_permission(inode, mask); | |
132 | } | |
133 | ||
e9be9d5e MS |
134 | /* Careful in RCU walk mode */ |
135 | realinode = ACCESS_ONCE(realdentry->d_inode); | |
136 | if (!realinode) { | |
137 | WARN_ON(!(mask & MAY_NOT_BLOCK)); | |
138 | err = -ENOENT; | |
139 | goto out_dput; | |
140 | } | |
141 | ||
142 | if (mask & MAY_WRITE) { | |
143 | umode_t mode = realinode->i_mode; | |
144 | ||
145 | /* | |
146 | * Writes will always be redirected to upper layer, so | |
147 | * ignore lower layer being read-only. | |
148 | * | |
149 | * If the overlay itself is read-only then proceed | |
150 | * with the permission check, don't return EROFS. | |
151 | * This will only happen if this is the lower layer of | |
152 | * another overlayfs. | |
153 | * | |
154 | * If upper fs becomes read-only after the overlay was | |
155 | * constructed return EROFS to prevent modification of | |
156 | * upper layer. | |
157 | */ | |
158 | err = -EROFS; | |
159 | if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && | |
160 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) | |
161 | goto out_dput; | |
162 | } | |
163 | ||
164 | err = __inode_permission(realinode, mask); | |
165 | out_dput: | |
166 | dput(alias); | |
167 | return err; | |
168 | } | |
169 | ||
6b255391 | 170 | static const char *ovl_get_link(struct dentry *dentry, |
fceef393 AV |
171 | struct inode *inode, |
172 | struct delayed_call *done) | |
e9be9d5e | 173 | { |
e9be9d5e MS |
174 | struct dentry *realdentry; |
175 | struct inode *realinode; | |
176 | ||
6b255391 AV |
177 | if (!dentry) |
178 | return ERR_PTR(-ECHILD); | |
179 | ||
e9be9d5e MS |
180 | realdentry = ovl_dentry_real(dentry); |
181 | realinode = realdentry->d_inode; | |
182 | ||
6b255391 | 183 | if (WARN_ON(!realinode->i_op->get_link)) |
e9be9d5e MS |
184 | return ERR_PTR(-EPERM); |
185 | ||
fceef393 | 186 | return realinode->i_op->get_link(realdentry, realinode, done); |
e9be9d5e MS |
187 | } |
188 | ||
189 | static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) | |
190 | { | |
191 | struct path realpath; | |
192 | struct inode *realinode; | |
193 | ||
194 | ovl_path_real(dentry, &realpath); | |
195 | realinode = realpath.dentry->d_inode; | |
196 | ||
197 | if (!realinode->i_op->readlink) | |
198 | return -EINVAL; | |
199 | ||
200 | touch_atime(&realpath); | |
201 | ||
202 | return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); | |
203 | } | |
204 | ||
205 | ||
206 | static bool ovl_is_private_xattr(const char *name) | |
207 | { | |
cead89bb | 208 | return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; |
e9be9d5e MS |
209 | } |
210 | ||
211 | int ovl_setxattr(struct dentry *dentry, const char *name, | |
212 | const void *value, size_t size, int flags) | |
213 | { | |
214 | int err; | |
215 | struct dentry *upperdentry; | |
216 | ||
217 | err = ovl_want_write(dentry); | |
218 | if (err) | |
219 | goto out; | |
220 | ||
221 | err = -EPERM; | |
222 | if (ovl_is_private_xattr(name)) | |
223 | goto out_drop_write; | |
224 | ||
225 | err = ovl_copy_up(dentry); | |
226 | if (err) | |
227 | goto out_drop_write; | |
228 | ||
229 | upperdentry = ovl_dentry_upper(dentry); | |
230 | err = vfs_setxattr(upperdentry, name, value, size, flags); | |
231 | ||
232 | out_drop_write: | |
233 | ovl_drop_write(dentry); | |
234 | out: | |
235 | return err; | |
236 | } | |
237 | ||
52148463 MS |
238 | static bool ovl_need_xattr_filter(struct dentry *dentry, |
239 | enum ovl_path_type type) | |
240 | { | |
1afaba1e MS |
241 | if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER) |
242 | return S_ISDIR(dentry->d_inode->i_mode); | |
243 | else | |
244 | return false; | |
52148463 MS |
245 | } |
246 | ||
e9be9d5e MS |
247 | ssize_t ovl_getxattr(struct dentry *dentry, const char *name, |
248 | void *value, size_t size) | |
249 | { | |
52148463 MS |
250 | struct path realpath; |
251 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); | |
252 | ||
253 | if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) | |
e9be9d5e MS |
254 | return -ENODATA; |
255 | ||
52148463 | 256 | return vfs_getxattr(realpath.dentry, name, value, size); |
e9be9d5e MS |
257 | } |
258 | ||
259 | ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) | |
260 | { | |
52148463 MS |
261 | struct path realpath; |
262 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); | |
e9be9d5e MS |
263 | ssize_t res; |
264 | int off; | |
265 | ||
52148463 | 266 | res = vfs_listxattr(realpath.dentry, list, size); |
e9be9d5e MS |
267 | if (res <= 0 || size == 0) |
268 | return res; | |
269 | ||
52148463 | 270 | if (!ovl_need_xattr_filter(dentry, type)) |
e9be9d5e MS |
271 | return res; |
272 | ||
273 | /* filter out private xattrs */ | |
274 | for (off = 0; off < res;) { | |
275 | char *s = list + off; | |
276 | size_t slen = strlen(s) + 1; | |
