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
  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
  34 #define DM_VERITY_OPTS_MAX              1
  35
  36 static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
  37
  38 module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
  39
  40 struct dm_verity_prefetch_work {
  41         struct work_struct work;
  42         struct dm_verity *v;
  43         sector_t block;
  44         unsigned n_blocks;
  45 };
  46
  47 /*
  48  * Auxiliary structure appended to each dm-bufio buffer. If the value
  49  * hash_verified is nonzero, hash of the block has been verified.
  50  *
  51  * The variable hash_verified is set to 0 when allocating the buffer, then
  52  * it can be changed to 1 and it is never reset to 0 again.
  53  *
  54  * There is no lock around this value, a race condition can at worst cause
  55  * that multiple processes verify the hash of the same buffer simultaneously
  56  * and write 1 to hash_verified simultaneously.
  57  * This condition is harmless, so we don't need locking.
  58  */
  59 struct buffer_aux {
  60         int hash_verified;
  61 };
  62
  63 /*
  64  * Initialize struct buffer_aux for a freshly created buffer.
  65  */
  66 static void dm_bufio_alloc_callback(struct dm_buffer *buf)
  67 {
  68         struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
  69
  70         aux->hash_verified = 0;
  71 }
  72
  73 /*
  74  * Translate input sector number to the sector number on the target device.
  75  */
  76 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
  77 {
  78         return v->data_start + dm_target_offset(v->ti, bi_sector);
  79 }
  80
  81 /*
  82  * Return hash position of a specified block at a specified tree level
  83  * (0 is the lowest level).
  84  * The lowest "hash_per_block_bits"-bits of the result denote hash position
  85  * inside a hash block. The remaining bits denote location of the hash block.
  86  */
  87 static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
  88                                          int level)
  89 {
  90         return block >> (level * v->hash_per_block_bits);
  91 }
  92
  93 /*
  94  * Wrapper for crypto_shash_init, which handles verity salting.
  95  */
  96 static int verity_hash_init(struct dm_verity *v, struct shash_desc *desc)
  97 {
  98         int r;
  99
 100         desc->tfm = v->tfm;
 101         desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 102
 103         r = crypto_shash_init(desc);
 104
 105         if (unlikely(r < 0)) {
 106                 DMERR("crypto_shash_init failed: %d", r);
 107                 return r;
 108         }
 109
 110         if (likely(v->version >= 1)) {
 111                 r = crypto_shash_update(desc, v->salt, v->salt_size);
 112
 113                 if (unlikely(r < 0)) {
 114                         DMERR("crypto_shash_update failed: %d", r);
 115                         return r;
 116                 }
 117         }
 118
 119         return 0;
 120 }
 121
 122 static int verity_hash_update(struct dm_verity *v, struct shash_desc *desc,
 123                               const u8 *data, size_t len)
 124 {
 125         int r = crypto_shash_update(desc, data, len);
 126
 127         if (unlikely(r < 0))
 128                 DMERR("crypto_shash_update failed: %d", r);
 129
 130         return r;
 131 }
 132
 133 static int verity_hash_final(struct dm_verity *v, struct shash_desc *desc,
 134                              u8 *digest)
 135 {
 136         int r;
 137
 138         if (unlikely(!v->version)) {
 139                 r = crypto_shash_update(desc, v->salt, v->salt_size);
 140
 141                 if (r < 0) {
 142                         DMERR("crypto_shash_update failed: %d", r);
 143                         return r;
 144                 }
 145         }
 146
 147         r = crypto_shash_final(desc, digest);
 148
 149         if (unlikely(r < 0))
 150                 DMERR("crypto_shash_final failed: %d", r);
 151
 152         return r;
 153 }
 154
 155 int verity_hash(struct dm_verity *v, struct shash_desc *desc,
 156                 const u8 *data, size_t len, u8 *digest)
 157 {
 158         int r;
 159
 160         r = verity_hash_init(v, desc);
 161         if (unlikely(r < 0))
 162                 return r;
 163
 164         r = verity_hash_update(v, desc, data, len);
 165         if (unlikely(r < 0))
 166                 return r;
 167
 168         return verity_hash_final(v, desc, digest);
 169 }
 170
 171 static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
 172                                  sector_t *hash_block, unsigned *offset)
 173 {
 174         sector_t position = verity_position_at_level(v, block, level);
 175         unsigned idx;
 176
 177         *hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
 178
 179         if (!offset)
 180                 return;
 181
 182         idx = position & ((1 << v->hash_per_block_bits) - 1);
 183         if (!v->version)
 184                 *offset = idx * v->digest_size;
 185         else
 186                 *offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
 187 }
 188
 189 /*
 190  * Handle verification errors.
