drivers/md/dm-verity-target.c

   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 #include <linux/scatterlist.h>
  22 #include <linux/string.h>
  23
  24 #define DM_MSG_PREFIX                   "verity"
  25
  26 #define DM_VERITY_ENV_LENGTH            42
  27 #define DM_VERITY_ENV_VAR_NAME          "DM_VERITY_ERR_BLOCK_NR"
  28
  29 #define DM_VERITY_DEFAULT_PREFETCH_SIZE 262144
  30
  31 #define DM_VERITY_MAX_CORRUPTED_ERRS    100
  32
  33 #define DM_VERITY_OPT_LOGGING           "ignore_corruption"
  34 #define DM_VERITY_OPT_RESTART           "restart_on_corruption"
  35 #define DM_VERITY_OPT_PANIC             "panic_on_corruption"
  36 #define DM_VERITY_OPT_IGN_ZEROES        "ignore_zero_blocks"
  37 #define DM_VERITY_OPT_AT_MOST_ONCE      "check_at_most_once"
  38
  39 #define DM_VERITY_OPTS_MAX              (3 + DM_VERITY_OPTS_FEC + \
  40                                          DM_VERITY_ROOT_HASH_VERIFICATION_OPTS)
  41
  42 static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
  43
  44 module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
  45
  46 struct dm_verity_prefetch_work {
  47         struct work_struct work;
  48         struct dm_verity *v;
  49         sector_t block;
  50         unsigned n_blocks;
  51 };
  52
  53 /*
  54  * Auxiliary structure appended to each dm-bufio buffer. If the value
  55  * hash_verified is nonzero, hash of the block has been verified.
  56  *
  57  * The variable hash_verified is set to 0 when allocating the buffer, then
  58  * it can be changed to 1 and it is never reset to 0 again.
  59  *
  60  * There is no lock around this value, a race condition can at worst cause
  61  * that multiple processes verify the hash of the same buffer simultaneously
  62  * and write 1 to hash_verified simultaneously.
  63  * This condition is harmless, so we don't need locking.
  64  */
  65 struct buffer_aux {
  66         int hash_verified;
  67 };
  68
  69 /*
  70  * Initialize struct buffer_aux for a freshly created buffer.
  71  */
  72 static void dm_bufio_alloc_callback(struct dm_buffer *buf)
  73 {
  74         struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
  75
  76         aux->hash_verified = 0;
  77 }
  78
  79 /*
  80  * Translate input sector number to the sector number on the target device.
  81  */
  82 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
  83 {
  84         return v->data_start + dm_target_offset(v->ti, bi_sector);
  85 }
  86
  87 /*
  88  * Return hash position of a specified block at a specified tree level
  89  * (0 is the lowest level).
  90  * The lowest "hash_per_block_bits"-bits of the result denote hash position
  91  * inside a hash block. The remaining bits denote location of the hash block.
  92  */
  93 static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
  94                                          int level)
  95 {
  96         return block >> (level * v->hash_per_block_bits);
  97 }
  98
  99 static int verity_hash_update(struct dm_verity *v, struct ahash_request *req,
 100                                 const u8 *data, size_t len,
 101                                 struct crypto_wait *wait)
 102 {
 103         struct scatterlist sg;
 104
 105         if (likely(!is_vmalloc_addr(data))) {
 106                 sg_init_one(&sg, data, len);
 107                 ahash_request_set_crypt(req, &sg, NULL, len);
 108                 return crypto_wait_req(crypto_ahash_update(req), wait);
 109         } else {
 110                 do {
 111                         int r;
 112                         size_t this_step = min_t(size_t, len, PAGE_SIZE - offset_in_page(data));
 113                         flush_kernel_vmap_range((void *)data, this_step);
 114                         sg_init_table(&sg, 1);
 115                         sg_set_page(&sg, vmalloc_to_page(data), this_step, offset_in_page(data));
 116                         ahash_request_set_crypt(req, &sg, NULL, this_step);
 117                         r = crypto_wait_req(crypto_ahash_update(req), wait);
 118                         if (unlikely(r))
 119                                 return r;
 120                         data += this_step;
 121                         len -= this_step;
 122                 } while (len);
 123                 return 0;
 124         }
 125 }
 126
 127 /*
 128  * Wrapper for crypto_ahash_init, which handles verity salting.
 129  */
 130 static int verity_hash_init(struct dm_verity *v, struct ahash_request *req,
 131                                 struct crypto_wait *wait)
 132 {
 133         int r;
 134
 135         ahash_request_set_tfm(req, v->tfm);
 136         ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP |
 137                                         CRYPTO_TFM_REQ_MAY_BACKLOG,
 138                                         crypto_req_done, (void *)wait);
 139         crypto_init_wait(wait);
 140
 141         r = crypto_wait_req(crypto_ahash_init(req), wait);
 142
 143         if (unlikely(r < 0)) {
 144                 DMERR("crypto_ahash_init failed: %d", r);
 145                 return r;
 146         }
 147
 148         if (likely(v->salt_size && (v->version >= 1)))
 149                 r = verity_hash_update(v, req, v->salt, v->salt_size, wait);
 150
 151         return r;
 152 }
 153
 154 static int verity_hash_final(struct dm_verity *v, struct ahash_request *req,
 155                              u8 *digest, struct crypto_wait *wait)
 156 {
 157         int r;
 158
 159         if (unlikely(v->salt_size && (!v->version))) {
 160                 r = verity_hash_update(v, req, v->salt, v->salt_size, wait);
 161
 162                 if (r < 0) {
 163                         DMERR("verity_hash_final failed updating salt: %d", r);
 164                         goto out;
 165                 }
 166         }
 167
 168         ahash_request_set_crypt(req, NULL, digest, 0);
 169         r = crypto_wait_req(crypto_ahash_final(req), wait);
 170 out:
 171         return r;
 172 }
 173
 174 int verity_hash(struct dm_verity *v, struct ahash_request *req,
 175                 const u8 *data, size_t len, u8 *digest)
 176 {
 177         int r;
 178         struct crypto_wait wait;
 179
 180         r = verity_hash_init(v, req, &wait);
 181         if (unlikely(r < 0))
 182                 goto out;
 183
 184         r = verity_hash_update(v, req, data, len, &wait);
 185         if (unlikely(r < 0))
 186                 goto out;
 187
 188         r = verity_hash_final(v, req, digest, &wait);
 189
 190 out:
 191         return r;
 192 }
 193
 194 static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
 195                                  sector_t *hash_block, unsigned *offset)
 196 {
 197         sector_t position = verity_position_at_level(v, block, level);
 198         unsigned idx;
 199
 200         *hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
 201
 202         if (!offset)
 203                 return;
 204
 205         idx = position & ((1 << v->hash_per_block_bits) - 1);
 206         if (!v->version)
 207                 *offset = idx * v->digest_size;
 208         else
 209                 *offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
 210 }
 211
 212 /*
 213  * Handle verification errors.
