1
2
3
4
5
6
7
8
9
10#include <linux/fs.h>
11#include <linux/slab.h>
12#include <linux/namei.h>
13#include <linux/file.h>
14#include <linux/xattr.h>
15#include <linux/rbtree.h>
16#include <linux/security.h>
17#include <linux/cred.h>
18#include "overlayfs.h"
19
20struct ovl_cache_entry {
21 unsigned int len;
22 unsigned int type;
23 u64 ino;
24 struct list_head l_node;
25 struct rb_node node;
26 bool is_whiteout;
27 char name[];
28};
29
30struct ovl_dir_cache {
31 long refcount;
32 u64 version;
33 struct list_head entries;
34};
35
36struct ovl_readdir_data {
37 struct dir_context ctx;
38 bool is_merge;
39 struct rb_root root;
40 struct list_head *list;
41 struct list_head middle;
42 struct dentry *dir;
43 int count;
44 int err;
45};
46
47struct ovl_dir_file {
48 bool is_real;
49 bool is_upper;
50 struct ovl_dir_cache *cache;
51 struct list_head *cursor;
52 struct file *realfile;
53 struct file *upperfile;
54};
55
56static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
57{
58 return container_of(n, struct ovl_cache_entry, node);
59}
60
61static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
62 const char *name, int len)
63{
64 struct rb_node *node = root->rb_node;
65 int cmp;
66
67 while (node) {
68 struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
69
70 cmp = strncmp(name, p->name, len);
71 if (cmp > 0)
72 node = p->node.rb_right;
73 else if (cmp < 0 || len < p->len)
74 node = p->node.rb_left;
75 else
76 return p;
77 }
78
79 return NULL;
80}
81
82static struct ovl_cache_entry *ovl_cache_entry_new(struct dentry *dir,
83 const char *name, int len,
84 u64 ino, unsigned int d_type)
85{
86 struct ovl_cache_entry *p;
87 size_t size = offsetof(struct ovl_cache_entry, name[len + 1]);
88
89 p = kmalloc(size, GFP_KERNEL);
90 if (!p)
91 return NULL;
92
93 memcpy(p->name, name, len);
94 p->name[len] = '\0';
95 p->len = len;
96 p->type = d_type;
97 p->ino = ino;
98 p->is_whiteout = false;
99
100 if (d_type == DT_CHR) {
101 struct dentry *dentry;
102 const struct cred *old_cred;
103 struct cred *override_cred;
104
105 override_cred = prepare_creds();
106 if (!override_cred) {
107 kfree(p);
108 return NULL;
109 }
110
111
112
113
114 cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
115 old_cred = override_creds(override_cred);
116
117 dentry = lookup_one_len(name, dir, len);
118 if (!IS_ERR(dentry)) {
119 p->is_whiteout = ovl_is_whiteout(dentry);
120 dput(dentry);
121 }
122 revert_creds(old_cred);
123 put_cred(override_cred);
124 }
125 return p;
126}
127
128static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
129 const char *name, int len, u64 ino,
130 unsigned int d_type)
131{
132 struct rb_node **newp = &rdd->root.rb_node;
133 struct rb_node *parent = NULL;
134 struct ovl_cache_entry *p;
135
136 while (*newp) {
137 int cmp;
138 struct ovl_cache_entry *tmp;
139
140 parent = *newp;
141 tmp = ovl_cache_entry_from_node(*newp);
142 cmp = strncmp(name, tmp->name, len);
143 if (cmp > 0)
144 newp = &tmp->node.rb_right;
145 else if (cmp < 0 || len < tmp->len)
146 newp = &tmp->node.rb_left;
147 else
148 return 0;
149 }
150
151 p = ovl_cache_entry_new(rdd->dir, name, len, ino, d_type);
152 if (p == NULL)
153 return -ENOMEM;
154
155 list_add_tail(&p->l_node, rdd->list);
156 rb_link_node(&p->node, parent, newp);
157 rb_insert_color(&p->node, &rdd->root);
158
159 return 0;
160}
161
162static int ovl_fill_lower(struct ovl_readdir_data *rdd,
163 const char *name, int namelen,
164 loff_t offset, u64 ino, unsigned int d_type)
165{
166 struct ovl_cache_entry *p;
167
168 p = ovl_cache_entry_find(&rdd->root, name, namelen);
169 if (p) {
170 list_move_tail(&p->l_node, &rdd->middle);
171 } else {
172 p = ovl_cache_entry_new(rdd->dir, name, namelen, ino, d_type);
173 if (p == NULL)
174 rdd->err = -ENOMEM;
175 else
176 list_add_tail(&p->l_node, &rdd->middle);
177 }
178
179 return rdd->err;
180}
181
182void ovl_cache_free(struct list_head *list)
183{
184 struct ovl_cache_entry *p;
185 struct ovl_cache_entry *n;
186
187 list_for_each_entry_safe(p, n, list, l_node)
188 kfree(p);
189
190 INIT_LIST_HEAD(list);
191}
192
193static void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry)
194{
195 struct ovl_dir_cache *cache = od->cache;
