From 78a52ad5acca7053b774fcc80290e7b7e224c80a Mon Sep 17 00:00:00 2001 From: Peter Lieven Date: Tue, 12 Nov 2013 13:48:07 +0100 Subject: [PATCH] qcow2: fix possible corruption when reading multiple clusters if multiple sectors spanning multiple clusters are read the function count_contiguous_clusters should ensure that the cluster type should not change between the clusters. Especially the for-loop should break when we have one or more normal clusters followed by a compressed cluster. Unfortunately the wrong macro was used in the mask to compare the flags. This was discovered while debugging a data corruption issue when converting a compressed qcow2 image to raw. qemu-img reads 2MB chunks which span multiple clusters. CC: qemu-stable@nongnu.org Signed-off-by: Peter Lieven Signed-off-by: Kevin Wolf --- block/qcow2-cluster.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index f242244918..791083a0ef 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -290,7 +290,7 @@ static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size, uint64_t *l2_table, uint64_t stop_flags) { int i; - uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW2_CLUSTER_COMPRESSED; + uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED; uint64_t first_entry = be64_to_cpu(l2_table[0]); uint64_t offset = first_entry & mask;