kernel/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_IO_VEC_INLINE         16
  30 #define DM_VERITY_MEMPOOL_SIZE          4
  31 #define DM_VERITY_DEFAULT_PREFETCH_SIZE 262144
  32
  33 #define DM_VERITY_MAX_LEVELS            63
  34 #define DM_VERITY_MAX_CORRUPTED_ERRS    100
  35
  36 #define DM_VERITY_OPT_LOGGING           "ignore_corruption"
  37 #define DM_VERITY_OPT_RESTART           "restart_on_corruption"
  38
  39 static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
  40
  41 module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
  42
  43 enum verity_mode {
  44         DM_VERITY_MODE_EIO,
  45         DM_VERITY_MODE_LOGGING,
  46         DM_VERITY_MODE_RESTART
  47 };
  48
  49 enum verity_block_type {
  50         DM_VERITY_BLOCK_TYPE_DATA,
  51         DM_VERITY_BLOCK_TYPE_METADATA
  52 };
  53
  54 struct dm_verity {
  55         struct dm_dev *data_dev;
  56         struct dm_dev *hash_dev;
  57         struct dm_target *ti;
  58         struct dm_bufio_client *bufio;
  59         char *alg_name;
  60         struct crypto_shash *tfm;
  61         u8 *root_digest;        /* digest of the root block */
  62         u8 *salt;               /* salt: its size is salt_size */
  63         unsigned salt_size;
  64         sector_t data_start;    /* data offset in 512-byte sectors */
  65         sector_t hash_start;    /* hash start in blocks */
  66         sector_t data_blocks;   /* the number of data blocks */
  67         sector_t hash_blocks;   /* the number of hash blocks */
  68         unsigned char data_dev_block_bits;      /* log2(data blocksize) */
  69         unsigned char hash_dev_block_bits;      /* log2(hash blocksize) */
  70         unsigned char hash_per_block_bits;      /* log2(hashes in hash block) */
  71         unsigned char levels;   /* the number of tree levels */
  72         unsigned char version;
  73         unsigned digest_size;   /* digest size for the current hash algorithm */
  74         unsigned shash_descsize;/* the size of temporary space for crypto */
  75         int hash_failed;        /* set to 1 if hash of any block failed */
  76         enum verity_mode mode;  /* mode for handling verification errors */
  77         unsigned corrupted_errs;/* Number of errors for corrupted blocks */
  78
  79         mempool_t *vec_mempool; /* mempool of bio vector */
  80
  81         struct workqueue_struct *verify_wq;
  82
  83         /* starting blocks for each tree level. 0 is the lowest level. */
  84         sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
  85 };
  86
  87 struct dm_verity_io {
  88         struct dm_verity *v;
  89
  90         /* original values of bio->bi_end_io and bio->bi_private */
  91         bio_end_io_t *orig_bi_end_io;
  92         void *orig_bi_private;
  93
  94         sector_t block;
  95         unsigned n_blocks;
  96
  97         struct bvec_iter iter;
  98
  99         struct work_struct work;
 100
 101         /*
 102          * Three variably-size fields follow this struct:
 103          *
 104          * u8 hash_desc[v->shash_descsize];
 105          * u8 real_digest[v->digest_size];
 106          * u8 want_digest[v->digest_size];
 107          *
 108          * To access them use: io_hash_desc(), io_real_digest() and io_want_digest().
 109          */
 110 };
 111
 112 struct dm_verity_prefetch_work {
 113         struct work_struct work;
 114         struct dm_verity *v;
 115         sector_t block;
 116         unsigned n_blocks;
 117 };
 118
 119 static struct shash_desc *io_hash_desc(struct dm_verity *v, struct dm_verity_io *io)
 120 {
 121         return (struct shash_desc *)(io + 1);
 122 }
 123
 124 static u8 *io_real_digest(struct dm_verity *v, struct dm_verity_io *io)
 125 {
 126         return (u8 *)(io + 1) + v->shash_descsize;
 127 }
 128
 129 static u8 *io_want_digest(struct dm_verity *v, struct dm_verity_io *io)
 130 {
 131         return (u8 *)(io + 1) + v->shash_descsize + v->digest_size;
 132 }
 133
 134 /*
 135  * Auxiliary structure appended to each dm-bufio buffer. If the value
 136  * hash_verified is nonzero, hash of the block has been verified.
