path: root/drivers/md
diff options
authorMikulas Patocka <>2013-07-10 23:41:16 +0100
committerGreg Kroah-Hartman <>2013-08-04 16:51:02 +0800
commitdabd2582219f0b1b1724a42e7be4045fa3686598 (patch)
treecee95361d2d37594d000872c46cfdbe7cf6deefb /drivers/md
parentba0e6dd5e64bbf820669f7451ac03f4f11cd64f7 (diff)
dm verity: fix inability to use a few specific devices sizes
commit b1bf2de07271932326af847a3c6a01fdfd29d4be upstream. Fix a boundary condition that caused failure for certain device sizes. The problem is reported at 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 <> Cc: Milan Broz <> Signed-off-by: Alasdair G Kergon <> Signed-off-by: Greg Kroah-Hartman <>
Diffstat (limited to 'drivers/md')
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index b948fd864d45..0d2e812d424b 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;