drivers/md/dm-verity.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-bufio.h"
  18
  19 #include <linux/module.h>
  20 #include <linux/device-mapper.h>
  21 #include <linux/reboot.h>
  22 #include <crypto/hash.h>
  23
  24 #define DM_MSG_PREFIX                   "verity"
  25
  26 #define DM_VERITY_ENV_LENGTH            42
  27 #define DM_VERITY_ENV_VAR_NAME          "DM_VERITY_ERR_BLOCK_NR"
  28
  29 #define DM_VERITY_DEFAULT_PREFETCH_SIZE 262144
  30
  31 #define DM_VERITY_MAX_LEVELS            63
  32 #define DM_VERITY_MAX_CORRUPTED_ERRS    100
  33
  34 #define DM_VERITY_OPT_LOGGING           "ignore_corruption"
  35 #define DM_VERITY_OPT_RESTART           "restart_on_corruption"
  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 enum verity_mode {
  42         DM_VERITY_MODE_EIO,
  43         DM_VERITY_MODE_LOGGING,
  44         DM_VERITY_MODE_RESTART
  45 };
  46
  47 enum verity_block_type {
  48         DM_VERITY_BLOCK_TYPE_DATA,
  49         DM_VERITY_BLOCK_TYPE_METADATA
  50 };
  51
  52 struct dm_verity {
  53         struct dm_dev *data_dev;
  54         struct dm_dev *hash_dev;
  55         struct dm_target *ti;
  56         struct dm_bufio_client *bufio;
  57         char *alg_name;
  58         struct crypto_shash *tfm;
  59         u8 *root_digest;        /* digest of the root block */
  60         u8 *salt;               /* salt: its size is salt_size */
  61         unsigned salt_size;
  62         sector_t data_start;    /* data offset in 512-byte sectors */
  63         sector_t hash_start;    /* hash start in blocks */
  64         sector_t data_blocks;   /* the number of data blocks */
  65         sector_t hash_blocks;   /* the number of hash blocks */
  66         unsigned char data_dev_block_bits;      /* log2(data blocksize) */
  67         unsigned char hash_dev_block_bits;      /* log2(hash blocksize) */
  68         unsigned char hash_per_block_bits;      /* log2(hashes in hash block) */
  69         unsigned char levels;   /* the number of tree levels */
  70         unsigned char version;
  71         unsigned digest_size;   /* digest size for the current hash algorithm */
  72         unsigned shash_descsize;/* the size of temporary space for crypto */
  73         int hash_failed;        /* set to 1 if hash of any block failed */
  74         enum verity_mode mode;  /* mode for handling verification errors */
  75         unsigned corrupted_errs;/* Number of errors for corrupted blocks */
  76
  77         struct workqueue_struct *verify_wq;
  78
  79         /* starting blocks for each tree level. 0 is the lowest level. */
  80         sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
  81 };
  82
  83 struct dm_verity_io {
  84         struct dm_verity *v;
  85
  86         /* original values of bio->bi_end_io and bio->bi_private */
  87         bio_end_io_t *orig_bi_end_io;
  88         void *orig_bi_private;
  89
  90         sector_t block;
  91         unsigned n_blocks;
  92
  93         struct bvec_iter iter;
  94
  95         struct work_struct work;
  96
  97         /*
  98          * Three variably-size fields follow this struct:
  99          *
 100          * u8 hash_desc[v->shash_descsize];
 101          * u8 real_digest[v->digest_size];
 102          * u8 want_digest[v->digest_size];
 103          *
 104          * To access them use: io_hash_desc(), io_real_digest() and io_want_digest().
