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
  35 #define DM_VERITY_OPTS_MAX              (1 + DM_VERITY_OPTS_FEC)
  36
  37 static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
  38
  39 module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
  40
  41 struct dm_verity_prefetch_work {
  42         struct work_struct work;
  43         struct dm_verity *v;
  44         sector_t block;
  45         unsigned n_blocks;
  46 };
  47
  48 /*
  49  * Auxiliary structure appended to each dm-bufio buffer. If the value
  50  * hash_verified is nonzero, hash of the block has been verified.
  51  *
  52  * The variable hash_verified is set to 0 when allocating the buffer, then
  53  * it can be changed to 1 and it is never reset to 0 again.
  54  *
  55  * There is no lock around this value, a race condition can at worst cause
  56  * that multiple processes verify the hash of the same buffer simultaneously
  57  * and write 1 to hash_verified simultaneously.
  58  * This condition is harmless, so we don't need locking.
  59  */
  60 struct buffer_aux {
  61         int hash_verified;
  62 };
  63
  64 /*
  65  * Initialize struct buffer_aux for a freshly created buffer.
  66  */
  67 static void dm_bufio_alloc_callback(struct dm_buffer *buf)
  68 {
  69         struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
  70
  71         aux->hash_verified = 0;
  72 }
  73
  74 /*
  75  * Translate input sector number to the sector number on the target device.
  76  */
  77 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
  78 {
  79         return v->data_start + dm_target_offset(v->ti, bi_sector);
  80 }
  81
  82 /*
  83  * Return hash position of a specified block at a specified tree level
  84  * (0 is the lowest level).
  85  * The lowest "hash_per_block_bits"-bits of the result denote hash position
  86  * inside a hash block. The remaining bits denote location of the hash block.
  87  */
  88 static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
  89                                          int level)
  90 {
  91         return block >> (level * v->hash_per_block_bits);
  92 }
  93
  94 /*
  95  * Wrapper for crypto_shash_init, which handles verity salting.
  96  */
  97 static int verity_hash_init(struct dm_verity *v, struct shash_desc *desc)
  98 {
  99         int r;
 100
 101         desc->tfm = v->tfm;
 102         desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 103
 104         r = crypto_shash_init(desc);
 105
 106         if (unlikely(r < 0)) {
 107                 DMERR("crypto_shash_init failed: %d", r);
 108                 return r;
 109         }
 110
 111         if (likely(v->version >= 1)) {
 112                 r = crypto_shash_update(desc, v->salt, v->salt_size);
 113
 114                 if (unlikely(r < 0)) {
 115                         DMERR("crypto_shash_update failed: %d", r);
 116                         return r;
 117                 }
 118         }
 119
 120         return 0;
 121 }
 122
 123 static int verity_hash_update(struct dm_verity *v, struct shash_desc *desc,
 124                               const u8 *data, size_t len)
 125 {
 126         int r = crypto_shash_update(desc, data, len);
 127
 128         if (unlikely(r < 0))
 129                 DMERR("crypto_shash_update failed: %d", r);
 130
 131         return r;
 132 }
 133
 134 static int verity_hash_final(struct dm_verity *v, struct shash_desc *desc,
 135                              u8 *digest)
 136 {
 137         int r;
 138
 139         if (unlikely(!v->version)) {
 140                 r = crypto_shash_update(desc, v->salt, v->salt_size);
 141
 142                 if (r < 0) {
 143                         DMERR("crypto_shash_update failed: %d", r);
 144                         return r;
 145                 }
 146         }
 147
 148         r = crypto_shash_final(desc, digest);
 149
 150         if (unlikely(r < 0))
 151                 DMERR("crypto_shash_final failed: %d", r);
 152
 153         return r;
 154 }
 155
 156 int verity_hash(struct dm_verity *v, struct shash_desc *desc,
 157                 const u8 *data, size_t len, u8 *digest)
 158 {
 159         int r;
 160
 161         r = verity_hash_init(v, desc);
 162         if (unlikely(r < 0))
 163                 return r;
 164
 165         r = verity_hash_update(v, desc, data, len);
 166         if (unlikely(r < 0))
 167                 return r;
 168
 169         return verity_hash_final(v, desc, digest);
 170 }
 171
 172 static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
 173                                  sector_t *hash_block, unsigned *offset)
 174 {
 175         sector_t position = verity_position_at_level(v, block, level);
 176         unsigned idx;
 177
 178         *hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
 179
 180         if (!offset)
 181                 return;
 182
 183         idx = position & ((1 << v->hash_per_block_bits) - 1);
 184         if (!v->version)
 185                 *offset = idx * v->digest_size;
 186         else
 187                 *offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
 188 }
 189
 190 /*
 191  * Handle verification errors.
