xref: /openbmc/linux/drivers/md/dm-verity-target.c (revision 15e3ae36)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2012 Red Hat, Inc.
4  *
5  * Author: Mikulas Patocka <mpatocka@redhat.com>
6  *
7  * Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
8  *
9  * In the file "/sys/module/dm_verity/parameters/prefetch_cluster" you can set
10  * default prefetch value. Data are read in "prefetch_cluster" chunks from the
11  * hash device. Setting this greatly improves performance when data and hash
12  * are on the same disk on different partitions on devices with poor random
13  * access behavior.
14  */
15 
16 #include "dm-verity.h"
17 #include "dm-verity-fec.h"
18 #include "dm-verity-verify-sig.h"
19 #include <linux/module.h>
20 #include <linux/reboot.h>
21 
22 #define DM_MSG_PREFIX			"verity"
23 
24 #define DM_VERITY_ENV_LENGTH		42
25 #define DM_VERITY_ENV_VAR_NAME		"DM_VERITY_ERR_BLOCK_NR"
26 
27 #define DM_VERITY_DEFAULT_PREFETCH_SIZE	262144
28 
29 #define DM_VERITY_MAX_CORRUPTED_ERRS	100
30 
31 #define DM_VERITY_OPT_LOGGING		"ignore_corruption"
32 #define DM_VERITY_OPT_RESTART		"restart_on_corruption"
33 #define DM_VERITY_OPT_IGN_ZEROES	"ignore_zero_blocks"
34 #define DM_VERITY_OPT_AT_MOST_ONCE	"check_at_most_once"
35 
36 #define DM_VERITY_OPTS_MAX		(2 + DM_VERITY_OPTS_FEC + \
37 					 DM_VERITY_ROOT_HASH_VERIFICATION_OPTS)
38 
39 static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
40 
41 module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
42 
43 struct dm_verity_prefetch_work {
44 	struct work_struct work;
45 	struct dm_verity *v;
46 	sector_t block;
47 	unsigned n_blocks;
48 };
49 
50 /*
51  * Auxiliary structure appended to each dm-bufio buffer. If the value
52  * hash_verified is nonzero, hash of the block has been verified.
53  *
54  * The variable hash_verified is set to 0 when allocating the buffer, then
55  * it can be changed to 1 and it is never reset to 0 again.
56  *
57  * There is no lock around this value, a race condition can at worst cause
58  * that multiple processes verify the hash of the same buffer simultaneously
59  * and write 1 to hash_verified simultaneously.
60  * This condition is harmless, so we don't need locking.
61  */
62 struct buffer_aux {
63 	int hash_verified;
64 };
65 
66 /*
67  * Initialize struct buffer_aux for a freshly created buffer.
68  */
69 static void dm_bufio_alloc_callback(struct dm_buffer *buf)
70 {
71 	struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
72 
73 	aux->hash_verified = 0;
74 }
75 
76 /*
77  * Translate input sector number to the sector number on the target device.
78  */
79 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
80 {
81 	return v->data_start + dm_target_offset(v->ti, bi_sector);
82 }
83 
84 /*
85  * Return hash position of a specified block at a specified tree level
86  * (0 is the lowest level).
87  * The lowest "hash_per_block_bits"-bits of the result denote hash position
88  * inside a hash block. The remaining bits denote location of the hash block.
89  */
90 static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
91 					 int level)
92 {
93 	return block >> (level * v->hash_per_block_bits);
94 }
95 
96 static int verity_hash_update(struct dm_verity *v, struct ahash_request *req,
97 				const u8 *data, size_t len,
98 				struct crypto_wait *wait)
99 {
100 	struct scatterlist sg;
101 
102 	if (likely(!is_vmalloc_addr(data))) {
103 		sg_init_one(&sg, data, len);
104 		ahash_request_set_crypt(req, &sg, NULL, len);
105 		return crypto_wait_req(crypto_ahash_update(req), wait);
106 	} else {
107 		do {
108 			int r;
109 			size_t this_step = min_t(size_t, len, PAGE_SIZE - offset_in_page(data));
110 			flush_kernel_vmap_range((void *)data, this_step);
111 			sg_init_table(&sg, 1);
112 			sg_set_page(&sg, vmalloc_to_page(data), this_step, offset_in_page(data));
113 			ahash_request_set_crypt(req, &sg, NULL, this_step);
114 			r = crypto_wait_req(crypto_ahash_update(req), wait);
115 			if (unlikely(r))
116 				return r;
117 			data += this_step;
118 			len -= this_step;
119 		} while (len);
120 		return 0;
121 	}
122 }
123 
124 /*
125  * Wrapper for crypto_ahash_init, which handles verity salting.