 137  *
 138  * The variable hash_verified is set to 0 when allocating the buffer, then
 139  * it can be changed to 1 and it is never reset to 0 again.
 140  *
 141  * There is no lock around this value, a race condition can at worst cause
 142  * that multiple processes verify the hash of the same buffer simultaneously
 143  * and write 1 to hash_verified simultaneously.
 144  * This condition is harmless, so we don't need locking.
 145  */
 146 struct buffer_aux {
 147         int hash_verified;
 148 };
 149
 150 /*
 151  * Initialize struct buffer_aux for a freshly created buffer.
 152  */
 153 static void dm_bufio_alloc_callback(struct dm_buffer *buf)
 154 {
 155         struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
 156
 157         aux->hash_verified = 0;
 158 }
 159
 160 /*
 161  * Translate input sector number to the sector number on the target device.
 162  */
 163 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
 164 {
 165         return v->data_start + dm_target_offset(v->ti, bi_sector);
 166 }
 167
 168 /*
 169  * Return hash position of a specified block at a specified tree level
 170  * (0 is the lowest level).
 171  * The lowest "hash_per_block_bits"-bits of the result denote hash position
 172  * inside a hash block. The remaining bits denote location of the hash block.
 173  */
 174 static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
 175                                          int level)
 176 {
 177         return block >> (level * v->hash_per_block_bits);
 178 }
 179
 180 static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
 181                                  sector_t *hash_block, unsigned *offset)
 182 {
 183         sector_t position = verity_position_at_level(v, block, level);
 184         unsigned idx;
 185
 186         *hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
 187
 188         if (!offset)
 189                 return;
 190
 191         idx = position & ((1 << v->hash_per_block_bits) - 1);
 192         if (!v->version)
 193                 *offset = idx * v->digest_size;
 194         else
 195                 *offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
 196 }
 197
 198 /*
 199  * Handle verification errors.
 200  */
 201 static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
 202                              unsigned long long block)
 203 {
 204         char verity_env[DM_VERITY_ENV_LENGTH];
 205         char *envp[] = { verity_env, NULL };
 206         const char *type_str = "";
 207         struct mapped_device *md = dm_table_get_md(v->ti->table);
 208
 209         /* Corruption should be visible in device status in all modes */
 210         v->hash_failed = 1;
 211
 212         if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
 213                 goto out;
 214
 215         v->corrupted_errs++;
 216
 217         switch (type) {
 218         case DM_VERITY_BLOCK_TYPE_DATA:
 219                 type_str = "data";
 220                 break;
 221         case DM_VERITY_BLOCK_TYPE_METADATA:
 222                 type_str = "metadata";
 223                 break;
 224         default:
 225                 BUG();
 226         }
 227
 228         DMERR("%s: %s block %llu is corrupted", v->data_dev->name, type_str,
 229                 block);
 230
 231         if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
 232                 DMERR("%s: reached maximum errors", v->data_dev->name);
 233
 234         snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
 235                 DM_VERITY_ENV_VAR_NAME, type, block);
 236
 237         kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
 238
 239 out:
 240         if (v->mode == DM_VERITY_MODE_LOGGING)
 241                 return 0;
 242
 243         if (v->mode == DM_VERITY_MODE_RESTART)
 244                 kernel_restart("dm-verity device corrupted");
 245
 246         return 1;
 247 }
 248
 249 /*
 250  * Verify hash of a metadata block pertaining to the specified data block
 251  * ("block" argument) at a specified level ("level" argument).
 252  *
 253  * On successful return, io_want_digest(v, io) contains the hash value for
 254  * a lower tree level or for the data block (if we're at the lowest leve).
 255  *
 256  * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
 257  * If "skip_unverified" is false, unverified buffer is hashed and verified
 258  * against current value of io_want_digest(v, io).
