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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 | ||
15 | static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr, | |
16 | bool no_data) | |
17 | { | |
18 | int err; | |
19 | struct dentry *parent; | |
20 | struct kstat stat; | |
21 | struct path lowerpath; | |
22 | ||
23 | parent = dget_parent(dentry); | |
24 | err = ovl_copy_up(parent); | |
25 | if (err) | |
26 | goto out_dput_parent; | |
27 | ||
28 | ovl_path_lower(dentry, &lowerpath); | |
29 | err = vfs_getattr(&lowerpath, &stat); | |
30 | if (err) | |
31 | goto out_dput_parent; | |
32 | ||
33 | if (no_data) | |
34 | stat.size = 0; | |
35 | ||
36 | err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat, attr); | |
37 | ||
38 | out_dput_parent: | |
39 | dput(parent); | |
40 | return err; | |
41 | } | |
42 | ||
43 | int ovl_setattr(struct dentry *dentry, struct iattr *attr) | |
44 | { | |
45 | int err; | |
46 | struct dentry *upperdentry; | |
47 | ||
48 | err = ovl_want_write(dentry); | |
49 | if (err) | |
50 | goto out; | |
51 | ||
52 | upperdentry = ovl_dentry_upper(dentry); | |
53 | if (upperdentry) { | |
54 | mutex_lock(&upperdentry->d_inode->i_mutex); | |
55 | err = notify_change(upperdentry, attr, NULL); | |
56 | mutex_unlock(&upperdentry->d_inode->i_mutex); | |
57 | } else { | |
58 | err = ovl_copy_up_last(dentry, attr, false); | |
59 | } | |
60 | ovl_drop_write(dentry); | |
61 | out: | |
62 | return err; | |
63 | } | |
64 | ||
65 | static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, | |
66 | struct kstat *stat) | |
67 | { | |
68 | struct path realpath; | |
69 | ||
70 | ovl_path_real(dentry, &realpath); | |
71 | return vfs_getattr(&realpath, stat); | |
72 | } | |
73 | ||
74 | int ovl_permission(struct inode *inode, int mask) | |
75 | { | |
76 | struct ovl_entry *oe; | |
77 | struct dentry *alias = NULL; | |
78 | struct inode *realinode; | |
79 | struct dentry *realdentry; | |
80 | bool is_upper; | |
81 | int err; | |
82 | ||
83 | if (S_ISDIR(inode->i_mode)) { | |
84 | oe = inode->i_private; | |
85 | } else if (mask & MAY_NOT_BLOCK) { | |
86 | return -ECHILD; | |
87 | } else { | |
88 | /* | |
89 | * For non-directories find an alias and get the info | |
90 | * from there. | |
91 | */ | |
92 | alias = d_find_any_alias(inode); | |
93 | if (WARN_ON(!alias)) | |
94 | return -ENOENT; | |
95 | ||
96 | oe = alias->d_fsdata; | |
97 | } | |
98 | ||
99 | realdentry = ovl_entry_real(oe, &is_upper); | |
100 | ||
101 | /* Careful in RCU walk mode */ | |
102 | realinode = ACCESS_ONCE(realdentry->d_inode); | |
103 | if (!realinode) { | |
104 | WARN_ON(!(mask & MAY_NOT_BLOCK)); | |
105 | err = -ENOENT; | |
106 | goto out_dput; | |
107 | } | |
108 | ||
109 | if (mask & MAY_WRITE) { | |
110 | umode_t mode = realinode->i_mode; | |
111 | ||
112 | /* | |
113 | * Writes will always be redirected to upper layer, so | |
114 | * ignore lower layer being read-only. | |
115 | * | |
116 | * If the overlay itself is read-only then proceed | |
117 | * with the permission check, don't return EROFS. | |
118 | * This will only happen if this is the lower layer of | |
119 | * another overlayfs. | |
120 | * | |
121 | * If upper fs becomes read-only after the overlay was | |
122 | * constructed return EROFS to prevent modification of | |
123 | * upper layer. | |
124 | */ | |
125 | err = -EROFS; | |
126 | if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && | |
127 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) | |
128 | goto out_dput; | |
129 | } | |
130 | ||
131 | err = __inode_permission(realinode, mask); | |
132 | out_dput: | |
133 | dput(alias); | |
134 | return err; | |
135 | } | |
136 | ||
137 | ||
138 | struct ovl_link_data { | |
139 | struct dentry *realdentry; | |
140 | void *cookie; | |
141 | }; | |
142 | ||
143 | static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd) | |
144 | { | |
145 | void *ret; | |
146 | struct dentry *realdentry; | |
147 | struct inode *realinode; | |