 214  */
 215 static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
 216                              unsigned long long block)
 217 {
 218         char verity_env[DM_VERITY_ENV_LENGTH];
 219         char *envp[] = { verity_env, NULL };
 220         const char *type_str = "";
 221         struct mapped_device *md = dm_table_get_md(v->ti->table);
 222
 223         /* Corruption should be visible in device status in all modes */
 224         v->hash_failed = 1;
 225
 226         if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
 227                 goto out;
 228
 229         v->corrupted_errs++;
 230
 231         switch (type) {
 232         case DM_VERITY_BLOCK_TYPE_DATA:
 233                 type_str = "data";
 234                 break;
 235         case DM_VERITY_BLOCK_TYPE_METADATA:
 236                 type_str = "metadata";
 237                 break;
 238         default:
 239                 BUG();
 240         }
 241
 242         DMERR_LIMIT("%s: %s block %llu is corrupted", v->data_dev->name,
 243                     type_str, block);
 244
 245         if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
 246                 DMERR("%s: reached maximum errors", v->data_dev->name);
 247
 248         snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
 249                 DM_VERITY_ENV_VAR_NAME, type, block);
 250
 251         kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
 252
 253 out:
 254         if (v->mode == DM_VERITY_MODE_LOGGING)
 255                 return 0;
 256
 257         if (v->mode == DM_VERITY_MODE_RESTART)
 258                 kernel_restart("dm-verity device corrupted");
 259
 260         if (v->mode == DM_VERITY_MODE_PANIC)
 261                 panic("dm-verity device corrupted");
 262
 263         return 1;
 264 }
 265
 266 /*
 267  * Verify hash of a metadata block pertaining to the specified data block
 268  * ("block" argument) at a specified level ("level" argument).
 269  *
 270  * On successful return, verity_io_want_digest(v, io) contains the hash value
 271  * for a lower tree level or for the data block (if we're at the lowest level).
 272  *
 273  * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
 274  * If "skip_unverified" is false, unverified buffer is hashed and verified
 275  * against current value of verity_io_want_digest(v, io).
 276  */
 277 static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 278                                sector_t block, int level, bool skip_unverified,
 279                                u8 *want_digest)
 280 {
 281         struct dm_buffer *buf;
 282         struct buffer_aux *aux;
 283         u8 *data;
 284         int r;
 285         sector_t hash_block;
 286         unsigned offset;
 287
 288         verity_hash_at_level(v, block, level, &hash_block, &offset);
 289
 290         data = dm_bufio_read(v->bufio, hash_block, &buf);
 291         if (IS_ERR(data))
 292                 return PTR_ERR(data);
 293
 294         aux = dm_bufio_get_aux_data(buf);
 295
 296         if (!aux->hash_verified) {
 297                 if (skip_unverified) {
 298                         r = 1;
 299                         goto release_ret_r;
 300                 }
 301
 302                 r = verity_hash(v, verity_io_hash_req(v, io),
 303                                 data, 1 << v->hash_dev_block_bits,
 304                                 verity_io_real_digest(v, io));
 305                 if (unlikely(r < 0))
 306                         goto release_ret_r;
 307
 308                 if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
 309                                   v->digest_size) == 0))
 310                         aux->hash_verified = 1;
 311                 else if (verity_fec_decode(v, io,
 312                                            DM_VERITY_BLOCK_TYPE_METADATA,
 313                                            hash_block, data, NULL) == 0)
 314                         aux->hash_verified = 1;
 315                 else if (verity_handle_err(v,
 316                                            DM_VERITY_BLOCK_TYPE_METADATA,
 317                                            hash_block)) {
 318                         r = -EIO;
 319                         goto release_ret_r;
 320                 }
 321         }
 322
 323         data += offset;
 324         memcpy(want_digest, data, v->digest_size);
 325         r = 0;
 326
 327 release_ret_r:
 328         dm_bufio_release(buf);
 329         return r;
 330 }
 331
 332 /*
 333  * Find a hash for a given block, write it to digest and verify the integrity
 334  * of the hash tree if necessary.
 335  */
 336 int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
 337                           sector_t block, u8 *digest, bool *is_zero)
 338 {
 339         int r = 0, i;
 340
 341         if (likely(v->levels)) {
 342                 /*
 343                  * First, we try to get the requested hash for
 344                  * the current block. If the hash block itself is
 345                  * verified, zero is returned. If it isn't, this
 346                  * function returns 1 and we fall back to whole
 347                  * chain verification.