277 | ||
278 | BUG_ON(off + slen > res); | |
279 | ||
280 | if (ovl_is_private_xattr(s)) { | |
281 | res -= slen; | |
282 | memmove(s, s + slen, res - off); | |
283 | } else { | |
284 | off += slen; | |
285 | } | |
286 | } | |
287 | ||
288 | return res; | |
289 | } | |
290 | ||
291 | int ovl_removexattr(struct dentry *dentry, const char *name) | |
292 | { | |
293 | int err; | |
294 | struct path realpath; | |
52148463 | 295 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); |
e9be9d5e MS |
296 | |
297 | err = ovl_want_write(dentry); | |
298 | if (err) | |
299 | goto out; | |
300 | ||
52148463 MS |
301 | err = -ENODATA; |
302 | if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) | |
e9be9d5e MS |
303 | goto out_drop_write; |
304 | ||
1afaba1e | 305 | if (!OVL_TYPE_UPPER(type)) { |
e9be9d5e MS |
306 | err = vfs_getxattr(realpath.dentry, name, NULL, 0); |
307 | if (err < 0) | |
308 | goto out_drop_write; | |
309 | ||
310 | err = ovl_copy_up(dentry); | |
311 | if (err) | |
312 | goto out_drop_write; | |
313 | ||
314 | ovl_path_upper(dentry, &realpath); | |
315 | } | |
316 | ||
317 | err = vfs_removexattr(realpath.dentry, name); | |
318 | out_drop_write: | |
319 | ovl_drop_write(dentry); | |
320 | out: | |
321 | return err; | |
322 | } | |
323 | ||
324 | static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, | |
325 | struct dentry *realdentry) | |
326 | { | |
1afaba1e | 327 | if (OVL_TYPE_UPPER(type)) |
e9be9d5e MS |
328 | return false; |
329 | ||
330 | if (special_file(realdentry->d_inode->i_mode)) | |
331 | return false; | |
332 | ||
333 | if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) | |
334 | return false; | |
335 | ||
336 | return true; | |
337 | } | |
338 | ||
4bacc9c9 | 339 | struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags) |
e9be9d5e MS |
340 | { |
341 | int err; | |
342 | struct path realpath; | |
343 | enum ovl_path_type type; | |
e9be9d5e | 344 | |
9391dd00 AV |
345 | if (d_is_dir(dentry)) |
346 | return d_backing_inode(dentry); | |
347 | ||
e9be9d5e | 348 | type = ovl_path_real(dentry, &realpath); |
4bacc9c9 | 349 | if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { |
e9be9d5e MS |
350 | err = ovl_want_write(dentry); |
351 | if (err) | |
4bacc9c9 | 352 | return ERR_PTR(err); |
e9be9d5e | 353 | |
4bacc9c9 | 354 | if (file_flags & O_TRUNC) |
0f7ff2da | 355 | err = ovl_copy_up_truncate(dentry); |
e9be9d5e MS |
356 | else |
357 | err = ovl_copy_up(dentry); | |
f25801ee | 358 | ovl_drop_write(dentry); |
e9be9d5e | 359 | if (err) |
4bacc9c9 | 360 | return ERR_PTR(err); |
e9be9d5e MS |
361 | |
362 | ovl_path_upper(dentry, &realpath); | |
363 | } | |
364 | ||
1c8a47df MS |
365 | if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE) |
366 | return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags); | |
367 | ||
4bacc9c9 | 368 | return d_backing_inode(realpath.dentry); |
e9be9d5e MS |
369 | } |
370 | ||
371 | static const struct inode_operations ovl_file_inode_operations = { | |
372 | .setattr = ovl_setattr, | |
373 | .permission = ovl_permission, | |
374 | .getattr = ovl_getattr, | |
375 | .setxattr = ovl_setxattr, | |
376 | .getxattr = ovl_getxattr, | |
377 | .listxattr = ovl_listxattr, | |
378 | .removexattr = ovl_removexattr, | |
e9be9d5e MS |
379 | }; |
380 | ||
381 | static const struct inode_operations ovl_symlink_inode_operations = { | |
382 | .setattr = ovl_setattr, | |
6b255391 | 383 | .get_link = ovl_get_link, |
e9be9d5e MS |
384 | .readlink = ovl_readlink, |
385 | .getattr = ovl_getattr, | |
386 | .setxattr = ovl_setxattr, | |
387 | .getxattr = ovl_getxattr, | |
388 | .listxattr = ovl_listxattr, | |
389 | .removexattr = ovl_removexattr, | |
390 | }; | |
391 | ||
392 | struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, | |
393 | struct ovl_entry *oe) | |
394 | { | |
395 | struct inode *inode; | |
396 | ||
397 | inode = new_inode(sb); | |
398 | if (!inode) | |
399 | return NULL; | |
400 | ||
401 | mode &= S_IFMT; | |
402 | ||
403 | inode->i_ino = get_next_ino(); | |
404 | inode->i_mode = mode; | |
405 | inode->i_flags |= S_NOATIME | S_NOCMTIME; | |
406 | ||
407 | switch (mode) { | |
408 | case S_IFDIR: | |
409 | inode->i_private = oe; | |
410 | inode->i_op = &ovl_dir_inode_operations; | |
411 | inode->i_fop = &ovl_dir_operations; | |
412 | break; | |
413 | ||
414 | case S_IFLNK: | |
415 | inode->i_op = &ovl_symlink_inode_operations; | |
416 | break; | |
417 | ||
418 | case S_IFREG: | |
419 | case S_IFSOCK: | |
420 | case S_IFBLK: | |
421 | case S_IFCHR: | |
422 | case S_IFIFO: | |
423 | inode->i_op = &ovl_file_inode_operations; | |
424 | break; | |
425 | ||
426 | default: | |
427 | WARN(1, "illegal file type: %i\n", mode); | |
428 | iput(inode); | |
429 | inode = NULL; | |
430 | } | |
431 | ||
432 | return inode; | |
e9be9d5e | 433 | } |