 191  */
 192 static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
 193                              unsigned long long block)
 194 {
 195         char verity_env[DM_VERITY_ENV_LENGTH];
 196         char *envp[] = { verity_env, NULL };
 197         const char *type_str = "";
 198         struct mapped_device *md = dm_table_get_md(v->ti->table);
 199
 200         /* Corruption should be visible in device status in all modes */
 201         v->hash_failed = 1;
 202
 203         if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
 204                 goto out;
 205
 206         v->corrupted_errs++;
 207
 208         switch (type) {
 209         case DM_VERITY_BLOCK_TYPE_DATA:
 210                 type_str = "data";
 211                 break;
 212         case DM_VERITY_BLOCK_TYPE_METADATA:
 213                 type_str = "metadata";
 214                 break;
 215         default:
 216                 BUG();
 217         }
 218
 219         DMERR("%s: %s block %llu is corrupted", v->data_dev->name, type_str,
 220                 block);
 221
 222         if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
 223                 DMERR("%s: reached maximum errors", v->data_dev->name);
 224
 225         snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
 226                 DM_VERITY_ENV_VAR_NAME, type, block);
 227
 228         kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
 229
 230 out:
 231         if (v->mode == DM_VERITY_MODE_LOGGING)
 232                 return 0;
 233
 234         if (v->mode == DM_VERITY_MODE_RESTART)
 235                 kernel_restart("dm-verity device corrupted");
 236
 237         return 1;
 238 }
 239
 240 /*
 241  * Verify hash of a metadata block pertaining to the specified data block
 242  * ("block" argument) at a specified level ("level" argument).
 243  *
 244  * On successful return, verity_io_want_digest(v, io) contains the hash value
 245  * for a lower tree level or for the data block (if we're at the lowest level).
 246  *
 247  * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
 248  * If "skip_unverified" is false, unverified buffer is hashed and verified
 249  * against current value of verity_io_want_digest(v, io).
 250  */
 251 static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 252                                sector_t block, int level, bool skip_unverified,
 253                                u8 *want_digest)
 254 {
 255         struct dm_buffer *buf;
 256         struct buffer_aux *aux;
 257         u8 *data;
 258         int r;
 259         sector_t hash_block;
 260         unsigned offset;
 261
 262         verity_hash_at_level(v, block, level, &hash_block, &offset);
 263
 264         data = dm_bufio_read(v->bufio, hash_block, &buf);
 265         if (IS_ERR(data))
 266                 return PTR_ERR(data);
 267
 268         aux = dm_bufio_get_aux_data(buf);
 269
 270         if (!aux->hash_verified) {
 271                 if (skip_unverified) {
 272                         r = 1;
 273                         goto release_ret_r;
 274                 }
 275
 276                 r = verity_hash(v, verity_io_hash_desc(v, io),
 277                                 data, 1 << v->hash_dev_block_bits,
 278                                 verity_io_real_digest(v, io));
 279                 if (unlikely(r < 0))
 280                         goto release_ret_r;
 281
 282                 if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
 283                                   v->digest_size) == 0))
 284                         aux->hash_verified = 1;
 285                 else if (verity_handle_err(v,
 286                                            DM_VERITY_BLOCK_TYPE_METADATA,
 287                                            hash_block)) {
 288                         r = -EIO;
 289                         goto release_ret_r;
 290                 }
 291         }
 292
 293         data += offset;
 294         memcpy(want_digest, data, v->digest_size);
 295         r = 0;
 296
 297 release_ret_r:
 298         dm_bufio_release(buf);
 299         return r;
 300 }
 301
 302 /*
 303  * Find a hash for a given block, write it to digest and verify the integrity
 304  * of the hash tree if necessary.