 259  */
 260 static int verity_verify_level(struct dm_verity_io *io, sector_t block,
 261                                int level, bool skip_unverified)
 262 {
 263         struct dm_verity *v = io->v;
 264         struct dm_buffer *buf;
 265         struct buffer_aux *aux;
 266         u8 *data;
 267         int r;
 268         sector_t hash_block;
 269         unsigned offset;
 270
 271         verity_hash_at_level(v, block, level, &hash_block, &offset);
 272
 273         data = dm_bufio_read(v->bufio, hash_block, &buf);
 274         if (unlikely(IS_ERR(data)))
 275                 return PTR_ERR(data);
 276
 277         aux = dm_bufio_get_aux_data(buf);
 278
 279         if (!aux->hash_verified) {
 280                 struct shash_desc *desc;
 281                 u8 *result;
 282
 283                 if (skip_unverified) {
 284                         r = 1;
 285                         goto release_ret_r;
 286                 }
 287
 288                 desc = io_hash_desc(v, io);
 289                 desc->tfm = v->tfm;
 290                 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 291                 r = crypto_shash_init(desc);
 292                 if (r < 0) {
 293                         DMERR("crypto_shash_init failed: %d", r);
 294                         goto release_ret_r;
 295                 }
 296
 297                 if (likely(v->version >= 1)) {
 298                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 299                         if (r < 0) {
 300                                 DMERR("crypto_shash_update failed: %d", r);
 301                                 goto release_ret_r;
 302                         }
 303                 }
 304
 305                 r = crypto_shash_update(desc, data, 1 << v->hash_dev_block_bits);
 306                 if (r < 0) {
 307                         DMERR("crypto_shash_update failed: %d", r);
 308                         goto release_ret_r;
 309                 }
 310
 311                 if (!v->version) {
 312                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 313                         if (r < 0) {
 314                                 DMERR("crypto_shash_update failed: %d", r);
 315                                 goto release_ret_r;
 316                         }
 317                 }
 318
 319                 result = io_real_digest(v, io);
 320                 r = crypto_shash_final(desc, result);
 321                 if (r < 0) {
 322                         DMERR("crypto_shash_final failed: %d", r);
 323                         goto release_ret_r;
 324                 }
 325                 if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
 326                         if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_METADATA,
 327                                               hash_block)) {
 328                                 r = -EIO;
 329                                 goto release_ret_r;
 330                         }
 331                 } else
 332                         aux->hash_verified = 1;
 333         }
 334
 335         data += offset;
 336
 337         memcpy(io_want_digest(v, io), data, v->digest_size);
 338
 339         dm_bufio_release(buf);
 340         return 0;
 341
 342 release_ret_r:
 343         dm_bufio_release(buf);
 344
 345         return r;
 346 }
 347
 348 /*
 349  * Verify one "dm_verity_io" structure.
 350  */
 351 static int verity_verify_io(struct dm_verity_io *io)
 352 {
 353         struct dm_verity *v = io->v;
 354         struct bio *bio = dm_bio_from_per_bio_data(io,
 355                                                    v->ti->per_bio_data_size);
 356         unsigned b;
 357         int i;
 358
 359         for (b = 0; b < io->n_blocks; b++) {
 360                 struct shash_desc *desc;
 361                 u8 *result;
 362                 int r;
 363                 unsigned todo;
 364
 365                 if (likely(v->levels)) {
 366                         /*
 367                          * First, we try to get the requested hash for
 368                          * the current block. If the hash block itself is
 369                          * verified, zero is returned. If it isn't, this
 370                          * function returns 0 and we fall back to whole
 371                          * chain verification.