 192  */
 193 static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
 194                              unsigned long long block)
 195 {
 196         char verity_env[DM_VERITY_ENV_LENGTH];
 197         char *envp[] = { verity_env, NULL };
 198         const char *type_str = "";
 199         struct mapped_device *md = dm_table_get_md(v->ti->table);
 200
 201         /* Corruption should be visible in device status in all modes */
 202         v->hash_failed = 1;
 203
 204         if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
 205                 goto out;
 206
 207         v->corrupted_errs++;
 208
 209         switch (type) {
 210         case DM_VERITY_BLOCK_TYPE_DATA:
 211                 type_str = "data";
 212                 break;
 213         case DM_VERITY_BLOCK_TYPE_METADATA:
 214                 type_str = "metadata";
 215                 break;
 216         default:
 217                 BUG();
 218         }
 219
 220         DMERR("%s: %s block %llu is corrupted", v->data_dev->name, type_str,
 221                 block);
 222
 223         if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
 224                 DMERR("%s: reached maximum errors", v->data_dev->name);
 225
 226         snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
 227                 DM_VERITY_ENV_VAR_NAME, type, block);
 228
 229         kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
 230
 231 out:
 232         if (v->mode == DM_VERITY_MODE_LOGGING)
 233                 return 0;
 234
 235         if (v->mode == DM_VERITY_MODE_RESTART)
 236                 kernel_restart("dm-verity device corrupted");
 237
 238         return 1;
 239 }
 240
 241 /*
 242  * Verify hash of a metadata block pertaining to the specified data block
 243  * ("block" argument) at a specified level ("level" argument).
 244  *
 245  * On successful return, verity_io_want_digest(v, io) contains the hash value
 246  * for a lower tree level or for the data block (if we're at the lowest level).
 247  *
 248  * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
 249  * If "skip_unverified" is false, unverified buffer is hashed and verified
 250  * against current value of verity_io_want_digest(v, io).
 251  */
 252 static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 253                                sector_t block, int level, bool skip_unverified,
 254                                u8 *want_digest)
 255 {
 256         struct dm_buffer *buf;
 257         struct buffer_aux *aux;
 258         u8 *data;
 259         int r;
 260         sector_t hash_block;
 261         unsigned offset;
 262
 263         verity_hash_at_level(v, block, level, &hash_block, &offset);
 264
 265         data = dm_bufio_read(v->bufio, hash_block, &buf);
 266         if (IS_ERR(data))
 267                 return PTR_ERR(data);
 268
 269         aux = dm_bufio_get_aux_data(buf);
 270
 271         if (!aux->hash_verified) {
 272                 if (skip_unverified) {
 273                         r = 1;
 274                         goto release_ret_r;
 275                 }
 276
 277                 r = verity_hash(v, verity_io_hash_desc(v, io),
 278                                 data, 1 << v->hash_dev_block_bits,
 279                                 verity_io_real_digest(v, io));
 280                 if (unlikely(r < 0))
 281                         goto release_ret_r;
 282
 283                 if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
 284                                   v->digest_size) == 0))
 285                         aux->hash_verified = 1;
 286                 else if (verity_fec_decode(v, io,
 287                                            DM_VERITY_BLOCK_TYPE_METADATA,
 288                                            hash_block, data, NULL) == 0)
 289                         aux->hash_verified = 1;
 290                 else if (verity_handle_err(v,
 291                                            DM_VERITY_BLOCK_TYPE_METADATA,
 292                                            hash_block)) {
 293                         r = -EIO;
 294                         goto release_ret_r;
 295                 }
 296         }
 297
 298         data += offset;
 299         memcpy(want_digest, data, v->digest_size);
 300         r = 0;
 301
 302 release_ret_r:
 303         dm_bufio_release(buf);
 304         return r;
 305 }
 306
 307 /*
 308  * Find a hash for a given block, write it to digest and verify the integrity
 309  * of the hash tree if necessary.
