drivers/md/dm-verity-target.c

   1 /*
   2  * Copyright (C) 2012 Red Hat, Inc.
   3  *
   4  * Author: Mikulas Patocka <mpatocka@redhat.com>
   5  *
   6  * Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
   7  *
   8  * This file is released under the GPLv2.
   9  *
  10  * In the file "/sys/module/dm_verity/parameters/prefetch_cluster" you can set
  11  * default prefetch value. Data are read in "prefetch_cluster" chunks from the
  12  * hash device. Setting this greatly improves performance when data and hash
  13  * are on the same disk on different partitions on devices with poor random
  14  * access behavior.
  15  */
  16
  17 #include "dm-verity.h"
  18 #include "dm-verity-fec.h"
  19
  20 #include <linux/module.h>
  21 #include <linux/reboot.h>
  22
  23 #define DM_MSG_PREFIX                   "verity"
  24
  25 #define DM_VERITY_ENV_LENGTH            42
  26 #define DM_VERITY_ENV_VAR_NAME          "DM_VERITY_ERR_BLOCK_NR"
  27
  28 #define DM_VERITY_DEFAULT_PREFETCH_SIZE 262144
  29
  30 #define DM_VERITY_MAX_CORRUPTED_ERRS    100
  31
  32 #define DM_VERITY_OPT_LOGGING           "ignore_corruption"
  33 #define DM_VERITY_OPT_RESTART           "restart_on_corruption"
  34 #define DM_VERITY_OPT_IGN_ZEROES        "ignore_zero_blocks"
  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 /*
  96  * Wrapper for crypto_shash_init, which handles verity salting.
  97  */
  98 static int verity_hash_init(struct dm_verity *v, struct shash_desc *desc)
  99 {
 100         int r;
 101
 102         desc->tfm = v->tfm;
 103         desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 104
 105         r = crypto_shash_init(desc);
 106
 107         if (unlikely(r < 0)) {
 108                 DMERR("crypto_shash_init failed: %d", r);
 109                 return r;
 110         }
 111
 112         if (likely(v->version >= 1)) {
 113                 r = crypto_shash_update(desc, v->salt, v->salt_size);
 114
 115                 if (unlikely(r < 0)) {
 116                         DMERR("crypto_shash_update failed: %d", r);
 117                         return r;
 118                 }
 119         }
 120
 121         return 0;
 122 }
 123
 124 static int verity_hash_update(struct dm_verity *v, struct shash_desc *desc,
 125                               const u8 *data, size_t len)
 126 {
 127         int r = crypto_shash_update(desc, data, len);
 128
 129         if (unlikely(r < 0))
 130                 DMERR("crypto_shash_update failed: %d", r);
 131
 132         return r;
 133 }
 134
 135 static int verity_hash_final(struct dm_verity *v, struct shash_desc *desc,
 136                              u8 *digest)
 137 {
 138         int r;
 139
 140         if (unlikely(!v->version)) {
 141                 r = crypto_shash_update(desc, v->salt, v->salt_size);
 142
 143                 if (r < 0) {
 144                         DMERR("crypto_shash_update failed: %d", r);
 145                         return r;
 146                 }
 147         }
 148
 149         r = crypto_shash_final(desc, digest);
 150
 151         if (unlikely(r < 0))
 152                 DMERR("crypto_shash_final failed: %d", r);
 153
 154         return r;
 155 }
 156
 157 int verity_hash(struct dm_verity *v, struct shash_desc *desc,
 158                 const u8 *data, size_t len, u8 *digest)
 159 {
 160         int r;
 161
 162         r = verity_hash_init(v, desc);
 163         if (unlikely(r < 0))
 164                 return r;
 165
 166         r = verity_hash_update(v, desc, data, len);
 167         if (unlikely(r < 0))
 168                 return r;
 169
 170         return verity_hash_final(v, desc, digest);
 171 }
 172
 173 static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
 174                                  sector_t *hash_block, unsigned *offset)
 175 {
 176         sector_t position = verity_position_at_level(v, block, level);
 177         unsigned idx;
 178
 179         *hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
 180
 181         if (!offset)
 182                 return;
 183
 184         idx = position & ((1 << v->hash_per_block_bits) - 1);
 185         if (!v->version)
 186                 *offset = idx * v->digest_size;
 187         else
 188                 *offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
 189 }
 190
 191 /*
 192  * Handle verification errors.
