From: Eric Biggers Date: Tue, 14 Oct 2025 21:16:56 +0000 (-0700) Subject: dm-verity: reduce scope of real and wanted digests X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=379475dc88fc44f57760e6057b038073e352aaea;p=thirdparty%2Fkernel%2Flinux.git dm-verity: reduce scope of real and wanted digests In preparation for supporting interleaved hashing where dm-verity will need to keep track of the real and wanted digests for multiple data blocks simultaneously, stop using the want_digest and real_digest fields of struct dm_verity_io from so many different places. Specifically: - Make various functions take want_digest as a parameter rather than having it be implicitly passed via the struct dm_verity_io. - Add a new tmp_digest field, and use this instead of real_digest when computing a digest solely for the purpose of immediately checking it. The result is that real_digest and want_digest are used only by verity_verify_io(). Signed-off-by: Eric Biggers Signed-off-by: Mikulas Patocka --- diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c index d382a390d39a..301a9c01bf86 100644 --- a/drivers/md/dm-verity-fec.c +++ b/drivers/md/dm-verity-fec.c @@ -188,14 +188,13 @@ error: * Locate data block erasures using verity hashes. */ static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io, - u8 *want_digest, u8 *data) + const u8 *want_digest, const u8 *data) { if (unlikely(verity_hash(v, io, data, 1 << v->data_dev_block_bits, - verity_io_real_digest(v, io)))) + io->tmp_digest))) return 0; - return memcmp(verity_io_real_digest(v, io), want_digest, - v->digest_size) != 0; + return memcmp(io->tmp_digest, want_digest, v->digest_size) != 0; } /* @@ -366,7 +365,7 @@ static void fec_init_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio) */ static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io, struct dm_verity_fec_io *fio, u64 rsb, u64 offset, - bool use_erasures) + const u8 *want_digest, bool use_erasures) { int r, neras = 0; unsigned int pos; @@ -392,12 +391,11 @@ static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io, /* Always re-validate the corrected block against the expected hash */ r = verity_hash(v, io, fio->output, 1 << v->data_dev_block_bits, - verity_io_real_digest(v, io)); + io->tmp_digest); if (unlikely(r < 0)) return r; - if (memcmp(verity_io_real_digest(v, io), verity_io_want_digest(v, io), - v->digest_size)) { + if (memcmp(io->tmp_digest, want_digest, v->digest_size)) { DMERR_LIMIT("%s: FEC %llu: failed to correct (%d erasures)", v->data_dev->name, (unsigned long long)rsb, neras); return -EILSEQ; @@ -408,7 +406,8 @@ static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io, /* Correct errors in a block. Copies corrected block to dest. */ int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io, - enum verity_block_type type, sector_t block, u8 *dest) + enum verity_block_type type, const u8 *want_digest, + sector_t block, u8 *dest) { int r; struct dm_verity_fec_io *fio = fec_io(io); @@ -451,9 +450,9 @@ int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io, * them first. Do a second attempt with erasures if the corruption is * bad enough. */ - r = fec_decode_rsb(v, io, fio, rsb, offset, false); + r = fec_decode_rsb(v, io, fio, rsb, offset, want_digest, false); if (r < 0) { - r = fec_decode_rsb(v, io, fio, rsb, offset, true); + r = fec_decode_rsb(v, io, fio, rsb, offset, want_digest, true); if (r < 0) goto done; } diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h index 09123a612953..a6689cdc489d 100644 --- a/drivers/md/dm-verity-fec.h +++ b/drivers/md/dm-verity-fec.h @@ -68,8 +68,8 @@ struct dm_verity_fec_io { extern bool verity_fec_is_enabled(struct dm_verity *v); extern int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io, - enum verity_block_type type, sector_t block, - u8 *dest); + enum verity_block_type type, const u8 *want_digest, + sector_t block, u8 *dest); extern unsigned int verity_fec_status_table(struct dm_verity *v, unsigned int sz, char *result, unsigned int maxlen); @@ -99,6 +99,7 @@ static inline bool verity_fec_is_enabled(struct dm_verity *v) static inline int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io, enum verity_block_type type, + const u8 *want_digest, sector_t block, u8 *dest) { return -EOPNOTSUPP; diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index bba981080563..af9f1544af3e 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -229,12 +229,12 @@ out: * Verify hash of a metadata block pertaining to the specified data block * ("block" argument) at a specified level ("level" argument). * - * On successful return, verity_io_want_digest(v, io) contains the hash value - * for a lower tree level or for the data block (if we're at the lowest level). + * On successful return, want_digest contains the hash value for a lower tree + * level or for the data block (if we're at the lowest level). * * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned. * If "skip_unverified" is false, unverified buffer is hashed and verified - * against current value of verity_io_want_digest(v, io). + * against current value of want_digest. */ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io, sector_t block, int level, bool skip_unverified, @@ -273,7 +273,7 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io, if (IS_ERR(data)) return r; if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA, - hash_block, data) == 0) { + want_digest, hash_block, data) == 0) { aux = dm_bufio_get_aux_data(buf); aux->hash_verified = 1; goto release_ok; @@ -293,11 +293,11 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io, } r = verity_hash(v, io, data, 1 << v->hash_dev_block_bits, - verity_io_real_digest(v, io)); + io->tmp_digest); if (unlikely(r < 0)) goto release_ret_r; - if (likely(memcmp(verity_io_real_digest(v, io), want_digest, + if (likely(memcmp(io->tmp_digest, want_digest, v->digest_size) == 0)) aux->hash_verified = 1; else if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) { @@ -308,7 +308,7 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io, r = -EAGAIN; goto release_ret_r; } else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA, - hash_block, data) == 0) + want_digest, hash_block, data) == 0) aux->hash_verified = 1; else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_METADATA, @@ -372,7 +372,8 @@ out: } static noinline int verity_recheck(struct dm_verity *v, struct dm_verity_io *io, - sector_t cur_block, u8 *dest) + const u8 *want_digest, sector_t cur_block, + u8 *dest) { struct page *page; void *buffer; @@ -396,12 +397,11 @@ static noinline int verity_recheck(struct dm_verity *v, struct dm_verity_io *io, goto free_ret; r = verity_hash(v, io, buffer, 1 << v->data_dev_block_bits, - verity_io_real_digest(v, io)); + io->tmp_digest); if (unlikely(r)) goto free_ret; - if (memcmp(verity_io_real_digest(v, io), - verity_io_want_digest(v, io), v->digest_size)) { + if (memcmp(io->tmp_digest, want_digest, v->digest_size)) { r = -EIO; goto free_ret; } @@ -416,8 +416,9 @@ free_ret: static int verity_handle_data_hash_mismatch(struct dm_verity *v, struct dm_verity_io *io, - struct bio *bio, sector_t blkno, - u8 *data) + struct bio *bio, + const u8 *want_digest, + sector_t blkno, u8 *data) { if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) { /* @@ -426,14 +427,14 @@ static int verity_handle_data_hash_mismatch(struct dm_verity *v, */ return -EAGAIN; } - if (verity_recheck(v, io, blkno, data) == 0) { + if (verity_recheck(v, io, want_digest, blkno, data) == 0) { if (v->validated_blocks) set_bit(blkno, v->validated_blocks); return 0; } #if defined(CONFIG_DM_VERITY_FEC) - if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA, blkno, - data) == 0) + if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA, want_digest, + blkno, data) == 0) return 0; #endif if (bio->bi_status) @@ -525,8 +526,9 @@ static int verity_verify_io(struct dm_verity_io *io) kunmap_local(data); continue; } - r = verity_handle_data_hash_mismatch(v, io, bio, cur_block, - data); + r = verity_handle_data_hash_mismatch(v, io, bio, + verity_io_want_digest(v, io), + cur_block, data); kunmap_local(data); if (unlikely(r)) return r; diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index cdcee68a4bc0..cf7973ed3059 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -99,6 +99,7 @@ struct dm_verity_io { struct work_struct work; struct work_struct bh_work; + u8 tmp_digest[HASH_MAX_DIGESTSIZE]; u8 real_digest[HASH_MAX_DIGESTSIZE]; u8 want_digest[HASH_MAX_DIGESTSIZE];