 348                  */
 349                 r = verity_verify_level(v, io, block, 0, true, digest);
 350                 if (likely(r <= 0))
 351                         goto out;
 352         }
 353
 354         memcpy(digest, v->root_digest, v->digest_size);
 355
 356         for (i = v->levels - 1; i >= 0; i--) {
 357                 r = verity_verify_level(v, io, block, i, false, digest);
 358                 if (unlikely(r))
 359                         goto out;
 360         }
 361 out:
 362         if (!r && v->zero_digest)
 363                 *is_zero = !memcmp(v->zero_digest, digest, v->digest_size);
 364         else
 365                 *is_zero = false;
 366
 367         return r;
 368 }
 369
 370 /*
 371  * Calculates the digest for the given bio
 372  */
 373 static int verity_for_io_block(struct dm_verity *v, struct dm_verity_io *io,
 374                                struct bvec_iter *iter, struct crypto_wait *wait)
 375 {
 376         unsigned int todo = 1 << v->data_dev_block_bits;
 377         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 378         struct scatterlist sg;
 379         struct ahash_request *req = verity_io_hash_req(v, io);
 380
 381         do {
 382                 int r;
 383                 unsigned int len;
 384                 struct bio_vec bv = bio_iter_iovec(bio, *iter);
 385
 386                 sg_init_table(&sg, 1);
 387
 388                 len = bv.bv_len;
 389
 390                 if (likely(len >= todo))
 391                         len = todo;
 392                 /*
 393                  * Operating on a single page at a time looks suboptimal
 394                  * until you consider the typical block size is 4,096B.
 395                  * Going through this loops twice should be very rare.
 396                  */
 397                 sg_set_page(&sg, bv.bv_page, len, bv.bv_offset);
 398                 ahash_request_set_crypt(req, &sg, NULL, len);
 399                 r = crypto_wait_req(crypto_ahash_update(req), wait);
 400
 401                 if (unlikely(r < 0)) {
 402                         DMERR("verity_for_io_block crypto op failed: %d", r);
 403                         return r;
 404                 }
 405
 406                 bio_advance_iter(bio, iter, len);
 407                 todo -= len;
 408         } while (todo);
 409
 410         return 0;
 411 }
 412
 413 /*
 414  * Calls function process for 1 << v->data_dev_block_bits bytes in the bio_vec
 415  * starting from iter.
 416  */
 417 int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
 418                         struct bvec_iter *iter,
 419                         int (*process)(struct dm_verity *v,
 420                                        struct dm_verity_io *io, u8 *data,
 421                                        size_t len))
 422 {
 423         unsigned todo = 1 << v->data_dev_block_bits;
 424         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 425
 426         do {
 427                 int r;
 428                 u8 *page;
 429                 unsigned len;
 430                 struct bio_vec bv = bio_iter_iovec(bio, *iter);
 431
 432                 page = bvec_kmap_local(&bv);
 433                 len = bv.bv_len;
 434
 435                 if (likely(len >= todo))
 436                         len = todo;
 437
 438                 r = process(v, io, page, len);
 439                 kunmap_local(page);
 440
 441                 if (r < 0)
 442                         return r;
 443
 444                 bio_advance_iter(bio, iter, len);
 445                 todo -= len;
 446         } while (todo);
 447
 448         return 0;
 449 }
 450
 451 static int verity_bv_zero(struct dm_verity *v, struct dm_verity_io *io,
 452                           u8 *data, size_t len)
 453 {
 454         memset(data, 0, len);
 455         return 0;
 456 }
 457
 458 /*
 459  * Moves the bio iter one data block forward.
 460  */
 461 static inline void verity_bv_skip_block(struct dm_verity *v,
 462                                         struct dm_verity_io *io,
 463                                         struct bvec_iter *iter)
 464 {
 465         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 466
 467         bio_advance_iter(bio, iter, 1 << v->data_dev_block_bits);
 468 }
 469
 470 /*
 471  * Verify one "dm_verity_io" structure.
 472  */
 473 static int verity_verify_io(struct dm_verity_io *io)
 474 {
 475         bool is_zero;
 476         struct dm_verity *v = io->v;
 477         struct bvec_iter start;
 478         unsigned b;
 479         struct crypto_wait wait;
 480         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 481
 482         for (b = 0; b < io->n_blocks; b++) {
 483                 int r;
 484                 sector_t cur_block = io->block + b;
 485                 struct ahash_request *req = verity_io_hash_req(v, io);
 486
 487                 if (v->validated_blocks &&
 488                     likely(test_bit(cur_block, v->validated_blocks))) {
 489                         verity_bv_skip_block(v, io, &io->iter);
 490                         continue;
 491                 }
 492
 493                 r = verity_hash_for_block(v, io, cur_block,
 494                                           verity_io_want_digest(v, io),
 495                                           &is_zero);
 496                 if (unlikely(r < 0))
 497                         return r;
 498
 499                 if (is_zero) {
 500                         /*
 501                          * If we expect a zero block, don't validate, just
 502                          * return zeros.