 193  */
 194 static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
 195                              unsigned long long block)
 196 {
 197         char verity_env[DM_VERITY_ENV_LENGTH];
 198         char *envp[] = { verity_env, NULL };
 199         const char *type_str = "";
 200         struct mapped_device *md = dm_table_get_md(v->ti->table);
 201
 202         /* Corruption should be visible in device status in all modes */
 203         v->hash_failed = 1;
 204
 205         if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
 206                 goto out;
 207
 208         v->corrupted_errs++;
 209
 210         switch (type) {
 211         case DM_VERITY_BLOCK_TYPE_DATA:
 212                 type_str = "data";
 213                 break;
 214         case DM_VERITY_BLOCK_TYPE_METADATA:
 215                 type_str = "metadata";
 216                 break;
 217         default:
 218                 BUG();
 219         }
 220
 221         DMERR("%s: %s block %llu is corrupted", v->data_dev->name, type_str,
 222                 block);
 223
 224         if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
 225                 DMERR("%s: reached maximum errors", v->data_dev->name);
 226
 227         snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
 228                 DM_VERITY_ENV_VAR_NAME, type, block);
 229
 230         kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
 231
 232 out:
 233         if (v->mode == DM_VERITY_MODE_LOGGING)
 234                 return 0;
 235
 236         if (v->mode == DM_VERITY_MODE_RESTART)
 237                 kernel_restart("dm-verity device corrupted");
 238
 239         return 1;
 240 }
 241
 242 /*
 243  * Verify hash of a metadata block pertaining to the specified data block
 244  * ("block" argument) at a specified level ("level" argument).
 245  *
 246  * On successful return, verity_io_want_digest(v, io) contains the hash value
 247  * for a lower tree level or for the data block (if we're at the lowest level).
 248  *
 249  * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
 250  * If "skip_unverified" is false, unverified buffer is hashed and verified
 251  * against current value of verity_io_want_digest(v, io).
 252  */
 253 static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 254                                sector_t block, int level, bool skip_unverified,
 255                                u8 *want_digest)
 256 {
 257         struct dm_buffer *buf;
 258         struct buffer_aux *aux;
 259         u8 *data;
 260         int r;
 261         sector_t hash_block;
 262         unsigned offset;
 263
 264         verity_hash_at_level(v, block, level, &hash_block, &offset);
 265
 266         data = dm_bufio_read(v->bufio, hash_block, &buf);
 267         if (IS_ERR(data))
 268                 return PTR_ERR(data);
 269
 270         aux = dm_bufio_get_aux_data(buf);
 271
 272         if (!aux->hash_verified) {
 273                 if (skip_unverified) {
 274                         r = 1;
 275                         goto release_ret_r;
 276                 }
 277
 278                 r = verity_hash(v, verity_io_hash_desc(v, io),
 279                                 data, 1 << v->hash_dev_block_bits,
 280                                 verity_io_real_digest(v, io));
 281                 if (unlikely(r < 0))
 282                         goto release_ret_r;
 283
 284                 if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
 285                                   v->digest_size) == 0))
 286                         aux->hash_verified = 1;
 287                 else if (verity_fec_decode(v, io,
 288                                            DM_VERITY_BLOCK_TYPE_METADATA,
 289                                            hash_block, data, NULL) == 0)
 290                         aux->hash_verified = 1;
 291                 else if (verity_handle_err(v,
 292                                            DM_VERITY_BLOCK_TYPE_METADATA,
 293                                            hash_block)) {
 294                         r = -EIO;
 295                         goto release_ret_r;
 296                 }
 297         }
 298
 299         data += offset;
 300         memcpy(want_digest, data, v->digest_size);
 301         r = 0;
 302
 303 release_ret_r:
 304         dm_bufio_release(buf);
 305         return r;
 306 }
 307
 308 /*
 309  * Find a hash for a given block, write it to digest and verify the integrity
 310  * of the hash tree if necessary.
