From c6d60e982ece9c213ad400a8b030db7ee2d4cde3 Mon Sep 17 00:00:00 2001
From: Johannes Lorenz <j.git@lorenz-ho.me>
Date: Fri, 28 Feb 2020 19:39:13 +0100
Subject: [PATCH] Audio/MidiJack: Fix invalid read: (1) of #5408

This fixes reading from jack MIDI events in case where
there are no jack MIDI events.
---
 src/core/midi/MidiJack.cpp | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/core/midi/MidiJack.cpp b/src/core/midi/MidiJack.cpp
index 568b6dae1..664e1f16d 100644
--- a/src/core/midi/MidiJack.cpp
+++ b/src/core/midi/MidiJack.cpp
@@ -174,19 +174,22 @@ void MidiJack::JackMidiRead(jack_nframes_t nframes)
 	jack_nframes_t event_index = 0;
 	jack_nframes_t event_count = jack_midi_get_event_count(port_buf);
 
-	jack_midi_event_get(&in_event, port_buf, 0);
-	for(i=0; i<nframes; i++)
+	int rval = jack_midi_event_get(&in_event, port_buf, 0);
+	if (rval == 0 /* 0 = success */)
 	{
-		if((in_event.time == i) && (event_index < event_count))
+		for(i=0; i<nframes; i++)
 		{
-			// lmms is setup to parse bytes coming from a device
-			// parse it byte by byte as it expects
-			for(b=0;b<in_event.size;b++)
-				parseData( *(in_event.buffer + b) );
+			if((in_event.time == i) && (event_index < event_count))
+			{
+				// lmms is setup to parse bytes coming from a device
+				// parse it byte by byte as it expects
+				for(b=0;b<in_event.size;b++)
+					parseData( *(in_event.buffer + b) );
 
-			event_index++;
-			if(event_index < event_count)
-				jack_midi_event_get(&in_event, port_buf, event_index);
+				event_index++;
+				if(event_index < event_count)
+					jack_midi_event_get(&in_event, port_buf, event_index);
+			}
 		}
 	}
 }