 503                          */
 504                         r = verity_for_bv_block(v, io, &io->iter,
 505                                                 verity_bv_zero);
 506                         if (unlikely(r < 0))
 507                                 return r;
 508
 509                         continue;
 510                 }
 511
 512                 r = verity_hash_init(v, req, &wait);
 513                 if (unlikely(r < 0))
 514                         return r;
 515
 516                 start = io->iter;
 517                 r = verity_for_io_block(v, io, &io->iter, &wait);
 518                 if (unlikely(r < 0))
 519                         return r;
 520
 521                 r = verity_hash_final(v, req, verity_io_real_digest(v, io),
 522                                         &wait);
 523                 if (unlikely(r < 0))
 524                         return r;
 525
 526                 if (likely(memcmp(verity_io_real_digest(v, io),
 527                                   verity_io_want_digest(v, io), v->digest_size) == 0)) {
 528                         if (v->validated_blocks)
 529                                 set_bit(cur_block, v->validated_blocks);
 530                         continue;
 531                 } else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
 532                                            cur_block, NULL, &start) == 0) {
 533                         continue;
 534                 } else {
 535                         if (bio->bi_status) {
 536                                 /*
 537                                  * Error correction failed; Just return error
 538                                  */
 539                                 return -EIO;
 540                         }
 541                         if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
 542                                               cur_block))
 543                                 return -EIO;
 544                 }
 545         }
 546
 547         return 0;
 548 }
 549
 550 /*
 551  * Skip verity work in response to I/O error when system is shutting down.
 552  */
 553 static inline bool verity_is_system_shutting_down(void)
 554 {
 555         return system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF
 556                 || system_state == SYSTEM_RESTART;
 557 }
 558
 559 /*
 560  * End one "io" structure with a given error.
 561  */
 562 static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)
 563 {
 564         struct dm_verity *v = io->v;
 565         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 566
 567         bio->bi_end_io = io->orig_bi_end_io;
 568         bio->bi_status = status;
 569
 570         verity_fec_finish_io(io);
 571
 572         bio_endio(bio);
 573 }
 574
 575 static void verity_work(struct work_struct *w)
 576 {
 577         struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
 578
 579         verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));
 580 }
 581
 582 static void verity_end_io(struct bio *bio)
 583 {
 584         struct dm_verity_io *io = bio->bi_private;
 585
 586         if (bio->bi_status &&
 587             (!verity_fec_is_enabled(io->v) || verity_is_system_shutting_down())) {
 588                 verity_finish_io(io, bio->bi_status);
 589                 return;
 590         }
 591
 592         INIT_WORK(&io->work, verity_work);
 593         queue_work(io->v->verify_wq, &io->work);
 594 }
 595
 596 /*
 597  * Prefetch buffers for the specified io.
 598  * The root buffer is not prefetched, it is assumed that it will be cached
 599  * all the time.
 600  */
 601 static void verity_prefetch_io(struct work_struct *work)
 602 {
 603         struct dm_verity_prefetch_work *pw =
 604                 container_of(work, struct dm_verity_prefetch_work, work);
 605         struct dm_verity *v = pw->v;
 606         int i;
 607
 608         for (i = v->levels - 2; i >= 0; i--) {
 609                 sector_t hash_block_start;
 610                 sector_t hash_block_end;
 611                 verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
 612                 verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
 613                 if (!i) {
 614                         unsigned cluster = READ_ONCE(dm_verity_prefetch_cluster);
 615
 616                         cluster >>= v->data_dev_block_bits;
 617                         if (unlikely(!cluster))
 618                                 goto no_prefetch_cluster;
 619
 620                         if (unlikely(cluster & (cluster - 1)))
 621                                 cluster = 1 << __fls(cluster);
 622
 623                         hash_block_start &= ~(sector_t)(cluster - 1);
 624                         hash_block_end |= cluster - 1;
 625                         if (unlikely(hash_block_end >= v->hash_blocks))
 626                                 hash_block_end = v->hash_blocks - 1;
 627                 }
 628 no_prefetch_cluster:
 629                 dm_bufio_prefetch(v->bufio, hash_block_start,
 630                                   hash_block_end - hash_block_start + 1);
 631         }
 632
 633         kfree(pw);
 634 }
 635
 636 static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
 637 {
 638         sector_t block = io->block;
 639         unsigned int n_blocks = io->n_blocks;
 640         struct dm_verity_prefetch_work *pw;
 641
 642         if (v->validated_blocks) {
 643                 while (n_blocks && test_bit(block, v->validated_blocks)) {
 644                         block++;
 645                         n_blocks--;
 646                 }
 647                 while (n_blocks && test_bit(block + n_blocks - 1,
 648                                             v->validated_blocks))
 649                         n_blocks--;
 650                 if (!n_blocks)
 651                         return;
 652         }
 653
 654         pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
 655                 GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 656
 657         if (!pw)
 658                 return;
 659
 660         INIT_WORK(&pw->work, verity_prefetch_io);
 661         pw->v = v;
 662         pw->block = block;
 663         pw->n_blocks = n_blocks;
 664         queue_work(v->verify_wq, &pw->work);
 665 }
 666
 667 /*
 668  * Bio map function. It allocates dm_verity_io structure and bio vector and
 669  * fills them. Then it issues prefetches and the I/O.