 311  */
 312 int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
 313                           sector_t block, u8 *digest, bool *is_zero)
 314 {
 315         int r = 0, i;
 316
 317         if (likely(v->levels)) {
 318                 /*
 319                  * First, we try to get the requested hash for
 320                  * the current block. If the hash block itself is
 321                  * verified, zero is returned. If it isn't, this
 322                  * function returns 1 and we fall back to whole
 323                  * chain verification.
 324                  */
 325                 r = verity_verify_level(v, io, block, 0, true, digest);
 326                 if (likely(r <= 0))
 327                         goto out;
 328         }
 329
 330         memcpy(digest, v->root_digest, v->digest_size);
 331
 332         for (i = v->levels - 1; i >= 0; i--) {
 333                 r = verity_verify_level(v, io, block, i, false, digest);
 334                 if (unlikely(r))
 335                         goto out;
 336         }
 337 out:
 338         if (!r && v->zero_digest)
 339                 *is_zero = !memcmp(v->zero_digest, digest, v->digest_size);
 340         else
 341                 *is_zero = false;
 342
 343         return r;
 344 }
 345
 346 /*
 347  * Calls function process for 1 << v->data_dev_block_bits bytes in the bio_vec
 348  * starting from iter.
 349  */
 350 int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
 351                         struct bvec_iter *iter,
 352                         int (*process)(struct dm_verity *v,
 353                                        struct dm_verity_io *io, u8 *data,
 354                                        size_t len))
 355 {
 356         unsigned todo = 1 << v->data_dev_block_bits;
 357         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 358
 359         do {
 360                 int r;
 361                 u8 *page;
 362                 unsigned len;
 363                 struct bio_vec bv = bio_iter_iovec(bio, *iter);
 364
 365                 page = kmap_atomic(bv.bv_page);
 366                 len = bv.bv_len;
 367
 368                 if (likely(len >= todo))
 369                         len = todo;
 370
 371                 r = process(v, io, page + bv.bv_offset, len);
 372                 kunmap_atomic(page);
 373
 374                 if (r < 0)
 375                         return r;
 376
 377                 bio_advance_iter(bio, iter, len);
 378                 todo -= len;
 379         } while (todo);
 380
 381         return 0;
 382 }
 383
 384 static int verity_bv_hash_update(struct dm_verity *v, struct dm_verity_io *io,
 385                                  u8 *data, size_t len)
 386 {
 387         return verity_hash_update(v, verity_io_hash_desc(v, io), data, len);
 388 }
 389
 390 static int verity_bv_zero(struct dm_verity *v, struct dm_verity_io *io,
 391                           u8 *data, size_t len)
 392 {
 393         memset(data, 0, len);
 394         return 0;
 395 }
 396
 397 /*
 398  * Verify one "dm_verity_io" structure.
 399  */
 400 static int verity_verify_io(struct dm_verity_io *io)
 401 {
 402         bool is_zero;
 403         struct dm_verity *v = io->v;
 404         struct bvec_iter start;
 405         unsigned b;
 406
 407         for (b = 0; b < io->n_blocks; b++) {
 408                 int r;
 409                 struct shash_desc *desc = verity_io_hash_desc(v, io);
 410
 411                 r = verity_hash_for_block(v, io, io->block + b,
 412                                           verity_io_want_digest(v, io),
 413                                           &is_zero);
 414                 if (unlikely(r < 0))
 415                         return r;
 416
 417                 if (is_zero) {
 418                         /*
 419                          * If we expect a zero block, don't validate, just
 420                          * return zeros.
