Commit 379475dc authored by Eric Biggers's avatar Eric Biggers Committed by Mikulas Patocka
Browse files

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: default avatarEric Biggers <ebiggers@kernel.org>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent ba0f428c

drivers/md/dm-verity-fec.c

+10 −11
Original line number Diff line number Diff line
@@ -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;

	}

drivers/md/dm-verity-fec.h

+3 −2
Original line number Diff line number Diff line
@@ -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;

drivers/md/dm-verity-target.c

+20 −18
Original line number Diff line number Diff line
@@ -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;

drivers/md/dm-verity.h

+1 −0
Original line number Diff line number Diff line
@@ -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];