 305  */
 306 int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
 307                           sector_t block, u8 *digest)
 308 {
 309         int i;
 310         int r;
 311
 312         if (likely(v->levels)) {
 313                 /*
 314                  * First, we try to get the requested hash for
 315                  * the current block. If the hash block itself is
 316                  * verified, zero is returned. If it isn't, this
 317                  * function returns 1 and we fall back to whole
 318                  * chain verification.
 319                  */
 320                 r = verity_verify_level(v, io, block, 0, true, digest);
 321                 if (likely(r <= 0))
 322                         return r;
 323         }
 324
 325         memcpy(digest, v->root_digest, v->digest_size);
 326
 327         for (i = v->levels - 1; i >= 0; i--) {
 328                 r = verity_verify_level(v, io, block, i, false, digest);
 329                 if (unlikely(r))
 330                         return r;
 331         }
 332
 333         return 0;
 334 }
 335
 336 /*
 337  * Calls function process for 1 << v->data_dev_block_bits bytes in the bio_vec
 338  * starting from iter.
 339  */
 340 int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
 341                         struct bvec_iter *iter,
 342                         int (*process)(struct dm_verity *v,
 343                                        struct dm_verity_io *io, u8 *data,
 344                                        size_t len))
 345 {
 346         unsigned todo = 1 << v->data_dev_block_bits;
 347         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_bio_data_size);
 348
 349         do {
 350                 int r;
 351                 u8 *page;
 352                 unsigned len;
 353                 struct bio_vec bv = bio_iter_iovec(bio, *iter);
 354
 355                 page = kmap_atomic(bv.bv_page);
 356                 len = bv.bv_len;
 357
 358                 if (likely(len >= todo))
 359                         len = todo;
 360
 361                 r = process(v, io, page + bv.bv_offset, len);
 362                 kunmap_atomic(page);
 363
 364                 if (r < 0)
 365                         return r;
 366
 367                 bio_advance_iter(bio, iter, len);
 368                 todo -= len;
 369         } while (todo);
 370
 371         return 0;
 372 }
 373
 374 static int verity_bv_hash_update(struct dm_verity *v, struct dm_verity_io *io,
 375                                  u8 *data, size_t len)
 376 {
 377         return verity_hash_update(v, verity_io_hash_desc(v, io), data, len);
 378 }
 379
 380 /*
 381  * Verify one "dm_verity_io" structure.
 382  */
 383 static int verity_verify_io(struct dm_verity_io *io)
 384 {
 385         struct dm_verity *v = io->v;
 386         struct bvec_iter start;
 387         unsigned b;
 388
 389         for (b = 0; b < io->n_blocks; b++) {
 390                 int r;
 391                 struct shash_desc *desc = verity_io_hash_desc(v, io);
 392
 393                 r = verity_hash_for_block(v, io, io->block + b,
 394                                           verity_io_want_digest(v, io));
 395                 if (unlikely(r < 0))
 396                         return r;
 397
 398                 r = verity_hash_init(v, desc);
 399                 if (unlikely(r < 0))
 400                         return r;
 401
 402                 start = io->iter;
 403                 r = verity_for_bv_block(v, io, &io->iter, verity_bv_hash_update);
 404                 if (unlikely(r < 0))
 405                         return r;
 406
 407                 r = verity_hash_final(v, desc, verity_io_real_digest(v, io));
 408                 if (unlikely(r < 0))
 409                         return r;
 410
 411                 if (likely(memcmp(verity_io_real_digest(v, io),
 412                                   verity_io_want_digest(v, io), v->digest_size) == 0))
 413                         continue;
 414                 else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
 415                                 io->block + b))
 416                         return -EIO;
 417         }
 418
 419         return 0;
 420 }
 421
 422 /*
 423  * End one "io" structure with a given error.
 424  */
 425 static void verity_finish_io(struct dm_verity_io *io, int error)
 426 {
 427         struct dm_verity *v = io->v;
 428         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_bio_data_size);
 429
 430         bio->bi_end_io = io->orig_bi_end_io;
 431         bio->bi_error = error;
 432
 433         bio_endio(bio);
 434 }
 435
 436 static void verity_work(struct work_struct *w)
 437 {
 438         struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
 439
 440         verity_finish_io(io, verity_verify_io(io));
 441 }
 442
 443 static void verity_end_io(struct bio *bio)
 444 {
 445         struct dm_verity_io *io = bio->bi_private;
 446
 447         if (bio->bi_error) {
 448                 verity_finish_io(io, bio->bi_error);
 449                 return;
 450         }
 451
 452         INIT_WORK(&io->work, verity_work);
 453         queue_work(io->v->verify_wq, &io->work);
 454 }
 455
 456 /*
 457  * Prefetch buffers for the specified io.
