[Qemu-devel] [PATCH v1 2/3] qcow2: fix offset overflow

[Hu Tao <hutao@cn.fujitsu.com>]

When cluster size is big enough it can lead offset overflow
in qcow2_alloc_clusters_at(). This patch fixes it.

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
---
 block/qcow2-refcount.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index c974abe..b3ebb7f 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -676,7 +676,12 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
     BDRVQcowState *s = bs->opaque;
     uint64_t cluster_index;
     uint64_t old_free_cluster_index;
-    int i, refcount, ret;
+    uint64_t i;
+    int refcount, ret;
+
+    if (nb_clusters <= 0) {
+        return 0;
+    }
 
     /* Check how many clusters there are free */
     cluster_index = offset >> s->cluster_bits;
-- 
1.7.11.7