196
197 WARN_ON(cache->refcount <= 0);
198 cache->refcount--;
199 if (!cache->refcount) {
200 if (ovl_dir_cache(dentry) == cache)
201 ovl_set_dir_cache(dentry, NULL);
202
203 ovl_cache_free(&cache->entries);
204 kfree(cache);
205 }
206}
207
208static int ovl_fill_merge(struct dir_context *ctx, const char *name,
209 int namelen, loff_t offset, u64 ino,
210 unsigned int d_type)
211{
212 struct ovl_readdir_data *rdd =
213 container_of(ctx, struct ovl_readdir_data, ctx);
214
215 rdd->count++;
216 if (!rdd->is_merge)
217 return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
218 else
219 return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
220}
221
222static inline int ovl_dir_read(struct path *realpath,
223 struct ovl_readdir_data *rdd)
224{
225 struct file *realfile;
226 int err;
227
228 realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY);
229 if (IS_ERR(realfile))
230 return PTR_ERR(realfile);
231
232 rdd->dir = realpath->dentry;
233 rdd->ctx.pos = 0;
234 do {
235 rdd->count = 0;
236 rdd->err = 0;
237 err = iterate_dir(realfile, &rdd->ctx);
238 if (err >= 0)
239 err = rdd->err;
240 } while (!err && rdd->count);
241 fput(realfile);
242
243 return err;
244}
245
246static void ovl_dir_reset(struct file *file)
247{
248 struct ovl_dir_file *od = file->private_data;
249 struct ovl_dir_cache *cache = od->cache;
250 struct dentry *dentry = file->f_path.dentry;
251 enum ovl_path_type type = ovl_path_type(dentry);
252
253 if (cache && ovl_dentry_version_get(dentry) != cache->version) {
254 ovl_cache_put(od, dentry);
255 od->cache = NULL;
256 od->cursor = NULL;
257 }
258 WARN_ON(!od->is_real && !OVL_TYPE_MERGE(type));
259 if (od->is_real && OVL_TYPE_MERGE(type))
260 od->is_real = false;
261}
262
263static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
264{
265 int err;
266 struct path realpath;
267 struct ovl_readdir_data rdd = {
268 .ctx.actor = ovl_fill_merge,
269 .list = list,
270 .root = RB_ROOT,
271 .is_merge = false,
272 };
273 int idx, next;
274
275 for (idx = 0; idx != -1; idx = next) {
276 next = ovl_path_next(idx, dentry, &realpath);
277
278 if (next != -1) {
279 err = ovl_dir_read(&realpath, &rdd);
280 if (err)
281 break;
282 } else {
283
284
285
286
287 list_add(&rdd.middle, rdd.list);
288 rdd.is_merge = true;
289 err = ovl_dir_read(&realpath, &rdd);
290 list_del(&rdd.middle);
291 }
292 }
293 return err;
294}
295
296static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
297{
298 struct list_head *p;
299 loff_t off = 0;
300
301 list_for_each(p, &od->cache->entries) {
302 if (off >= pos)
303 break;
304 off++;
305 }
306
307 od->cursor = p;
308}
309
310static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
311{
312 int res;
313 struct ovl_dir_cache *cache;
314
315 cache = ovl_dir_cache(dentry);
316 if (cache && ovl_dentry_version_get(dentry) == cache->version) {
317 cache->refcount++;
318 return cache;
319 }
320 ovl_set_dir_cache(dentry, NULL);
321
322 cache = kzalloc(sizeof(struct ovl_dir_cache), GFP_KERNEL);
323 if (!cache)
324 return ERR_PTR(-ENOMEM);
325
326 cache->refcount = 1;
327 INIT_LIST_HEAD(&cache->entries);
328
329 res = ovl_dir_read_merged(dentry, &cache->entries);
330 if (res) {
331 ovl_cache_free(&cache->entries);
332 kfree(cache);
333 return ERR_PTR(res);
334 }
335
336 cache->version = ovl_dentry_version_get(dentry);
337 ovl_set_dir_cache(dentry, cache);
338
339 return cache;
340}
341
342static int ovl_iterate(struct file *file, struct dir_context *ctx)
343{
344 struct ovl_dir_file *od = file->private_data;
345 struct dentry *dentry = file->f_path.dentry;
346 struct ovl_cache_entry *p;
347
348 if (!ctx->pos)
349 ovl_dir_reset(file);
350
351 if (od->is_real)
352 return iterate_dir(od->realfile, ctx);
353
354 if (!od->cache) {
355 struct ovl_dir_cache *cache;
356
357 cache = ovl_cache_get(dentry);
358 if (IS_ERR(cache))
359 return PTR_ERR(cache);
360
361 od->cache = cache;
362 ovl_seek_cursor(od, ctx->pos);
363 }
364
365 while (od->cursor != &od->cache->entries) {
366 p = list_entry(od->cursor, struct ovl_cache_entry, l_node);
367 if (!p->is_whiteout)
368 if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
369 break;
370 od->cursor = p->l_node.next;
371 ctx->pos++;
372 }
