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-rw-r--r--block/qcow2-cluster.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index e7c5f486cd..5b36018b3e 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1119,6 +1119,17 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
return 0;
}
+ /* !*host_offset would overwrite the image header and is reserved for "no
+ * host offset preferred". If 0 was a valid host offset, it'd trigger the
+ * following overlap check; do that now to avoid having an invalid value in
+ * *host_offset. */
+ if (!alloc_cluster_offset) {
+ ret = qcow2_pre_write_overlap_check(bs, 0, alloc_cluster_offset,
+ nb_clusters * s->cluster_size);
+ assert(ret < 0);
+ goto fail;
+ }
+
/*
* Save info needed for meta data update.
*