148 | struct ovl_link_data *data = NULL; | |
149 | ||
150 | realdentry = ovl_dentry_real(dentry); | |
151 | realinode = realdentry->d_inode; | |
152 | ||
153 | if (WARN_ON(!realinode->i_op->follow_link)) | |
154 | return ERR_PTR(-EPERM); | |
155 | ||
156 | if (realinode->i_op->put_link) { | |
157 | data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL); | |
158 | if (!data) | |
159 | return ERR_PTR(-ENOMEM); | |
160 | data->realdentry = realdentry; | |
161 | } | |
162 | ||
163 | ret = realinode->i_op->follow_link(realdentry, nd); | |
164 | if (IS_ERR(ret)) { | |
165 | kfree(data); | |
166 | return ret; | |
167 | } | |
168 | ||
169 | if (data) | |
170 | data->cookie = ret; | |
171 | ||
172 | return data; | |
173 | } | |
174 | ||
175 | static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c) | |
176 | { | |
177 | struct inode *realinode; | |
178 | struct ovl_link_data *data = c; | |
179 | ||
180 | if (!data) | |
181 | return; | |
182 | ||
183 | realinode = data->realdentry->d_inode; | |
184 | realinode->i_op->put_link(data->realdentry, nd, data->cookie); | |
185 | kfree(data); | |
186 | } | |
187 | ||
188 | static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) | |
189 | { | |
190 | struct path realpath; | |
191 | struct inode *realinode; | |
192 | ||
193 | ovl_path_real(dentry, &realpath); | |
194 | realinode = realpath.dentry->d_inode; | |
195 | ||
196 | if (!realinode->i_op->readlink) | |
197 | return -EINVAL; | |
198 | ||
199 | touch_atime(&realpath); | |
200 | ||
201 | return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); | |
202 | } | |
203 | ||
204 | ||
205 | static bool ovl_is_private_xattr(const char *name) | |
206 | { | |
207 | return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; | |
208 | } | |
209 | ||
210 | int ovl_setxattr(struct dentry *dentry, const char *name, | |
211 | const void *value, size_t size, int flags) | |
212 | { | |
213 | int err; | |
214 | struct dentry *upperdentry; | |
215 | ||
216 | err = ovl_want_write(dentry); | |
217 | if (err) | |
218 | goto out; | |
219 | ||
220 | err = -EPERM; | |
221 | if (ovl_is_private_xattr(name)) | |
222 | goto out_drop_write; | |
223 | ||
224 | err = ovl_copy_up(dentry); | |
225 | if (err) | |
226 | goto out_drop_write; | |
227 | ||
228 | upperdentry = ovl_dentry_upper(dentry); | |
229 | err = vfs_setxattr(upperdentry, name, value, size, flags); | |
230 | ||
231 | out_drop_write: | |
232 | ovl_drop_write(dentry); | |
233 | out: | |
234 | return err; | |
235 | } | |
236 | ||
237 | static bool ovl_need_xattr_filter(struct dentry *dentry, | |
238 | enum ovl_path_type type) | |
239 | { | |
240 | if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER) | |
241 | return S_ISDIR(dentry->d_inode->i_mode); | |
242 | else | |
243 | return false; | |
244 | } | |
245 | ||
246 | ssize_t ovl_getxattr(struct dentry *dentry, const char *name, | |
247 | void *value, size_t size) | |
248 | { | |
249 | struct path realpath; | |
250 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); | |
251 | ||
252 | if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) | |
253 | return -ENODATA; | |
254 | ||
255 | return vfs_getxattr(realpath.dentry, name, value, size); | |
256 | } | |
257 | ||
258 | ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) | |
259 | { | |
260 | struct path realpath; | |
261 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); | |
262 | ssize_t res; | |
263 | int off; | |
264 | ||
265 | res = vfs_listxattr(realpath.dentry, list, size); | |
266 | if (res <= 0 || size == 0) | |
267 | return res; | |
268 | ||
269 | if (!ovl_need_xattr_filter(dentry, type)) | |
270 | return res; | |
271 | ||
272 | /* filter out private xattrs */ | |
273 | for (off = 0; off < res;) { | |
274 | char *s = list + off; | |
275 | size_t slen = strlen(s) + 1; | |
276 | ||
277 | BUG_ON(off + slen > res); | |
278 | ||
279 | if (ovl_is_private_xattr(s)) { | |
280 | res -= slen; | |
281 | memmove(s, s + slen, res - off); | |
282 | } else { | |
283 | off += slen; | |
284 | } | |
