Commit | Line | Data |
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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 | { | |
02b69b28 MS |
157 | const char *s = d->name.name; |
158 | struct dentry *dentry = NULL; | |
159 | int err; | |
160 | ||
161 | if (*s != '/') | |
162 | return ovl_lookup_single(base, d, d->name.name, d->name.len, | |
163 | 0, "", ret); | |
164 | ||
165 | while (*s++ == '/' && !IS_ERR_OR_NULL(base) && d_can_lookup(base)) { | |
166 | const char *next = strchrnul(s, '/'); | |
167 | size_t slen = strlen(s); | |
168 | ||
169 | if (WARN_ON(slen > d->name.len) || | |
170 | WARN_ON(strcmp(d->name.name + d->name.len - slen, s))) | |
171 | return -EIO; | |
172 | ||
173 | err = ovl_lookup_single(base, d, s, next - s, | |
174 | d->name.len - slen, next, &base); | |
175 | dput(dentry); | |
176 | if (err) | |
177 | return err; | |
178 | dentry = base; | |
179 | s = next; | |
180 | } | |
181 | *ret = dentry; | |
182 | return 0; | |
e28edc46 MS |
183 | } |
184 | ||
bbb1e54d MS |
185 | /* |
186 | * Returns next layer in stack starting from top. | |
187 | * Returns -1 if this is the last layer. | |
188 | */ | |
189 | int ovl_path_next(int idx, struct dentry *dentry, struct path *path) | |
190 | { | |
191 | struct ovl_entry *oe = dentry->d_fsdata; | |
192 | ||
193 | BUG_ON(idx < 0); | |
194 | if (idx == 0) { | |
195 | ovl_path_upper(dentry, path); | |
196 | if (path->dentry) | |
197 | return oe->numlower ? 1 : -1; | |
198 | idx++; | |
199 | } | |
200 | BUG_ON(idx > oe->numlower); | |
201 | *path = oe->lowerstack[idx - 1]; | |
202 | ||
203 | return (idx < oe->numlower) ? idx + 1 : -1; | |
204 | } | |
205 | ||
206 | struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, | |
207 | unsigned int flags) | |
208 | { | |
209 | struct ovl_entry *oe; | |
210 | const struct cred *old_cred; | |
6b2d5fe4 | 211 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
bbb1e54d MS |
212 | struct ovl_entry *poe = dentry->d_parent->d_fsdata; |
213 | struct path *stack = NULL; | |
214 | struct dentry *upperdir, *upperdentry = NULL; | |
215 | unsigned int ctr = 0; | |
216 | struct inode *inode = NULL; | |
217 | bool upperopaque = false; | |
02b69b28 | 218 | char *upperredirect = NULL; |
bbb1e54d MS |
219 | struct dentry *this; |
220 | unsigned int i; | |
221 | int err; | |
e28edc46 MS |
222 | struct ovl_lookup_data d = { |
223 | .name = dentry->d_name, | |
224 | .is_dir = false, | |
225 | .opaque = false, | |
226 | .stop = false, | |
227 | .last = !poe->numlower, | |
02b69b28 | 228 | .redirect = NULL, |
e28edc46 | 229 | }; |
bbb1e54d | 230 | |
6b2d5fe4 MS |
231 | if (dentry->d_name.len > ofs->namelen) |
232 | return ERR_PTR(-ENAMETOOLONG); | |
233 | ||
bbb1e54d MS |
234 | old_cred = ovl_override_creds(dentry->d_sb); |
235 | upperdir = ovl_upperdentry_dereference(poe); | |
236 | if (upperdir) { | |
e28edc46 MS |
237 | err = ovl_lookup_layer(upperdir, &d, &upperdentry); |
238 | if (err) | |
bbb1e54d MS |
239 | goto out; |
240 | ||
e28edc46 MS |
241 | if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) { |
242 | dput(upperdentry); | |
243 | err = -EREMOTE; | |
244 | goto out; | |
bbb1e54d | 245 | } |
02b69b28 MS |
246 | |
247 | if (d.redirect) { | |
248 | upperredirect = kstrdup(d.redirect, GFP_KERNEL); | |
249 | if (!upperredirect) | |
250 | goto out_put_upper; | |
251 | if (d.redirect[0] == '/') | |
252 | poe = dentry->d_sb->s_root->d_fsdata; | |
253 | } | |
e28edc46 | 254 | upperopaque = d.opaque; |
bbb1e54d MS |
255 | } |
256 | ||
e28edc46 | 257 | if (!d.stop && poe->numlower) { |
bbb1e54d | 258 | err = -ENOMEM; |
02b69b28 | 259 | stack = kcalloc(ofs->numlower, sizeof(struct path), |
e28edc46 | 260 | GFP_TEMPORARY); |
bbb1e54d MS |
261 | if (!stack) |
262 | goto out_put_upper; | |
263 | } | |
264 | ||
e28edc46 | 265 | for (i = 0; !d.stop && i < poe->numlower; i++) { |
bbb1e54d MS |
266 | struct path lowerpath = poe->lowerstack[i]; |
267 | ||
e28edc46 MS |
268 | d.last = i == poe->numlower - 1; |