 310  */
 311 int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
 312                           sector_t block, u8 *digest)
 313 {
 314         int i;
 315         int r;
 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                         return r;
 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                         return r;
 336         }
 337
 338         return 0;
 339 }
 340
 341 /*
 342  * Calls function process for 1 << v->data_dev_block_bits bytes in the bio_vec
 343  * starting from iter.
 344  */
 345 int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
 346                         struct bvec_iter *iter,
 347                         int (*process)(struct dm_verity *v,
 348                                        struct dm_verity_io *io, u8 *data,
 349                                        size_t len))
 350 {
 351         unsigned todo = 1 << v->data_dev_block_bits;
 352         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_bio_data_size);
 353
 354         do {
 355                 int r;
 356                 u8 *page;
 357                 unsigned len;
 358                 struct bio_vec bv = bio_iter_iovec(bio, *iter);
 359
 360                 page = kmap_atomic(bv.bv_page);
 361                 len = bv.bv_len;
 362
 363                 if (likely(len >= todo))
 364                         len = todo;
 365
 366                 r = process(v, io, page + bv.bv_offset, len);
 367                 kunmap_atomic(page);
 368
 369                 if (r < 0)
 370                         return r;
 371
 372                 bio_advance_iter(bio, iter, len);
 373                 todo -= len;
 374         } while (todo);
 375
 376         return 0;
 377 }
 378
 379 static int verity_bv_hash_update(struct dm_verity *v, struct dm_verity_io *io,
 380                                  u8 *data, size_t len)
 381 {
 382         return verity_hash_update(v, verity_io_hash_desc(v, io), data, len);
 383 }
 384
 385 /*
 386  * Verify one "dm_verity_io" structure.
 387  */
 388 static int verity_verify_io(struct dm_verity_io *io)
 389 {
 390         struct dm_verity *v = io->v;
 391         struct bvec_iter start;
 392         unsigned b;
 393
 394         for (b = 0; b < io->n_blocks; b++) {
 395                 int r;
 396                 struct shash_desc *desc = verity_io_hash_desc(v, io);
 397
 398                 r = verity_hash_for_block(v, io, io->block + b,
 399                                           verity_io_want_digest(v, io));
 400                 if (unlikely(r < 0))
 401                         return r;
 402
 403                 r = verity_hash_init(v, desc);
 404                 if (unlikely(r < 0))
 405                         return r;
 406
 407                 start = io->iter;
 408                 r = verity_for_bv_block(v, io, &io->iter, verity_bv_hash_update);
 409                 if (unlikely(r < 0))
 410                         return r;
 411
 412                 r = verity_hash_final(v, desc, verity_io_real_digest(v, io));
 413                 if (unlikely(r < 0))
 414                         return r;
 415
 416                 if (likely(memcmp(verity_io_real_digest(v, io),
 417                                   verity_io_want_digest(v, io), v->digest_size) == 0))
 418                         continue;
 419                 else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
 420                                            io->block + b, NULL, &start) == 0)
 421                         continue;
 422                 else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
 423                                            io->block + b))
 424                         return -EIO;
 425         }
 426
 427         return 0;
 428 }
 429
 430 /*
 431  * End one "io" structure with a given error.
 432  */
 433 static void verity_finish_io(struct dm_verity_io *io, int error)
 434 {
 435         struct dm_verity *v = io->v;
 436         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_bio_data_size);
 437
 438         bio->bi_end_io = io->orig_bi_end_io;
 439         bio->bi_error = error;
 440
 441         verity_fec_finish_io(io);
 442
 443         bio_endio(bio);
 444 }
 445
 446 static void verity_work(struct work_struct *w)
 447 {
 448         struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
 449
 450         verity_finish_io(io, verity_verify_io(io));
 451 }
 452
 453 static void verity_end_io(struct bio *bio)
 454 {
 455         struct dm_verity_io *io = bio->bi_private;
 456
 457         if (bio->bi_error && !verity_fec_is_enabled(io->v)) {
 458                 verity_finish_io(io, bio->bi_error);
 459                 return;
 460         }
 461
 462         INIT_WORK(&io->work, verity_work);
 463         queue_work(io->v->verify_wq, &io->work);
 464 }
 465
 466 /*
 467  * Prefetch buffers for the specified io.
 468  * The root buffer is not prefetched, it is assumed that it will be cached
 469  * all the time.