 458  * The root buffer is not prefetched, it is assumed that it will be cached
 459  * all the time.
 460  */
 461 static void verity_prefetch_io(struct work_struct *work)
 462 {
 463         struct dm_verity_prefetch_work *pw =
 464                 container_of(work, struct dm_verity_prefetch_work, work);
 465         struct dm_verity *v = pw->v;
 466         int i;
 467
 468         for (i = v->levels - 2; i >= 0; i--) {
 469                 sector_t hash_block_start;
 470                 sector_t hash_block_end;
 471                 verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
 472                 verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
 473                 if (!i) {
 474                         unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);
 475
 476                         cluster >>= v->data_dev_block_bits;
 477                         if (unlikely(!cluster))
 478                                 goto no_prefetch_cluster;
 479
 480                         if (unlikely(cluster & (cluster - 1)))
 481                                 cluster = 1 << __fls(cluster);
 482
 483                         hash_block_start &= ~(sector_t)(cluster - 1);
 484                         hash_block_end |= cluster - 1;
 485                         if (unlikely(hash_block_end >= v->hash_blocks))
 486                                 hash_block_end = v->hash_blocks - 1;
 487                 }
 488 no_prefetch_cluster:
 489                 dm_bufio_prefetch(v->bufio, hash_block_start,
 490                                   hash_block_end - hash_block_start + 1);
 491         }
 492
 493         kfree(pw);
 494 }
 495
 496 static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
 497 {
 498         struct dm_verity_prefetch_work *pw;
 499
 500         pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
 501                 GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 502
 503         if (!pw)
 504                 return;
 505
 506         INIT_WORK(&pw->work, verity_prefetch_io);
 507         pw->v = v;
 508         pw->block = io->block;
 509         pw->n_blocks = io->n_blocks;
 510         queue_work(v->verify_wq, &pw->work);
 511 }
 512
 513 /*
 514  * Bio map function. It allocates dm_verity_io structure and bio vector and
 515  * fills them. Then it issues prefetches and the I/O.
 516  */
 517 static int verity_map(struct dm_target *ti, struct bio *bio)
 518 {
 519         struct dm_verity *v = ti->private;
 520         struct dm_verity_io *io;
 521
 522         bio->bi_bdev = v->data_dev->bdev;
 523         bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
 524
 525         if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
 526             ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
 527                 DMERR_LIMIT("unaligned io");
 528                 return -EIO;
 529         }
 530
 531         if (bio_end_sector(bio) >>
 532             (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
 533                 DMERR_LIMIT("io out of range");
 534                 return -EIO;
 535         }
 536
 537         if (bio_data_dir(bio) == WRITE)
 538                 return -EIO;
 539
 540         io = dm_per_bio_data(bio, ti->per_bio_data_size);
 541         io->v = v;
 542         io->orig_bi_end_io = bio->bi_end_io;
 543         io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
 544         io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
 545
 546         bio->bi_end_io = verity_end_io;
 547         bio->bi_private = io;
 548         io->iter = bio->bi_iter;
 549
 550         verity_submit_prefetch(v, io);
 551
 552         generic_make_request(bio);
 553
 554         return DM_MAPIO_SUBMITTED;
 555 }
 556
 557 /*
 558  * Status: V (valid) or C (corruption found)
 559  */
 560 static void verity_status(struct dm_target *ti, status_type_t type,
 561                           unsigned status_flags, char *result, unsigned maxlen)
 562 {
 563         struct dm_verity *v = ti->private;
 564         unsigned sz = 0;
 565         unsigned x;
 566
 567         switch (type) {
 568         case STATUSTYPE_INFO:
 569                 DMEMIT("%c", v->hash_failed ? 'C' : 'V');
 570                 break;
 571         case STATUSTYPE_TABLE:
 572                 DMEMIT("%u %s %s %u %u %llu %llu %s ",
 573                         v->version,
 574                         v->data_dev->name,
 575                         v->hash_dev->name,
 576                         1 << v->data_dev_block_bits,