 372                          */
 373                         int r = verity_verify_level(io, io->block + b, 0, true);
 374                         if (likely(!r))
 375                                 goto test_block_hash;
 376                         if (r < 0)
 377                                 return r;
 378                 }
 379
 380                 memcpy(io_want_digest(v, io), v->root_digest, v->digest_size);
 381
 382                 for (i = v->levels - 1; i >= 0; i--) {
 383                         int r = verity_verify_level(io, io->block + b, i, false);
 384                         if (unlikely(r))
 385                                 return r;
 386                 }
 387
 388 test_block_hash:
 389                 desc = io_hash_desc(v, io);
 390                 desc->tfm = v->tfm;
 391                 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 392                 r = crypto_shash_init(desc);
 393                 if (r < 0) {
 394                         DMERR("crypto_shash_init failed: %d", r);
 395                         return r;
 396                 }
 397
 398                 if (likely(v->version >= 1)) {
 399                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 400                         if (r < 0) {
 401                                 DMERR("crypto_shash_update failed: %d", r);
 402                                 return r;
 403                         }
 404                 }
 405                 todo = 1 << v->data_dev_block_bits;
 406                 do {
 407                         u8 *page;
 408                         unsigned len;
 409                         struct bio_vec bv = bio_iter_iovec(bio, io->iter);
 410
 411                         page = kmap_atomic(bv.bv_page);
 412                         len = bv.bv_len;
 413                         if (likely(len >= todo))
 414                                 len = todo;
 415                         r = crypto_shash_update(desc, page + bv.bv_offset, len);
 416                         kunmap_atomic(page);
 417
 418                         if (r < 0) {
 419                                 DMERR("crypto_shash_update failed: %d", r);
 420                                 return r;
 421                         }
 422
 423                         bio_advance_iter(bio, &io->iter, len);
 424                         todo -= len;
 425                 } while (todo);
 426
 427                 if (!v->version) {
 428                         r = crypto_shash_update(desc, v->salt, v->salt_size);
 429                         if (r < 0) {
 430                                 DMERR("crypto_shash_update failed: %d", r);
 431                                 return r;
 432                         }
 433                 }
 434
 435                 result = io_real_digest(v, io);
 436                 r = crypto_shash_final(desc, result);
 437                 if (r < 0) {
 438                         DMERR("crypto_shash_final failed: %d", r);
 439                         return r;
 440                 }
 441                 if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
 442                         if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
 443                                               io->block + b))
 444                                 return -EIO;
 445                 }
 446         }
 447
 448         return 0;
 449 }
 450
 451 /*
 452  * End one "io" structure with a given error.
 453  */
 454 static void verity_finish_io(struct dm_verity_io *io, int error)
 455 {
 456         struct dm_verity *v = io->v;
 457         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_bio_data_size);
 458
 459         bio->bi_end_io = io->orig_bi_end_io;
 460         bio->bi_private = io->orig_bi_private;
 461
 462         bio_endio_nodec(bio, error);
 463 }
 464
 465 static void verity_work(struct work_struct *w)
 466 {
 467         struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
 468
 469         verity_finish_io(io, verity_verify_io(io));
 470 }
 471
 472 static void verity_end_io(struct bio *bio, int error)
 473 {
 474         struct dm_verity_io *io = bio->bi_private;
 475
 476         if (error) {
 477                 verity_finish_io(io, error);
 478                 return;
 479         }
 480
 481         INIT_WORK(&io->work, verity_work);
 482         queue_work(io->v->verify_wq, &io->work);
 483 }
 484
 485 /*
 486  * Prefetch buffers for the specified io.
 487  * The root buffer is not prefetched, it is assumed that it will be cached
 488  * all the time.
 489  */
 490 static void verity_prefetch_io(struct work_struct *work)
 491 {
 492         struct dm_verity_prefetch_work *pw =
 493                 container_of(work, struct dm_verity_prefetch_work, work);
 494         struct dm_verity *v = pw->v;
 495         int i;
 496
 497         for (i = v->levels - 2; i >= 0; i--) {
 498                 sector_t hash_block_start;
 499                 sector_t hash_block_end;
 500                 verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
 501                 verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
 502                 if (!i) {
 503                         unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);
 504
 505                         cluster >>= v->data_dev_block_bits;
 506                         if (unlikely(!cluster))
 507                                 goto no_prefetch_cluster;
 508
 509                         if (unlikely(cluster & (cluster - 1)))
 510                                 cluster = 1 << __fls(cluster);
 511
 512                         hash_block_start &= ~(sector_t)(cluster - 1);
 513                         hash_block_end |= cluster - 1;
 514                         if (unlikely(hash_block_end >= v->hash_blocks))
 515                                 hash_block_end = v->hash_blocks - 1;
 516                 }
 517 no_prefetch_cluster:
 518                 dm_bufio_prefetch(v->bufio, hash_block_start,
 519                                   hash_block_end - hash_block_start + 1);
 520         }
 521
 522         kfree(pw);
 523 }
 524
 525 static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
 526 {
 527         struct dm_verity_prefetch_work *pw;
 528
 529         pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
 530                 GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 531
 532         if (!pw)
 533                 return;
 534
 535         INIT_WORK(&pw->work, verity_prefetch_io);
 536         pw->v = v;
 537         pw->block = io->block;
 538         pw->n_blocks = io->n_blocks;
 539         queue_work(v->verify_wq, &pw->work);
 540 }
 541
 542 /*
 543  * Bio map function. It allocates dm_verity_io structure and bio vector and
 544  * fills them. Then it issues prefetches and the I/O.