 470  */
 471 static void verity_prefetch_io(struct work_struct *work)
 472 {
 473         struct dm_verity_prefetch_work *pw =
 474                 container_of(work, struct dm_verity_prefetch_work, work);
 475         struct dm_verity *v = pw->v;
 476         int i;
 477
 478         for (i = v->levels - 2; i >= 0; i--) {
 479                 sector_t hash_block_start;
 480                 sector_t hash_block_end;
 481                 verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
 482                 verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
 483                 if (!i) {
 484                         unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);
 485
 486                         cluster >>= v->data_dev_block_bits;
 487                         if (unlikely(!cluster))
 488                                 goto no_prefetch_cluster;
 489
 490                         if (unlikely(cluster & (cluster - 1)))
 491                                 cluster = 1 << __fls(cluster);
 492
 493                         hash_block_start &= ~(sector_t)(cluster - 1);
 494                         hash_block_end |= cluster - 1;
 495                         if (unlikely(hash_block_end >= v->hash_blocks))
 496                                 hash_block_end = v->hash_blocks - 1;
 497                 }
 498 no_prefetch_cluster:
 499                 dm_bufio_prefetch(v->bufio, hash_block_start,
 500                                   hash_block_end - hash_block_start + 1);
 501         }
 502
 503         kfree(pw);
 504 }
 505
 506 static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
 507 {
 508         struct dm_verity_prefetch_work *pw;
 509
 510         pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
 511                 GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 512
 513         if (!pw)
 514                 return;
 515
 516         INIT_WORK(&pw->work, verity_prefetch_io);
 517         pw->v = v;
 518         pw->block = io->block;
 519         pw->n_blocks = io->n_blocks;
 520         queue_work(v->verify_wq, &pw->work);
 521 }
 522
 523 /*
 524  * Bio map function. It allocates dm_verity_io structure and bio vector and
 525  * fills them. Then it issues prefetches and the I/O.
 526  */
 527 static int verity_map(struct dm_target *ti, struct bio *bio)
 528 {
 529         struct dm_verity *v = ti->private;
 530         struct dm_verity_io *io;
 531
 532         bio->bi_bdev = v->data_dev->bdev;
 533         bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
 534
 535         if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
 536             ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
 537                 DMERR_LIMIT("unaligned io");
 538                 return -EIO;
 539         }
 540
 541         if (bio_end_sector(bio) >>
 542             (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
 543                 DMERR_LIMIT("io out of range");
 544                 return -EIO;
 545         }
 546
 547         if (bio_data_dir(bio) == WRITE)
 548                 return -EIO;
 549
 550         io = dm_per_bio_data(bio, ti->per_bio_data_size);
 551         io->v = v;
 552         io->orig_bi_end_io = bio->bi_end_io;
 553         io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
 554         io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
 555
 556         bio->bi_end_io = verity_end_io;
 557         bio->bi_private = io;
 558         io->iter = bio->bi_iter;
 559
 560         verity_fec_init_io(io);
 561
 562         verity_submit_prefetch(v, io);
 563
 564         generic_make_request(bio);
 565
 566         return DM_MAPIO_SUBMITTED;
 567 }
 568
 569 /*
 570  * Status: V (valid) or C (corruption found)
 571  */
 572 static void verity_status(struct dm_target *ti, status_type_t type,
 573                           unsigned status_flags, char *result, unsigned maxlen)
 574 {
 575         struct dm_verity *v = ti->private;
 576         unsigned args = 0;
 577         unsigned sz = 0;
 578         unsigned x;
 579
 580         switch (type) {
 581         case STATUSTYPE_INFO:
 582                 DMEMIT("%c", v->hash_failed ? 'C' : 'V');
 583                 break;
 584         case STATUSTYPE_TABLE:
 585                 DMEMIT("%u %s %s %u %u %llu %llu %s ",
 586                         v->version,
 587                         v->data_dev->name,
 588                         v->hash_dev->name,
 589                         1 << v->data_dev_block_bits,
 590                         1 << v->hash_dev_block_bits,
 591                         (unsigned long long)v->data_blocks,
 592                         (unsigned long long)v->hash_start,
 593                         v->alg_name
 594                         );
 595                 for (x = 0; x < v->digest_size; x++)
 596                         DMEMIT("%02x", v->root_digest[x]);
 597                 DMEMIT(" ");
