linux-kernel - [PATCH 4.19 12/37] dm verity fec: fix hash block number in verity_fec

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Date:   Mon,  4 May 2020 19:57:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sunwook Eom <speed.eom@...sung.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.19 12/37] dm verity fec: fix hash block number in verity_fec_decode

From: Sunwook Eom <speed.eom@...sung.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@...r.kernel.org
Signed-off-by: Sunwook Eom <speed.eom@...sung.com>
Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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
@@ -436,7 +436,7 @@ 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