 545  */
 546 static int verity_map(struct dm_target *ti, struct bio *bio)
 547 {
 548         struct dm_verity *v = ti->private;
 549         struct dm_verity_io *io;
 550
 551         bio->bi_bdev = v->data_dev->bdev;
 552         bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
 553
 554         if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
 555             ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
 556                 DMERR_LIMIT("unaligned io");
 557                 return -EIO;
 558         }
 559
 560         if (bio_end_sector(bio) >>
 561             (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
 562                 DMERR_LIMIT("io out of range");
 563                 return -EIO;
 564         }
 565
 566         if (bio_data_dir(bio) == WRITE)
 567                 return -EIO;
 568
 569         io = dm_per_bio_data(bio, ti->per_bio_data_size);
 570         io->v = v;
 571         io->orig_bi_end_io = bio->bi_end_io;
 572         io->orig_bi_private = bio->bi_private;
 573         io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
 574         io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
 575
 576         bio->bi_end_io = verity_end_io;
 577         bio->bi_private = io;
 578         io->iter = bio->bi_iter;
 579
 580         verity_submit_prefetch(v, io);
 581
 582         generic_make_request(bio);
 583
 584         return DM_MAPIO_SUBMITTED;
 585 }
 586
 587 /*
 588  * Status: V (valid) or C (corruption found)
 589  */
 590 static void verity_status(struct dm_target *ti, status_type_t type,
 591                           unsigned status_flags, char *result, unsigned maxlen)
 592 {
 593         struct dm_verity *v = ti->private;
 594         unsigned sz = 0;
 595         unsigned x;
 596
 597         switch (type) {
 598         case STATUSTYPE_INFO:
 599                 DMEMIT("%c", v->hash_failed ? 'C' : 'V');
 600                 break;
 601         case STATUSTYPE_TABLE:
 602                 DMEMIT("%u %s %s %u %u %llu %llu %s ",
 603                         v->version,
 604                         v->data_dev->name,
 605                         v->hash_dev->name,
 606                         1 << v->data_dev_block_bits,
 607                         1 << v->hash_dev_block_bits,
 608                         (unsigned long long)v->data_blocks,
 609                         (unsigned long long)v->hash_start,
 610                         v->alg_name
 611                         );
 612                 for (x = 0; x < v->digest_size; x++)
 613                         DMEMIT("%02x", v->root_digest[x]);
 614                 DMEMIT(" ");
 615                 if (!v->salt_size)
 616                         DMEMIT("-");
 617                 else
 618                         for (x = 0; x < v->salt_size; x++)
 619                                 DMEMIT("%02x", v->salt[x]);
 620                 if (v->mode != DM_VERITY_MODE_EIO) {
 621                         DMEMIT(" 1 ");
 622                         switch (v->mode) {
 623                         case DM_VERITY_MODE_LOGGING:
 624                                 DMEMIT(DM_VERITY_OPT_LOGGING);
 625                                 break;
 626                         case DM_VERITY_MODE_RESTART:
 627                                 DMEMIT(DM_VERITY_OPT_RESTART);
