From: Hu Tao <hu...@cn.fujitsu.com>
When cluster size is big enough it can lead to an offset overflow
in qcow2_alloc_clusters_at(). This patch fixes it.
The allocation is stopped each time at L2 table boundary
(see handle_alloc()), so the possible maximum bytes could be
2^(cluster_bits - 3 + cluster_bits)
cluster_bits - 3 is used to compute the number of entry by L2
and the additional cluster_bits is to take into account each
clusters referenced by the L2 entries.
so int is safe for cluster_bits<=17, unsafe otherwise.
Signed-off-by: Hu Tao <hu...@cn.fujitsu.com>
Reviewed-by: Max Reitz <mre...@redhat.com>
Reviewed-by: Benoit Canet <ben...@irqsave.net>
Signed-off-by: Kevin Wolf <kw...@redhat.com>
(cherry picked from commit 33304ec9fa484e765c6249673e09e1b7d49c5b85)
Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
---
block/qcow2-refcount.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 8c57016..6c212c9 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -678,7 +678,13 @@ 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;
+
+ assert(nb_clusters >= 0);
+ if (nb_clusters == 0) {
+ return 0;
+ }
/* Check how many clusters there are free */
cluster_index = offset >> s->cluster_bits;
--
1.9.1
