[PATCH 5.4 30/57] dm verity fec: fix hash block number in verity_fec_decode

Greg Kroah-Hartman
2020-05-04T18:10:50Z

From: Sunwook Eom <speed.eom@samsung.com>

commit ad4e80a639fc61d5ecebb03caa5cdbfb91fcebfc upstream.

The error correction data is computed as if data and hash blocks
were concatenated. But hash block number starts from v->hash_start.
So, we have to calculate hash block number based on that.

Fixes: a739ff3f543af ("dm verity: add support for forward error correction")
Cc: stable@vger.kernel.org
Signed-off-by: Sunwook Eom <speed.eom@samsung.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-verity-fec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -435,7 +435,7 @@ int verity_fec_decode(struct dm_verity *
fio->level++;

if (type == DM_VERITY_BLOCK_TYPE_METADATA)
- block += v->data_blocks;
+ block = block - v->hash_start + v->data_blocks;

/*
* For RS(M, N), the continuous FEC data is divided into blocks of N