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bbb1e54d MS |
1 | /* |
2 | * Copyright (C) 2011 Novell Inc. | |
3 | * Copyright (C) 2016 Red Hat, 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/namei.h> | |
12 | #include <linux/xattr.h> | |
02b69b28 | 13 | #include <linux/ratelimit.h> |
bbb1e54d MS |
14 | #include "overlayfs.h" |
15 | #include "ovl_entry.h" | |
16 | ||
e28edc46 MS |
17 | struct ovl_lookup_data { |
18 | struct qstr name; | |
19 | bool is_dir; | |
20 | bool opaque; | |
21 | bool stop; | |
22 | bool last; | |
02b69b28 | 23 | char *redirect; |
e28edc46 | 24 | }; |
bbb1e54d | 25 | |
02b69b28 MS |
26 | static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d, |
27 | size_t prelen, const char *post) | |
28 | { | |
29 | int res; | |
30 | char *s, *next, *buf = NULL; | |
31 | ||
32 | res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0); | |
33 | if (res < 0) { | |
34 | if (res == -ENODATA || res == -EOPNOTSUPP) | |
35 | return 0; | |
36 | goto fail; | |
37 | } | |
38 | buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY); | |
39 | if (!buf) | |
40 | return -ENOMEM; | |
41 | ||
42 | if (res == 0) | |
43 | goto invalid; | |
44 | ||
45 | res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res); | |
46 | if (res < 0) | |
47 | goto fail; | |
48 | if (res == 0) | |
49 | goto invalid; | |
50 | if (buf[0] == '/') { | |
51 | for (s = buf; *s++ == '/'; s = next) { | |
52 | next = strchrnul(s, '/'); | |
53 | if (s == next) | |
54 | goto invalid; | |
55 | } | |
56 | } else { | |
57 | if (strchr(buf, '/') != NULL) | |
58 | goto invalid; | |
59 | ||
60 | memmove(buf + prelen, buf, res); | |
61 | memcpy(buf, d->name.name, prelen); | |
62 | } | |
63 | ||
64 | strcat(buf, post); | |
65 | kfree(d->redirect); | |
66 | d->redirect = buf; | |
67 | d->name.name = d->redirect; | |
68 | d->name.len = strlen(d->redirect); | |
69 | ||
70 | return 0; | |
71 | ||
72 | err_free: | |
73 | kfree(buf); | |
74 | return 0; | |
75 | fail: | |
76 | pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res); | |
77 | goto err_free; | |
78 | invalid: | |
79 | pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf); | |
80 | goto err_free; | |
81 | } | |
82 | ||
bbb1e54d MS |
83 | static bool ovl_is_opaquedir(struct dentry *dentry) |
84 | { | |
85 | int res; | |
86 | char val; | |
87 | ||
88 | if (!d_is_dir(dentry)) | |
89 | return false; | |
90 | ||
91 | res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1); | |
92 | if (res == 1 && val == 'y') | |
93 | return true; | |
94 | ||
95 | return false; | |
96 | } | |
97 | ||
e28edc46 MS |
98 | static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d, |
99 | const char *name, unsigned int namelen, | |
02b69b28 | 100 | size_t prelen, const char *post, |
e28edc46 MS |
101 | struct dentry **ret) |
102 | { | |
103 | struct dentry *this; | |
104 | int err; | |
105 | ||
106 | this = lookup_one_len_unlocked(name, base, namelen); | |
107 | if (IS_ERR(this)) { | |
108 | err = PTR_ERR(this); | |
109 | this = NULL; | |
110 | if (err == -ENOENT || err == -ENAMETOOLONG) | |
111 | goto out; | |
112 | goto out_err; | |
113 | } | |