 670  */
 671 static int verity_map(struct dm_target *ti, struct bio *bio)
 672 {
 673         struct dm_verity *v = ti->private;
 674         struct dm_verity_io *io;
 675
 676         bio_set_dev(bio, v->data_dev->bdev);
 677         bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
 678
 679         if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
 680             ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
 681                 DMERR_LIMIT("unaligned io");
 682                 return DM_MAPIO_KILL;
 683         }
 684
 685         if (bio_end_sector(bio) >>
 686             (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
 687                 DMERR_LIMIT("io out of range");
 688                 return DM_MAPIO_KILL;
 689         }
 690
 691         if (bio_data_dir(bio) == WRITE)
 692                 return DM_MAPIO_KILL;
 693
 694         io = dm_per_bio_data(bio, ti->per_io_data_size);
 695         io->v = v;
 696         io->orig_bi_end_io = bio->bi_end_io;
 697         io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
 698         io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
 699
 700         bio->bi_end_io = verity_end_io;
 701         bio->bi_private = io;
 702         io->iter = bio->bi_iter;
 703
 704         verity_fec_init_io(io);
 705
 706         verity_submit_prefetch(v, io);
 707
 708         submit_bio_noacct(bio);
 709
 710         return DM_MAPIO_SUBMITTED;
 711 }
 712
 713 /*
 714  * Status: V (valid) or C (corruption found)
 715  */
 716 static void verity_status(struct dm_target *ti, status_type_t type,
 717                           unsigned status_flags, char *result, unsigned maxlen)
 718 {
 719         struct dm_verity *v = ti->private;
 720         unsigned args = 0;
 721         unsigned sz = 0;
 722         unsigned x;
 723
 724         switch (type) {
 725         case STATUSTYPE_INFO:
 726                 DMEMIT("%c", v->hash_failed ? 'C' : 'V');
 727                 break;
 728         case STATUSTYPE_TABLE:
 729                 DMEMIT("%u %s %s %u %u %llu %llu %s ",
 730                         v->version,
 731                         v->data_dev->name,
 732                         v->hash_dev->name,
 733                         1 << v->data_dev_block_bits,
 734                         1 << v->hash_dev_block_bits,
 735                         (unsigned long long)v->data_blocks,
 736                         (unsigned long long)v->hash_start,
 737                         v->alg_name
 738                         );
 739                 for (x = 0; x < v->digest_size; x++)
 740                         DMEMIT("%02x", v->root_digest[x]);
 741                 DMEMIT(" ");
 742                 if (!v->salt_size)
 743                         DMEMIT("-");
 744                 else
 745                         for (x = 0; x < v->salt_size; x++)
 746                                 DMEMIT("%02x", v->salt[x]);
 747                 if (v->mode != DM_VERITY_MODE_EIO)
 748                         args++;
 749                 if (verity_fec_is_enabled(v))
 750                         args += DM_VERITY_OPTS_FEC;
 751                 if (v->zero_digest)
 752                         args++;
 753                 if (v->validated_blocks)
 754                         args++;
 755                 if (v->signature_key_desc)
 756                         args += DM_VERITY_ROOT_HASH_VERIFICATION_OPTS;
 757                 if (!args)
 758                         return;
 759                 DMEMIT(" %u", args);
 760                 if (v->mode != DM_VERITY_MODE_EIO) {
 761                         DMEMIT(" ");
 762                         switch (v->mode) {
 763                         case DM_VERITY_MODE_LOGGING:
 764                                 DMEMIT(DM_VERITY_OPT_LOGGING);
 765                                 break;
 766                         case DM_VERITY_MODE_RESTART:
 767                                 DMEMIT(DM_VERITY_OPT_RESTART);
 768                                 break;
 769                         case DM_VERITY_MODE_PANIC:
 770                                 DMEMIT(DM_VERITY_OPT_PANIC);
 771                                 break;
 772                         default:
 773                                 BUG();
 774                         }
 775                 }
 776                 if (v->zero_digest)
 777                         DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);
 778                 if (v->validated_blocks)
 779                         DMEMIT(" " DM_VERITY_OPT_AT_MOST_ONCE);
 780                 sz = verity_fec_status_table(v, sz, result, maxlen);
 781                 if (v->signature_key_desc)
 782                         DMEMIT(" " DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY
 783                                 " %s", v->signature_key_desc);
 784                 break;
 785
 786         case STATUSTYPE_IMA:
 787                 DMEMIT_TARGET_NAME_VERSION(ti->type);
 788                 DMEMIT(",hash_failed=%c", v->hash_failed ? 'C' : 'V');
 789                 DMEMIT(",verity_version=%u", v->version);
 790                 DMEMIT(",data_device_name=%s", v->data_dev->name);
 791                 DMEMIT(",hash_device_name=%s", v->hash_dev->name);
 792                 DMEMIT(",verity_algorithm=%s", v->alg_name);
 793
 794                 DMEMIT(",root_digest=");
 795                 for (x = 0; x < v->digest_size; x++)
 796                         DMEMIT("%02x", v->root_digest[x]);
 797
 798                 DMEMIT(",salt=");
 799                 if (!v->salt_size)
 800                         DMEMIT("-");
 801                 else
 802                         for (x = 0; x < v->salt_size; x++)
 803                                 DMEMIT("%02x", v->salt[x]);
 804
 805                 DMEMIT(",ignore_zero_blocks=%c", v->zero_digest ? 'y' : 'n');
 806                 DMEMIT(",check_at_most_once=%c", v->validated_blocks ? 'y' : 'n');
 807                 if (v->signature_key_desc)
 808                         DMEMIT(",root_hash_sig_key_desc=%s", v->signature_key_desc);
 809
 810                 if (v->mode != DM_VERITY_MODE_EIO) {
 811                         DMEMIT(",verity_mode=");
 812                         switch (v->mode) {
 813                         case DM_VERITY_MODE_LOGGING:
 814                                 DMEMIT(DM_VERITY_OPT_LOGGING);
 815                                 break;
 816                         case DM_VERITY_MODE_RESTART:
 817                                 DMEMIT(DM_VERITY_OPT_RESTART);
 818                                 break;
 819                         case DM_VERITY_MODE_PANIC:
 820                                 DMEMIT(DM_VERITY_OPT_PANIC);
 821                                 break;
 822                         default:
 823                                 DMEMIT("invalid");
 824                         }
 825                 }
 826                 DMEMIT(";");
 827                 break;
 828         }
 829 }
 830
 831 static int verity_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
 832 {
 833         struct dm_verity *v = ti->private;
 834
