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