linux-kernel - [PATCH 131/145] dm verity: fix inability to use a few specific devices sizes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1374101277-7915-132-git-send-email-kamal@canonical.com>
Date:	Wed, 17 Jul 2013 15:47:43 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Mikulas Patocka <mpatocka@...hat.com>,
	Milan Broz <gmazyland@...il.com>,
	Alasdair G Kergon <agk@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 131/145] dm verity: fix inability to use a few specific devices sizes

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

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

From: Mikulas Patocka <mpatocka@...hat.com>

commit b1bf2de07271932326af847a3c6a01fdfd29d4be upstream.

Fix a boundary condition that caused failure for certain device sizes.

The problem is reported at
  http://code.google.com/p/cryptsetup/issues/detail?id=160

For certain device sizes the number of hashes at a specific level was
calculated incorrectly.

It happens for example for a device with data and metadata block size 4096
that has 16385 blocks and algorithm sha256.

The user can test if he is affected by this bug by running the
"veritysetup verify" command and also by activating the dm-verity kernel
driver and reading the whole block device. If it passes without an error,
then the user is not affected.

The condition for the bug is:

Split the total number of data blocks (data_block_bits) into bit strings,
each string has hash_per_block_bits bits. hash_per_block_bits is
rounddown(log2(metadata_block_size/hash_digest_size)). Equivalently, you
can say that you convert data_blocks_bits to 2^hash_per_block_bits base.

If there some zero bit string below the most significant bit string and at
least one bit below this zero bit string is set, then the bug happens.

The same bug exists in the userspace veritysetup tool, so you must use
fixed veritysetup too if you want to use devices that are affected by
this boundary condition.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Cc: Milan Broz <gmazyland@...il.com>
Signed-off-by: Alasdair G Kergon <agk@...hat.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/md/dm-verity.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index a746f1d..4112d90 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -831,9 +831,8 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	for (i = v->levels - 1; i >= 0; i--) {
 		sector_t s;
 		v->hash_level_block[i] = hash_position;
-		s = verity_position_at_level(v, v->data_blocks, i);
-		s = (s >> v->hash_per_block_bits) +
-		    !!(s & ((1 << v->hash_per_block_bits) - 1));
+		s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
+					>> ((i + 1) * v->hash_per_block_bits);
 		if (hash_position + s < hash_position) {
 			ti->error = "Hash device offset overflow";
 			r = -E2BIG;
-- 
1.8.1.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/