 835         *bdev = v->data_dev->bdev;
 836
 837         if (v->data_start || ti->len != bdev_nr_sectors(v->data_dev->bdev))
 838                 return 1;
 839         return 0;
 840 }
 841
 842 static int verity_iterate_devices(struct dm_target *ti,
 843                                   iterate_devices_callout_fn fn, void *data)
 844 {
 845         struct dm_verity *v = ti->private;
 846
 847         return fn(ti, v->data_dev, v->data_start, ti->len, data);
 848 }
 849
 850 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
 851 {
 852         struct dm_verity *v = ti->private;
 853
 854         if (limits->logical_block_size < 1 << v->data_dev_block_bits)
 855                 limits->logical_block_size = 1 << v->data_dev_block_bits;
 856
 857         if (limits->physical_block_size < 1 << v->data_dev_block_bits)
 858                 limits->physical_block_size = 1 << v->data_dev_block_bits;
 859
 860         blk_limits_io_min(limits, limits->logical_block_size);
 861 }
 862
 863 static void verity_dtr(struct dm_target *ti)
 864 {
 865         struct dm_verity *v = ti->private;
 866
 867         if (v->verify_wq)
 868                 destroy_workqueue(v->verify_wq);
 869
 870         if (v->bufio)
 871                 dm_bufio_client_destroy(v->bufio);
 872
 873         kvfree(v->validated_blocks);
 874         kfree(v->salt);
 875         kfree(v->root_digest);
 876         kfree(v->zero_digest);
 877
 878         if (v->tfm)
 879                 crypto_free_ahash(v->tfm);
 880
 881         kfree(v->alg_name);
 882
 883         if (v->hash_dev)
 884                 dm_put_device(ti, v->hash_dev);
 885
 886         if (v->data_dev)
 887                 dm_put_device(ti, v->data_dev);
 888
 889         verity_fec_dtr(v);
 890
 891         kfree(v->signature_key_desc);
 892
 893         kfree(v);
 894 }
 895
 896 static int verity_alloc_most_once(struct dm_verity *v)
 897 {
 898         struct dm_target *ti = v->ti;
 899
 900         /* the bitset can only handle INT_MAX blocks */
 901         if (v->data_blocks > INT_MAX) {
 902                 ti->error = "device too large to use check_at_most_once";
 903                 return -E2BIG;
 904         }
 905
 906         v->validated_blocks = kvcalloc(BITS_TO_LONGS(v->data_blocks),
 907                                        sizeof(unsigned long),
 908                                        GFP_KERNEL);
 909         if (!v->validated_blocks) {
 910                 ti->error = "failed to allocate bitset for check_at_most_once";
 911                 return -ENOMEM;
 912         }
 913
 914         return 0;
 915 }
 916
 917 static int verity_alloc_zero_digest(struct dm_verity *v)
 918 {
 919         int r = -ENOMEM;
 920         struct ahash_request *req;
 921         u8 *zero_data;
 922
 923         v->zero_digest = kmalloc(v->digest_size, GFP_KERNEL);
 924
 925         if (!v->zero_digest)
 926                 return r;
 927
 928         req = kmalloc(v->ahash_reqsize, GFP_KERNEL);
 929
 930         if (!req)
 931                 return r; /* verity_dtr will free zero_digest */
 932
 933         zero_data = kzalloc(1 << v->data_dev_block_bits, GFP_KERNEL);
 934
 935         if (!zero_data)
 936                 goto out;
 937
 938         r = verity_hash(v, req, zero_data, 1 << v->data_dev_block_bits,
 939                         v->zero_digest);
 940
 941 out:
 942         kfree(req);
 943         kfree(zero_data);
 944
 945         return r;
 946 }
 947
 948 static inline bool verity_is_verity_mode(const char *arg_name)
 949 {
 950         return (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING) ||
 951                 !strcasecmp(arg_name, DM_VERITY_OPT_RESTART) ||
 952                 !strcasecmp(arg_name, DM_VERITY_OPT_PANIC));
 953 }
 954
 955 static int verity_parse_verity_mode(struct dm_verity *v, const char *arg_name)
 956 {
 957         if (v->mode)
 958                 return -EINVAL;
 959
 960         if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING))
 961                 v->mode = DM_VERITY_MODE_LOGGING;
 962         else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART))
 963                 v->mode = DM_VERITY_MODE_RESTART;
 964         else if (!strcasecmp(arg_name, DM_VERITY_OPT_PANIC))
 965                 v->mode = DM_VERITY_MODE_PANIC;
 966
 967         return 0;
 968 }
 969
 970 static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
 971                                  struct dm_verity_sig_opts *verify_args)
 972 {
 973         int r;
 974         unsigned argc;
 975         struct dm_target *ti = v->ti;
 976         const char *arg_name;
 977
 978         static const struct dm_arg _args[] = {
 979                 {0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
 980         };
 981
 982         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 983         if (r)
 984                 return -EINVAL;
 985
 986         if (!argc)
 987                 return 0;
 988
 989         do {
 990                 arg_name = dm_shift_arg(as);
 991                 argc--;
 992
 993                 if (verity_is_verity_mode(arg_name)) {
 994                         r = verity_parse_verity_mode(v, arg_name);
 995                         if (r) {
 996                                 ti->error = "Conflicting error handling parameters";
 997                                 return r;
 998                         }
 999                         continue;
1000
1001                 } else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
1002                         r = verity_alloc_zero_digest(v);
1003                         if (r) {
1004                                 ti->error = "Cannot allocate zero digest";
1005                                 return r;
1006                         }
1007                         continue;
1008
1009                 } else if (!strcasecmp(arg_name, DM_VERITY_OPT_AT_MOST_ONCE)) {
1010                         r = verity_alloc_most_once(v);
1011                         if (r)
1012                                 return r;
1013                         continue;
1014
1015                 } else if (verity_is_fec_opt_arg(arg_name)) {
1016                         r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
1017                         if (r)
1018                                 return r;
1019                         continue;
1020                 } else if (verity_verify_is_sig_opt_arg(arg_name)) {
1021                         r = verity_verify_sig_parse_opt_args(as, v,
1022                                                              verify_args,
1023                                                              &argc, arg_name);
1024                         if (r)
1025                                 return r;
1026                         continue;
1027
1028                 }
1029
1030                 ti->error = "Unrecognized verity feature request";
1031                 return -EINVAL;
1032         } while (argc && !r);
1033
1034         return r;
1035 }
1036
1037 /*
1038  * Target parameters:
1039  *      <version>       The current format is version 1.
