@@ -587,6 +587,7 @@ 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;
/* Check how many clusters there are free */
@@ -602,11 +603,16 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
}
/* And then allocate them */
+ old_free_cluster_index = s->free_cluster_index;
+ s->free_cluster_index = cluster_index + i;
+
ret = update_refcount(bs, offset, i << s->cluster_bits, 1);
if (ret < 0) {
return ret;
}
+ s->free_cluster_index = old_free_cluster_index;
+
return i;
}
Refcount block allocation and refcount table growth rely on s->free_cluster_index pointing to somewhere after the current allocation. Change qcow2_alloc_cluster_at() to fulfill this assumption. Without this change it could happen that a newly allocated refcount block and the allocated data block point to the same area in the image file, causing data corruption in the long run. This fixes a bug that became first visible after commit 250196f1. Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- block/qcow2-refcount.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)