From: Sami Tolvanen <samitolvanen@google.com>
Date: Tue, 21 Jun 2016 18:02:42 +0000 (-0700)
Subject: dm verity fec: fix block calculation
X-Git-Tag: v4.7.2~130
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cc8b0d2118eeb430e7f5e74bb3b983a64861fc6b;p=thirdparty%2Fkernel%2Fstable.git

dm verity fec: fix block calculation

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@google.com>
Fixes: a739ff3f543a ("dm verity: add support for forward error correction")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index 459a9f8905edb..0f0eb8a3d922a 100644
--- 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 *v, struct dm_verity_io *io,
 	 */
 
 	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