285 | } | |
286 | ||
287 | return res; | |
288 | } | |
289 | ||
290 | int ovl_removexattr(struct dentry *dentry, const char *name) | |
291 | { | |
292 | int err; | |
293 | struct path realpath; | |
294 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); | |
295 | ||
296 | err = ovl_want_write(dentry); | |
297 | if (err) | |
298 | goto out; | |
299 | ||
300 | err = -ENODATA; | |
301 | if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) | |
302 | goto out_drop_write; | |
303 | ||
304 | if (!OVL_TYPE_UPPER(type)) { | |
305 | err = vfs_getxattr(realpath.dentry, name, NULL, 0); | |
306 | if (err < 0) | |
307 | goto out_drop_write; | |
308 | ||
309 | err = ovl_copy_up(dentry); | |
310 | if (err) | |
311 | goto out_drop_write; | |
312 | ||
313 | ovl_path_upper(dentry, &realpath); | |
314 | } | |
315 | ||
316 | err = vfs_removexattr(realpath.dentry, name); | |
317 | out_drop_write: | |
318 | ovl_drop_write(dentry); | |
319 | out: | |
320 | return err; | |
321 | } | |
322 | ||
323 | static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, | |
324 | struct dentry *realdentry) | |
325 | { | |
326 | if (OVL_TYPE_UPPER(type)) | |
327 | return false; | |
328 | ||
329 | if (special_file(realdentry->d_inode->i_mode)) | |
330 | return false; | |
331 | ||
332 | if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) | |
333 | return false; | |
334 | ||
335 | return true; | |
336 | } | |
337 | ||
338 | static int ovl_dentry_open(struct dentry *dentry, struct file *file, | |
339 | const struct cred *cred) | |
340 | { | |
341 | int err; | |
342 | struct path realpath; | |
343 | enum ovl_path_type type; | |
344 | bool want_write = false; | |
345 | ||
346 | type = ovl_path_real(dentry, &realpath); | |
347 | if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) { | |
348 | want_write = true; | |
349 | err = ovl_want_write(dentry); | |
350 | if (err) | |
351 | goto out; | |
352 | ||
353 | if (file->f_flags & O_TRUNC) | |
354 | err = ovl_copy_up_last(dentry, NULL, true); | |
355 | else | |
356 | err = ovl_copy_up(dentry); | |
357 | if (err) | |
358 | goto out_drop_write; | |
359 | ||
360 | ovl_path_upper(dentry, &realpath); | |
361 | } | |
362 | ||
363 | err = vfs_open(&realpath, file, cred); | |
364 | out_drop_write: | |
365 | if (want_write) | |
366 | ovl_drop_write(dentry); | |
367 | out: | |
368 | return err; | |
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, | |
379 | .dentry_open = ovl_dentry_open, | |
380 | }; | |
381 | ||
382 | static const struct inode_operations ovl_symlink_inode_operations = { | |
383 | .setattr = ovl_setattr, | |
384 | .follow_link = ovl_follow_link, | |
385 | .put_link = ovl_put_link, | |
386 | .readlink = ovl_readlink, | |
387 | .getattr = ovl_getattr, | |
388 | .setxattr = ovl_setxattr, | |
389 | .getxattr = ovl_getxattr, | |
390 | .listxattr = ovl_listxattr, | |
391 | .removexattr = ovl_removexattr, | |
392 | }; | |
393 | ||
394 | struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, | |
395 | struct ovl_entry *oe) | |
396 | { | |
397 | struct inode *inode; | |
398 | ||
399 | inode = new_inode(sb); | |
400 | if (!inode) | |
401 | return NULL; | |
402 | ||
403 | mode &= S_IFMT; | |
404 | ||
405 | inode->i_ino = get_next_ino(); | |
406 | inode->i_mode = mode; | |
407 | inode->i_flags |= S_NOATIME | S_NOCMTIME; | |
408 | ||
409 | switch (mode) { | |
410 | case S_IFDIR: | |
411 | inode->i_private = oe; | |
412 | inode->i_op = &ovl_dir_inode_operations; | |
413 | inode->i_fop = &ovl_dir_operations; | |
414 | break; | |
415 | ||
416 | case S_IFLNK: | |
417 | inode->i_op = &ovl_symlink_inode_operations; | |
418 | break; | |
419 | ||
420 | case S_IFREG: | |
421 | case S_IFSOCK: | |
422 | case S_IFBLK: | |
423 | case S_IFCHR: | |
424 | case S_IFIFO: | |
425 | inode->i_op = &ovl_file_inode_operations; | |
426 | break; | |
427 | ||
428 | default: | |
429 | WARN(1, "illegal file type: %i\n", mode); | |
430 | iput(inode); | |
431 | inode = NULL; | |
432 | } | |
433 | ||
434 | return inode; | |
435 | } |