126  */
127 static int verity_hash_init(struct dm_verity *v, struct ahash_request *req,
128 				struct crypto_wait *wait)
129 {
130 	int r;
131 
132 	ahash_request_set_tfm(req, v->tfm);
133 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP |
134 					CRYPTO_TFM_REQ_MAY_BACKLOG,
135 					crypto_req_done, (void *)wait);
136 	crypto_init_wait(wait);
137 
138 	r = crypto_wait_req(crypto_ahash_init(req), wait);
139 
140 	if (unlikely(r < 0)) {
141 		DMERR("crypto_ahash_init failed: %d", r);
142 		return r;
143 	}
144 
145 	if (likely(v->salt_size && (v->version >= 1)))
146 		r = verity_hash_update(v, req, v->salt, v->salt_size, wait);
147 
148 	return r;
149 }
150 
151 static int verity_hash_final(struct dm_verity *v, struct ahash_request *req,
152 			     u8 *digest, struct crypto_wait *wait)
153 {
154 	int r;
155 
156 	if (unlikely(v->salt_size && (!v->version))) {
157 		r = verity_hash_update(v, req, v->salt, v->salt_size, wait);
158 
159 		if (r < 0) {
160 			DMERR("verity_hash_final failed updating salt: %d", r);
161 			goto out;
162 		}
163 	}
164 
165 	ahash_request_set_crypt(req, NULL, digest, 0);
166 	r = crypto_wait_req(crypto_ahash_final(req), wait);
167 out:
168 	return r;
169 }
170 
171 int verity_hash(struct dm_verity *v, struct ahash_request *req,
172 		const u8 *data, size_t len, u8 *digest)
173 {
174 	int r;
175 	struct crypto_wait wait;
176 
177 	r = verity_hash_init(v, req, &wait);
178 	if (unlikely(r < 0))
179 		goto out;
180 
181 	r = verity_hash_update(v, req, data, len, &wait);
182 	if (unlikely(r < 0))
183 		goto out;
184 
185 	r = verity_hash_final(v, req, digest, &wait);
186 
187 out:
188 	return r;
189 }
190 
191 static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
192 				 sector_t *hash_block, unsigned *offset)
193 {
194 	sector_t position = verity_position_at_level(v, block, level);
195 	unsigned idx;
196 
197 	*hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
198 
199 	if (!offset)
200 		return;
201 
202 	idx = position & ((1 << v->hash_per_block_bits) - 1);
203 	if (!v->version)
204 		*offset = idx * v->digest_size;
205 	else
206 		*offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
207 }
208 
209 /*
210  * Handle verification errors.
211  */
212 static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
213 			     unsigned long long block)
214 {
215 	char verity_env[DM_VERITY_ENV_LENGTH];
216 	char *envp[] = { verity_env, NULL };
217 	const char *type_str = "";
218 	struct mapped_device *md = dm_table_get_md(v->ti->table);
219 
220 	/* Corruption should be visible in device status in all modes */
221 	v->hash_failed = 1;
222 
223 	if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
224 		goto out;
225 
226 	v->corrupted_errs++;
227 
228 	switch (type) {
229 	case DM_VERITY_BLOCK_TYPE_DATA:
230 		type_str = "data";
231 		break;
232 	case DM_VERITY_BLOCK_TYPE_METADATA:
233 		type_str = "metadata";
234 		break;
235 	default:
236 		BUG();
237 	}
238 
239 	DMERR_LIMIT("%s: %s block %llu is corrupted", v->data_dev->name,
240 		    type_str, block);
241 
242 	if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
243 		DMERR("%s: reached maximum errors", v->data_dev->name);
244 
245 	snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
246 		DM_VERITY_ENV_VAR_NAME, type, block);
247 
248 	kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
249 
250 out:
251 	if (v->mode == DM_VERITY_MODE_LOGGING)
252 		return 0;
253 
254 	if (v->mode == DM_VERITY_MODE_RESTART)
255 		kernel_restart("dm-verity device corrupted");
256 
257 	return 1;
258 }
259 
260 /*
261  * Verify hash of a metadata block pertaining to the specified data block
262  * ("block" argument) at a specified level ("level" argument).
263  *
264  * On successful return, verity_io_want_digest(v, io) contains the hash value
265  * for a lower tree level or for the data block (if we're at the lowest level).
266  *
267  * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
268  * If "skip_unverified" is false, unverified buffer is hashed and verified
269  * against current value of verity_io_want_digest(v, io).
270  */
271 static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
272 			       sector_t block, int level, bool skip_unverified,
273 			       u8 *want_digest)
274 {
275 	struct dm_buffer *buf;
276 	struct buffer_aux *aux;
277 	u8 *data;
278 	int r;
279 	sector_t hash_block;
280 	unsigned offset;
281 
282 	verity_hash_at_level(v, block, level, &hash_block, &offset);
283 
284 	data = dm_bufio_read(v->bufio, hash_block, &buf);
285 	if (IS_ERR(data))
286 		return PTR_ERR(data);
287 
288 	aux = dm_bufio_get_aux_data(buf);
289 
290 	if (!aux->hash_verified) {
291 		if (skip_unverified) {
292 			r = 1;
293 			goto release_ret_r;
294 		}
295 
296 		r = verity_hash(v, verity_io_hash_req(v, io),
297 				data, 1 << v->hash_dev_block_bits,
298 				verity_io_real_digest(v, io));
299 		if (unlikely(r < 0))
300 			goto release_ret_r;
301 
302 		if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
303 				  v->digest_size) == 0))
304 			aux->hash_verified = 1;
305 		else if (verity_fec_decode(v, io,
306 					   DM_VERITY_BLOCK_TYPE_METADATA,
307 					   hash_block, data, NULL) == 0)
308 			aux->hash_verified = 1;
309 		else if (verity_handle_err(v,
310 					   DM_VERITY_BLOCK_TYPE_METADATA,
311 					   hash_block)) {
312 			r = -EIO;
313 			goto release_ret_r;
314 		}
315 	}
316 
317 	data += offset;
318 	memcpy(want_digest, data, v->digest_size);
319 	r = 0;
320 
321 release_ret_r:
322 	dm_bufio_release(buf);
323 	return r;
324 }
325 
326 /*
327  * Find a hash for a given block, write it to digest and verify the integrity
328  * of the hash tree if necessary.