1040  *                      Vsn 0 is compatible with original Chromium OS releases.
1041  *      <data device>
1042  *      <hash device>
1043  *      <data block size>
1044  *      <hash block size>
1045  *      <the number of data blocks>
1046  *      <hash start block>
1047  *      <algorithm>
1048  *      <digest>
1049  *      <salt>          Hex string or "-" if no salt.
1050  */
1051 static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
1052 {
1053         struct dm_verity *v;
1054         struct dm_verity_sig_opts verify_args = {0};
1055         struct dm_arg_set as;
1056         unsigned int num;
1057         unsigned long long num_ll;
1058         int r;
1059         int i;
1060         sector_t hash_position;
1061         char dummy;
1062         char *root_hash_digest_to_validate;
1063
1064         v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
1065         if (!v) {
1066                 ti->error = "Cannot allocate verity structure";
1067                 return -ENOMEM;
1068         }
1069         ti->private = v;
1070         v->ti = ti;
1071
1072         r = verity_fec_ctr_alloc(v);
1073         if (r)
1074                 goto bad;
1075
1076         if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
1077                 ti->error = "Device must be readonly";
1078                 r = -EINVAL;
1079                 goto bad;
1080         }
1081
1082         if (argc < 10) {
1083                 ti->error = "Not enough arguments";
1084                 r = -EINVAL;
1085                 goto bad;
1086         }
1087
1088         if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
1089             num > 1) {
1090                 ti->error = "Invalid version";
1091                 r = -EINVAL;
1092                 goto bad;
1093         }
1094         v->version = num;
1095
1096         r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
1097         if (r) {
1098                 ti->error = "Data device lookup failed";
1099                 goto bad;
1100         }
1101
1102         r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
1103         if (r) {
1104                 ti->error = "Hash device lookup failed";
1105                 goto bad;
1106         }
1107
1108         if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
1109             !num || (num & (num - 1)) ||
1110             num < bdev_logical_block_size(v->data_dev->bdev) ||
1111             num > PAGE_SIZE) {
1112                 ti->error = "Invalid data device block size";
1113                 r = -EINVAL;
1114                 goto bad;
1115         }
1116         v->data_dev_block_bits = __ffs(num);
1117
1118         if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
1119             !num || (num & (num - 1)) ||
1120             num < bdev_logical_block_size(v->hash_dev->bdev) ||
1121             num > INT_MAX) {
1122                 ti->error = "Invalid hash device block size";
1123                 r = -EINVAL;
1124                 goto bad;
1125         }
1126         v->hash_dev_block_bits = __ffs(num);
1127
1128         if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
1129             (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
1130             >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
1131                 ti->error = "Invalid data blocks";
1132                 r = -EINVAL;
1133                 goto bad;
1134         }
1135         v->data_blocks = num_ll;
1136
1137         if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
1138                 ti->error = "Data device is too small";
1139                 r = -EINVAL;
1140                 goto bad;
1141         }
1142
1143         if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
1144             (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
1145             >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
1146                 ti->error = "Invalid hash start";
1147                 r = -EINVAL;
1148                 goto bad;
1149         }
1150         v->hash_start = num_ll;
1151
1152         v->alg_name = kstrdup(argv[7], GFP_KERNEL);
1153         if (!v->alg_name) {
1154                 ti->error = "Cannot allocate algorithm name";
1155                 r = -ENOMEM;
1156                 goto bad;
1157         }
1158
1159         v->tfm = crypto_alloc_ahash(v->alg_name, 0, 0);
1160         if (IS_ERR(v->tfm)) {
1161                 ti->error = "Cannot initialize hash function";
1162                 r = PTR_ERR(v->tfm);
1163                 v->tfm = NULL;
1164                 goto bad;
1165         }
1166
1167         /*
1168          * dm-verity performance can vary greatly depending on which hash
1169          * algorithm implementation is used.  Help people debug performance
1170          * problems by logging the ->cra_driver_name.
