linux-kernel - [PATCH 4.7 056/186] dm verity fec: fix block calculation

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Message-Id: <20160818135934.547411164@linuxfoundation.org>
Date:	Thu, 18 Aug 2016 15:57:53 +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, Sami Tolvanen <samitolvanen@...gle.com>,
	Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.7 056/186] dm verity fec: fix block calculation

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sami Tolvanen <samitolvanen@...gle.com>

commit 602d1657c603eedd7379a8bcde1ad3a2972ecc5f upstream.

do_div was replaced with div64_u64 at some point, causing a bug with
block calculation due to incompatible semantics of the two functions.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
Fixes: a739ff3f543a ("dm verity: add support for forward error correction")
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-verity-fec.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -453,9 +453,7 @@ int verity_fec_decode(struct dm_verity *
 	 */
 
 	offset = block << v->data_dev_block_bits;
-
-	res = offset;
-	div64_u64(res, v->fec->rounds << v->data_dev_block_bits);
+	res = div64_u64(offset, v->fec->rounds << v->data_dev_block_bits);
 
 	/*
 	 * The base RS block we can feed to the interleaver to find out all