dm-log: fix a bitset_size overflow on 32bit machines

Commit c20e36b7631d ("dm log: fix out-of-bounds write due to
region_count overflow") made sure that region_count could fit in an
unsigned int. But the bitmap memory isn't allocated based on
region_count. It uses bitset_size (a size_t variable). The first step of
calculating bitset_size is to set it to region_count, rounded up to a
multiple of BITS_PER_LONG. If region_size is less than BITS_PER_LONG
smaller than UINT_MAX, it will get rounded up to 2^32. On a 32bit
architecture, this will make bitset_size wrap around to 0 and fail,
despite region_count being valid.

Since bitset_size gets divided by 8, it can hold any valid region_count.
It just needs a special case to handle the rollover. If it is 0, the
value rolled over, and bitset size should be set to the number of bytes
needed to hold 2^32 bits.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: c20e36b7631d ("dm log: fix out-of-bounds write due to region_count overflow")
Cc: stable@vger.kernel.org

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index d316757a328beccfefa33373e79a077675fbba84..2ddeb4250c5929d9636cae00dcefe2d0f441c966 100644 (file)
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -425,6 +425,9 @@ static int create_log_context(struct dm_dirty_log *log, struct dm_target *ti,
         */
        bitset_size = dm_round_up(region_count, BITS_PER_LONG);
        bitset_size >>= BYTE_SHIFT;
+       /* Handle dm_round_up rollover on 32-bit systems */
+       if (!bitset_size)
+               bitset_size = 1UL << (BITS_PER_LONG - BYTE_SHIFT);
 
        lc->bitset_uint32_count = bitset_size / sizeof(*lc->clean_bits);