329  */
330 int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
331 			  sector_t block, u8 *digest, bool *is_zero)
332 {
333 	int r = 0, i;
334 
335 	if (likely(v->levels)) {
336 		/*
337 		 * First, we try to get the requested hash for
338 		 * the current block. If the hash block itself is
339 		 * verified, zero is returned. If it isn't, this
340 		 * function returns 1 and we fall back to whole
341 		 * chain verification.
342 		 */
343 		r = verity_verify_level(v, io, block, 0, true, digest);
344 		if (likely(r <= 0))
345 			goto out;
346 	}
347 
348 	memcpy(digest, v->root_digest, v->digest_size);
349 
350 	for (i = v->levels - 1; i >= 0; i--) {
351 		r = verity_verify_level(v, io, block, i, false, digest);
352 		if (unlikely(r))
353 			goto out;
354 	}
355 out:
356 	if (!r && v->zero_digest)
357 		*is_zero = !memcmp(v->zero_digest, digest, v->digest_size);
358 	else
359 		*is_zero = false;
360 
361 	return r;
362 }
363 
364 /*
365  * Calculates the digest for the given bio
366  */
367 static int verity_for_io_block(struct dm_verity *v, struct dm_verity_io *io,
368 			       struct bvec_iter *iter, struct crypto_wait *wait)
369 {
370 	unsigned int todo = 1 << v->data_dev_block_bits;
371 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
372 	struct scatterlist sg;
373 	struct ahash_request *req = verity_io_hash_req(v, io);
374 
375 	do {
376 		int r;
377 		unsigned int len;
378 		struct bio_vec bv = bio_iter_iovec(bio, *iter);
379 
380 		sg_init_table(&sg, 1);
381 
382 		len = bv.bv_len;
383 
384 		if (likely(len >= todo))
385 			len = todo;
386 		/*
387 		 * Operating on a single page at a time looks suboptimal
388 		 * until you consider the typical block size is 4,096B.
389 		 * Going through this loops twice should be very rare.
390 		 */
391 		sg_set_page(&sg, bv.bv_page, len, bv.bv_offset);
392 		ahash_request_set_crypt(req, &sg, NULL, len);
393 		r = crypto_wait_req(crypto_ahash_update(req), wait);
394 
395 		if (unlikely(r < 0)) {
396 			DMERR("verity_for_io_block crypto op failed: %d", r);
397 			return r;
398 		}
399 
400 		bio_advance_iter(bio, iter, len);
401 		todo -= len;
402 	} while (todo);
403 
404 	return 0;
405 }
406 
407 /*
408  * Calls function process for 1 << v->data_dev_block_bits bytes in the bio_vec
409  * starting from iter.
410  */
411 int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
412 			struct bvec_iter *iter,
413 			int (*process)(struct dm_verity *v,
414 				       struct dm_verity_io *io, u8 *data,
415 				       size_t len))
416 {
417 	unsigned todo = 1 << v->data_dev_block_bits;
418 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
419 
420 	do {
421 		int r;
422 		u8 *page;
423 		unsigned len;
424 		struct bio_vec bv = bio_iter_iovec(bio, *iter);
425 
426 		page = kmap_atomic(bv.bv_page);
427 		len = bv.bv_len;
428 
429 		if (likely(len >= todo))
430 			len = todo;
431 
432 		r = process(v, io, page + bv.bv_offset, len);
433 		kunmap_atomic(page);
434 
435 		if (r < 0)
436 			return r;
437 
438 		bio_advance_iter(bio, iter, len);
439 		todo -= len;
440 	} while (todo);
441 
442 	return 0;
443 }
444 
445 static int verity_bv_zero(struct dm_verity *v, struct dm_verity_io *io,
446 			  u8 *data, size_t len)
447 {
448 	memset(data, 0, len);
449 	return 0;
450 }
451 
452 /*
453  * Moves the bio iter one data block forward.
454  */
455 static inline void verity_bv_skip_block(struct dm_verity *v,
456 					struct dm_verity_io *io,
457 					struct bvec_iter *iter)
458 {
459 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
460 
461 	bio_advance_iter(bio, iter, 1 << v->data_dev_block_bits);
462 }
463 
464 /*
465  * Verify one "dm_verity_io" structure.