 598                 if (!v->salt_size)
 599                         DMEMIT("-");
 600                 else
 601                         for (x = 0; x < v->salt_size; x++)
 602                                 DMEMIT("%02x", v->salt[x]);
 603                 if (v->mode != DM_VERITY_MODE_EIO)
 604                         args++;
 605                 if (verity_fec_is_enabled(v))
 606                         args += DM_VERITY_OPTS_FEC;
 607                 if (!args)
 608                         return;
 609                 DMEMIT(" %u", args);
 610                 if (v->mode != DM_VERITY_MODE_EIO) {
 611                         DMEMIT(" ");
 612                         switch (v->mode) {
 613                         case DM_VERITY_MODE_LOGGING:
 614                                 DMEMIT(DM_VERITY_OPT_LOGGING);
 615                                 break;
 616                         case DM_VERITY_MODE_RESTART:
 617                                 DMEMIT(DM_VERITY_OPT_RESTART);
 618                                 break;
 619                         default:
 620                                 BUG();
 621                         }
 622                 }
 623                 sz = verity_fec_status_table(v, sz, result, maxlen);
 624                 break;
 625         }
 626 }
 627
 628 static int verity_prepare_ioctl(struct dm_target *ti,
 629                 struct block_device **bdev, fmode_t *mode)
 630 {
 631         struct dm_verity *v = ti->private;
 632
 633         *bdev = v->data_dev->bdev;
 634
 635         if (v->data_start ||
 636             ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
 637                 return 1;
 638         return 0;
 639 }
 640
 641 static int verity_iterate_devices(struct dm_target *ti,
 642                                   iterate_devices_callout_fn fn, void *data)
 643 {
 644         struct dm_verity *v = ti->private;
 645
 646         return fn(ti, v->data_dev, v->data_start, ti->len, data);
 647 }
 648
 649 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
 650 {
 651         struct dm_verity *v = ti->private;
 652
 653         if (limits->logical_block_size < 1 << v->data_dev_block_bits)
 654                 limits->logical_block_size = 1 << v->data_dev_block_bits;
 655
 656         if (limits->physical_block_size < 1 << v->data_dev_block_bits)
 657                 limits->physical_block_size = 1 << v->data_dev_block_bits;
 658
 659         blk_limits_io_min(limits, limits->logical_block_size);
 660 }
 661
 662 static void verity_dtr(struct dm_target *ti)
 663 {
 664         struct dm_verity *v = ti->private;
 665
 666         if (v->verify_wq)
 667                 destroy_workqueue(v->verify_wq);
 668
 669         if (v->bufio)
 670                 dm_bufio_client_destroy(v->bufio);
 671
 672         kfree(v->salt);
 673         kfree(v->root_digest);
 674
 675         if (v->tfm)
 676                 crypto_free_shash(v->tfm);
 677
 678         kfree(v->alg_name);
 679
 680         if (v->hash_dev)
 681                 dm_put_device(ti, v->hash_dev);
 682
 683         if (v->data_dev)
 684                 dm_put_device(ti, v->data_dev);
 685
 686         verity_fec_dtr(v);
 687
 688         kfree(v);
 689 }
 690
 691 static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v)
 692 {
 693         int r;
 694         unsigned argc;
 695         struct dm_target *ti = v->ti;
 696         const char *arg_name;
 697
 698         static struct dm_arg _args[] = {
 699                 {0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
 700         };
 701
 702         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 703         if (r)
 704                 return -EINVAL;
 705
 706         if (!argc)
 707                 return 0;
 708
 709         do {
 710                 arg_name = dm_shift_arg(as);
 711                 argc--;
 712
 713                 if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING)) {
 714                         v->mode = DM_VERITY_MODE_LOGGING;
 715                         continue;
 716
 717                 } else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) {
 718                         v->mode = DM_VERITY_MODE_RESTART;
 719                         continue;
 720
 721                 } else if (verity_is_fec_opt_arg(arg_name)) {
 722                         r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
 723                         if (r)
 724                                 return r;
 725                         continue;
 726                 }
 727
 728                 ti->error = "Unrecognized verity feature request";
 729                 return -EINVAL;
 730         } while (argc && !r);
 731
 732         return r;
 733 }
 734
 735 /*
 736  * Target parameters:
 737  *      <version>       The current format is version 1.
 738  *                      Vsn 0 is compatible with original Chromium OS releases.