 105          */
 106 };
 107
 108 struct dm_verity_prefetch_work {
 109         struct work_struct work;
 110         struct dm_verity *v;
 111         sector_t block;
 112         unsigned n_blocks;
 113 };
 114
 115 static struct shash_desc *io_hash_desc(struct dm_verity *v, struct dm_verity_io *io)
 116 {
 117         return (struct shash_desc *)(io + 1);
 118 }
 119
 120 static u8 *io_real_digest(struct dm_verity *v, struct dm_verity_io *io)
 121 {
 122         return (u8 *)(io + 1) + v->shash_descsize;
 123 }
 124
 125 static u8 *io_want_digest(struct dm_verity *v, struct dm_verity_io *io)
 126 {
 127         return (u8 *)(io + 1) + v->shash_descsize + v->digest_size;
 128 }
 129
 130 /*
 131  * Auxiliary structure appended to each dm-bufio buffer. If the value
 132  * hash_verified is nonzero, hash of the block has been verified.
 133  *
 134  * The variable hash_verified is set to 0 when allocating the buffer, then
 135  * it can be changed to 1 and it is never reset to 0 again.
 136  *
 137  * There is no lock around this value, a race condition can at worst cause
 138  * that multiple processes verify the hash of the same buffer simultaneously
 139  * and write 1 to hash_verified simultaneously.
 140  * This condition is harmless, so we don't need locking.
 141  */
 142 struct buffer_aux {
 143         int hash_verified;
 144 };
 145
 146 /*
 147  * Initialize struct buffer_aux for a freshly created buffer.
 148  */
 149 static void dm_bufio_alloc_callback(struct dm_buffer *buf)
 150 {
 151         struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
 152
 153         aux->hash_verified = 0;
 154 }
 155
 156 /*
 157  * Translate input sector number to the sector number on the target device.
 158  */
 159 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
 160 {
 161         return v->data_start + dm_target_offset(v->ti, bi_sector);
 162 }
 163
 164 /*
 165  * Return hash position of a specified block at a specified tree level
 166  * (0 is the lowest level).
 167  * The lowest "hash_per_block_bits"-bits of the result denote hash position
 168  * inside a hash block. The remaining bits denote location of the hash block.
 169  */
 170 static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
 171                                          int level)
 172 {
 173         return block >> (level * v->hash_per_block_bits);
 174 }
 175
 176 static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
 177                                  sector_t *hash_block, unsigned *offset)
 178 {
 179         sector_t position = verity_position_at_level(v, block, level);
 180         unsigned idx;
 181
 182         *hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
 183
 184         if (!offset)
 185                 return;
 186
 187         idx = position & ((1 << v->hash_per_block_bits) - 1);
 188         if (!v->version)
 189                 *offset = idx * v->digest_size;
 190         else
 191                 *offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
 192 }
 193
 194 /*
 195  * Handle verification errors.
 196  */
 197 static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
 198                              unsigned long long block)
 199 {
 200         char verity_env[DM_VERITY_ENV_LENGTH];
 201         char *envp[] = { verity_env, NULL };
 202         const char *type_str = "";
 203         struct mapped_device *md = dm_table_get_md(v->ti->table);
 204
 205         /* Corruption should be visible in device status in all modes */
 206         v->hash_failed = 1;
 207
 208         if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
 209                 goto out;
 210
 211         v->corrupted_errs++;
 212
 213         switch (type) {
 214         case DM_VERITY_BLOCK_TYPE_DATA:
 215                 type_str = "data";
 216                 break;
 217         case DM_VERITY_BLOCK_TYPE_METADATA:
 218                 type_str = "metadata";
 219                 break;
 220         default:
 221                 BUG();
 222         }
 223
 224         DMERR("%s: %s block %llu is corrupted", v->data_dev->name, type_str,
 225                 block);
 226
 227         if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
 228                 DMERR("%s: reached maximum errors", v->data_dev->name);
 229
 230         snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
 231                 DM_VERITY_ENV_VAR_NAME, type, block);
 232
 233         kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
 234
 235 out:
 236         if (v->mode == DM_VERITY_MODE_LOGGING)
 237                 return 0;
 238
 239         if (v->mode == DM_VERITY_MODE_RESTART)
 240                 kernel_restart("dm-verity device corrupted");
 241
 242         return 1;
 243 }
 244
 245 /*
 246  * Verify hash of a metadata block pertaining to the specified data block
 247  * ("block" argument) at a specified level ("level" argument).