466  */
467 static int verity_verify_io(struct dm_verity_io *io)
468 {
469 	bool is_zero;
470 	struct dm_verity *v = io->v;
471 	struct bvec_iter start;
472 	unsigned b;
473 	struct crypto_wait wait;
474 
475 	for (b = 0; b < io->n_blocks; b++) {
476 		int r;
477 		sector_t cur_block = io->block + b;
478 		struct ahash_request *req = verity_io_hash_req(v, io);
479 
480 		if (v->validated_blocks &&
481 		    likely(test_bit(cur_block, v->validated_blocks))) {
482 			verity_bv_skip_block(v, io, &io->iter);
483 			continue;
484 		}
485 
486 		r = verity_hash_for_block(v, io, cur_block,
487 					  verity_io_want_digest(v, io),
488 					  &is_zero);
489 		if (unlikely(r < 0))
490 			return r;
491 
492 		if (is_zero) {
493 			/*
494 			 * If we expect a zero block, don't validate, just
495 			 * return zeros.
496 			 */
497 			r = verity_for_bv_block(v, io, &io->iter,
498 						verity_bv_zero);
499 			if (unlikely(r < 0))
500 				return r;
501 
502 			continue;
503 		}
504 
505 		r = verity_hash_init(v, req, &wait);
506 		if (unlikely(r < 0))
507 			return r;
508 
509 		start = io->iter;
510 		r = verity_for_io_block(v, io, &io->iter, &wait);
511 		if (unlikely(r < 0))
512 			return r;
513 
514 		r = verity_hash_final(v, req, verity_io_real_digest(v, io),
515 					&wait);
516 		if (unlikely(r < 0))
517 			return r;
518 
519 		if (likely(memcmp(verity_io_real_digest(v, io),
520 				  verity_io_want_digest(v, io), v->digest_size) == 0)) {
521 			if (v->validated_blocks)
522 				set_bit(cur_block, v->validated_blocks);
523 			continue;
524 		}
525 		else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
526 					   cur_block, NULL, &start) == 0)
527 			continue;
528 		else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
529 					   cur_block))
530 			return -EIO;
531 	}
532 
533 	return 0;
534 }
535 
536 /*
537  * End one "io" structure with a given error.
538  */
539 static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)
540 {
541 	struct dm_verity *v = io->v;
542 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
543 
544 	bio->bi_end_io = io->orig_bi_end_io;
545 	bio->bi_status = status;
546 
547 	verity_fec_finish_io(io);
548 
549 	bio_endio(bio);
550 }
551 
552 static void verity_work(struct work_struct *w)
553 {
554 	struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
555 
556 	verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));
557 }
558 
559 static void verity_end_io(struct bio *bio)
560 {
561 	struct dm_verity_io *io = bio->bi_private;
562 
563 	if (bio->bi_status && !verity_fec_is_enabled(io->v)) {
564 		verity_finish_io(io, bio->bi_status);
565 		return;
566 	}
567 
568 	INIT_WORK(&io->work, verity_work);
569 	queue_work(io->v->verify_wq, &io->work);
570 }
571 
572 /*
573  * Prefetch buffers for the specified io.
574  * The root buffer is not prefetched, it is assumed that it will be cached
575  * all the time.
576  */
577 static void verity_prefetch_io(struct work_struct *work)
578 {
579 	struct dm_verity_prefetch_work *pw =
580 		container_of(work, struct dm_verity_prefetch_work, work);
581 	struct dm_verity *v = pw->v;
582 	int i;
583 
584 	for (i = v->levels - 2; i >= 0; i--) {
585 		sector_t hash_block_start;
586 		sector_t hash_block_end;
587 		verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
588 		verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
589 		if (!i) {
590 			unsigned cluster = READ_ONCE(dm_verity_prefetch_cluster);
591 
592 			cluster >>= v->data_dev_block_bits;
593 			if (unlikely(!cluster))
594 				goto no_prefetch_cluster;
595 
596 			if (unlikely(cluster & (cluster - 1)))
597 				cluster = 1 << __fls(cluster);
598 
599 			hash_block_start &= ~(sector_t)(cluster - 1);
600 			hash_block_end |= cluster - 1;
601 			if (unlikely(hash_block_end >= v->hash_blocks))
602 				hash_block_end = v->hash_blocks - 1;
603 		}
604 no_prefetch_cluster:
605 		dm_bufio_prefetch(v->bufio, hash_block_start,
606 				  hash_block_end - hash_block_start + 1);
607 	}
608 
609 	kfree(pw);
610 }
611 
612 static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
613 {
614 	sector_t block = io->block;
615 	unsigned int n_blocks = io->n_blocks;
616 	struct dm_verity_prefetch_work *pw;
617 
618 	if (v->validated_blocks) {
619 		while (n_blocks && test_bit(block, v->validated_blocks)) {
620 			block++;
621 			n_blocks--;
622 		}
623 		while (n_blocks && test_bit(block + n_blocks - 1,
624 					    v->validated_blocks))
625 			n_blocks--;
626 		if (!n_blocks)
627 			return;
628 	}
629 
630 	pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
631 		GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
632 
633 	if (!pw)
634 		return;
635 
636 	INIT_WORK(&pw->work, verity_prefetch_io);
637 	pw->v = v;
638 	pw->block = block;
639 	pw->n_blocks = n_blocks;
640 	queue_work(v->verify_wq, &pw->work);
641 }
642 
643 /*
644  * Bio map function. It allocates dm_verity_io structure and bio vector and
645  * fills them. Then it issues prefetches and the I/O.
