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dm-verity: reduce scope of real and wanted digests

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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 <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
Eric Biggers 2025-10-14 14:16:56 -07:00 committed by Mikulas Patocka
parent ba0f428c9b
commit 379475dc88
4 changed files with 34 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
drivers/md/dm-verity-fec.c
View File

@ -188,14 +188,13 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
* 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;
}

5
drivers/md/dm-verity-fec.h
View File

@ -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;

38
drivers/md/dm-verity-target.c
View File

@ -229,12 +229,12 @@ static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
* 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 @@ int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
}
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 @@ static noinline int verity_recheck(struct dm_verity *v, struct dm_verity_io *io,
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;

1
drivers/md/dm-verity.h
View File

@ -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];