dm mirror log: round up region bitmap size to BITS_PER_LONG

The code in dm-log rounds up bitset_size to 32 bits. It then uses
find_next_zero_bit_le on the allocated region. find_next_zero_bit_le
accesses the bitmap using unsigned long pointers. So, on 64-bit
architectures, it may access 4 bytes beyond the allocated size.

Fix this bug by rounding up bitset_size to BITS_PER_LONG.

This bug was found by running the lvm2 testsuite with kasan.

Fixes: fccf92f72768 ("[PATCH] dm mirror log: bitset_size fix")
Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 06f328928a7f52948eb3ac0c895cd2014faa503b..2dda05aada2312509f3aba6658e7d9d9f7fad22e 100644 (file)
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -415,8 +415,7 @@ static int create_log_context(struct dm_dirty_log *log, struct dm_target *ti,
        /*
         * Work out how many "unsigned long"s we need to hold the bitset.
         */
-       bitset_size = dm_round_up(region_count,
-                                 sizeof(*lc->clean_bits) << BYTE_SHIFT);
+       bitset_size = dm_round_up(region_count, BITS_PER_LONG);
        bitset_size >>= BYTE_SHIFT;
 
        lc->bitset_uint32_count = bitset_size / sizeof(*lc->clean_bits);