114 | if (!this->d_inode) | |
115 | goto put_and_out; | |
116 | ||
117 | if (ovl_dentry_weird(this)) { | |
118 | /* Don't support traversing automounts and other weirdness */ | |
119 | err = -EREMOTE; | |
120 | goto out_err; | |
121 | } | |
122 | if (ovl_is_whiteout(this)) { | |
123 | d->stop = d->opaque = true; | |
124 | goto put_and_out; | |
125 | } | |
126 | if (!d_can_lookup(this)) { | |
127 | d->stop = true; | |
128 | if (d->is_dir) | |
129 | goto put_and_out; | |
130 | goto out; | |
131 | } | |
132 | d->is_dir = true; | |
133 | if (!d->last && ovl_is_opaquedir(this)) { | |
134 | d->stop = d->opaque = true; | |
135 | goto out; | |
136 | } | |
02b69b28 MS |
137 | err = ovl_check_redirect(this, d, prelen, post); |
138 | if (err) | |
139 | goto out_err; | |
e28edc46 MS |
140 | out: |
141 | *ret = this; | |
142 | return 0; | |
143 | ||
144 | put_and_out: | |
145 | dput(this); | |
146 | this = NULL; | |
147 | goto out; | |
148 | ||
149 | out_err: | |
150 | dput(this); | |
151 | return err; | |
152 | } | |
153 | ||
154 | static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d, | |
155 | struct dentry **ret) | |
156 | { | |
4c7d0c9c AG |
157 | /* Counting down from the end, since the prefix can change */ |
158 | size_t rem = d->name.len - 1; | |
02b69b28 MS |
159 | struct dentry *dentry = NULL; |
160 | int err; | |
161 | ||
4c7d0c9c | 162 | if (d->name.name[0] != '/') |
02b69b28 MS |
163 | return ovl_lookup_single(base, d, d->name.name, d->name.len, |
164 | 0, "", ret); | |
165 | ||
4c7d0c9c AG |
166 | while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) { |
167 | const char *s = d->name.name + d->name.len - rem; | |
02b69b28 | 168 | const char *next = strchrnul(s, '/'); |
4c7d0c9c AG |
169 | size_t thislen = next - s; |
170 | bool end = !next[0]; | |
02b69b28 | 171 | |
4c7d0c9c AG |
172 | /* Verify we did not go off the rails */ |
173 | if (WARN_ON(s[-1] != '/')) | |
02b69b28 MS |
174 | return -EIO; |
175 | ||
4c7d0c9c AG |
176 | err = ovl_lookup_single(base, d, s, thislen, |
177 | d->name.len - rem, next, &base); | |
02b69b28 MS |
178 | dput(dentry); |
179 | if (err) | |
180 | return err; | |
181 | dentry = base; | |
4c7d0c9c AG |
182 | if (end) |
183 | break; | |
184 | ||
185 | rem -= thislen + 1; | |
186 | ||
187 | if (WARN_ON(rem >= d->name.len)) | |
188 | return -EIO; | |
02b69b28 MS |
189 | } |
190 | *ret = dentry; | |
191 | return 0; | |
e28edc46 MS |
192 | } |
193 | ||
bbb1e54d MS |
194 | /* |
195 | * Returns next layer in stack starting from top. | |
196 | * Returns -1 if this is the last layer. | |
197 | */ | |
198 | int ovl_path_next(int idx, struct dentry *dentry, struct path *path) | |
199 | { | |
200 | struct ovl_entry *oe = dentry->d_fsdata; | |
201 | ||
202 | BUG_ON(idx < 0); | |
203 | if (idx == 0) { | |
204 | ovl_path_upper(dentry, path); | |
205 | if (path->dentry) | |
206 | return oe->numlower ? 1 : -1; | |
207 | idx++; | |
208 | } | |
209 | BUG_ON(idx > oe->numlower); | |
210 | *path = oe->lowerstack[idx - 1]; | |
211 | ||
212 | return (idx < oe->numlower) ? idx + 1 : -1; | |
213 | } | |
214 | ||
215 | struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, | |