 421                          */
 422                         r = verity_for_bv_block(v, io, &io->iter,
 423                                                 verity_bv_zero);
 424                         if (unlikely(r < 0))
 425                                 return r;
 426
 427                         continue;
 428                 }
 429
 430                 r = verity_hash_init(v, desc);
 431                 if (unlikely(r < 0))
 432                         return r;
 433
 434                 start = io->iter;
 435                 r = verity_for_bv_block(v, io, &io->iter, verity_bv_hash_update);
 436                 if (unlikely(r < 0))
 437                         return r;
 438
 439                 r = verity_hash_final(v, desc, verity_io_real_digest(v, io));
 440                 if (unlikely(r < 0))
 441                         return r;
 442
 443                 if (likely(memcmp(verity_io_real_digest(v, io),
 444                                   verity_io_want_digest(v, io), v->digest_size) == 0))
 445                         continue;
 446                 else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
 447                                            io->block + b, NULL, &start) == 0)
 448                         continue;
 449                 else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
 450                                            io->block + b))
 451                         return -EIO;
 452         }
 453
 454         return 0;
 455 }
 456
 457 /*
 458  * End one "io" structure with a given error.
 459  */
 460 static void verity_finish_io(struct dm_verity_io *io, int error)
 461 {
 462         struct dm_verity *v = io->v;
 463         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 464
 465         bio->bi_end_io = io->orig_bi_end_io;
 466         bio->bi_error = error;
 467
 468         verity_fec_finish_io(io);
 469
 470         bio_endio(bio);
 471 }
 472
 473 static void verity_work(struct work_struct *w)
 474 {
 475         struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
 476
 477         verity_finish_io(io, verity_verify_io(io));
 478 }
 479
 480 static void verity_end_io(struct bio *bio)
 481 {
 482         struct dm_verity_io *io = bio->bi_private;
 483
 484         if (bio->bi_error && !verity_fec_is_enabled(io->v)) {
 485                 verity_finish_io(io, bio->bi_error);
 486                 return;
 487         }
 488
 489         INIT_WORK(&io->work, verity_work);
 490         queue_work(io->v->verify_wq, &io->work);
 491 }
 492
 493 /*
 494  * Prefetch buffers for the specified io.
 495  * The root buffer is not prefetched, it is assumed that it will be cached
 496  * all the time.
 497  */
 498 static void verity_prefetch_io(struct work_struct *work)
 499 {
 500         struct dm_verity_prefetch_work *pw =
 501                 container_of(work, struct dm_verity_prefetch_work, work);
 502         struct dm_verity *v = pw->v;
 503         int i;
 504
 505         for (i = v->levels - 2; i >= 0; i--) {
 506                 sector_t hash_block_start;
 507                 sector_t hash_block_end;
 508                 verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
 509                 verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
 510                 if (!i) {
 511                         unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);
 512
 513                         cluster >>= v->data_dev_block_bits;
 514                         if (unlikely(!cluster))
 515                                 goto no_prefetch_cluster;
 516
 517                         if (unlikely(cluster & (cluster - 1)))
 518                                 cluster = 1 << __fls(cluster);
 519
 520                         hash_block_start &= ~(sector_t)(cluster - 1);
 521                         hash_block_end |= cluster - 1;
 522                         if (unlikely(hash_block_end >= v->hash_blocks))
 523                                 hash_block_end = v->hash_blocks - 1;
 524                 }
 525 no_prefetch_cluster:
 526                 dm_bufio_prefetch(v->bufio, hash_block_start,
 527                                   hash_block_end - hash_block_start + 1);
 528         }
 529
 530         kfree(pw);
 531 }
 532
 533 static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
 534 {
 535         struct dm_verity_prefetch_work *pw;
 536
 537         pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
 538                 GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 539
 540         if (!pw)
 541                 return;
 542
 543         INIT_WORK(&pw->work, verity_prefetch_io);
 544         pw->v = v;
 545         pw->block = io->block;
 546         pw->n_blocks = io->n_blocks;
 547         queue_work(v->verify_wq, &pw->work);
 548 }
 549
 550 /*
 551  * Bio map function. It allocates dm_verity_io structure and bio vector and
 552  * fills them. Then it issues prefetches and the I/O.