 628                                 break;
 629                         default:
 630                                 BUG();
 631                         }
 632                 }
 633                 break;
 634         }
 635 }
 636
 637 static int verity_ioctl(struct dm_target *ti, unsigned cmd,
 638                         unsigned long arg)
 639 {
 640         struct dm_verity *v = ti->private;
 641         int r = 0;
 642
 643         if (v->data_start ||
 644             ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
 645                 r = scsi_verify_blk_ioctl(NULL, cmd);
 646
 647         return r ? : __blkdev_driver_ioctl(v->data_dev->bdev, v->data_dev->mode,
 648                                      cmd, arg);
 649 }
 650
 651 static int verity_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 652                         struct bio_vec *biovec, int max_size)
 653 {
 654         struct dm_verity *v = ti->private;
 655         struct request_queue *q = bdev_get_queue(v->data_dev->bdev);
 656
 657         if (!q->merge_bvec_fn)
 658                 return max_size;
 659
 660         bvm->bi_bdev = v->data_dev->bdev;
 661         bvm->bi_sector = verity_map_sector(v, bvm->bi_sector);
 662
 663         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 664 }
 665
 666 static int verity_iterate_devices(struct dm_target *ti,
 667                                   iterate_devices_callout_fn fn, void *data)
 668 {
 669         struct dm_verity *v = ti->private;
 670
 671         return fn(ti, v->data_dev, v->data_start, ti->len, data);
 672 }
 673
 674 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
 675 {
 676         struct dm_verity *v = ti->private;
 677
 678         if (limits->logical_block_size < 1 << v->data_dev_block_bits)
 679                 limits->logical_block_size = 1 << v->data_dev_block_bits;
 680
 681         if (limits->physical_block_size < 1 << v->data_dev_block_bits)
 682                 limits->physical_block_size = 1 << v->data_dev_block_bits;
 683
 684         blk_limits_io_min(limits, limits->logical_block_size);
 685 }
 686
 687 static void verity_dtr(struct dm_target *ti)
 688 {
 689         struct dm_verity *v = ti->private;
 690
 691         if (v->verify_wq)
 692                 destroy_workqueue(v->verify_wq);
 693
 694         if (v->vec_mempool)
 695                 mempool_destroy(v->vec_mempool);
 696
 697         if (v->bufio)
 698                 dm_bufio_client_destroy(v->bufio);
 699
 700         kfree(v->salt);
 701         kfree(v->root_digest);
 702
 703         if (v->tfm)
 704                 crypto_free_shash(v->tfm);
 705
 706         kfree(v->alg_name);
 707
 708         if (v->hash_dev)
 709                 dm_put_device(ti, v->hash_dev);
 710
 711         if (v->data_dev)
 712                 dm_put_device(ti, v->data_dev);
 713
 714         kfree(v);
 715 }
 716
 717 /*
 718  * Target parameters:
 719  *      <version>       The current format is version 1.
 720  *                      Vsn 0 is compatible with original Chromium OS releases.
 721  *      <data device>
 722  *      <hash device>
 723  *      <data block size>
 724  *      <hash block size>
 725  *      <the number of data blocks>
 726  *      <hash start block>
 727  *      <algorithm>
 728  *      <digest>
 729  *      <salt>          Hex string or "-" if no salt.