 577                         1 << v->hash_dev_block_bits,
 578                         (unsigned long long)v->data_blocks,
 579                         (unsigned long long)v->hash_start,
 580                         v->alg_name
 581                         );
 582                 for (x = 0; x < v->digest_size; x++)
 583                         DMEMIT("%02x", v->root_digest[x]);
 584                 DMEMIT(" ");
 585                 if (!v->salt_size)
 586                         DMEMIT("-");
 587                 else
 588                         for (x = 0; x < v->salt_size; x++)
 589                                 DMEMIT("%02x", v->salt[x]);
 590                 if (v->mode != DM_VERITY_MODE_EIO) {
 591                         DMEMIT(" 1 ");
 592                         switch (v->mode) {
 593                         case DM_VERITY_MODE_LOGGING:
 594                                 DMEMIT(DM_VERITY_OPT_LOGGING);
 595                                 break;
 596                         case DM_VERITY_MODE_RESTART:
 597                                 DMEMIT(DM_VERITY_OPT_RESTART);
 598                                 break;
 599                         default:
 600                                 BUG();
 601                         }
 602                 }
 603                 break;
 604         }
 605 }
 606
 607 static int verity_prepare_ioctl(struct dm_target *ti,
 608                 struct block_device **bdev, fmode_t *mode)
 609 {
 610         struct dm_verity *v = ti->private;
 611
 612         *bdev = v->data_dev->bdev;
 613
 614         if (v->data_start ||
 615             ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
 616                 return 1;
 617         return 0;
 618 }
 619
 620 static int verity_iterate_devices(struct dm_target *ti,
 621                                   iterate_devices_callout_fn fn, void *data)
 622 {
 623         struct dm_verity *v = ti->private;
 624
 625         return fn(ti, v->data_dev, v->data_start, ti->len, data);
 626 }
 627
 628 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
 629 {
 630         struct dm_verity *v = ti->private;
 631
 632         if (limits->logical_block_size < 1 << v->data_dev_block_bits)
 633                 limits->logical_block_size = 1 << v->data_dev_block_bits;
 634
 635         if (limits->physical_block_size < 1 << v->data_dev_block_bits)
 636                 limits->physical_block_size = 1 << v->data_dev_block_bits;
 637
 638         blk_limits_io_min(limits, limits->logical_block_size);
 639 }
 640
 641 static void verity_dtr(struct dm_target *ti)
 642 {
 643         struct dm_verity *v = ti->private;
 644
 645         if (v->verify_wq)
 646                 destroy_workqueue(v->verify_wq);
 647
 648         if (v->bufio)
 649                 dm_bufio_client_destroy(v->bufio);
 650
 651         kfree(v->salt);
 652         kfree(v->root_digest);
 653
 654         if (v->tfm)
 655                 crypto_free_shash(v->tfm);
 656
 657         kfree(v->alg_name);
 658
 659         if (v->hash_dev)
 660                 dm_put_device(ti, v->hash_dev);
 661
 662         if (v->data_dev)
 663                 dm_put_device(ti, v->data_dev);
 664
 665         kfree(v);
 666 }
 667
 668 static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v)
 669 {
 670         int r;
 671         unsigned argc;
 672         struct dm_target *ti = v->ti;
 673         const char *arg_name;
 674
 675         static struct dm_arg _args[] = {
 676                 {0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
 677         };
 678
 679         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 680         if (r)
 681                 return -EINVAL;
 682
 683         if (!argc)
 684                 return 0;
 685
 686         do {
 687                 arg_name = dm_shift_arg(as);
 688                 argc--;
 689
 690                 if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING)) {
 691                         v->mode = DM_VERITY_MODE_LOGGING;
 692                         continue;
 693
 694                 } else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) {
 695                         v->mode = DM_VERITY_MODE_RESTART;
 696                         continue;
 697                 }
 698
 699                 ti->error = "Unrecognized verity feature request";
 700                 return -EINVAL;
 701         } while (argc && !r);
 702
 703         return r;
 704 }
 705
 706 /*
 707  * Target parameters:
 708  *      <version>       The current format is version 1.
