This is a note to let you know that I've just added the patch titled
dm verity: fix inability to use a few specific devices sizes
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-verity-fix-inability-to-use-a-few-specific-devices-sizes.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b1bf2de07271932326af847a3c6a01fdfd29d4be Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Wed, 10 Jul 2013 23:41:16 +0100
Subject: dm verity: fix inability to use a few specific devices sizes
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Milan Broz <gmazyland@xxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-verity.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -813,9 +813,8 @@ static int verity_ctr(struct dm_target *
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;
Patches currently in stable-queue which might be from mpatocka@xxxxxxxxxx are
queue-3.4/dm-verity-fix-inability-to-use-a-few-specific-devices-sizes.patch
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