216 | unsigned int flags) | |
217 | { | |
218 | struct ovl_entry *oe; | |
219 | const struct cred *old_cred; | |
6b2d5fe4 | 220 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
bbb1e54d MS |
221 | struct ovl_entry *poe = dentry->d_parent->d_fsdata; |
222 | struct path *stack = NULL; | |
223 | struct dentry *upperdir, *upperdentry = NULL; | |
224 | unsigned int ctr = 0; | |
225 | struct inode *inode = NULL; | |
226 | bool upperopaque = false; | |
02b69b28 | 227 | char *upperredirect = NULL; |
bbb1e54d MS |
228 | struct dentry *this; |
229 | unsigned int i; | |
230 | int err; | |
e28edc46 MS |
231 | struct ovl_lookup_data d = { |
232 | .name = dentry->d_name, | |
233 | .is_dir = false, | |
234 | .opaque = false, | |
235 | .stop = false, | |
236 | .last = !poe->numlower, | |
02b69b28 | 237 | .redirect = NULL, |
e28edc46 | 238 | }; |
bbb1e54d | 239 | |
6b2d5fe4 MS |
240 | if (dentry->d_name.len > ofs->namelen) |
241 | return ERR_PTR(-ENAMETOOLONG); | |
242 | ||
bbb1e54d MS |
243 | old_cred = ovl_override_creds(dentry->d_sb); |
244 | upperdir = ovl_upperdentry_dereference(poe); | |
245 | if (upperdir) { | |
e28edc46 MS |
246 | err = ovl_lookup_layer(upperdir, &d, &upperdentry); |
247 | if (err) | |
bbb1e54d MS |
248 | goto out; |
249 | ||
e28edc46 MS |
250 | if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) { |
251 | dput(upperdentry); | |
252 | err = -EREMOTE; | |
253 | goto out; | |
bbb1e54d | 254 | } |
02b69b28 MS |
255 | |
256 | if (d.redirect) { | |
257 | upperredirect = kstrdup(d.redirect, GFP_KERNEL); | |
258 | if (!upperredirect) | |
259 | goto out_put_upper; | |
260 | if (d.redirect[0] == '/') | |
261 | poe = dentry->d_sb->s_root->d_fsdata; | |
262 | } | |
e28edc46 | 263 | upperopaque = d.opaque; |
bbb1e54d MS |
264 | } |
265 | ||
e28edc46 | 266 | if (!d.stop && poe->numlower) { |
bbb1e54d | 267 | err = -ENOMEM; |
02b69b28 | 268 | stack = kcalloc(ofs->numlower, sizeof(struct path), |
e28edc46 | 269 | GFP_TEMPORARY); |
bbb1e54d MS |
270 | if (!stack) |
271 | goto out_put_upper; | |
272 | } | |
273 | ||
e28edc46 | 274 | for (i = 0; !d.stop && i < poe->numlower; i++) { |
bbb1e54d MS |
275 | struct path lowerpath = poe->lowerstack[i]; |
276 | ||
e28edc46 MS |
277 | d.last = i == poe->numlower - 1; |
278 | err = ovl_lookup_layer(lowerpath.dentry, &d, &this); | |
279 | if (err) | |
bbb1e54d | 280 | goto out_put; |
6b2d5fe4 | 281 | |
bbb1e54d MS |
282 | if (!this) |
283 | continue; | |
bbb1e54d MS |
284 | |
285 | stack[ctr].dentry = this; | |
286 | stack[ctr].mnt = lowerpath.mnt; | |
287 | ctr++; | |
02b69b28 MS |
288 | |
289 | if (d.stop) | |
290 | break; | |
291 | ||
292 | if (d.redirect && | |
293 | d.redirect[0] == '/' && | |
294 | poe != dentry->d_sb->s_root->d_fsdata) { | |
295 | poe = dentry->d_sb->s_root->d_fsdata; | |
296 | ||
297 | /* Find the current layer on the root dentry */ | |
298 | for (i = 0; i < poe->numlower; i++) | |
299 | if (poe->lowerstack[i].mnt == lowerpath.mnt) | |
300 | break; | |
301 | if (WARN_ON(i == poe->numlower)) | |
302 | break; | |
303 | } | |
bbb1e54d MS |
304 | } |
305 | ||
306 | oe = ovl_alloc_entry(ctr); | |