 248  *
 249  * On successful return, io_want_digest(v, io) contains the hash value for
 250  * a lower tree level or for the data block (if we're at the lowest leve).
 251  *
 252  * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
 253  * If "skip_unverified" is false, unverified buffer is hashed and verified
 254  * against current value of io_want_digest(v, io).
 255  */
 256 static int verity_verify_level(struct dm_verity_io *io, sector_t block,
 257                                int level, bool skip_unverified)
 258 {
 259         struct dm_verity *v = io->v;
 260         struct dm_buffer *buf;
 261         struct buffer_aux *aux;
 262         u8 *data;
 263         int r;
 264         sector_t hash_block;
 265         unsigned offset;
 266
 267         verity_hash_at_level(v, block, level, &hash_block, &offset);
 268
 269         data = dm_bufio_read(v->bufio, hash_block, &buf);
 270         if (IS_ERR(data))
 271                 return PTR_ERR(data);
 272
 273         aux = dm_bufio_get_aux_data(buf);
 274
 275         if (!aux->hash_verified) {
 276                 struct shash_desc *desc;
 277                 u8 *result;
 278
 279                 if (skip_unverified) {
 280                         r = 1;
 281                         goto release_ret_r;
 282                 }
 283
 284                 desc = io_hash_desc(v, io);
 285                 desc->tfm = v->tfm;
 286                 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 287                 r = crypto_shash_init(desc);
 288                 if (r < 0) {
 289                         DMERR("crypto_shash_init failed: %d", r);
 290                         goto release_ret_r;
 291                 }
 292
 293                 if (likely(v->version >= 1)) {
 294                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 295                         if (r < 0) {
 296                                 DMERR("crypto_shash_update failed: %d", r);
 297                                 goto release_ret_r;
 298                         }
 299                 }
 300
 301                 r = crypto_shash_update(desc, data, 1 << v->hash_dev_block_bits);
 302                 if (r < 0) {
 303                         DMERR("crypto_shash_update failed: %d", r);
 304                         goto release_ret_r;
 305                 }
 306
 307                 if (!v->version) {
 308                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 309                         if (r < 0) {
 310                                 DMERR("crypto_shash_update failed: %d", r);
 311                                 goto release_ret_r;
 312                         }
 313                 }
 314
 315                 result = io_real_digest(v, io);
 316                 r = crypto_shash_final(desc, result);
 317                 if (r < 0) {
 318                         DMERR("crypto_shash_final failed: %d", r);
 319                         goto release_ret_r;
 320                 }
 321                 if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
 322                         if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_METADATA,
 323                                               hash_block)) {
 324                                 r = -EIO;
 325                                 goto release_ret_r;
 326                         }
 327                 } else
 328                         aux->hash_verified = 1;
 329         }
 330
 331         data += offset;
 332
 333         memcpy(io_want_digest(v, io), data, v->digest_size);
 334
 335         dm_bufio_release(buf);
 336         return 0;
 337
 338 release_ret_r:
 339         dm_bufio_release(buf);
 340
 341         return r;
 342 }
 343
 344 /*
 345  * Verify one "dm_verity_io" structure.
 346  */
 347 static int verity_verify_io(struct dm_verity_io *io)
 348 {
 349         struct dm_verity *v = io->v;
 350         struct bio *bio = dm_bio_from_per_bio_data(io,
 351                                                    v->ti->per_bio_data_size);
 352         unsigned b;
 353         int i;
 354
 355         for (b = 0; b < io->n_blocks; b++) {
 356                 struct shash_desc *desc;
 357                 u8 *result;
 358                 int r;
 359                 unsigned todo;
 360
 361                 if (likely(v->levels)) {
 362                         /*
 363                          * First, we try to get the requested hash for
 364                          * the current block. If the hash block itself is
 365                          * verified, zero is returned. If it isn't, this
 366                          * function returns 0 and we fall back to whole
 367                          * chain verification.
