summaryrefslogtreecommitdiff
path: root/fs/overlayfs/readdir.c
blob: 2a7ef4f8e2a6c37e033b771413fc66f75b567556 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
/*
 *
 * Copyright (C) 2011 Novell Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/namei.h>
#include <linux/file.h>
#include <linux/xattr.h>
#include <linux/rbtree.h>
#include <linux/security.h>
#include <linux/cred.h>
#include "overlayfs.h"

struct ovl_cache_entry {
	unsigned int len;
	unsigned int type;
	u64 ino;
	struct list_head l_node;
	struct rb_node node;
	bool is_whiteout;
	bool is_cursor;
	char name[];
};

struct ovl_dir_cache {
	long refcount;
	u64 version;
	struct list_head entries;
};

struct ovl_readdir_data {
	struct dir_context ctx;
	bool is_merge;
	struct rb_root root;
	struct list_head *list;
	struct list_head middle;
	int count;
	int err;
};

struct ovl_dir_file {
	bool is_real;
	bool is_upper;
	struct ovl_dir_cache *cache;
	struct ovl_cache_entry cursor;
	struct file *realfile;
	struct file *upperfile;
};

static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
{
	return container_of(n, struct ovl_cache_entry, node);
}

static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
						    const char *name, int len)
{
	struct rb_node *node = root->rb_node;
	int cmp;

	while (node) {
		struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);

		cmp = strncmp(name, p->name, len);
		if (cmp > 0)
			node = p->node.rb_right;
		else if (cmp < 0 || len < p->len)
			node = p->node.rb_left;
		else
			return p;
	}

	return NULL;
}

static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
						   u64 ino, unsigned int d_type)
{
	struct ovl_cache_entry *p;
	size_t size = offsetof(struct ovl_cache_entry, name[len + 1]);

	p = kmalloc(size, GFP_KERNEL);
	if (p) {
		memcpy(p->name, name, len);
		p->name[len] = '\0';
		p->len = len;
		p->type = d_type;
		p->ino = ino;
		p->is_whiteout = false;
		p->is_cursor = false;
	}

	return p;
}

static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
				  const char *name, int len, u64 ino,
				  unsigned int d_type)
{
	struct rb_node **newp = &rdd->root.rb_node;
	struct rb_node *parent = NULL;
	struct ovl_cache_entry *p;

	while (*newp) {
		int cmp;
		struct ovl_cache_entry *tmp;

		parent = *newp;
		tmp = ovl_cache_entry_from_node(*newp);
		cmp = strncmp(name, tmp->name, len);
		if (cmp > 0)
			newp = &tmp->node.rb_right;
		else if (cmp < 0 || len < tmp->len)
			newp = &tmp->node.rb_left;
		else
			return 0;
	}

	p = ovl_cache_entry_new(name, len, ino, d_type);
	if (p == NULL)
		return -ENOMEM;

	list_add_tail(&p->l_node, rdd->list);
	rb_link_node(&p->node, parent, newp);
	rb_insert_color(&p->node, &rdd->root);

	return 0;
}

static int ovl_fill_lower(struct ovl_readdir_data *rdd,
			  const char *name, int namelen,
			  loff_t offset, u64 ino, unsigned int d_type)
{
	struct ovl_cache_entry *p;

	p = ovl_cache_entry_find(&rdd->root, name, namelen);
	if (p) {
		list_move_tail(&p->l_node, &rdd->middle);
	} else {
		p = ovl_cache_entry_new(name, namelen, ino, d_type);
		if (p == NULL)
			rdd->err = -ENOMEM;
		else
			list_add_tail(&p->l_node, &rdd->middle);
	}

	return rdd->err;
}

void ovl_cache_free(struct list_head *list)
{
	struct ovl_cache_entry *p;
	struct ovl_cache_entry *n;

	list_for_each_entry_safe(p, n, list, l_node)
		kfree(p);

	INIT_LIST_HEAD(list);
}

static void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry)
{
	struct ovl_dir_cache *cache = od->cache;

	list_del_init(&od->cursor.l_node);
	WARN_ON(cache->refcount <= 0);
	cache->refcount--;
	if (!cache->refcount) {
		if (ovl_dir_cache(dentry) == cache)
			ovl_set_dir_cache(dentry, NULL);

		ovl_cache_free(&cache->entries);
		kfree(cache);
	}
}

static int ovl_fill_merge(void *buf, const char *name, int namelen,
			  loff_t offset, u64 ino, unsigned int d_type)
{
	struct ovl_readdir_data *rdd = buf;

	rdd->count++;
	if (!rdd->is_merge)
		return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
	else
		return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
}

static inline int ovl_dir_read(struct path *realpath,
			       struct ovl_readdir_data *rdd)
{
	struct file *realfile;
	int err;

	realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY);
	if (IS_ERR(realfile))
		return PTR_ERR(realfile);

	rdd->ctx.pos = 0;
	do {
		rdd->count = 0;
		rdd->err = 0;
		err = iterate_dir(realfile, &rdd->ctx);
		if (err >= 0)
			err = rdd->err;
	} while (!err && rdd->count);
	fput(realfile);