1171          */
1172         DMINFO("%s using implementation \"%s\"", v->alg_name,
1173                crypto_hash_alg_common(v->tfm)->base.cra_driver_name);
1174
1175         v->digest_size = crypto_ahash_digestsize(v->tfm);
1176         if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
1177                 ti->error = "Digest size too big";
1178                 r = -EINVAL;
1179                 goto bad;
1180         }
1181         v->ahash_reqsize = sizeof(struct ahash_request) +
1182                 crypto_ahash_reqsize(v->tfm);
1183
1184         v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
1185         if (!v->root_digest) {
1186                 ti->error = "Cannot allocate root digest";
1187                 r = -ENOMEM;
1188                 goto bad;
1189         }
1190         if (strlen(argv[8]) != v->digest_size * 2 ||
1191             hex2bin(v->root_digest, argv[8], v->digest_size)) {
1192                 ti->error = "Invalid root digest";
1193                 r = -EINVAL;
1194                 goto bad;
1195         }
1196         root_hash_digest_to_validate = argv[8];
1197
1198         if (strcmp(argv[9], "-")) {
1199                 v->salt_size = strlen(argv[9]) / 2;
1200                 v->salt = kmalloc(v->salt_size, GFP_KERNEL);
1201                 if (!v->salt) {
1202                         ti->error = "Cannot allocate salt";
1203                         r = -ENOMEM;
1204                         goto bad;
1205                 }
1206                 if (strlen(argv[9]) != v->salt_size * 2 ||
1207                     hex2bin(v->salt, argv[9], v->salt_size)) {
1208                         ti->error = "Invalid salt";
1209                         r = -EINVAL;
1210                         goto bad;
1211                 }
1212         }
1213
1214         argv += 10;
1215         argc -= 10;
1216
1217         /* Optional parameters */
1218         if (argc) {
1219                 as.argc = argc;
1220                 as.argv = argv;
1221
1222                 r = verity_parse_opt_args(&as, v, &verify_args);
1223                 if (r < 0)
1224                         goto bad;
1225         }
1226
1227         /* Root hash signature is  a optional parameter*/
1228         r = verity_verify_root_hash(root_hash_digest_to_validate,
1229                                     strlen(root_hash_digest_to_validate),
1230                                     verify_args.sig,
1231                                     verify_args.sig_size);
1232         if (r < 0) {
1233                 ti->error = "Root hash verification failed";
1234                 goto bad;
1235         }
1236         v->hash_per_block_bits =
1237                 __fls((1 << v->hash_dev_block_bits) / v->digest_size);
1238
1239         v->levels = 0;
1240         if (v->data_blocks)
1241                 while (v->hash_per_block_bits * v->levels < 64 &&
1242                        (unsigned long long)(v->data_blocks - 1) >>
1243                        (v->hash_per_block_bits * v->levels))
1244                         v->levels++;
1245
1246         if (v->levels > DM_VERITY_MAX_LEVELS) {
1247                 ti->error = "Too many tree levels";
1248                 r = -E2BIG;
1249                 goto bad;
1250         }
1251
1252         hash_position = v->hash_start;
1253         for (i = v->levels - 1; i >= 0; i--) {
1254                 sector_t s;
1255                 v->hash_level_block[i] = hash_position;
1256                 s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
1257                                         >> ((i + 1) * v->hash_per_block_bits);
1258                 if (hash_position + s < hash_position) {
1259                         ti->error = "Hash device offset overflow";
1260                         r = -E2BIG;
1261                         goto bad;
1262                 }
1263                 hash_position += s;
1264         }
1265         v->hash_blocks = hash_position;
1266
1267         v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
1268                 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
1269                 dm_bufio_alloc_callback, NULL);
1270         if (IS_ERR(v->bufio)) {
1271                 ti->error = "Cannot initialize dm-bufio";
1272                 r = PTR_ERR(v->bufio);
1273                 v->bufio = NULL;
1274                 goto bad;
1275         }
1276
1277         if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
1278                 ti->error = "Hash device is too small";
1279                 r = -E2BIG;
1280                 goto bad;
1281         }
1282
1283         /* WQ_UNBOUND greatly improves performance when running on ramdisk */
1284         v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
1285         if (!v->verify_wq) {
1286                 ti->error = "Cannot allocate workqueue";
1287                 r = -ENOMEM;
1288                 goto bad;
1289         }
1290
1291         ti->per_io_data_size = sizeof(struct dm_verity_io) +
1292                                 v->ahash_reqsize + v->digest_size * 2;
1293
1294         r = verity_fec_ctr(v);
1295         if (r)
1296                 goto bad;
1297
1298         ti->per_io_data_size = roundup(ti->per_io_data_size,
1299                                        __alignof__(struct dm_verity_io));
1300
1301         verity_verify_sig_opts_cleanup(&verify_args);
1302
1303         return 0;
1304
1305 bad:
1306
1307         verity_verify_sig_opts_cleanup(&verify_args);
1308         verity_dtr(ti);
1309
1310         return r;
1311 }
1312
1313 /*
1314  * Check whether a DM target is a verity target.
1315  */
1316 bool dm_is_verity_target(struct dm_target *ti)
1317 {
1318         return ti->type->module == THIS_MODULE;
1319 }
1320
1321 /*
1322  * Get the root digest of a verity target.
1323  *
1324  * Returns a copy of the root digest, the caller is responsible for
1325  * freeing the memory of the digest.
1326  */
1327 int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned int *digest_size)
1328 {
1329         struct dm_verity *v = ti->private;
1330
1331         if (!dm_is_verity_target(ti))
1332                 return -EINVAL;
1333
1334         *root_digest = kmemdup(v->root_digest, v->digest_size, GFP_KERNEL);
1335         if (*root_digest == NULL)
1336                 return -ENOMEM;
1337
1338         *digest_size = v->digest_size;
1339
1340         return 0;
1341 }
1342
1343 static struct target_type verity_target = {
1344         .name           = "verity",
1345         .features       = DM_TARGET_IMMUTABLE,
1346         .version        = {1, 8, 1},
1347         .module         = THIS_MODULE,
1348         .ctr            = verity_ctr,
1349         .dtr            = verity_dtr,
1350         .map            = verity_map,
1351         .status         = verity_status,
1352         .prepare_ioctl  = verity_prepare_ioctl,
1353         .iterate_devices = verity_iterate_devices,
1354         .io_hints       = verity_io_hints,
1355 };
1356
1357 static int __init dm_verity_init(void)
1358 {
1359         int r;
1360
1361         r = dm_register_target(&verity_target);
1362         if (r < 0)
1363                 DMERR("register failed %d", r);
1364
1365         return r;
1366 }
1367
1368 static void __exit dm_verity_exit(void)
1369 {
1370         dm_unregister_target(&verity_target);
1371 }
1372
1373 module_init(dm_verity_init);
1374 module_exit(dm_verity_exit);
1375
1376 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
1377 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
1378 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
1379 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
1380 MODULE_LICENSE("GPL");