 368                          */
 369                         int r = verity_verify_level(io, io->block + b, 0, true);
 370                         if (likely(!r))
 371                                 goto test_block_hash;
 372                         if (r < 0)
 373                                 return r;
 374                 }
 375
 376                 memcpy(io_want_digest(v, io), v->root_digest, v->digest_size);
 377
 378                 for (i = v->levels - 1; i >= 0; i--) {
 379                         int r = verity_verify_level(io, io->block + b, i, false);
 380                         if (unlikely(r))
 381                                 return r;
 382                 }
 383
 384 test_block_hash:
 385                 desc = io_hash_desc(v, io);
 386                 desc->tfm = v->tfm;
 387                 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 388                 r = crypto_shash_init(desc);
 389                 if (r < 0) {
 390                         DMERR("crypto_shash_init failed: %d", r);
 391                         return r;
 392                 }
 393
 394                 if (likely(v->version >= 1)) {
 395                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 396                         if (r < 0) {
 397                                 DMERR("crypto_shash_update failed: %d", r);
 398                                 return r;
 399                         }
 400                 }
 401                 todo = 1 << v->data_dev_block_bits;
 402                 do {
 403                         u8 *page;
 404                         unsigned len;
 405                         struct bio_vec bv = bio_iter_iovec(bio, io->iter);
 406
 407                         page = kmap_atomic(bv.bv_page);
 408                         len = bv.bv_len;
 409                         if (likely(len >= todo))
 410                                 len = todo;
 411                         r = crypto_shash_update(desc, page + bv.bv_offset, len);
 412                         kunmap_atomic(page);
 413
 414                         if (r < 0) {
 415                                 DMERR("crypto_shash_update failed: %d", r);
 416                                 return r;
 417                         }
 418
 419                         bio_advance_iter(bio, &io->iter, len);
 420                         todo -= len;
 421                 } while (todo);
 422
 423                 if (!v->version) {
 424                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 425                         if (r < 0) {
 426                                 DMERR("crypto_shash_update failed: %d", r);
 427                                 return r;
 428                         }
 429                 }
 430
 431                 result = io_real_digest(v, io);
 432                 r = crypto_shash_final(desc, result);
 433                 if (r < 0) {
 434                         DMERR("crypto_shash_final failed: %d", r);
 435                         return r;
 436                 }
 437                 if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
 438                         if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
 439                                               io->block + b))
 440                                 return -EIO;
 441                 }
 442         }
 443
 444         return 0;
 445 }
 446
 447 /*
 448  * End one "io" structure with a given error.
 449  */
 450 static void verity_finish_io(struct dm_verity_io *io, int error)
 451 {
 452         struct dm_verity *v = io->v;
 453         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_bio_data_size);
 454
 455         bio->bi_end_io = io->orig_bi_end_io;
 456         bio->bi_private = io->orig_bi_private;
 457         bio->bi_error = error;
 458
 459         bio_endio(bio);
 460 }
 461
 462 static void verity_work(struct work_struct *w)
 463 {
 464         struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
 465
 466         verity_finish_io(io, verity_verify_io(io));
 467 }
 468
 469 static void verity_end_io(struct bio *bio)
 470 {
 471         struct dm_verity_io *io = bio->bi_private;
 472
 473         if (bio->bi_error) {
 474                 verity_finish_io(io, bio->bi_error);
 475                 return;
 476         }
 477
 478         INIT_WORK(&io->work, verity_work);
 479         queue_work(io->v->verify_wq, &io->work);
 480 }
 481
 482 /*
 483  * Prefetch buffers for the specified io.
 484  * The root buffer is not prefetched, it is assumed that it will be cached
 485  * all the time.