	return err;
}

static void ovl_dir_reset(struct file *file)
{
	struct ovl_dir_file *od = file->private_data;
	struct ovl_dir_cache *cache = od->cache;
	struct dentry *dentry = file->f_path.dentry;
	enum ovl_path_type type = ovl_path_type(dentry);

	if (cache && ovl_dentry_version_get(dentry) != cache->version) {
		ovl_cache_put(od, dentry);
		od->cache = NULL;
	}
	WARN_ON(!od->is_real && type != OVL_PATH_MERGE);
	if (od->is_real && type == OVL_PATH_MERGE)
		od->is_real = false;
}

static int ovl_dir_mark_whiteouts(struct dentry *dir,
				  struct ovl_readdir_data *rdd)
{
	struct ovl_cache_entry *p;
	struct dentry *dentry;
	const struct cred *old_cred;
	struct cred *override_cred;

	override_cred = prepare_creds();
	if (!override_cred) {
		ovl_cache_free(rdd->list);
		return -ENOMEM;
	}

	/*
	 * CAP_DAC_OVERRIDE for lookup
	 */
	cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
	old_cred = override_creds(override_cred);

	mutex_lock(&dir->d_inode->i_mutex);
	list_for_each_entry(p, rdd->list, l_node) {
		if (p->is_cursor)
			continue;

		if (p->type != DT_CHR)
			continue;

		dentry = lookup_one_len(p->name, dir, p->len);
		if (IS_ERR(dentry))
			continue;

		p->is_whiteout = ovl_is_whiteout(dentry);
		dput(dentry);
	}
	mutex_unlock(&dir->d_inode->i_mutex);

	revert_creds(old_cred);
	put_cred(override_cred);

	return 0;
}

static inline int ovl_dir_read_merged(struct path *upperpath,
				      struct path *lowerpath,
				      struct list_head *list)
{
	int err;
	struct ovl_readdir_data rdd = {
		.ctx.actor = ovl_fill_merge,
		.list = list,
		.root = RB_ROOT,
		.is_merge = false,
	};

	if (upperpath->dentry) {
		err = ovl_dir_read(upperpath, &rdd);
		if (err)
			goto out;

		if (lowerpath->dentry) {
			err = ovl_dir_mark_whiteouts(upperpath->dentry, &rdd);
			if (err)
				goto out;
		}
	}
	if (lowerpath->dentry) {
		/*
		 * Insert lowerpath entries before upperpath ones, this allows
		 * offsets to be reasonably constant
		 */
		list_add(&rdd.middle, rdd.list);
		rdd.is_merge = true;
		err = ovl_dir_read(lowerpath, &rdd);
		list_del(&rdd.middle);
	}
out:
	return err;
}

static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
{
	struct ovl_cache_entry *p;
	loff_t off = 0;

	list_for_each_entry(p, &od->cache->entries, l_node) {
		if (p->is_cursor)
			continue;
		if (off >= pos)
			break;
		off++;
	}
	list_move_tail(&od->cursor.l_node, &p->l_node);
}

static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
{
	int res;
	struct path lowerpath;
	struct path upperpath;
	struct ovl_dir_cache *cache;

	cache = ovl_dir_cache(dentry);
	if (cache && ovl_dentry_version_get(dentry) == cache->version) {
		cache->refcount++;
		return cache;
	}
	ovl_set_dir_cache(dentry, NULL);

	cache = kzalloc(sizeof(struct ovl_dir_cache), GFP_KERNEL);
	if (!cache)
		return ERR_PTR(-ENOMEM);

	cache->refcount = 1;
	INIT_LIST_HEAD(&cache->entries);

	ovl_path_lower(dentry, &lowerpath);
	ovl_path_upper(dentry, &upperpath);

	res = ovl_dir_read_merged(&upperpath, &lowerpath, &cache->entries);
	if (res) {
		ovl_cache_free(&cache->entries);
		kfree(cache);
		return ERR_PTR(res);
	}

	cache->version = ovl_dentry_version_get(dentry);
	ovl_set_dir_cache(dentry, cache);

	return cache;
}

static int ovl_iterate(struct file *file, struct dir_context *ctx)
{
	struct ovl_dir_file *od = file->private_data;
	struct dentry *dentry = file->f_path.dentry;

	if (!ctx->pos)
		ovl_dir_reset(file);

	if (od->is_real)
		return iterate_dir(od->realfile, ctx);

	if (!od->cache) {
		struct ovl_dir_cache *cache;

		cache = ovl_cache_get(dentry);
		if (IS_ERR(cache))
			return PTR_ERR(cache);

		od->cache = cache;
		ovl_seek_cursor(od, ctx->pos);
	}

	while (od->cursor.l_node.next != &od->cache->entries) {
		struct ovl_cache_entry *p;

		p = list_entry(od->cursor.l_node.next, struct ovl_cache_entry, l_node);
		/* Skip cursors */
		if (!p->is_cursor) {
			if (!p->is_whiteout) {
				if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
					break;
			}
			ctx->pos++;
		}
		list_move(&od->cursor.l_node, &p->l_node);
	}
	return 0;
}