 709  *                      Vsn 0 is compatible with original Chromium OS releases.
 710  *      <data device>
 711  *      <hash device>
 712  *      <data block size>
 713  *      <hash block size>
 714  *      <the number of data blocks>
 715  *      <hash start block>
 716  *      <algorithm>
 717  *      <digest>
 718  *      <salt>          Hex string or "-" if no salt.
 719  */
 720 static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 721 {
 722         struct dm_verity *v;
 723         struct dm_arg_set as;
 724         unsigned int num;
 725         unsigned long long num_ll;
 726         int r;
 727         int i;
 728         sector_t hash_position;
 729         char dummy;
 730
 731         v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
 732         if (!v) {
 733                 ti->error = "Cannot allocate verity structure";
 734                 return -ENOMEM;
 735         }
 736         ti->private = v;
 737         v->ti = ti;
 738
 739         if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
 740                 ti->error = "Device must be readonly";
 741                 r = -EINVAL;
 742                 goto bad;
 743         }
 744
 745         if (argc < 10) {
 746                 ti->error = "Not enough arguments";
 747                 r = -EINVAL;
 748                 goto bad;
 749         }
 750
 751         if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
 752             num > 1) {
 753                 ti->error = "Invalid version";
 754                 r = -EINVAL;
 755                 goto bad;
 756         }
 757         v->version = num;
 758
 759         r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
 760         if (r) {
 761                 ti->error = "Data device lookup failed";
 762                 goto bad;
 763         }
 764
 765         r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
 766         if (r) {
 767                 ti->error = "Data device lookup failed";
 768                 goto bad;
 769         }
 770
 771         if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
 772             !num || (num & (num - 1)) ||
 773             num < bdev_logical_block_size(v->data_dev->bdev) ||
 774             num > PAGE_SIZE) {
 775                 ti->error = "Invalid data device block size";
 776                 r = -EINVAL;
 777                 goto bad;
 778         }
 779         v->data_dev_block_bits = __ffs(num);
 780
 781         if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
 782             !num || (num & (num - 1)) ||
 783             num < bdev_logical_block_size(v->hash_dev->bdev) ||
 784             num > INT_MAX) {
 785                 ti->error = "Invalid hash device block size";
 786                 r = -EINVAL;
 787                 goto bad;
 788         }
 789         v->hash_dev_block_bits = __ffs(num);
 790
 791         if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
 792             (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
 793             >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 794                 ti->error = "Invalid data blocks";
 795                 r = -EINVAL;
 796                 goto bad;
 797         }
 798         v->data_blocks = num_ll;
 799
 800         if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
 801                 ti->error = "Data device is too small";
 802                 r = -EINVAL;
 803                 goto bad;
 804         }
 805
 806         if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
 807             (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
 808             >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 809                 ti->error = "Invalid hash start";
 810                 r = -EINVAL;
 811                 goto bad;
 812         }
 813         v->hash_start = num_ll;
 814
 815         v->alg_name = kstrdup(argv[7], GFP_KERNEL);
 816         if (!v->alg_name) {
 817                 ti->error = "Cannot allocate algorithm name";
 818                 r = -ENOMEM;
 819                 goto bad;
 820         }
 821
 822         v->tfm = crypto_alloc_shash(v->alg_name, 0, 0);
 823         if (IS_ERR(v->tfm)) {
 824                 ti->error = "Cannot initialize hash function";
 825                 r = PTR_ERR(v->tfm);
 826                 v->tfm = NULL;
 827                 goto bad;
 828         }
 829         v->digest_size = crypto_shash_digestsize(v->tfm);
 830         if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
 831                 ti->error = "Digest size too big";
 832                 r = -EINVAL;
 833                 goto bad;
 834         }
 835         v->shash_descsize =
 836                 sizeof(struct shash_desc) + crypto_shash_descsize(v->tfm);
 837
 838         v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
 839         if (!v->root_digest) {
 840                 ti->error = "Cannot allocate root digest";
 841                 r = -ENOMEM;
 842                 goto bad;
 843         }
