[mojo-edk] Add some buffer checks and fix UAF on NodeChannel

mojo/edk/system/data_pipe_producer_dispatcher.cc

Index: mojo/edk/system/data_pipe_producer_dispatcher.cc
diff --git a/mojo/edk/system/data_pipe_producer_dispatcher.cc b/mojo/edk/system/data_pipe_producer_dispatcher.cc
index d3b2530035889b2a5446edd1f33596d096dc6563..364b898e236e07cd99dd077a7c639074c0f06921 100644
--- a/mojo/edk/system/data_pipe_producer_dispatcher.cc
+++ b/mojo/edk/system/data_pipe_producer_dispatcher.cc
@@ -513,10 +513,14 @@ void DataPipeProducerDispatcher::UpdateSignalsStateNoLock() {
       if (rv != ports::OK)
         peer_closed_ = true;
       if (message) {
-        PortsMessage* ports_message = static_cast<PortsMessage*>(message.get());
+        if (message->num_payload_bytes() < sizeof(DataPipeControlMessage)) {
+          peer_closed_ = true;
+          break;
+        }
+
         const DataPipeControlMessage* m =
             static_cast<const DataPipeControlMessage*>(
-                ports_message->payload_bytes());
+                message->payload_bytes());
 
         if (m->command != DataPipeCommand::DATA_WAS_READ) {
           DLOG(ERROR) << "Unexpected message from consumer.";