ext_proc fuzzer test exposed a race issue which leads to ENVOY_BUG in…

… ext_proc filter when opens a gRPC stream.

Signed-off-by: Yanjun Xiang <[email protected]>

source/extensions/filters/http/ext_proc/ext_proc.cc

@@ -118,15 +118,16 @@ void Filter::setEncoderFilterCallbacks(Http::StreamEncoderFilterCallbacks& callb
 }
 
 Filter::StreamOpenState Filter::openStream() {
-  ENVOY_BUG(!processing_complete_, "openStream should not have been called");
+  // If processing already completes, no need to open a gRPC stream.
+  if (processing_complete_) {
+    // Stream failed while starting and either onGrpcError or onGrpcClose was already called
+    return sent_immediate_response_ ? StreamOpenState::Error : StreamOpenState::IgnoreError;
+  }
   if (!stream_) {
     ENVOY_LOG(debug, "Opening gRPC stream to external processor");
     stream_ = client_->start(*this, grpc_service_, decoder_callbacks_->streamInfo());
     stats_.streams_started_.inc();
-    if (processing_complete_) {
-      // Stream failed while starting and either onGrpcError or onGrpcClose was already called
-      return sent_immediate_response_ ? StreamOpenState::Error : StreamOpenState::IgnoreError;
-    }
+
     // For custom access logging purposes. Applicable only for Envoy gRPC as Google gRPC does not
     // have a proper implementation of streamInfo.
     if (grpc_service_.has_envoy_grpc()) {