 739  *      <data device>
 740  *      <hash device>
 741  *      <data block size>
 742  *      <hash block size>
 743  *      <the number of data blocks>
 744  *      <hash start block>
 745  *      <algorithm>
 746  *      <digest>
 747  *      <salt>          Hex string or "-" if no salt.
 748  */
 749 static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 750 {
 751         struct dm_verity *v;
 752         struct dm_arg_set as;
 753         unsigned int num;
 754         unsigned long long num_ll;
 755         int r;
 756         int i;
 757         sector_t hash_position;
 758         char dummy;
 759
 760         v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
 761         if (!v) {
 762                 ti->error = "Cannot allocate verity structure";
 763                 return -ENOMEM;
 764         }
 765         ti->private = v;
 766         v->ti = ti;
 767
 768         r = verity_fec_ctr_alloc(v);
 769         if (r)
 770                 goto bad;
 771
 772         if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
 773                 ti->error = "Device must be readonly";
 774                 r = -EINVAL;
 775                 goto bad;
 776         }
 777
 778         if (argc < 10) {
 779                 ti->error = "Not enough arguments";
 780                 r = -EINVAL;
 781                 goto bad;
 782         }
 783
 784         if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
 785             num > 1) {
 786                 ti->error = "Invalid version";
 787                 r = -EINVAL;
 788                 goto bad;
 789         }
 790         v->version = num;
 791
 792         r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
 793         if (r) {
 794                 ti->error = "Data device lookup failed";
 795                 goto bad;
 796         }
 797
 798         r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
 799         if (r) {
 800                 ti->error = "Data device lookup failed";
 801                 goto bad;
 802         }
 803
 804         if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
 805             !num || (num & (num - 1)) ||
 806             num < bdev_logical_block_size(v->data_dev->bdev) ||
 807             num > PAGE_SIZE) {
 808                 ti->error = "Invalid data device block size";
 809                 r = -EINVAL;
 810                 goto bad;
 811         }
 812         v->data_dev_block_bits = __ffs(num);
 813
 814         if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
 815             !num || (num & (num - 1)) ||
 816             num < bdev_logical_block_size(v->hash_dev->bdev) ||
 817             num > INT_MAX) {
 818                 ti->error = "Invalid hash device block size";
 819                 r = -EINVAL;
 820                 goto bad;
 821         }
 822         v->hash_dev_block_bits = __ffs(num);
 823
 824         if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
 825             (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
 826             >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 827                 ti->error = "Invalid data blocks";
 828                 r = -EINVAL;
 829                 goto bad;
 830         }
 831         v->data_blocks = num_ll;
 832
 833         if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
 834                 ti->error = "Data device is too small";
 835                 r = -EINVAL;
 836                 goto bad;
 837         }
 838
 839         if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
 840             (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
 841             >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 842                 ti->error = "Invalid hash start";
 843                 r = -EINVAL;
 844                 goto bad;
 845         }
 846         v->hash_start = num_ll;
 847
 848         v->alg_name = kstrdup(argv[7], GFP_KERNEL);
 849         if (!v->alg_name) {
 850                 ti->error = "Cannot allocate algorithm name";
 851                 r = -ENOMEM;
 852                 goto bad;
 853         }
 854
 855         v->tfm = crypto_alloc_shash(v->alg_name, 0, 0);
 856         if (IS_ERR(v->tfm)) {
 857                 ti->error = "Cannot initialize hash function";
 858                 r = PTR_ERR(v->tfm);
 859                 v->tfm = NULL;
 860                 goto bad;
 861         }
 862         v->digest_size = crypto_shash_digestsize(v->tfm);
 863         if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
 864                 ti->error = "Digest size too big";
 865                 r = -EINVAL;
 866                 goto bad;
 867         }
 868         v->shash_descsize =
 869                 sizeof(struct shash_desc) + crypto_shash_descsize(v->tfm);
 870
 871         v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
 872         if (!v->root_digest) {
 873                 ti->error = "Cannot allocate root digest";
 874                 r = -ENOMEM;
 875                 goto bad;
 876         }
 877         if (strlen(argv[8]) != v->digest_size * 2 ||
 878             hex2bin(v->root_digest, argv[8], v->digest_size)) {