646  */
647 static int verity_map(struct dm_target *ti, struct bio *bio)
648 {
649 	struct dm_verity *v = ti->private;
650 	struct dm_verity_io *io;
651 
652 	bio_set_dev(bio, v->data_dev->bdev);
653 	bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
654 
655 	if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
656 	    ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
657 		DMERR_LIMIT("unaligned io");
658 		return DM_MAPIO_KILL;
659 	}
660 
661 	if (bio_end_sector(bio) >>
662 	    (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
663 		DMERR_LIMIT("io out of range");
664 		return DM_MAPIO_KILL;
665 	}
666 
667 	if (bio_data_dir(bio) == WRITE)
668 		return DM_MAPIO_KILL;
669 
670 	io = dm_per_bio_data(bio, ti->per_io_data_size);
671 	io->v = v;
672 	io->orig_bi_end_io = bio->bi_end_io;
673 	io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
674 	io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
675 
676 	bio->bi_end_io = verity_end_io;
677 	bio->bi_private = io;
678 	io->iter = bio->bi_iter;
679 
680 	verity_fec_init_io(io);
681 
682 	verity_submit_prefetch(v, io);
683 
684 	generic_make_request(bio);
685 
686 	return DM_MAPIO_SUBMITTED;
687 }
688 
689 /*
690  * Status: V (valid) or C (corruption found)
691  */
692 static void verity_status(struct dm_target *ti, status_type_t type,
693 			  unsigned status_flags, char *result, unsigned maxlen)
694 {
695 	struct dm_verity *v = ti->private;
696 	unsigned args = 0;
697 	unsigned sz = 0;
698 	unsigned x;
699 
700 	switch (type) {
701 	case STATUSTYPE_INFO:
702 		DMEMIT("%c", v->hash_failed ? 'C' : 'V');
703 		break;
704 	case STATUSTYPE_TABLE:
705 		DMEMIT("%u %s %s %u %u %llu %llu %s ",
706 			v->version,
707 			v->data_dev->name,
708 			v->hash_dev->name,
709 			1 << v->data_dev_block_bits,
710 			1 << v->hash_dev_block_bits,
711 			(unsigned long long)v->data_blocks,
712 			(unsigned long long)v->hash_start,
713 			v->alg_name
714 			);
715 		for (x = 0; x < v->digest_size; x++)
716 			DMEMIT("%02x", v->root_digest[x]);
717 		DMEMIT(" ");
718 		if (!v->salt_size)
719 			DMEMIT("-");
720 		else
721 			for (x = 0; x < v->salt_size; x++)
722 				DMEMIT("%02x", v->salt[x]);
723 		if (v->mode != DM_VERITY_MODE_EIO)
724 			args++;
725 		if (verity_fec_is_enabled(v))
726 			args += DM_VERITY_OPTS_FEC;
727 		if (v->zero_digest)
728 			args++;
729 		if (v->validated_blocks)
730 			args++;
731 		if (v->signature_key_desc)
732 			args += DM_VERITY_ROOT_HASH_VERIFICATION_OPTS;
733 		if (!args)
734 			return;
735 		DMEMIT(" %u", args);
736 		if (v->mode != DM_VERITY_MODE_EIO) {
737 			DMEMIT(" ");
738 			switch (v->mode) {
739 			case DM_VERITY_MODE_LOGGING:
740 				DMEMIT(DM_VERITY_OPT_LOGGING);
741 				break;
742 			case DM_VERITY_MODE_RESTART:
743 				DMEMIT(DM_VERITY_OPT_RESTART);
744 				break;
745 			default:
746 				BUG();
747 			}
748 		}
749 		if (v->zero_digest)
750 			DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);
751 		if (v->validated_blocks)
752 			DMEMIT(" " DM_VERITY_OPT_AT_MOST_ONCE);
753 		sz = verity_fec_status_table(v, sz, result, maxlen);
754 		if (v->signature_key_desc)
755 			DMEMIT(" " DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY
756 				" %s", v->signature_key_desc);
757 		break;
758 	}
759 }
760 
761 static int verity_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
762 {
763 	struct dm_verity *v = ti->private;
764 
765 	*bdev = v->data_dev->bdev;
766 
767 	if (v->data_start ||
768 	    ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
769 		return 1;
770 	return 0;
771 }
772 
773 static int verity_iterate_devices(struct dm_target *ti,
774 				  iterate_devices_callout_fn fn, void *data)
775 {
776 	struct dm_verity *v = ti->private;
777 
778 	return fn(ti, v->data_dev, v->data_start, ti->len, data);
779 }
780 
781 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
782 {
783 	struct dm_verity *v = ti->private;
784 
785 	if (limits->logical_block_size < 1 << v->data_dev_block_bits)
786 		limits->logical_block_size = 1 << v->data_dev_block_bits;
