kernel: check object refcount before performing a recursive deletion

kernel/object.c

@@ -110,7 +110,16 @@ static void object_cleanup(struct object *obj, unsigned long flags)
 		struct queue_entry *entry = queue_pop_front(&queue);
 		struct object *child = NULL;
 		obj->ob_type->ob_ops.destroy_recurse(entry, &child);
-		if (child) {
+		if (!child) {
+			continue;
+		}
+
+		if (child->ob_refcount > 1) {
+			child->ob_refcount--;
+			continue;
+		}
+
+		if (child->ob_refcount == 0 && child->ob_handles == 0) {
 			__cleanup(child, &queue);
 		}
 	}