static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
{
	loff_t res;
	struct ovl_dir_file *od = file->private_data;

	mutex_lock(&file_inode(file)->i_mutex);
	if (!file->f_pos)
		ovl_dir_reset(file);

	if (od->is_real) {
		res = vfs_llseek(od->realfile, offset, origin);
		file->f_pos = od->realfile->f_pos;
	} else {
		res = -EINVAL;

		switch (origin) {
		case SEEK_CUR:
			offset += file->f_pos;
			break;
		case SEEK_SET:
			break;
		default:
			goto out_unlock;
		}
		if (offset < 0)
			goto out_unlock;

		if (offset != file->f_pos) {
			file->f_pos = offset;
			if (od->cache)
				ovl_seek_cursor(od, offset);
		}
		res = offset;
	}
out_unlock:
	mutex_unlock(&file_inode(file)->i_mutex);

	return res;
}

static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
			 int datasync)
{
	struct ovl_dir_file *od = file->private_data;
	struct dentry *dentry = file->f_path.dentry;
	struct file *realfile = od->realfile;

	/*
	 * Need to check if we started out being a lower dir, but got copied up
	 */
	if (!od->is_upper && ovl_path_type(dentry) == OVL_PATH_MERGE) {
		struct inode *inode = file_inode(file);

		realfile =lockless_dereference(od->upperfile);
		if (!realfile) {
			struct path upperpath;

			ovl_path_upper(dentry, &upperpath);
			realfile = ovl_path_open(&upperpath, O_RDONLY);
			smp_mb__before_spinlock();
			mutex_lock(&inode->i_mutex);
			if (!od->upperfile) {
				if (IS_ERR(realfile)) {
					mutex_unlock(&inode->i_mutex);
					return PTR_ERR(realfile);
				}
				od->upperfile = realfile;
			} else {
				/* somebody has beaten us to it */
				if (!IS_ERR(realfile))
					fput(realfile);
				realfile = od->upperfile;
			}
			mutex_unlock(&inode->i_mutex);
		}
	}

	return vfs_fsync_range(realfile, start, end, datasync);
}

static int ovl_dir_release(struct inode *inode, struct file *file)
{
	struct ovl_dir_file *od = file->private_data;

	if (od->cache) {
		mutex_lock(&inode->i_mutex);
		ovl_cache_put(od, file->f_path.dentry);
		mutex_unlock(&inode->i_mutex);
	}
	fput(od->realfile);
	if (od->upperfile)
		fput(od->upperfile);
	kfree(od);

	return 0;
}

static int ovl_dir_open(struct inode *inode, struct file *file)
{
	struct path realpath;
	struct file *realfile;
	struct ovl_dir_file *od;
	enum ovl_path_type type;

	od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
	if (!od)
		return -ENOMEM;

	type = ovl_path_real(file->f_path.dentry, &realpath);
	realfile = ovl_path_open(&realpath, file->f_flags);
	if (IS_ERR(realfile)) {
		kfree(od);
		return PTR_ERR(realfile);
	}
	INIT_LIST_HEAD(&od->cursor.l_node);
	od->realfile = realfile;
	od->is_real = (type != OVL_PATH_MERGE);
	od->is_upper = (type != OVL_PATH_LOWER);
	od->cursor.is_cursor = true;
	file->private_data = od;

	return 0;
}

const struct file_operations ovl_dir_operations = {
	.read		= generic_read_dir,
	.open		= ovl_dir_open,
	.iterate	= ovl_iterate,
	.llseek		= ovl_dir_llseek,
	.fsync		= ovl_dir_fsync,
	.release	= ovl_dir_release,
};

int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
{
	int err;
	struct path lowerpath;
	struct path upperpath;
	struct ovl_cache_entry *p;

	ovl_path_upper(dentry, &upperpath);
	ovl_path_lower(dentry, &lowerpath);

	err = ovl_dir_read_merged(&upperpath, &lowerpath, list);
	if (err)
		return err;

	err = 0;

	list_for_each_entry(p, list, l_node) {
		if (p->is_whiteout)
			continue;

		if (p->name[0] == '.') {
			if (p->len == 1)
				continue;
			if (p->len == 2 && p->name[1] == '.')
				continue;
		}
		err = -ENOTEMPTY;
		break;
	}

	return err;
}

void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list)
{
	struct ovl_cache_entry *p;

	mutex_lock_nested(&upper->d_inode->i_mutex, I_MUTEX_CHILD);
	list_for_each_entry(p, list, l_node) {
		struct dentry *dentry;

		if (!p->is_whiteout)
			continue;

		dentry = lookup_one_len(p->name, upper, p->len);
		if (IS_ERR(dentry)) {
			pr_err("overlayfs: lookup '%s/%.*s' failed (%i)\n",
			       upper->d_name.name, p->len, p->name,
			       (int) PTR_ERR(dentry));
			continue;
		}
		ovl_cleanup(upper->d_inode, dentry);
		dput(dentry);
	}
	mutex_unlock(&upper->d_inode->i_mutex);
}