307 | err = -ENOMEM; | |
308 | if (!oe) | |
309 | goto out_put; | |
310 | ||
311 | if (upperdentry || ctr) { | |
312 | struct dentry *realdentry; | |
313 | struct inode *realinode; | |
314 | ||
315 | realdentry = upperdentry ? upperdentry : stack[0].dentry; | |
316 | realinode = d_inode(realdentry); | |
317 | ||
318 | err = -ENOMEM; | |
319 | if (upperdentry && !d_is_dir(upperdentry)) { | |
320 | inode = ovl_get_inode(dentry->d_sb, realinode); | |
321 | } else { | |
322 | inode = ovl_new_inode(dentry->d_sb, realinode->i_mode, | |
323 | realinode->i_rdev); | |
324 | if (inode) | |
325 | ovl_inode_init(inode, realinode, !!upperdentry); | |
326 | } | |
327 | if (!inode) | |
328 | goto out_free_oe; | |
329 | ovl_copyattr(realdentry->d_inode, inode); | |
330 | } | |
331 | ||
332 | revert_creds(old_cred); | |
333 | oe->opaque = upperopaque; | |
02b69b28 | 334 | oe->redirect = upperredirect; |
bbb1e54d MS |
335 | oe->__upperdentry = upperdentry; |
336 | memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr); | |
337 | kfree(stack); | |
02b69b28 | 338 | kfree(d.redirect); |
bbb1e54d MS |
339 | dentry->d_fsdata = oe; |
340 | d_add(dentry, inode); | |
341 | ||
342 | return NULL; | |
343 | ||
344 | out_free_oe: | |
345 | kfree(oe); | |
346 | out_put: | |
347 | for (i = 0; i < ctr; i++) | |
348 | dput(stack[i].dentry); | |
349 | kfree(stack); | |
350 | out_put_upper: | |
351 | dput(upperdentry); | |
02b69b28 | 352 | kfree(upperredirect); |
bbb1e54d | 353 | out: |
02b69b28 | 354 | kfree(d.redirect); |
bbb1e54d MS |
355 | revert_creds(old_cred); |
356 | return ERR_PTR(err); | |
357 | } | |
358 | ||
359 | bool ovl_lower_positive(struct dentry *dentry) | |
360 | { | |
361 | struct ovl_entry *oe = dentry->d_fsdata; | |
362 | struct ovl_entry *poe = dentry->d_parent->d_fsdata; | |
363 | const struct qstr *name = &dentry->d_name; | |
364 | unsigned int i; | |
365 | bool positive = false; | |
366 | bool done = false; | |
367 | ||
368 | /* | |
369 | * If dentry is negative, then lower is positive iff this is a | |
370 | * whiteout. | |
371 | */ | |
372 | if (!dentry->d_inode) | |
373 | return oe->opaque; | |
374 | ||
375 | /* Negative upper -> positive lower */ | |
376 | if (!oe->__upperdentry) | |
377 | return true; | |
378 | ||
379 | /* Positive upper -> have to look up lower to see whether it exists */ | |
380 | for (i = 0; !done && !positive && i < poe->numlower; i++) { | |
381 | struct dentry *this; | |
382 | struct dentry *lowerdir = poe->lowerstack[i].dentry; | |
383 | ||
384 | this = lookup_one_len_unlocked(name->name, lowerdir, | |
385 | name->len); | |
386 | if (IS_ERR(this)) { | |
387 | switch (PTR_ERR(this)) { | |
388 | case -ENOENT: | |
389 | case -ENAMETOOLONG: | |
390 | break; | |
391 | ||
392 | default: | |
393 | /* | |
394 | * Assume something is there, we just couldn't | |
395 | * access it. | |
396 | */ | |
397 | positive = true; | |
398 | break; | |
399 | } | |
400 | } else { | |
401 | if (this->d_inode) { | |
402 | positive = !ovl_is_whiteout(this); | |
403 | done = true; | |
404 | } | |
405 | dput(this); | |
406 | } | |
407 | } | |
408 | ||
409 | return positive; | |
410 | } |