373 return 0;
374}
375
376static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
377{
378 loff_t res;
379 struct ovl_dir_file *od = file->private_data;
380
381 mutex_lock(&file_inode(file)->i_mutex);
382 if (!file->f_pos)
383 ovl_dir_reset(file);
384
385 if (od->is_real) {
386 res = vfs_llseek(od->realfile, offset, origin);
387 file->f_pos = od->realfile->f_pos;
388 } else {
389 res = -EINVAL;
390
391 switch (origin) {
392 case SEEK_CUR:
393 offset += file->f_pos;
394 break;
395 case SEEK_SET:
396 break;
397 default:
398 goto out_unlock;
399 }
400 if (offset < 0)
401 goto out_unlock;
402
403 if (offset != file->f_pos) {
404 file->f_pos = offset;
405 if (od->cache)
406 ovl_seek_cursor(od, offset);
407 }
408 res = offset;
409 }
410out_unlock:
411 mutex_unlock(&file_inode(file)->i_mutex);
412
413 return res;
414}
415
416static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
417 int datasync)
418{
419 struct ovl_dir_file *od = file->private_data;
420 struct dentry *dentry = file->f_path.dentry;
421 struct file *realfile = od->realfile;
422
423
424
425
426 if (!od->is_upper && OVL_TYPE_UPPER(ovl_path_type(dentry))) {
427 struct inode *inode = file_inode(file);
428
429 realfile = lockless_dereference(od->upperfile);
430 if (!realfile) {
431 struct path upperpath;
432
433 ovl_path_upper(dentry, &upperpath);
434 realfile = ovl_path_open(&upperpath, O_RDONLY);
435 smp_mb__before_spinlock();
436 mutex_lock(&inode->i_mutex);
437 if (!od->upperfile) {
438 if (IS_ERR(realfile)) {
439 mutex_unlock(&inode->i_mutex);
440 return PTR_ERR(realfile);
441 }
442 od->upperfile = realfile;
443 } else {
444
445 if (!IS_ERR(realfile))
446 fput(realfile);
447 realfile = od->upperfile;
448 }
449 mutex_unlock(&inode->i_mutex);
450 }
451 }
452
453 return vfs_fsync_range(realfile, start, end, datasync);
454}
455
456static int ovl_dir_release(struct inode *inode, struct file *file)
457{
458 struct ovl_dir_file *od = file->private_data;
459
460 if (od->cache) {
461 mutex_lock(&inode->i_mutex);
462 ovl_cache_put(od, file->f_path.dentry);
463 mutex_unlock(&inode->i_mutex);
464 }
465 fput(od->realfile);
466 if (od->upperfile)
467 fput(od->upperfile);
468 kfree(od);
469
470 return 0;
471}
472
473static int ovl_dir_open(struct inode *inode, struct file *file)
474{
475 struct path realpath;
476 struct file *realfile;
477 struct ovl_dir_file *od;
478 enum ovl_path_type type;
479
480 od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
481 if (!od)
482 return -ENOMEM;
483
484 type = ovl_path_real(file->f_path.dentry, &realpath);
485 realfile = ovl_path_open(&realpath, file->f_flags);
486 if (IS_ERR(realfile)) {
487 kfree(od);
488 return PTR_ERR(realfile);
489 }
490 od->realfile = realfile;
491 od->is_real = !OVL_TYPE_MERGE(type);
492 od->is_upper = OVL_TYPE_UPPER(type);
493 file->private_data = od;
494
495 return 0;
496}
497
498const struct file_operations ovl_dir_operations = {
499 .read = generic_read_dir,
500 .open = ovl_dir_open,
501 .iterate = ovl_iterate,
502 .llseek = ovl_dir_llseek,
503 .fsync = ovl_dir_fsync,
504 .release = ovl_dir_release,
505};
506
507int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
508{
509 int err;
510 struct ovl_cache_entry *p;
511
512 err = ovl_dir_read_merged(dentry, list);
513 if (err)
514 return err;
515
516 err = 0;
517
518 list_for_each_entry(p, list, l_node) {
519 if (p->is_whiteout)
520 continue;
521
522 if (p->name[0] == '.') {
523 if (p->len == 1)
524 continue;
525 if (p->len == 2 && p->name[1] == '.')
526 continue;
527 }
528 err = -ENOTEMPTY;
529 break;
530 }
531
532 return err;
533}
534
535void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list)
536{
537 struct ovl_cache_entry *p;
538
539 mutex_lock_nested(&upper->d_inode->i_mutex, I_MUTEX_CHILD);
540 list_for_each_entry(p, list, l_node) {
541 struct dentry *dentry;
542
543 if (!p->is_whiteout)
544 continue;
545
546 dentry = lookup_one_len(p->name, upper, p->len);
547 if (IS_ERR(dentry)) {
548 pr_err("overlayfs: lookup '%s/%.*s' failed (%i)\n",
549 upper->d_name.name, p->len, p->name,
550 (int) PTR_ERR(dentry));
551 continue;
552 }
553 ovl_cleanup(upper->d_inode, dentry);
554 dput(dentry);
555 }
556 mutex_unlock(&upper->d_inode->i_mutex);
557}
558
