dm cache: fix truncation bug when mapping I/O to >2TB fast device

When remapping a block to the cache's fast device that is larger than
2TB we must not truncate the destination sector to 32bits.  The 32bit
temporary result of from_cblock() was being overflowed in
remap_to_cache() due to the logical left shift.

Use an intermediate 64bit type to store the 32bit from_cblock() result
to fix the overflow.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index db0944465127..1af70145fab9 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -671,15 +671,16 @@ static void remap_to_cache(struct cache *cache, struct bio *bio,
                            dm_cblock_t cblock)
 {
         sector_t bi_sector = bio->bi_iter.bi_sector;
+        sector_t block = from_cblock(cblock);
 
         bio->bi_bdev = cache->cache_dev->bdev;
         if (!block_size_is_power_of_two(cache))
                 bio->bi_iter.bi_sector =
-                        (from_cblock(cblock) * cache->sectors_per_block) +
+                        (block * cache->sectors_per_block) +
                         sector_div(bi_sector, cache->sectors_per_block);
         else
                 bio->bi_iter.bi_sector =
-                        (from_cblock(cblock) << cache->sectors_per_block_shift) |
+                        (block << cache->sectors_per_block_shift) |
                         (bi_sector & (cache->sectors_per_block - 1));
 }