add assert to tf graph simplifier to address security concerns

modules/dnn/src/tensorflow/tf_graph_simplifier.cpp

@@ -1035,7 +1035,7 @@ void sortByExecutionOrder(tensorflow::GraphDef& net)
         nodesToAdd.pop_back();
 
         permIds.push_back(nodeToAdd);
-
+        CV_Assert(nodeToAdd < edges.size());
         for (int i = 0; i < edges[nodeToAdd].size(); ++i)
         {
             int consumerId = edges[nodeToAdd][i];

modules/dnn/test/test_tf_importer.cpp

@@ -1571,6 +1571,13 @@ TEST_P(Test_TensorFlow_layers, tf2_permute_nhwc_ncwh)
     runTensorFlowNet("tf2_permute_nhwc_ncwh");
 }
 
+// issue #21852
+TEST_P(Test_TensorFlow_layers, tf_graph_simplifier_buffer_overflow)
+{
+    // This just shouldn't segfault, otherwise it's fine
+    EXPECT_ANY_THROW(readNetFromTensorflow(path("tf_graph_simplifier_buffer_overflow_net.pb")));
+}
+
 TEST_P(Test_TensorFlow_layers, squeeze)
 {
 #if defined(INF_ENGINE_RELEASE)