 844         if (strlen(argv[8]) != v->digest_size * 2 ||
 845             hex2bin(v->root_digest, argv[8], v->digest_size)) {
 846                 ti->error = "Invalid root digest";
 847                 r = -EINVAL;
 848                 goto bad;
 849         }
 850
 851         if (strcmp(argv[9], "-")) {
 852                 v->salt_size = strlen(argv[9]) / 2;
 853                 v->salt = kmalloc(v->salt_size, GFP_KERNEL);
 854                 if (!v->salt) {
 855                         ti->error = "Cannot allocate salt";
 856                         r = -ENOMEM;
 857                         goto bad;
 858                 }
 859                 if (strlen(argv[9]) != v->salt_size * 2 ||
 860                     hex2bin(v->salt, argv[9], v->salt_size)) {
 861                         ti->error = "Invalid salt";
 862                         r = -EINVAL;
 863                         goto bad;
 864                 }
 865         }
 866
 867         argv += 10;
 868         argc -= 10;
 869
 870         /* Optional parameters */
 871         if (argc) {
 872                 as.argc = argc;
 873                 as.argv = argv;
 874
 875                 r = verity_parse_opt_args(&as, v);
 876                 if (r < 0)
 877                         goto bad;
 878         }
 879
 880         v->hash_per_block_bits =
 881                 __fls((1 << v->hash_dev_block_bits) / v->digest_size);
 882
 883         v->levels = 0;
 884         if (v->data_blocks)
 885                 while (v->hash_per_block_bits * v->levels < 64 &&
 886                        (unsigned long long)(v->data_blocks - 1) >>
 887                        (v->hash_per_block_bits * v->levels))
 888                         v->levels++;
 889
 890         if (v->levels > DM_VERITY_MAX_LEVELS) {
 891                 ti->error = "Too many tree levels";
 892                 r = -E2BIG;
 893                 goto bad;
 894         }
 895
 896         hash_position = v->hash_start;
 897         for (i = v->levels - 1; i >= 0; i--) {
 898                 sector_t s;
 899                 v->hash_level_block[i] = hash_position;
 900                 s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
 901                                         >> ((i + 1) * v->hash_per_block_bits);
 902                 if (hash_position + s < hash_position) {
 903                         ti->error = "Hash device offset overflow";
 904                         r = -E2BIG;
 905                         goto bad;
 906                 }
 907                 hash_position += s;
 908         }
 909         v->hash_blocks = hash_position;
 910
 911         v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
 912                 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
 913                 dm_bufio_alloc_callback, NULL);
 914         if (IS_ERR(v->bufio)) {
 915                 ti->error = "Cannot initialize dm-bufio";
 916                 r = PTR_ERR(v->bufio);
 917                 v->bufio = NULL;
 918                 goto bad;
 919         }
 920
 921         if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
 922                 ti->error = "Hash device is too small";
 923                 r = -E2BIG;
 924                 goto bad;
 925         }
 926
 927         ti->per_bio_data_size = roundup(sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2, __alignof__(struct dm_verity_io));
 928
 929         /* WQ_UNBOUND greatly improves performance when running on ramdisk */
 930         v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
 931         if (!v->verify_wq) {
 932                 ti->error = "Cannot allocate workqueue";
 933                 r = -ENOMEM;
 934                 goto bad;
 935         }
 936
 937         return 0;
 938
 939 bad:
 940         verity_dtr(ti);
 941
 942         return r;
 943 }
 944
 945 static struct target_type verity_target = {
 946         .name           = "verity",
 947         .version        = {1, 2, 0},
 948         .module         = THIS_MODULE,
 949         .ctr            = verity_ctr,
 950         .dtr            = verity_dtr,
 951         .map            = verity_map,
 952         .status         = verity_status,
 953         .prepare_ioctl  = verity_prepare_ioctl,
 954         .iterate_devices = verity_iterate_devices,
 955         .io_hints       = verity_io_hints,
 956 };
 957
 958 static int __init dm_verity_init(void)
 959 {
 960         int r;
 961
 962         r = dm_register_target(&verity_target);
 963         if (r < 0)
 964                 DMERR("register failed %d", r);
 965
 966         return r;
 967 }
 968
 969 static void __exit dm_verity_exit(void)
 970 {
 971         dm_unregister_target(&verity_target);
 972 }
 973
 974 module_init(dm_verity_init);
 975 module_exit(dm_verity_exit);
 976
 977 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
 978 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
 979 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
 980 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
 981 MODULE_LICENSE("GPL");