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