 486  */
 487 static void verity_prefetch_io(struct work_struct *work)
 488 {
 489         struct dm_verity_prefetch_work *pw =
 490                 container_of(work, struct dm_verity_prefetch_work, work);
 491         struct dm_verity *v = pw->v;
 492         int i;
 493
 494         for (i = v->levels - 2; i >= 0; i--) {
 495                 sector_t hash_block_start;
 496                 sector_t hash_block_end;
 497                 verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
 498                 verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
 499                 if (!i) {
 500                         unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);
 501
 502                         cluster >>= v->data_dev_block_bits;
 503                         if (unlikely(!cluster))
 504                                 goto no_prefetch_cluster;
 505
 506                         if (unlikely(cluster & (cluster - 1)))
 507                                 cluster = 1 << __fls(cluster);
 508
 509                         hash_block_start &= ~(sector_t)(cluster - 1);
 510                         hash_block_end |= cluster - 1;
 511                         if (unlikely(hash_block_end >= v->hash_blocks))
 512                                 hash_block_end = v->hash_blocks - 1;
 513                 }
 514 no_prefetch_cluster:
 515                 dm_bufio_prefetch(v->bufio, hash_block_start,
 516                                   hash_block_end - hash_block_start + 1);
 517         }
 518
 519         kfree(pw);
 520 }
 521
 522 static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
 523 {
 524         struct dm_verity_prefetch_work *pw;
 525
 526         pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
 527                 GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 528
 529         if (!pw)
 530                 return;
 531
 532         INIT_WORK(&pw->work, verity_prefetch_io);
 533         pw->v = v;
 534         pw->block = io->block;
 535         pw->n_blocks = io->n_blocks;
 536         queue_work(v->verify_wq, &pw->work);
 537 }
 538
 539 /*
 540  * Bio map function. It allocates dm_verity_io structure and bio vector and
 541  * fills them. Then it issues prefetches and the I/O.
 542  */
 543 static int verity_map(struct dm_target *ti, struct bio *bio)
 544 {
 545         struct dm_verity *v = ti->private;
 546         struct dm_verity_io *io;
 547
 548         bio->bi_bdev = v->data_dev->bdev;
 549         bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
 550
 551         if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
 552             ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
 553                 DMERR_LIMIT("unaligned io");
 554                 return -EIO;
 555         }
 556
 557         if (bio_end_sector(bio) >>
 558             (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
 559                 DMERR_LIMIT("io out of range");
 560                 return -EIO;
 561         }
 562
 563         if (bio_data_dir(bio) == WRITE)
 564                 return -EIO;
 565
 566         io = dm_per_bio_data(bio, ti->per_bio_data_size);
 567         io->v = v;
 568         io->orig_bi_end_io = bio->bi_end_io;
 569         io->orig_bi_private = bio->bi_private;
 570         io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
 571         io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
 572
 573         bio->bi_end_io = verity_end_io;
 574         bio->bi_private = io;
 575         io->iter = bio->bi_iter;
 576
 577         verity_submit_prefetch(v, io);
 578
 579         generic_make_request(bio);
 580
 581         return DM_MAPIO_SUBMITTED;
 582 }
 583
 584 /*
 585  * Status: V (valid) or C (corruption found)
 586  */
 587 static void verity_status(struct dm_target *ti, status_type_t type,
 588                           unsigned status_flags, char *result, unsigned maxlen)
 589 {
 590         struct dm_verity *v = ti->private;
 591         unsigned sz = 0;
 592         unsigned x;
 593
 594         switch (type) {
 595         case STATUSTYPE_INFO:
 596                 DMEMIT("%c", v->hash_failed ? 'C' : 'V');