 553  */
 554 static int verity_map(struct dm_target *ti, struct bio *bio)
 555 {
 556         struct dm_verity *v = ti->private;
 557         struct dm_verity_io *io;
 558
 559         bio->bi_bdev = v->data_dev->bdev;
 560         bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
 561
 562         if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
 563             ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
 564                 DMERR_LIMIT("unaligned io");
 565                 return -EIO;
 566         }
 567
 568         if (bio_end_sector(bio) >>
 569             (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
 570                 DMERR_LIMIT("io out of range");
 571                 return -EIO;
 572         }
 573
 574         if (bio_data_dir(bio) == WRITE)
 575                 return -EIO;
 576
 577         io = dm_per_bio_data(bio, ti->per_io_data_size);
 578         io->v = v;
 579         io->orig_bi_end_io = bio->bi_end_io;
 580         io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
 581         io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
 582
 583         bio->bi_end_io = verity_end_io;
 584         bio->bi_private = io;
 585         io->iter = bio->bi_iter;
 586
 587         verity_fec_init_io(io);
 588
 589         verity_submit_prefetch(v, io);
 590
 591         generic_make_request(bio);
 592
 593         return DM_MAPIO_SUBMITTED;
 594 }
 595
 596 /*
 597  * Status: V (valid) or C (corruption found)
 598  */
 599 static void verity_status(struct dm_target *ti, status_type_t type,
 600                           unsigned status_flags, char *result, unsigned maxlen)
 601 {
 602         struct dm_verity *v = ti->private;
 603         unsigned args = 0;
 604         unsigned sz = 0;
 605         unsigned x;
 606
 607         switch (type) {
 608         case STATUSTYPE_INFO:
 609                 DMEMIT("%c", v->hash_failed ? 'C' : 'V');
 610                 break;
 611         case STATUSTYPE_TABLE:
 612                 DMEMIT("%u %s %s %u %u %llu %llu %s ",
 613                         v->version,
 614                         v->data_dev->name,
 615                         v->hash_dev->name,
 616                         1 << v->data_dev_block_bits,
 617                         1 << v->hash_dev_block_bits,
 618                         (unsigned long long)v->data_blocks,
 619                         (unsigned long long)v->hash_start,
 620                         v->alg_name
 621                         );
 622                 for (x = 0; x < v->digest_size; x++)
 623                         DMEMIT("%02x", v->root_digest[x]);
 624                 DMEMIT(" ");
 625                 if (!v->salt_size)
 626                         DMEMIT("-");
 627                 else
 628                         for (x = 0; x < v->salt_size; x++)
 629                                 DMEMIT("%02x", v->salt[x]);
 630                 if (v->mode != DM_VERITY_MODE_EIO)
 631                         args++;
 632                 if (verity_fec_is_enabled(v))
 633                         args += DM_VERITY_OPTS_FEC;
 634                 if (v->zero_digest)
 635                         args++;
 636                 if (!args)
 637                         return;
 638                 DMEMIT(" %u", args);
 639                 if (v->mode != DM_VERITY_MODE_EIO) {
 640                         DMEMIT(" ");
 641                         switch (v->mode) {
 642                         case DM_VERITY_MODE_LOGGING:
 643                                 DMEMIT(DM_VERITY_OPT_LOGGING);
 644                                 break;
 645                         case DM_VERITY_MODE_RESTART:
 646                                 DMEMIT(DM_VERITY_OPT_RESTART);
 647                                 break;
 648                         default:
 649                                 BUG();
 650                         }
 651                 }
 652                 if (v->zero_digest)
 653                         DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);
 654                 sz = verity_fec_status_table(v, sz, result, maxlen);
 655                 break;
 656         }
 657 }
 658
 659 static int verity_prepare_ioctl(struct dm_target *ti,
 660                 struct block_device **bdev, fmode_t *mode)
 661 {
 662         struct dm_verity *v = ti->private;
 663
 664         *bdev = v->data_dev->bdev;
 665
 666         if (v->data_start ||
 667             ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
 668                 return 1;
 669         return 0;
 670 }
 671
 672 static int verity_iterate_devices(struct dm_target *ti,
 673                                   iterate_devices_callout_fn fn, void *data)