 730  */
 731 static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 732 {
 733         struct dm_verity *v;
 734         struct dm_arg_set as;
 735         const char *opt_string;
 736         unsigned int num, opt_params;
 737         unsigned long long num_ll;
 738         int r;
 739         int i;
 740         sector_t hash_position;
 741         char dummy;
 742
 743         static struct dm_arg _args[] = {
 744                 {0, 1, "Invalid number of feature args"},
 745         };
 746
 747         v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
 748         if (!v) {
 749                 ti->error = "Cannot allocate verity structure";
 750                 return -ENOMEM;
 751         }
 752         ti->private = v;
 753         v->ti = ti;
 754
 755         if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
 756                 ti->error = "Device must be readonly";
 757                 r = -EINVAL;
 758                 goto bad;
 759         }
 760
 761         if (argc < 10) {
 762                 ti->error = "Not enough arguments";
 763                 r = -EINVAL;
 764                 goto bad;
 765         }
 766
 767         if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
 768             num > 1) {
 769                 ti->error = "Invalid version";
 770                 r = -EINVAL;
 771                 goto bad;
 772         }
 773         v->version = num;
 774
 775         r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
 776         if (r) {
 777                 ti->error = "Data device lookup failed";
 778                 goto bad;
 779         }
 780
 781         r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
 782         if (r) {
 783                 ti->error = "Data device lookup failed";
 784                 goto bad;
 785         }
 786
 787         if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
 788             !num || (num & (num - 1)) ||
 789             num < bdev_logical_block_size(v->data_dev->bdev) ||
 790             num > PAGE_SIZE) {
 791                 ti->error = "Invalid data device block size";
 792                 r = -EINVAL;
 793                 goto bad;
 794         }
 795         v->data_dev_block_bits = __ffs(num);
 796
 797         if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
 798             !num || (num & (num - 1)) ||
 799             num < bdev_logical_block_size(v->hash_dev->bdev) ||
 800             num > INT_MAX) {
 801                 ti->error = "Invalid hash device block size";
 802                 r = -EINVAL;
 803                 goto bad;
 804         }
 805         v->hash_dev_block_bits = __ffs(num);
 806
 807         if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
 808             (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
 809             >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 810                 ti->error = "Invalid data blocks";
 811                 r = -EINVAL;
 812                 goto bad;
 813         }
 814         v->data_blocks = num_ll;
 815
 816         if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
 817                 ti->error = "Data device is too small";
 818                 r = -EINVAL;
 819                 goto bad;
 820         }
 821
 822         if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
 823             (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
 824             >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
 825                 ti->error = "Invalid hash start";
 826                 r = -EINVAL;
 827                 goto bad;
 828         }
 829         v->hash_start = num_ll;
 830
 831         v->alg_name = kstrdup(argv[7], GFP_KERNEL);
 832         if (!v->alg_name) {
 833                 ti->error = "Cannot allocate algorithm name";
 834                 r = -ENOMEM;
 835                 goto bad;
 836         }
 837
 838         v->tfm = crypto_alloc_shash(v->alg_name, 0, 0);
 839         if (IS_ERR(v->tfm)) {
 840                 ti->error = "Cannot initialize hash function";
 841                 r = PTR_ERR(v->tfm);
 842                 v->tfm = NULL;
 843                 goto bad;
 844         }
 845         v->digest_size = crypto_shash_digestsize(v->tfm);
 846         if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
 847                 ti->error = "Digest size too big";
 848                 r = -EINVAL;
 849                 goto bad;
 850         }
 851         v->shash_descsize =
 852                 sizeof(struct shash_desc) + crypto_shash_descsize(v->tfm);
 853
 854         v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
 855         if (!v->root_digest) {
 856                 ti->error = "Cannot allocate root digest";
 857                 r = -ENOMEM;
 858                 goto bad;
 859         }
 860         if (strlen(argv[8]) != v->digest_size * 2 ||
 861             hex2bin(v->root_digest, argv[8], v->digest_size)) {
 862                 ti->error = "Invalid root digest";
 863                 r = -EINVAL;
 864                 goto bad;
 865         }
 866
 867         if (strcmp(argv[9], "-")) {
 868                 v->salt_size = strlen(argv[9]) / 2;
 869                 v->salt = kmalloc(v->salt_size, GFP_KERNEL);
 870                 if (!v->salt) {
 871                         ti->error = "Cannot allocate salt";
 872                         r = -ENOMEM;
 873                         goto bad;
 874                 }
 875                 if (strlen(argv[9]) != v->salt_size * 2 ||
 876                     hex2bin(v->salt, argv[9], v->salt_size)) {
 877                         ti->error = "Invalid salt";