 597                 break;
 598         case STATUSTYPE_TABLE:
 599                 DMEMIT("%u %s %s %u %u %llu %llu %s ",
 600                         v->version,
 601                         v->data_dev->name,
 602                         v->hash_dev->name,
 603                         1 << v->data_dev_block_bits,
 604                         1 << v->hash_dev_block_bits,
 605                         (unsigned long long)v->data_blocks,
 606                         (unsigned long long)v->hash_start,
 607                         v->alg_name
 608                         );
 609                 for (x = 0; x < v->digest_size; x++)
 610                         DMEMIT("%02x", v->root_digest[x]);
 611                 DMEMIT(" ");
 612                 if (!v->salt_size)
 613                         DMEMIT("-");
 614                 else
 615                         for (x = 0; x < v->salt_size; x++)
 616                                 DMEMIT("%02x", v->salt[x]);
 617                 if (v->mode != DM_VERITY_MODE_EIO) {
 618                         DMEMIT(" 1 ");
 619                         switch (v->mode) {
 620                         case DM_VERITY_MODE_LOGGING:
 621                                 DMEMIT(DM_VERITY_OPT_LOGGING);
 622                                 break;
 623                         case DM_VERITY_MODE_RESTART:
 624                                 DMEMIT(DM_VERITY_OPT_RESTART);
 625                                 break;
 626                         default:
 627                                 BUG();
 628                         }
 629                 }
 630                 break;
 631         }
 632 }
 633
 634 static int verity_ioctl(struct dm_target *ti, unsigned cmd,
 635                         unsigned long arg)
 636 {
 637         struct dm_verity *v = ti->private;
 638         int r = 0;
 639
 640         if (v->data_start ||
 641             ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
 642                 r = scsi_verify_blk_ioctl(NULL, cmd);
 643
 644         return r ? : __blkdev_driver_ioctl(v->data_dev->bdev, v->data_dev->mode,
 645                                      cmd, arg);
 646 }
 647
 648 static int verity_iterate_devices(struct dm_target *ti,
 649                                   iterate_devices_callout_fn fn, void *data)
 650 {
 651         struct dm_verity *v = ti->private;
 652
 653         return fn(ti, v->data_dev, v->data_start, ti->len, data);
 654 }
 655
 656 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
 657 {
 658         struct dm_verity *v = ti->private;
 659
 660         if (limits->logical_block_size < 1 << v->data_dev_block_bits)
 661                 limits->logical_block_size = 1 << v->data_dev_block_bits;
 662
 663         if (limits->physical_block_size < 1 << v->data_dev_block_bits)
 664                 limits->physical_block_size = 1 << v->data_dev_block_bits;
 665
 666         blk_limits_io_min(limits, limits->logical_block_size);
 667 }
 668
 669 static void verity_dtr(struct dm_target *ti)
 670 {
 671         struct dm_verity *v = ti->private;
 672
 673         if (v->verify_wq)
 674                 destroy_workqueue(v->verify_wq);
 675
 676         if (v->bufio)
 677                 dm_bufio_client_destroy(v->bufio);
 678
 679         kfree(v->salt);
 680         kfree(v->root_digest);
 681
 682         if (v->tfm)
 683                 crypto_free_shash(v->tfm);
 684
 685         kfree(v->alg_name);
 686
 687         if (v->hash_dev)
 688                 dm_put_device(ti, v->hash_dev);
 689
 690         if (v->data_dev)
 691                 dm_put_device(ti, v->data_dev);
 692
 693         kfree(v);
 694 }
 695
 696 /*
 697  * Target parameters:
 698  *      <version>       The current format is version 1.
 699  *                      Vsn 0 is compatible with original Chromium OS releases.
 700  *      <data device>
 701  *      <hash device>
 702  *      <data block size>
 703  *      <hash block size>
 704  *      <the number of data blocks>
 705  *      <hash start block>
 706  *      <algorithm>
 707  *      <digest>
 708  *      <salt>          Hex string or "-" if no salt.