787 
788 	if (limits->physical_block_size < 1 << v->data_dev_block_bits)
789 		limits->physical_block_size = 1 << v->data_dev_block_bits;
790 
791 	blk_limits_io_min(limits, limits->logical_block_size);
792 }
793 
794 static void verity_dtr(struct dm_target *ti)
795 {
796 	struct dm_verity *v = ti->private;
797 
798 	if (v->verify_wq)
799 		destroy_workqueue(v->verify_wq);
800 
801 	if (v->bufio)
802 		dm_bufio_client_destroy(v->bufio);
803 
804 	kvfree(v->validated_blocks);
805 	kfree(v->salt);
806 	kfree(v->root_digest);
807 	kfree(v->zero_digest);
808 
809 	if (v->tfm)
810 		crypto_free_ahash(v->tfm);
811 
812 	kfree(v->alg_name);
813 
814 	if (v->hash_dev)
815 		dm_put_device(ti, v->hash_dev);
816 
817 	if (v->data_dev)
818 		dm_put_device(ti, v->data_dev);
819 
820 	verity_fec_dtr(v);
821 
822 	kfree(v->signature_key_desc);
823 
824 	kfree(v);
825 }
826 
827 static int verity_alloc_most_once(struct dm_verity *v)
828 {
829 	struct dm_target *ti = v->ti;
830 
831 	/* the bitset can only handle INT_MAX blocks */
832 	if (v->data_blocks > INT_MAX) {
833 		ti->error = "device too large to use check_at_most_once";
834 		return -E2BIG;
835 	}
836 
837 	v->validated_blocks = kvcalloc(BITS_TO_LONGS(v->data_blocks),
838 				       sizeof(unsigned long),
839 				       GFP_KERNEL);
840 	if (!v->validated_blocks) {
841 		ti->error = "failed to allocate bitset for check_at_most_once";
842 		return -ENOMEM;
843 	}
844 
845 	return 0;
846 }
847 
848 static int verity_alloc_zero_digest(struct dm_verity *v)
849 {
850 	int r = -ENOMEM;
851 	struct ahash_request *req;
852 	u8 *zero_data;
853 
854 	v->zero_digest = kmalloc(v->digest_size, GFP_KERNEL);
855 
856 	if (!v->zero_digest)
857 		return r;
858 
859 	req = kmalloc(v->ahash_reqsize, GFP_KERNEL);
860 
861 	if (!req)
862 		return r; /* verity_dtr will free zero_digest */
863 
864 	zero_data = kzalloc(1 << v->data_dev_block_bits, GFP_KERNEL);
865 
866 	if (!zero_data)
867 		goto out;
868 
869 	r = verity_hash(v, req, zero_data, 1 << v->data_dev_block_bits,
870 			v->zero_digest);
871 
872 out:
873 	kfree(req);
874 	kfree(zero_data);
875 
876 	return r;
877 }
878 
879 static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
880 				 struct dm_verity_sig_opts *verify_args)
881 {
882 	int r;
883 	unsigned argc;
884 	struct dm_target *ti = v->ti;
885 	const char *arg_name;
886 
887 	static const struct dm_arg _args[] = {
888 		{0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
889 	};
890 
891 	r = dm_read_arg_group(_args, as, &argc, &ti->error);
892 	if (r)
893 		return -EINVAL;
894 
895 	if (!argc)
896 		return 0;
897 
898 	do {
899 		arg_name = dm_shift_arg(as);
900 		argc--;
901 
902 		if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING)) {
903 			v->mode = DM_VERITY_MODE_LOGGING;
904 			continue;
905 
906 		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) {
907 			v->mode = DM_VERITY_MODE_RESTART;
908 			continue;
909 
910 		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
911 			r = verity_alloc_zero_digest(v);
912 			if (r) {
913 				ti->error = "Cannot allocate zero digest";
914 				return r;
915 			}
916 			continue;
917 
918 		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_AT_MOST_ONCE)) {
919 			r = verity_alloc_most_once(v);
920 			if (r)
921 				return r;
922 			continue;
923 
924 		} else if (verity_is_fec_opt_arg(arg_name)) {
925 			r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
926 			if (r)
927 				return r;
928 			continue;
929 		} else if (verity_verify_is_sig_opt_arg(arg_name)) {
930 			r = verity_verify_sig_parse_opt_args(as, v,
931 							     verify_args,
932 							     &argc, arg_name);
933 			if (r)
934 				return r;
935 			continue;
936 
937 		}
938 
939 		ti->error = "Unrecognized verity feature request";
940 		return -EINVAL;
941 	} while (argc && !r);
942 
943 	return r;
944 }
945 
946 /*
947  * Target parameters:
948  *	<version>	The current format is version 1.
949  *			Vsn 0 is compatible with original Chromium OS releases.
