Add ignore_zero_blocks option, which returns zeros for blocks matching a zero hash without validating the content.
Signed-off-by: Sami Tolvanen <[email protected]> --- Documentation/device-mapper/verity.txt | 5 ++ drivers/md/dm-verity-fec.c | 8 +++- drivers/md/dm-verity-target.c | 84 ++++++++++++++++++++++++++++++---- drivers/md/dm-verity.h | 3 +- 4 files changed, 90 insertions(+), 10 deletions(-) diff --git a/Documentation/device-mapper/verity.txt b/Documentation/device-mapper/verity.txt index 1058f36..4d3bbda 100644 --- a/Documentation/device-mapper/verity.txt +++ b/Documentation/device-mapper/verity.txt @@ -79,6 +79,11 @@ restart_on_corruption not compatible with ignore_corruption and requires user space support to avoid restart loops. +ignore_zero_blocks + Do not verify blocks that are expected to contain zeros and always return + zeros instead. This may be useful if the partition contains unused blocks + that are not guaranteed to contain zeros. + use_fec_from_device Use forward error correction (FEC) to recover from corruption if hash verification fails. Use encoding data from the specified device. This diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c index c3a2531..599334f 100644 --- a/drivers/md/dm-verity-fec.c +++ b/drivers/md/dm-verity-fec.c @@ -210,6 +210,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, u64 rsb, u64 target, unsigned block_offset, int *neras) { + bool is_zero; int i, j, target_index = -1; struct dm_buffer *buf; struct dm_bufio_client *bufio; @@ -270,7 +271,12 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, /* locate erasures if the block is on the data device */ if (bufio == v->fec->data_bufio && - verity_hash_for_block(v, io, block, want_digest) == 0) { + verity_hash_for_block(v, io, block, want_digest, + &is_zero) == 0) { + /* skip known zero blocks entirely */ + if (is_zero) + continue; + /* * skip if we have already found the theoretical * maximum number (i.e. fec->roots) of erasures diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index ca5857b..a2bb3bc 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -31,8 +31,9 @@ #define DM_VERITY_OPT_LOGGING "ignore_corruption" #define DM_VERITY_OPT_RESTART "restart_on_corruption" +#define DM_VERITY_OPT_IGN_ZEROS "ignore_zero_blocks" -#define DM_VERITY_OPTS_MAX (1 + DM_VERITY_OPTS_FEC) +#define DM_VERITY_OPTS_MAX (2 + DM_VERITY_OPTS_FEC) static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE; @@ -309,10 +310,9 @@ release_ret_r: * of the hash tree if necessary. */ int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, - sector_t block, u8 *digest) + sector_t block, u8 *digest, bool *is_zero) { - int i; - int r; + int r = 0, i; if (likely(v->levels)) { /* @@ -324,7 +324,7 @@ int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, */ r = verity_verify_level(v, io, block, 0, true, digest); if (likely(r <= 0)) - return r; + goto out; } memcpy(digest, v->root_digest, v->digest_size); @@ -332,10 +332,16 @@ int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, for (i = v->levels - 1; i >= 0; i--) { r = verity_verify_level(v, io, block, i, false, digest); if (unlikely(r)) - return r; + goto out; } - return 0; +out: + if (!r && v->zero_digest) + *is_zero = !memcmp(v->zero_digest, digest, v->digest_size); + else + *is_zero = false; + + return r; } /* @@ -383,11 +389,19 @@ static int verity_bv_hash_update(struct dm_verity *v, struct dm_verity_io *io, return verity_hash_update(v, verity_io_hash_desc(v, io), data, len); } +static int verity_bv_zero(struct dm_verity *v, struct dm_verity_io *io, + u8 *data, size_t len) +{ + memset(data, 0, len); + return 0; +} + /* * Verify one "dm_verity_io" structure. */ static int verity_verify_io(struct dm_verity_io *io) { + bool is_zero; struct dm_verity *v = io->v; struct bvec_iter start; unsigned b; @@ -397,10 +411,24 @@ static int verity_verify_io(struct dm_verity_io *io) struct shash_desc *desc = verity_io_hash_desc(v, io); r = verity_hash_for_block(v, io, io->block + b, - verity_io_want_digest(v, io)); + verity_io_want_digest(v, io), + &is_zero); if (unlikely(r < 0)) return r; + if (is_zero) { + /* + * If we expect a zero block, don't validate, just + * return zeros. + */ + r = verity_for_bv_block(v, io, &io->iter, + verity_bv_zero); + if (unlikely(r < 0)) + return r; + + continue; + } + r = verity_hash_init(v, desc); if (unlikely(r < 0)) return r; @@ -607,6 +635,8 @@ static void verity_status(struct dm_target *ti, status_type_t type, args++; if (verity_fec_is_enabled(v)) args += DM_VERITY_OPTS_FEC; + if (v->zero_digest) + args++; if (!args) return; DMEMIT(" %u", args); @@ -623,6 +653,8 @@ static void verity_status(struct dm_target *ti, status_type_t type, BUG(); } } + if (v->zero_digest) + DMEMIT(" " DM_VERITY_OPT_IGN_ZEROS); sz = verity_fec_status_table(v, sz, result, maxlen); break; } @@ -674,6 +706,7 @@ static void verity_dtr(struct dm_target *ti) kfree(v->salt); kfree(v->root_digest); + kfree(v->zero_digest); if (v->tfm) crypto_free_shash(v->tfm); @@ -691,6 +724,37 @@ static void verity_dtr(struct dm_target *ti) kfree(v); } +static int verity_alloc_zero_digest(struct dm_verity *v) +{ + int r = -ENOMEM; + struct shash_desc *desc; + u8 *zero_data; + + v->zero_digest = kmalloc(v->digest_size, GFP_KERNEL); + + if (!v->zero_digest) + return r; + + desc = kmalloc(v->shash_descsize, GFP_KERNEL); + + if (!desc) + return r; /* verity_dtr will free zero_digest */ + + zero_data = kzalloc(1 << v->data_dev_block_bits, GFP_KERNEL); + + if (!zero_data) + goto out; + + r = verity_hash(v, desc, zero_data, 1 << v->data_dev_block_bits, + v->zero_digest); + +out: + kfree(desc); + kfree(zero_data); + + return r; +} + static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v) { int r; @@ -720,6 +784,10 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v) } else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) { v->mode = DM_VERITY_MODE_RESTART; continue; + } else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROS)) { + r = verity_alloc_zero_digest(v); + if (r) + ti->error = "Cannot allocate zero digest"; } else { r = verity_fec_parse_opt_args(as, v, &argc, arg_name); } diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index 8e85372..fb419f4 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -40,6 +40,7 @@ struct dm_verity { struct crypto_shash *tfm; u8 *root_digest; /* digest of the root block */ u8 *salt; /* salt: its size is salt_size */ + u8 *zero_digest; /* digest for a zero block */ unsigned salt_size; sector_t data_start; /* data offset in 512-byte sectors */ sector_t hash_start; /* hash start in blocks */ @@ -123,6 +124,6 @@ extern int verity_hash(struct dm_verity *v, struct shash_desc *desc, const u8 *data, size_t len, u8 *digest); extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, - sector_t block, u8 *digest); + sector_t block, u8 *digest, bool *is_zero); #endif /* DM_VERITY_H */ -- 2.6.0.rc2.230.g3dd15c0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