 709  */
 710 static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 711 {
 712         struct dm_verity *v;
 713         struct dm_arg_set as;
 714         const char *opt_string;
 715         unsigned int num, opt_params;
 716         unsigned long long num_ll;
 717         int r;
 718         int i;
 719         sector_t hash_position;
 720         char dummy;
 721
 722         static struct dm_arg _args[] = {
 723                 {0, 1, "Invalid number of feature args"},
 724         };
 725
 726         v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
 727         if (!v) {
 728                 ti->error = "Cannot allocate verity structure";
 729                 return -ENOMEM;
 730         }
 731         ti->private = v;
 732         v->ti = ti;
 733
 734         if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
 735                 ti->error = "Device must be readonly";
 736                 r = -EINVAL;
 737                 goto bad;
 738         }
 739
 740         if (argc < 10) {
 741                 ti->error = "Not enough arguments";
 742                 r = -EINVAL;
 743                 goto bad;
 744         }
 745
 746         if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
 747             num > 1) {
 748                 ti->error = "Invalid version";
 749                 r = -EINVAL;
 750                 goto bad;
 751         }
 752         v->version = num;
 753
 754         r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
 755         if (r) {
 756                 ti->error = "Data device lookup failed";
 757                 goto bad;
 758         }
 759
 760         r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
 761         if (r) {
 762                 ti->error = "Data device lookup failed";
 763                 goto bad;
 764         }
 765
 766         if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
 767             !num || (num & (num - 1)) ||
 768             num < bdev_logical_block_size(v->data_dev->bdev) ||
 769             num > PAGE_SIZE) {
 770                 ti->error = "Invalid data device block size";
 771                 r = -EINVAL;
 772                 goto bad;
 773         }
 774         v->data_dev_block_bits = __ffs(num);
 775
 776         if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
 777             !num || (num & (num - 1)) ||
 778             num < bdev_logical_block_size(v->hash_dev->bdev) ||
 779             num > INT_MAX) {
 780                 ti->error = "Invalid hash device block size";
 781                 r = -EINVAL;
 782                 goto bad;
 783         }
 784         v->hash_dev_block_bits = __ffs(num);
 785
 786         if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
 787             (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
 788             >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 789                 ti->error = "Invalid data blocks";
 790                 r = -EINVAL;
 791                 goto bad;
 792         }
 793         v->data_blocks = num_ll;
 794
 795         if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
 796                 ti->error = "Data device is too small";
 797                 r = -EINVAL;
 798                 goto bad;
 799         }
 800
 801         if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
 802             (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
 803             >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 804                 ti->error = "Invalid hash start";
 805                 r = -EINVAL;
 806                 goto bad;
 807         }
 808         v->hash_start = num_ll;
 809
 810         v->alg_name = kstrdup(argv[7], GFP_KERNEL);
 811         if (!v->alg_name) {
 812                 ti->error = "Cannot allocate algorithm name";
 813                 r = -ENOMEM;
 814                 goto bad;
 815         }
 816
 817         v->tfm = crypto_alloc_shash(v->alg_name, 0, 0);
 818         if (IS_ERR(v->tfm)) {
 819                 ti->error = "Cannot initialize hash function";
 820                 r = PTR_ERR(v->tfm);
 821                 v->tfm = NULL;
 822                 goto bad;
 823         }
 824         v->digest_size = crypto_shash_digestsize(v->tfm);
 825         if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
 826                 ti->error = "Digest size too big";
 827                 r = -EINVAL;
 828                 goto bad;
 829         }
 830         v->shash_descsize =
 831                 sizeof(struct shash_desc) + crypto_shash_descsize(v->tfm);
 832
 833         v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
 834         if (!v->root_digest) {
 835                 ti->error = "Cannot allocate root digest";
 836                 r = -ENOMEM;
 837                 goto bad;
 838         }
 839         if (strlen(argv[8]) != v->digest_size * 2 ||
 840             hex2bin(v->root_digest, argv[8], v->digest_size)) {
 841                 ti->error = "Invalid root digest";
 842                 r = -EINVAL;
 843                 goto bad;
 844         }
 845
 846         if (strcmp(argv[9], "-")) {
 847                 v->salt_size = strlen(argv[9]) / 2;
 848                 v->salt = kmalloc(v->salt_size, GFP_KERNEL);
 849                 if (!v->salt) {
 850                         ti->error = "Cannot allocate salt";
 851                         r = -ENOMEM;
 852                         goto bad;
