qcow2: Prevent numerical overflow

In qcow2_alloc_cluster_offset(), *num is limited to
INT_MAX >> BDRV_SECTOR_BITS by all callers. However, since remaining is
of type uint64_t, we might as well cast *num to that type before
performing the shift.

Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 11c89769dc3e638ef72915d97058411ddf79b64b)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index df0b2c9cec41ac2c92c4e45d1120b9dca1281da6..1fea5142d0530f95de9c21b669365602ff5b50ac 100644 (file)
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1263,7 +1263,7 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
 
 again:
     start = offset;
-    remaining = *num << BDRV_SECTOR_BITS;
+    remaining = (uint64_t)*num << BDRV_SECTOR_BITS;
     cluster_offset = 0;
     *host_offset = 0;
     cur_bytes = 0;