 674 {
 675         struct dm_verity *v = ti->private;
 676
 677         return fn(ti, v->data_dev, v->data_start, ti->len, data);
 678 }
 679
 680 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
 681 {
 682         struct dm_verity *v = ti->private;
 683
 684         if (limits->logical_block_size < 1 << v->data_dev_block_bits)
 685                 limits->logical_block_size = 1 << v->data_dev_block_bits;
 686
 687         if (limits->physical_block_size < 1 << v->data_dev_block_bits)
 688                 limits->physical_block_size = 1 << v->data_dev_block_bits;
 689
 690         blk_limits_io_min(limits, limits->logical_block_size);
 691 }
 692
 693 static void verity_dtr(struct dm_target *ti)
 694 {
 695         struct dm_verity *v = ti->private;
 696
 697         if (v->verify_wq)
 698                 destroy_workqueue(v->verify_wq);
 699
 700         if (v->bufio)
 701                 dm_bufio_client_destroy(v->bufio);
 702
 703         kfree(v->salt);
 704         kfree(v->root_digest);
 705         kfree(v->zero_digest);
 706
 707         if (v->tfm)
 708                 crypto_free_shash(v->tfm);
 709
 710         kfree(v->alg_name);
 711
 712         if (v->hash_dev)
 713                 dm_put_device(ti, v->hash_dev);
 714
 715         if (v->data_dev)
 716                 dm_put_device(ti, v->data_dev);
 717
 718         verity_fec_dtr(v);
 719
 720         kfree(v);
 721 }
 722
 723 static int verity_alloc_zero_digest(struct dm_verity *v)
 724 {
 725         int r = -ENOMEM;
 726         struct shash_desc *desc;
 727         u8 *zero_data;
 728
 729         v->zero_digest = kmalloc(v->digest_size, GFP_KERNEL);
 730
 731         if (!v->zero_digest)
 732                 return r;
 733
 734         desc = kmalloc(v->shash_descsize, GFP_KERNEL);
 735
 736         if (!desc)
 737                 return r; /* verity_dtr will free zero_digest */
 738
 739         zero_data = kzalloc(1 << v->data_dev_block_bits, GFP_KERNEL);
 740
 741         if (!zero_data)
 742                 goto out;
 743
 744         r = verity_hash(v, desc, zero_data, 1 << v->data_dev_block_bits,
 745                         v->zero_digest);
 746
 747 out:
 748         kfree(desc);
 749         kfree(zero_data);
 750
 751         return r;
 752 }
 753
 754 static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v)
 755 {
 756         int r;
 757         unsigned argc;
 758         struct dm_target *ti = v->ti;
 759         const char *arg_name;
 760
 761         static struct dm_arg _args[] = {
 762                 {0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
 763         };
 764
 765         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 766         if (r)
 767                 return -EINVAL;
 768
 769         if (!argc)
 770                 return 0;
 771
 772         do {
 773                 arg_name = dm_shift_arg(as);
 774                 argc--;
 775
 776                 if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING)) {
 777                         v->mode = DM_VERITY_MODE_LOGGING;
 778                         continue;
 779
 780                 } else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) {
 781                         v->mode = DM_VERITY_MODE_RESTART;
 782                         continue;
 783
 784                 } else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
 785                         r = verity_alloc_zero_digest(v);
 786                         if (r) {
 787                                 ti->error = "Cannot allocate zero digest";
 788                                 return r;
 789                         }
 790                         continue;
 791
 792                 } else if (verity_is_fec_opt_arg(arg_name)) {
 793                         r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
 794                         if (r)
 795                                 return r;
 796                         continue;
 797                 }
 798
 799                 ti->error = "Unrecognized verity feature request";
 800                 return -EINVAL;
 801         } while (argc && !r);
 802
 803         return r;
 804 }
 805
 806 /*
 807  * Target parameters:
 808  *      <version>       The current format is version 1.
 809  *                      Vsn 0 is compatible with original Chromium OS releases.
 810  *      <data device>
 811  *      <hash device>
 812  *      <data block size>
 813  *      <hash block size>
 814  *      <the number of data blocks>
 815  *      <hash start block>
 816  *      <algorithm>
 817  *      <digest>
 818  *      <salt>          Hex string or "-" if no salt.