950  *	<data device>
951  *	<hash device>
952  *	<data block size>
953  *	<hash block size>
954  *	<the number of data blocks>
955  *	<hash start block>
956  *	<algorithm>
957  *	<digest>
958  *	<salt>		Hex string or "-" if no salt.
959  */
960 static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
961 {
962 	struct dm_verity *v;
963 	struct dm_verity_sig_opts verify_args = {0};
964 	struct dm_arg_set as;
965 	unsigned int num;
966 	unsigned long long num_ll;
967 	int r;
968 	int i;
969 	sector_t hash_position;
970 	char dummy;
971 	char *root_hash_digest_to_validate;
972 
973 	v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
974 	if (!v) {
975 		ti->error = "Cannot allocate verity structure";
976 		return -ENOMEM;
977 	}
978 	ti->private = v;
979 	v->ti = ti;
980 
981 	r = verity_fec_ctr_alloc(v);
982 	if (r)
983 		goto bad;
984 
985 	if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
986 		ti->error = "Device must be readonly";
987 		r = -EINVAL;
988 		goto bad;
989 	}
990 
991 	if (argc < 10) {
992 		ti->error = "Not enough arguments";
993 		r = -EINVAL;
994 		goto bad;
995 	}
996 
997 	if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
998 	    num > 1) {
999 		ti->error = "Invalid version";
1000 		r = -EINVAL;
1001 		goto bad;
1002 	}
1003 	v->version = num;
1004 
1005 	r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
1006 	if (r) {
1007 		ti->error = "Data device lookup failed";
1008 		goto bad;
1009 	}
1010 
1011 	r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
1012 	if (r) {
1013 		ti->error = "Hash device lookup failed";
1014 		goto bad;
1015 	}
1016 
1017 	if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
1018 	    !num || (num & (num - 1)) ||
1019 	    num < bdev_logical_block_size(v->data_dev->bdev) ||
1020 	    num > PAGE_SIZE) {
1021 		ti->error = "Invalid data device block size";
1022 		r = -EINVAL;
1023 		goto bad;
1024 	}
1025 	v->data_dev_block_bits = __ffs(num);
1026 
1027 	if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
1028 	    !num || (num & (num - 1)) ||
1029 	    num < bdev_logical_block_size(v->hash_dev->bdev) ||
1030 	    num > INT_MAX) {
1031 		ti->error = "Invalid hash device block size";
1032 		r = -EINVAL;
1033 		goto bad;
1034 	}
1035 	v->hash_dev_block_bits = __ffs(num);
1036 
1037 	if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
1038 	    (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
1039 	    >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
1040 		ti->error = "Invalid data blocks";
1041 		r = -EINVAL;
1042 		goto bad;
1043 	}
1044 	v->data_blocks = num_ll;
1045 
1046 	if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
1047 		ti->error = "Data device is too small";
1048 		r = -EINVAL;
1049 		goto bad;
1050 	}
1051 
1052 	if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
1053 	    (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
1054 	    >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
1055 		ti->error = "Invalid hash start";
1056 		r = -EINVAL;
1057 		goto bad;
1058 	}
1059 	v->hash_start = num_ll;
1060 
1061 	v->alg_name = kstrdup(argv[7], GFP_KERNEL);
1062 	if (!v->alg_name) {
1063 		ti->error = "Cannot allocate algorithm name";
1064 		r = -ENOMEM;
1065 		goto bad;
1066 	}
1067 
1068 	v->tfm = crypto_alloc_ahash(v->alg_name, 0, 0);
1069 	if (IS_ERR(v->tfm)) {
1070 		ti->error = "Cannot initialize hash function";
1071 		r = PTR_ERR(v->tfm);
1072 		v->tfm = NULL;
1073 		goto bad;
1074 	}
1075 
1076 	/*
1077 	 * dm-verity performance can vary greatly depending on which hash
1078 	 * algorithm implementation is used.  Help people debug performance
1079 	 * problems by logging the ->cra_driver_name.