269 | err = ovl_lookup_layer(lowerpath.dentry, &d, &this); | |
270 | if (err) | |
bbb1e54d | 271 | goto out_put; |
6b2d5fe4 | 272 | |
bbb1e54d MS |
273 | if (!this) |
274 | continue; | |
bbb1e54d MS |
275 | |
276 | stack[ctr].dentry = this; | |
277 | stack[ctr].mnt = lowerpath.mnt; | |
278 | ctr++; | |
02b69b28 MS |
279 | |
280 | if (d.stop) | |
281 | break; | |
282 | ||
283 | if (d.redirect && | |
284 | d.redirect[0] == '/' && | |
285 | poe != dentry->d_sb->s_root->d_fsdata) { | |
286 | poe = dentry->d_sb->s_root->d_fsdata; | |
287 | ||
288 | /* Find the current layer on the root dentry */ | |
289 | for (i = 0; i < poe->numlower; i++) | |
290 | if (poe->lowerstack[i].mnt == lowerpath.mnt) | |
291 | break; | |
292 | if (WARN_ON(i == poe->numlower)) | |
293 | break; | |
294 | } | |
bbb1e54d MS |
295 | } |
296 | ||
297 | oe = ovl_alloc_entry(ctr); | |
298 | err = -ENOMEM; | |
299 | if (!oe) | |
300 | goto out_put; | |
301 | ||
302 | if (upperdentry || ctr) { | |
303 | struct dentry *realdentry; | |
304 | struct inode *realinode; | |
305 | ||
306 | realdentry = upperdentry ? upperdentry : stack[0].dentry; | |
307 | realinode = d_inode(realdentry); | |
308 | ||
309 | err = -ENOMEM; | |
310 | if (upperdentry && !d_is_dir(upperdentry)) { | |
311 | inode = ovl_get_inode(dentry->d_sb, realinode); | |
312 | } else { | |
313 | inode = ovl_new_inode(dentry->d_sb, realinode->i_mode, | |
314 | realinode->i_rdev); | |
315 | if (inode) | |
316 | ovl_inode_init(inode, realinode, !!upperdentry); | |
317 | } | |
318 | if (!inode) | |
319 | goto out_free_oe; | |
320 | ovl_copyattr(realdentry->d_inode, inode); | |
321 | } | |
322 | ||
323 | revert_creds(old_cred); | |
324 | oe->opaque = upperopaque; | |
02b69b28 | 325 | oe->redirect = upperredirect; |
bbb1e54d MS |
326 | oe->__upperdentry = upperdentry; |
327 | memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr); | |
328 | kfree(stack); | |
02b69b28 | 329 | kfree(d.redirect); |
bbb1e54d MS |
330 | dentry->d_fsdata = oe; |
331 | d_add(dentry, inode); | |
332 | ||
333 | return NULL; | |
334 | ||
335 | out_free_oe: | |
336 | kfree(oe); | |
337 | out_put: | |
338 | for (i = 0; i < ctr; i++) | |
339 | dput(stack[i].dentry); | |
340 | kfree(stack); | |
341 | out_put_upper: | |
342 | dput(upperdentry); | |
02b69b28 | 343 | kfree(upperredirect); |
bbb1e54d | 344 | out: |
02b69b28 | 345 | kfree(d.redirect); |
bbb1e54d MS |
346 | revert_creds(old_cred); |
347 | return ERR_PTR(err); | |
348 | } | |
349 | ||
350 | bool ovl_lower_positive(struct dentry *dentry) | |
351 | { | |
352 | struct ovl_entry *oe = dentry->d_fsdata; | |
353 | struct ovl_entry *poe = dentry->d_parent->d_fsdata; | |
354 | const struct qstr *name = &dentry->d_name; | |
355 | unsigned int i; | |
356 | bool positive = false; | |
357 | bool done = false; | |
358 | ||
359 | /* | |
360 | * If dentry is negative, then lower is positive iff this is a | |
361 | * whiteout. | |
362 | */ | |
363 | if (!dentry->d_inode) | |
364 | return oe->opaque; | |
365 | ||
366 | /* Negative upper -> positive lower */ | |
367 | if (!oe->__upperdentry) | |
368 | return true; | |
369 | ||
370 | /* Positive upper -> have to look up lower to see whether it exists */ | |
371 | for (i = 0; !done && !positive && i < poe->numlower; i++) { | |
372 | struct dentry *this; | |
373 | struct dentry *lowerdir = poe->lowerstack[i].dentry; | |
374 | ||
375 | this = lookup_one_len_unlocked(name->name, lowerdir, | |
376 | name->len); | |
377 | if (IS_ERR(this)) { | |
378 | switch (PTR_ERR(this)) { | |
379 | case -ENOENT: | |
380 | case -ENAMETOOLONG: | |
381 | break; | |
382 | ||
383 | default: | |
384 | /* | |
385 | * Assume something is there, we just couldn't | |
386 | * access it. | |
387 | */ | |
388 | positive = true; | |
389 | break; | |
390 | } | |
391 | } else { | |
392 | if (this->d_inode) { | |
393 | positive = !ovl_is_whiteout(this); | |
394 | done = true; | |
395 | } | |
396 | dput(this); | |
397 | } | |
398 | } | |
399 | ||
400 | return positive; | |
401 | } |