 819  */
 820 static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 821 {
 822         struct dm_verity *v;
 823         struct dm_arg_set as;
 824         unsigned int num;
 825         unsigned long long num_ll;
 826         int r;
 827         int i;
 828         sector_t hash_position;
 829         char dummy;
 830
 831         v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
 832         if (!v) {
 833                 ti->error = "Cannot allocate verity structure";
 834                 return -ENOMEM;
 835         }
 836         ti->private = v;
 837         v->ti = ti;
 838
 839         r = verity_fec_ctr_alloc(v);
 840         if (r)
 841                 goto bad;
 842
 843         if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
 844                 ti->error = "Device must be readonly";
 845                 r = -EINVAL;
 846                 goto bad;
 847         }
 848
 849         if (argc < 10) {
 850                 ti->error = "Not enough arguments";
 851                 r = -EINVAL;
 852                 goto bad;
 853         }
 854
 855         if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
 856             num > 1) {
 857                 ti->error = "Invalid version";
 858                 r = -EINVAL;
 859                 goto bad;
 860         }
 861         v->version = num;
 862
 863         r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
 864         if (r) {
 865                 ti->error = "Data device lookup failed";
 866                 goto bad;
 867         }
 868
 869         r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
 870         if (r) {
 871                 ti->error = "Data device lookup failed";
 872                 goto bad;
 873         }
 874
 875         if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
 876             !num || (num & (num - 1)) ||
 877             num < bdev_logical_block_size(v->data_dev->bdev) ||
 878             num > PAGE_SIZE) {
 879                 ti->error = "Invalid data device block size";
 880                 r = -EINVAL;
 881                 goto bad;
 882         }
 883         v->data_dev_block_bits = __ffs(num);
 884
 885         if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
 886             !num || (num & (num - 1)) ||
 887             num < bdev_logical_block_size(v->hash_dev->bdev) ||
 888             num > INT_MAX) {
 889                 ti->error = "Invalid hash device block size";
 890                 r = -EINVAL;
 891                 goto bad;
 892         }
 893         v->hash_dev_block_bits = __ffs(num);
 894
 895         if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
 896             (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
 897             >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 898                 ti->error = "Invalid data blocks";
 899                 r = -EINVAL;
 900                 goto bad;
 901         }
 902         v->data_blocks = num_ll;
 903
 904         if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
 905                 ti->error = "Data device is too small";
 906                 r = -EINVAL;
 907                 goto bad;
 908         }
 909
 910         if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
 911             (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
 912             >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 913                 ti->error = "Invalid hash start";
 914                 r = -EINVAL;
 915                 goto bad;
 916         }
 917         v->hash_start = num_ll;
 918
 919         v->alg_name = kstrdup(argv[7], GFP_KERNEL);
 920         if (!v->alg_name) {
 921                 ti->error = "Cannot allocate algorithm name";
 922                 r = -ENOMEM;
 923                 goto bad;
 924         }
 925
 926         v->tfm = crypto_alloc_shash(v->alg_name, 0, 0);
 927         if (IS_ERR(v->tfm)) {
 928                 ti->error = "Cannot initialize hash function";
 929                 r = PTR_ERR(v->tfm);
 930                 v->tfm = NULL;
 931                 goto bad;
 932         }
 933         v->digest_size = crypto_shash_digestsize(v->tfm);
 934         if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
 935                 ti->error = "Digest size too big";
 936                 r = -EINVAL;
 937                 goto bad;
 938         }
 939         v->shash_descsize =
 940                 sizeof(struct shash_desc) + crypto_shash_descsize(v->tfm);
 941
 942         v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
 943         if (!v->root_digest) {
 944                 ti->error = "Cannot allocate root digest";
 945                 r = -ENOMEM;
 946                 goto bad;
 947         }
 948         if (strlen(argv[8]) != v->digest_size * 2 ||
 949             hex2bin(v->root_digest, argv[8], v->digest_size)) {
 950                 ti->error = "Invalid root digest";
 951                 r = -EINVAL;
 952                 goto bad;
 953         }
 954