1080 	 */
1081 	DMINFO("%s using implementation \"%s\"", v->alg_name,
1082 	       crypto_hash_alg_common(v->tfm)->base.cra_driver_name);
1083 
1084 	v->digest_size = crypto_ahash_digestsize(v->tfm);
1085 	if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
1086 		ti->error = "Digest size too big";
1087 		r = -EINVAL;
1088 		goto bad;
1089 	}
1090 	v->ahash_reqsize = sizeof(struct ahash_request) +
1091 		crypto_ahash_reqsize(v->tfm);
1092 
1093 	v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
1094 	if (!v->root_digest) {
1095 		ti->error = "Cannot allocate root digest";
1096 		r = -ENOMEM;
1097 		goto bad;
1098 	}
1099 	if (strlen(argv[8]) != v->digest_size * 2 ||
1100 	    hex2bin(v->root_digest, argv[8], v->digest_size)) {
1101 		ti->error = "Invalid root digest";
1102 		r = -EINVAL;
1103 		goto bad;
1104 	}
1105 	root_hash_digest_to_validate = argv[8];
1106 
1107 	if (strcmp(argv[9], "-")) {
1108 		v->salt_size = strlen(argv[9]) / 2;
1109 		v->salt = kmalloc(v->salt_size, GFP_KERNEL);
1110 		if (!v->salt) {
1111 			ti->error = "Cannot allocate salt";
1112 			r = -ENOMEM;
1113 			goto bad;
1114 		}
1115 		if (strlen(argv[9]) != v->salt_size * 2 ||
1116 		    hex2bin(v->salt, argv[9], v->salt_size)) {
1117 			ti->error = "Invalid salt";
1118 			r = -EINVAL;
1119 			goto bad;
1120 		}
1121 	}
1122 
1123 	argv += 10;
1124 	argc -= 10;
1125 
1126 	/* Optional parameters */
1127 	if (argc) {
1128 		as.argc = argc;
1129 		as.argv = argv;
1130 
1131 		r = verity_parse_opt_args(&as, v, &verify_args);
1132 		if (r < 0)
1133 			goto bad;
1134 	}
1135 
1136 	/* Root hash signature is  a optional parameter*/
1137 	r = verity_verify_root_hash(root_hash_digest_to_validate,
1138 				    strlen(root_hash_digest_to_validate),
1139 				    verify_args.sig,
1140 				    verify_args.sig_size);
1141 	if (r < 0) {
1142 		ti->error = "Root hash verification failed";
1143 		goto bad;
1144 	}
1145 	v->hash_per_block_bits =
1146 		__fls((1 << v->hash_dev_block_bits) / v->digest_size);
1147 
1148 	v->levels = 0;
1149 	if (v->data_blocks)
1150 		while (v->hash_per_block_bits * v->levels < 64 &&
1151 		       (unsigned long long)(v->data_blocks - 1) >>
1152 		       (v->hash_per_block_bits * v->levels))
1153 			v->levels++;
1154 
1155 	if (v->levels > DM_VERITY_MAX_LEVELS) {
1156 		ti->error = "Too many tree levels";
1157 		r = -E2BIG;
1158 		goto bad;
1159 	}
1160 
1161 	hash_position = v->hash_start;
1162 	for (i = v->levels - 1; i >= 0; i--) {
1163 		sector_t s;
1164 		v->hash_level_block[i] = hash_position;
1165 		s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
1166 					>> ((i + 1) * v->hash_per_block_bits);
1167 		if (hash_position + s < hash_position) {
1168 			ti->error = "Hash device offset overflow";
1169 			r = -E2BIG;
1170 			goto bad;
1171 		}
1172 		hash_position += s;
1173 	}
1174 	v->hash_blocks = hash_position;
1175 
1176 	v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
1177 		1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
1178 		dm_bufio_alloc_callback, NULL);
1179 	if (IS_ERR(v->bufio)) {
1180 		ti->error = "Cannot initialize dm-bufio";
1181 		r = PTR_ERR(v->bufio);
1182 		v->bufio = NULL;
1183 		goto bad;
1184 	}
1185 
1186 	if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
1187 		ti->error = "Hash device is too small";
1188 		r = -E2BIG;
1189 		goto bad;
1190 	}
1191 
1192 	/* WQ_UNBOUND greatly improves performance when running on ramdisk */
1193 	v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
1194 	if (!v->verify_wq) {
1195 		ti->error = "Cannot allocate workqueue";
1196 		r = -ENOMEM;
1197 		goto bad;
1198 	}
1199 
1200 	ti->per_io_data_size = sizeof(struct dm_verity_io) +
1201 				v->ahash_reqsize + v->digest_size * 2;
1202 
1203 	r = verity_fec_ctr(v);
1204 	if (r)
1205 		goto bad;
1206 
1207 	ti->per_io_data_size = roundup(ti->per_io_data_size,
1208 				       __alignof__(struct dm_verity_io));
1209 
1210 	verity_verify_sig_opts_cleanup(&verify_args);
1211 
1212 	return 0;
1213 
1214 bad:
1215 
1216 	verity_verify_sig_opts_cleanup(&verify_args);
1217 	verity_dtr(ti);
1218 
1219 	return r;
1220 }
1221 
1222 static struct target_type verity_target = {
1223 	.name		= "verity",
1224 	.version	= {1, 6, 0},
1225 	.module		= THIS_MODULE,
1226 	.ctr		= verity_ctr,
1227 	.dtr		= verity_dtr,
1228 	.map		= verity_map,
1229 	.status		= verity_status,
1230 	.prepare_ioctl	= verity_prepare_ioctl,
1231 	.iterate_devices = verity_iterate_devices,
1232 	.io_hints	= verity_io_hints,
1233 };
1234 
1235 static int __init dm_verity_init(void)
1236 {
1237 	int r;
1238 
1239 	r = dm_register_target(&verity_target);
1240 	if (r < 0)
1241 		DMERR("register failed %d", r);
1242 
1243 	return r;
1244 }
1245 
1246 static void __exit dm_verity_exit(void)
1247 {
1248 	dm_unregister_target(&verity_target);
1249 }
1250 
1251 module_init(dm_verity_init);
1252 module_exit(dm_verity_exit);
1253 
1254 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
1255 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
1256 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
1257 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
1258 MODULE_LICENSE("GPL");
1259