From 15684a474286cc2c6106c756ddd095a21d058970 Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Fri, 27 Sep 2013 12:14:15 +0200 Subject: qcow2: count_contiguous_clusters and compression The function is not intended to be used on compressed clusters and will not work correctly, if used anyway, since L2E_OFFSET_MASK is not the right mask for determining the offset of compressed clusters. Therefore, assert that the first cluster is not compressed and always include the compression flag in the mask of significant flags, i.e., stop the search as soon as a compressed cluster occurs. Signed-off-by: Max Reitz Signed-off-by: Kevin Wolf --- block/qcow2-cluster.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'block/qcow2-cluster.c') diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 91d07f2203..8b2361a2ed 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -284,12 +284,15 @@ static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size, uint64_t *l2_table, uint64_t start, uint64_t stop_flags) { int i; - uint64_t mask = stop_flags | L2E_OFFSET_MASK; - uint64_t offset = be64_to_cpu(l2_table[0]) & mask; + uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW2_CLUSTER_COMPRESSED; + uint64_t first_entry = be64_to_cpu(l2_table[0]); + uint64_t offset = first_entry & mask; if (!offset) return 0; + assert(qcow2_get_cluster_type(first_entry) != QCOW2_CLUSTER_COMPRESSED); + for (i = start; i < start + nb_clusters; i++) { uint64_t l2_entry = be64_to_cpu(l2_table[i]) & mask; if (offset + (uint64_t) i * cluster_size != l2_entry) { -- cgit v1.2.1