 955         if (strcmp(argv[9], "-")) {
 956                 v->salt_size = strlen(argv[9]) / 2;
 957                 v->salt = kmalloc(v->salt_size, GFP_KERNEL);
 958                 if (!v->salt) {
 959                         ti->error = "Cannot allocate salt";
 960                         r = -ENOMEM;
 961                         goto bad;
 962                 }
 963                 if (strlen(argv[9]) != v->salt_size * 2 ||
 964                     hex2bin(v->salt, argv[9], v->salt_size)) {
 965                         ti->error = "Invalid salt";
 966                         r = -EINVAL;
 967                         goto bad;
 968                 }
 969         }
 970
 971         argv += 10;
 972         argc -= 10;
 973
 974         /* Optional parameters */
 975         if (argc) {
 976                 as.argc = argc;
 977                 as.argv = argv;
 978
 979                 r = verity_parse_opt_args(&as, v);
 980                 if (r < 0)
 981                         goto bad;
 982         }
 983
 984         v->hash_per_block_bits =
 985                 __fls((1 << v->hash_dev_block_bits) / v->digest_size);
 986
 987         v->levels = 0;
 988         if (v->data_blocks)
 989                 while (v->hash_per_block_bits * v->levels < 64 &&
 990                        (unsigned long long)(v->data_blocks - 1) >>
 991                        (v->hash_per_block_bits * v->levels))
 992                         v->levels++;
 993
 994         if (v->levels > DM_VERITY_MAX_LEVELS) {
 995                 ti->error = "Too many tree levels";
 996                 r = -E2BIG;
 997                 goto bad;
 998         }
 999
1000         hash_position = v->hash_start;
1001         for (i = v->levels - 1; i >= 0; i--) {
1002                 sector_t s;
1003                 v->hash_level_block[i] = hash_position;
1004                 s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
1005                                         >> ((i + 1) * v->hash_per_block_bits);
1006                 if (hash_position + s < hash_position) {
1007                         ti->error = "Hash device offset overflow";
1008                         r = -E2BIG;
1009                         goto bad;
1010                 }
1011                 hash_position += s;
1012         }
1013         v->hash_blocks = hash_position;
1014
1015         v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
1016                 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
1017                 dm_bufio_alloc_callback, NULL);
1018         if (IS_ERR(v->bufio)) {
1019                 ti->error = "Cannot initialize dm-bufio";
1020                 r = PTR_ERR(v->bufio);
1021                 v->bufio = NULL;
1022                 goto bad;
1023         }
1024
1025         if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
1026                 ti->error = "Hash device is too small";
1027                 r = -E2BIG;
1028                 goto bad;
1029         }
1030
1031         /* WQ_UNBOUND greatly improves performance when running on ramdisk */
1032         v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
1033         if (!v->verify_wq) {
1034                 ti->error = "Cannot allocate workqueue";
1035                 r = -ENOMEM;
1036                 goto bad;
1037         }
1038
1039         ti->per_io_data_size = sizeof(struct dm_verity_io) +
1040                                 v->shash_descsize + v->digest_size * 2;
1041
1042         r = verity_fec_ctr(v);
1043         if (r)
1044                 goto bad;
1045
1046         ti->per_io_data_size = roundup(ti->per_io_data_size,
1047                                        __alignof__(struct dm_verity_io));
1048
1049         return 0;
1050
1051 bad:
1052         verity_dtr(ti);
1053
1054         return r;
1055 }
1056
1057 static struct target_type verity_target = {
1058         .name           = "verity",
1059         .version        = {1, 3, 0},
1060         .module         = THIS_MODULE,
1061         .ctr            = verity_ctr,
1062         .dtr            = verity_dtr,
1063         .map            = verity_map,
1064         .status         = verity_status,
1065         .prepare_ioctl  = verity_prepare_ioctl,
1066         .iterate_devices = verity_iterate_devices,
1067         .io_hints       = verity_io_hints,
1068 };
1069
1070 static int __init dm_verity_init(void)
1071 {
1072         int r;
1073
1074         r = dm_register_target(&verity_target);
1075         if (r < 0)
1076                 DMERR("register failed %d", r);
1077
1078         return r;
1079 }
1080
1081 static void __exit dm_verity_exit(void)
1082 {
1083         dm_unregister_target(&verity_target);
1084 }
1085
1086 module_init(dm_verity_init);
1087 module_exit(dm_verity_exit);
1088
1089 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
1090 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
1091 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
1092 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
1093 MODULE_LICENSE("GPL");