From: Alexandre Ratchov <alex@caoua.org>
Subject: Re: audio/lmms: Fix memory corruption during MIDI input/output
To: izzy Meyer <izder456@disroot.org>
Cc: ports@openbsd.org
Date: Mon, 25 May 2026 14:46:39 +0200

On Fri, Apr 25, 2025 at 05:32:33PM -0500, izzy Meyer wrote:
> On Thu, 24 Apr 2025 15:33:18 +0200
> Alexandre Ratchov <alex@caoua.org> wrote:
> 
> > MIDI output and input are handled on different threads, so a mutex is
> > required to serialize access to the mio_hdl structure.
> > 
> > This diff fixes disconnection from sndiod caused by corruption of the
> > mio_hdl structure.
> > 
> > While we're at it, fix the input event loop to not stop if a signal is
> > received during poll(4). If so just recheck the m_quit flag and retry.
> > 
> > OK?
> > 
> 
> Thanks for this fix Alexandre. I produce on OpenBSD using LMMS. Tested
> on amd64. Seems good from some minimal testing on my production
> machine.
> 

I don't remember why, but this diff was forgotten. Here's a refreshed
version, with better error handling.

OK?

Index: Makefile
===================================================================
RCS file: /cvs/ports/audio/lmms/Makefile,v
diff -u -p -u -p -r1.29 Makefile
--- Makefile	13 Feb 2026 12:02:13 -0000	1.29
+++ Makefile	25 May 2026 12:34:20 -0000
@@ -5,7 +5,7 @@ DISTNAME =		lmms_$V
 PKGNAME =		lmms-$V
 WRKDIST =		${WRKDIR}/lmms
 EXTRACT_SUFX =		.tar.xz
-REVISION =		1
+REVISION =		2
 
 CATEGORIES =		audio
 
Index: patches/patch-include_MidiSndio_h
===================================================================
RCS file: patches/patch-include_MidiSndio_h
diff -N patches/patch-include_MidiSndio_h
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ patches/patch-include_MidiSndio_h	25 May 2026 12:34:20 -0000
@@ -0,0 +1,19 @@
+Index: include/MidiSndio.h
+--- include/MidiSndio.h.orig
++++ include/MidiSndio.h
+@@ -32,6 +32,7 @@
+ 
+ #include <QtCore/QThread>
+ #include <QtCore/QFile>
++#include <QtCore/QMutex>
+ 
+ #include <sndio.h>
+ 
+@@ -64,6 +65,7 @@ class MidiSndio : public MidiClientRaw, public QThread
+ 	virtual void run(void);
+ 
+ private:
++	QMutex m_hdlMutex;
+ 	struct mio_hdl *m_hdl;
+ 	volatile bool m_quit;
+ } ;
Index: patches/patch-src_core_midi_MidiSndio_cpp
===================================================================
RCS file: patches/patch-src_core_midi_MidiSndio_cpp
diff -N patches/patch-src_core_midi_MidiSndio_cpp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ patches/patch-src_core_midi_MidiSndio_cpp	25 May 2026 12:34:20 -0000
@@ -0,0 +1,61 @@
+␘Index: src/core/midi/MidiSndio.cpp
+--- src/core/midi/MidiSndio.cpp.orig
++++ src/core/midi/MidiSndio.cpp
+@@ -42,6 +42,7 @@
+ 
+ MidiSndio::MidiSndio( void ) :
+ 	MidiClientRaw(),
++	m_hdlMutex(),
+ 	m_quit( false )
+ {
+ 	QString dev = probeDevice();
+@@ -86,7 +87,9 @@ QString MidiSndio::probeDevice( void )
+ 
+ void MidiSndio::sendByte( const unsigned char c )
+ {
++	m_hdlMutex.lock();
+ 	mio_write( m_hdl, &c, 1 );
++	m_hdlMutex.unlock();
+ }
+ 
+ 
+@@ -96,20 +99,33 @@ void MidiSndio::run( void )
+ 	nfds_t nfds;
+ 	char buf[0x100], *p;
+ 	size_t n;
++	int revents;
+ 	int ret;
++
+ 	while( m_quit == false && m_hdl )
+ 	{
++		m_hdlMutex.lock();
+ 		nfds = mio_pollfd( m_hdl, &pfd, POLLIN );
++		m_hdlMutex.unlock();
+ 		ret = poll( &pfd, nfds, 100 );
+-		if ( ret < 0 )
++		if ( ret < 0 ) {
++			if (errno == EINTR)
++				continue;
++			fprintf(stderr, "sndio: poll: %s\n", strerror(errno));
+ 			break;
+-		if ( !ret || !( mio_revents( m_hdl, &pfd ) & POLLIN ) )
+-			continue;
+-		n = mio_read( m_hdl, buf, sizeof(buf) );
+-		if ( !n )
+-		{
++		}
++		m_hdlMutex.lock();
++		revents = mio_revents( m_hdl, &pfd );
++		if (revents & POLLHUP) {
++			fprintf(stderr, "sndio: device disconnected\n");
++			m_hdlMutex.unlock();
+ 			break;
+ 		}
++		if (revents & POLLIN) {
++			n = mio_read( m_hdl, buf, sizeof(buf) );
++		} else
++			n = 0;
++		m_hdlMutex.unlock();
+ 		for (p = buf; n > 0; n--, p++)
+ 		{
+ 			parseData( *p );