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BACKPORT: FROMLIST: dm-verity: reduce scope of real and wanted digests

Browse Source 
In preparation for supporting multibuffer 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 hash solely for the purpose of immediately checking it.

The result is that real_digest and want_digest are used only by
verity_verify_io().

Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Bug: 330611177
Link: https://lore.kernel.org/r/20240621165922.77672-15-ebiggers@kernel.org
(resolved conflict due to missing the upstream commit
 "dm-verity: Convert from tasklet to BH workqueue", which is hard to
 cherry-pick because it depends on workqueue subsystem changes)
Change-Id: I1d417ed3f79d9bcf11c09128e653e695dc25081e
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2024-06-21 10:37:59 -07:00 committed by William McVicker
parent 3503ed6feb
commit 6c33cbb433
4 changed files with 32 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
drivers/md/dm-verity-fec.c
View File

@ -187,11 +187,10 @@ static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
u8 *want_digest, u8 *data)
{
if (unlikely(verity_hash(v, io, data, 1 << v->data_dev_block_bits,
verity_io_real_digest(v, io), true)))
io->tmp_digest, true)))
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;
}
/*
@ -362,7 +361,7 @@ 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;
@ -388,12 +387,11 @@ 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), true);
io->tmp_digest, true);
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;
@ -404,7 +402,8 @@ 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);
@ -447,9 +446,9 @@ 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;

36
drivers/md/dm-verity-target.c
View File

@ -285,12 +285,12 @@ 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,
@ -333,11 +333,11 @@ 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->in_tasklet);
io->tmp_digest, !io->in_tasklet);
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_tasklet_enabled) &&
@ -349,7 +349,7 @@ 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,
@ -412,7 +412,8 @@ 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;
@ -436,12 +437,11 @@ 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), true);
io->tmp_digest, true);
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;
}
@ -456,8 +456,9 @@ 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_tasklet_enabled) && io->in_tasklet) {
/*
@ -466,14 +467,14 @@ 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)
@ -564,8 +565,9 @@ 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

@ -90,6 +90,7 @@ struct dm_verity_io {
struct work_struct work;
u8 tmp_digest[HASH_MAX_DIGESTSIZE];
u8 real_digest[HASH_MAX_DIGESTSIZE];
u8 want_digest[HASH_MAX_DIGESTSIZE];