 879                 ti->error = "Invalid root digest";
 880                 r = -EINVAL;
 881                 goto bad;
 882         }
 883
 884         if (strcmp(argv[9], "-")) {
 885                 v->salt_size = strlen(argv[9]) / 2;
 886                 v->salt = kmalloc(v->salt_size, GFP_KERNEL);
 887                 if (!v->salt) {
 888                         ti->error = "Cannot allocate salt";
 889                         r = -ENOMEM;
 890                         goto bad;
 891                 }
 892                 if (strlen(argv[9]) != v->salt_size * 2 ||
 893                     hex2bin(v->salt, argv[9], v->salt_size)) {
 894                         ti->error = "Invalid salt";
 895                         r = -EINVAL;
 896                         goto bad;
 897                 }
 898         }
 899
 900         argv += 10;
 901         argc -= 10;
 902
 903         /* Optional parameters */
 904         if (argc) {
 905                 as.argc = argc;
 906                 as.argv = argv;
 907
 908                 r = verity_parse_opt_args(&as, v);
 909                 if (r < 0)
 910                         goto bad;
 911         }
 912
 913         v->hash_per_block_bits =
 914                 __fls((1 << v->hash_dev_block_bits) / v->digest_size);
 915
 916         v->levels = 0;
 917         if (v->data_blocks)
 918                 while (v->hash_per_block_bits * v->levels < 64 &&
 919                        (unsigned long long)(v->data_blocks - 1) >>
 920                        (v->hash_per_block_bits * v->levels))
 921                         v->levels++;
 922
 923         if (v->levels > DM_VERITY_MAX_LEVELS) {
 924                 ti->error = "Too many tree levels";
 925                 r = -E2BIG;
 926                 goto bad;
 927         }
 928
 929         hash_position = v->hash_start;
 930         for (i = v->levels - 1; i >= 0; i--) {
 931                 sector_t s;
 932                 v->hash_level_block[i] = hash_position;
 933                 s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
 934                                         >> ((i + 1) * v->hash_per_block_bits);
 935                 if (hash_position + s < hash_position) {
 936                         ti->error = "Hash device offset overflow";
 937                         r = -E2BIG;
 938                         goto bad;
 939                 }
 940                 hash_position += s;
 941         }
 942         v->hash_blocks = hash_position;
 943
 944         v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
 945                 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
 946                 dm_bufio_alloc_callback, NULL);
 947         if (IS_ERR(v->bufio)) {
 948                 ti->error = "Cannot initialize dm-bufio";
 949                 r = PTR_ERR(v->bufio);
 950                 v->bufio = NULL;
 951                 goto bad;
 952         }
 953
 954         if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
 955                 ti->error = "Hash device is too small";
 956                 r = -E2BIG;
 957                 goto bad;
 958         }
 959
 960         /* WQ_UNBOUND greatly improves performance when running on ramdisk */
 961         v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
 962         if (!v->verify_wq) {
 963                 ti->error = "Cannot allocate workqueue";
 964                 r = -ENOMEM;
 965                 goto bad;
 966         }
 967
 968         ti->per_bio_data_size = sizeof(struct dm_verity_io) +
 969                                 v->shash_descsize + v->digest_size * 2;
 970
 971         r = verity_fec_ctr(v);
 972         if (r)
 973                 goto bad;
 974
 975         ti->per_bio_data_size = roundup(ti->per_bio_data_size,
 976                                         __alignof__(struct dm_verity_io));
 977
 978         return 0;
 979
 980 bad:
 981         verity_dtr(ti);
 982
 983         return r;
 984 }
 985
 986 static struct target_type verity_target = {
 987         .name           = "verity",
 988         .version        = {1, 3, 0},
 989         .module         = THIS_MODULE,
 990         .ctr            = verity_ctr,
 991         .dtr            = verity_dtr,
 992         .map            = verity_map,
 993         .status         = verity_status,
 994         .prepare_ioctl  = verity_prepare_ioctl,
 995         .iterate_devices = verity_iterate_devices,
 996         .io_hints       = verity_io_hints,
 997 };
 998
 999 static int __init dm_verity_init(void)
1000 {
1001         int r;
1002
1003         r = dm_register_target(&verity_target);
1004         if (r < 0)
1005                 DMERR("register failed %d", r);
1006
1007         return r;
1008 }
1009
1010 static void __exit dm_verity_exit(void)
1011 {
1012         dm_unregister_target(&verity_target);
1013 }
1014
1015 module_init(dm_verity_init);
1016 module_exit(dm_verity_exit);
1017
1018 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
1019 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
1020 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
1021 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
1022 MODULE_LICENSE("GPL");