message: Check the incoming message length before allocating memory for the message
diff: @@ -1311,6 +1311,11 @@ namespace eosio {
  uint32_t message_length;
  auto index = conn->pending_message_buffer.read_index();
  conn->pending_message_buffer.peek(&message_length, sizeof(message_length), index);
  + if(message_length > def_send_buffer_size*2) {
  + elog("incoming message length unexpected (${i})", ("i", message_length));
  + close(conn);
  + return;
  + }
  if (bytes_in_buffer >= message_length + message_header_size) {
  conn->pending_message_buffer.advance_read_ptr(message_header_size);
  if (!conn->process_next_message(*this, message_length)) {
  