 878                         r = -EINVAL;
 879                         goto bad;
 880                 }
 881         }
 882
 883         argv += 10;
 884         argc -= 10;
 885
 886         /* Optional parameters */
 887         if (argc) {
 888                 as.argc = argc;
 889                 as.argv = argv;
 890
 891                 r = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
 892                 if (r)
 893                         goto bad;
 894
 895                 while (opt_params) {
 896                         opt_params--;
 897                         opt_string = dm_shift_arg(&as);
 898                         if (!opt_string) {
 899                                 ti->error = "Not enough feature arguments";
 900                                 r = -EINVAL;
 901                                 goto bad;
 902                         }
 903
 904                         if (!strcasecmp(opt_string, DM_VERITY_OPT_LOGGING))
 905                                 v->mode = DM_VERITY_MODE_LOGGING;
 906                         else if (!strcasecmp(opt_string, DM_VERITY_OPT_RESTART))
 907                                 v->mode = DM_VERITY_MODE_RESTART;
 908                         else {
 909                                 ti->error = "Invalid feature arguments";
 910                                 r = -EINVAL;
 911                                 goto bad;
 912                         }
 913                 }
 914         }
 915
 916         v->hash_per_block_bits =
 917                 __fls((1 << v->hash_dev_block_bits) / v->digest_size);
 918
 919         v->levels = 0;
 920         if (v->data_blocks)
 921                 while (v->hash_per_block_bits * v->levels < 64 &&
 922                        (unsigned long long)(v->data_blocks - 1) >>
 923                        (v->hash_per_block_bits * v->levels))
 924                         v->levels++;
 925
 926         if (v->levels > DM_VERITY_MAX_LEVELS) {
 927                 ti->error = "Too many tree levels";
 928                 r = -E2BIG;
 929                 goto bad;
 930         }
 931
 932         hash_position = v->hash_start;
 933         for (i = v->levels - 1; i >= 0; i--) {
 934                 sector_t s;
 935                 v->hash_level_block[i] = hash_position;
 936                 s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
 937                                         >> ((i + 1) * v->hash_per_block_bits);
 938                 if (hash_position + s < hash_position) {
 939                         ti->error = "Hash device offset overflow";
 940                         r = -E2BIG;
 941                         goto bad;
 942                 }
 943                 hash_position += s;
 944         }
 945         v->hash_blocks = hash_position;
 946
 947         v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
 948                 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
 949                 dm_bufio_alloc_callback, NULL);
 950         if (IS_ERR(v->bufio)) {
 951                 ti->error = "Cannot initialize dm-bufio";
 952                 r = PTR_ERR(v->bufio);
 953                 v->bufio = NULL;
 954                 goto bad;
 955         }
 956
 957         if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
 958                 ti->error = "Hash device is too small";
 959                 r = -E2BIG;
 960                 goto bad;
 961         }
 962
 963         ti->per_bio_data_size = roundup(sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2, __alignof__(struct dm_verity_io));
 964
 965         v->vec_mempool = mempool_create_kmalloc_pool(DM_VERITY_MEMPOOL_SIZE,
 966                                         BIO_MAX_PAGES * sizeof(struct bio_vec));
 967         if (!v->vec_mempool) {
 968                 ti->error = "Cannot allocate vector mempool";
 969                 r = -ENOMEM;
 970                 goto bad;
 971         }
 972
 973         /* WQ_UNBOUND greatly improves performance when running on ramdisk */
 974         v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
 975         if (!v->verify_wq) {
 976                 ti->error = "Cannot allocate workqueue";
 977                 r = -ENOMEM;
 978                 goto bad;
 979         }
 980
 981         return 0;
 982
 983 bad:
 984         verity_dtr(ti);
 985
 986         return r;
 987 }
 988
 989 static struct target_type verity_target = {
 990         .name           = "verity",
 991         .version        = {1, 2, 0},
 992         .module         = THIS_MODULE,
 993         .ctr            = verity_ctr,
 994         .dtr            = verity_dtr,
 995         .map            = verity_map,
 996         .status         = verity_status,
 997         .ioctl          = verity_ioctl,
 998         .merge          = verity_merge,
 999         .iterate_devices = verity_iterate_devices,
1000         .io_hints       = verity_io_hints,
1001 };
1002
1003 static int __init dm_verity_init(void)
1004 {
1005         int r;
1006
1007         r = dm_register_target(&verity_target);
1008         if (r < 0)
1009                 DMERR("register failed %d", r);
1010
1011         return r;
1012 }
1013
1014 static void __exit dm_verity_exit(void)
1015 {
1016         dm_unregister_target(&verity_target);
1017 }
1018
1019 module_init(dm_verity_init);
1020 module_exit(dm_verity_exit);
1021
1022 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
1023 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
1024 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
1025 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
1026 MODULE_LICENSE("GPL");