 853                 }
 854                 if (strlen(argv[9]) != v->salt_size * 2 ||
 855                     hex2bin(v->salt, argv[9], v->salt_size)) {
 856                         ti->error = "Invalid salt";
 857                         r = -EINVAL;
 858                         goto bad;
 859                 }
 860         }
 861
 862         argv += 10;
 863         argc -= 10;
 864
 865         /* Optional parameters */
 866         if (argc) {
 867                 as.argc = argc;
 868                 as.argv = argv;
 869
 870                 r = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
 871                 if (r)
 872                         goto bad;
 873
 874                 while (opt_params) {
 875                         opt_params--;
 876                         opt_string = dm_shift_arg(&as);
 877                         if (!opt_string) {
 878                                 ti->error = "Not enough feature arguments";
 879                                 r = -EINVAL;
 880                                 goto bad;
 881                         }
 882
 883                         if (!strcasecmp(opt_string, DM_VERITY_OPT_LOGGING))
 884                                 v->mode = DM_VERITY_MODE_LOGGING;
 885                         else if (!strcasecmp(opt_string, DM_VERITY_OPT_RESTART))
 886                                 v->mode = DM_VERITY_MODE_RESTART;
 887                         else {
 888                                 ti->error = "Invalid feature arguments";
 889                                 r = -EINVAL;
 890                                 goto bad;
 891                         }
 892                 }
 893         }
 894
 895         v->hash_per_block_bits =
 896                 __fls((1 << v->hash_dev_block_bits) / v->digest_size);
 897
 898         v->levels = 0;
 899         if (v->data_blocks)
 900                 while (v->hash_per_block_bits * v->levels < 64 &&
 901                        (unsigned long long)(v->data_blocks - 1) >>
 902                        (v->hash_per_block_bits * v->levels))
 903                         v->levels++;
 904
 905         if (v->levels > DM_VERITY_MAX_LEVELS) {
 906                 ti->error = "Too many tree levels";
 907                 r = -E2BIG;
 908                 goto bad;
 909         }
 910
 911         hash_position = v->hash_start;
 912         for (i = v->levels - 1; i >= 0; i--) {
 913                 sector_t s;
 914                 v->hash_level_block[i] = hash_position;
 915                 s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
 916                                         >> ((i + 1) * v->hash_per_block_bits);
 917                 if (hash_position + s < hash_position) {
 918                         ti->error = "Hash device offset overflow";
 919                         r = -E2BIG;
 920                         goto bad;
 921                 }
 922                 hash_position += s;
 923         }
 924         v->hash_blocks = hash_position;
 925
 926         v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
 927                 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
 928                 dm_bufio_alloc_callback, NULL);
 929         if (IS_ERR(v->bufio)) {
 930                 ti->error = "Cannot initialize dm-bufio";
 931                 r = PTR_ERR(v->bufio);
 932                 v->bufio = NULL;
 933                 goto bad;
 934         }
 935
 936         if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
 937                 ti->error = "Hash device is too small";
 938                 r = -E2BIG;
 939                 goto bad;
 940         }
 941
 942         ti->per_bio_data_size = roundup(sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2, __alignof__(struct dm_verity_io));
 943
 944         /* WQ_UNBOUND greatly improves performance when running on ramdisk */
 945         v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
 946         if (!v->verify_wq) {
 947                 ti->error = "Cannot allocate workqueue";
 948                 r = -ENOMEM;
 949                 goto bad;
 950         }
 951
 952         return 0;
 953
 954 bad:
 955         verity_dtr(ti);
 956
 957         return r;
 958 }
 959
 960 static struct target_type verity_target = {
 961         .name           = "verity",
 962         .version        = {1, 2, 0},
 963         .module         = THIS_MODULE,
 964         .ctr            = verity_ctr,
 965         .dtr            = verity_dtr,
 966         .map            = verity_map,
 967         .status         = verity_status,
 968         .ioctl          = verity_ioctl,
 969         .iterate_devices = verity_iterate_devices,
 970         .io_hints       = verity_io_hints,
 971 };
 972
 973 static int __init dm_verity_init(void)
 974 {
 975         int r;
 976
 977         r = dm_register_target(&verity_target);
 978         if (r < 0)
 979                 DMERR("register failed %d", r);
 980
 981         return r;
 982 }
 983
 984 static void __exit dm_verity_exit(void)
 985 {
 986         dm_unregister_target(&verity_target);
 987 }
 988
 989 module_init(dm_verity_init);
 990 module_exit(dm_verity_exit);
 991
 992 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
 993 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
 994 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
 995 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
 996 MODULE_LICENSE("GPL");