From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210914122454.141075-8-vsementsov@virtuozzo.com>
[hreitz: Separated `type` declaration from statements]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
---
 block/qcow2.h          |  1 +
 block/qcow2-refcount.c | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index c0e1e83796..b8b1093b61 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -587,6 +587,7 @@ typedef enum QCow2MetadataOverlap {
 
 #define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
 #define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
+#define L2E_STD_RESERVED_MASK 0x3f000000000001feULL
 
 #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
 
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 9a5ae3cac4..bdac7b1780 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1680,10 +1680,22 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
     for (i = 0; i < s->l2_size; i++) {
         uint64_t coffset;
         int csize;
+        QCow2ClusterType type;
+
         l2_entry = get_l2_entry(s, l2_table, i);
         l2_bitmap = get_l2_bitmap(s, l2_table, i);
+        type = qcow2_get_cluster_type(bs, l2_entry);
+
+        if (type != QCOW2_CLUSTER_COMPRESSED) {
+            /* Check reserved bits of Standard Cluster Descriptor */
+            if (l2_entry & L2E_STD_RESERVED_MASK) {
+                fprintf(stderr, "ERROR found l2 entry with reserved bits set: "
+                        "%" PRIx64 "\n", l2_entry);
+                res->corruptions++;
+            }
+        }
 
-        switch (qcow2_get_cluster_type(bs, l2_entry)) {
+        switch (type) {
         case QCOW2_CLUSTER_COMPRESSED:
             /* Compressed clusters don't have QCOW_OFLAG_COPIED */
             if (l2_entry & QCOW_OFLAG_COPIED) {
-- 
2.31.1