Invalid read from MidiJack with Audio Interface "Dummy"

[JohannesLorenz]

Bug Summary

With Audio Interface "Dummy" + Midi Interface "Jack", you can get an invalid read when closing LMMS (see below). With both being Jack, it's OK.

Steps to reproduce

Go to the settings. Choose Audio Interface "Dummy" + Midi Interface "Jack. Restart LMMS. Close LMMS.

Expected behavior

No Crash.

Actual behavior

Crash.

Affected LMMS versions

All

Logs

Click to expand

Thread 1 received signal SIGTRAP, Trace/breakpoint trap.
std::__atomic_base::store (__m=std::memory_order_seq_cst, __p=0x0, this=0xa0) at /usr/include/c++/10.2.0/bits/atomic_base.h:725
725             __atomic_store_n(&_M_p, __p, int(__m));
(gdb) bt
#0  std::__atomic_base::store(MidiJack*, std::memory_order) (__m=std::memory_order_seq_cst, __p=0x0, this=0xa0) at /usr/include/c++/10.2.0/bits/atomic_base.h:725
#1  std::__atomic_base::operator=(MidiJack*) (this=0xa0, __p=0x0) at /usr/include/c++/10.2.0/bits/atomic_base.h:632
#2  0x00000000003d67e7 in std::atomic::operator=(MidiJack*) (this=0xa0, __p=0x0) at /usr/include/c++/10.2.0/atomic:385
#3  0x000000000040bf99 in AudioJack::removeMidiClient() (this=0x0) at /home/johannes/cprogs/lmms/lv2/include/AudioJack.h:61
#4  0x000000000040b8f0 in MidiJack::~MidiJack() (this=0x18a8af30, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/midi/MidiJack.cpp:122
#5  0x000000000040ba04 in MidiJack::~MidiJack() (this=0x18a8af30, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/midi/MidiJack.cpp:152
#6  0x000000000037483d in Mixer::~Mixer() (this=0xaffdec0, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/Mixer.cpp:189
#7  0x00000000003749f6 in Mixer::~Mixer() (this=0xaffdec0, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/Mixer.cpp:201
#8  0x000000000034b643 in LmmsCore::deleteHelper(Mixer**) (ptr=0x6fefb0 ) at /home/johannes/cprogs/lmms/lv2/include/Engine.h:137
#9  0x000000000034b01a in LmmsCore::destroy() () at /home/johannes/cprogs/lmms/lv2/src/core/Engine.cpp:101
#10 0x00000000004411d1 in MainWindow::~MainWindow() (this=0x1947f790, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/gui/MainWindow.cpp:276
#11 0x0000000000441246 in MainWindow::~MainWindow() (this=0x1947f790, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/gui/MainWindow.cpp:277
#12 0x00000000061245a0 in QObject::event(QEvent*) () at /usr/lib/libQt5Core.so.5
#13 0x0000000004a07752 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/libQt5Widgets.so.5
#14 0x00000000060f7cda in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/libQt5Core.so.5
#15 0x00000000060fa7d3 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /usr/lib/libQt5Core.so.5
#16 0x0000000006151304 in  () at /usr/lib/libQt5Core.so.5
#17 0x0000000007208914 in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0
#18 0x000000000725c7d1 in  () at /usr/lib/libglib-2.0.so.0
#19 0x0000000007207121 in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#20 0x0000000006150941 in QEventDispatcherGlib::processEvents(QFlags) () at /usr/lib/libQt5Core.so.5
#21 0x00000000060f665c in QEventLoop::exec(QFlags) () at /usr/lib/libQt5Core.so.5
#22 0x00000000060feaf4 in QCoreApplication::exec() () at /usr/lib/libQt5Core.so.5
#23 0x00000000002e6219 in main(int, char**) (argc=1, argv=0x1ffefffbf8) at /home/johannes/cprogs/lmms/lv2/src/core/main.cpp:988
(gdb) c
Continuing.
Thread 1 received signal SIGSEGV, Segmentation fault.

std::__atomic_base<MidiJack*>::store (__m=std::memory_order_seq_cst, __p=0x0, this=0xa0) at /usr/include/c++/10.2.0/bits/atomic_base.h:725

725             __atomic_store_n(&_M_p, __p, int(__m));

(gdb) bt

#0  std::__atomic_base<MidiJack*>::store(MidiJack*, std::memory_order) (__m=std::memory_order_seq_cst, __p=0x0, this=0xa0) at /usr/include/c++/10.2.0/bits/atomic_base.h:725

#1  std::__atomic_base<MidiJack*>::operator=(MidiJack*) (this=0xa0, __p=0x0) at /usr/include/c++/10.2.0/bits/atomic_base.h:632

#2  0x00000000003d67e7 in std::atomic<MidiJack*>::operator=(MidiJack*) (this=0xa0, __p=0x0) at /usr/include/c++/10.2.0/atomic:385

#3  0x000000000040bf99 in AudioJack::removeMidiClient() (this=0x0) at /home/johannes/cprogs/lmms/lv2/include/AudioJack.h:61

#4  0x000000000040b8f0 in MidiJack::~MidiJack() (this=0x18a8af30, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/midi/MidiJack.cpp:122

#5  0x000000000040ba04 in MidiJack::~MidiJack() (this=0x18a8af30, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/midi/MidiJack.cpp:152

#6  0x000000000037483d in Mixer::~Mixer() (this=0xaffdec0, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/Mixer.cpp:189

#7  0x00000000003749f6 in Mixer::~Mixer() (this=0xaffdec0, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/core/Mixer.cpp:201

#8  0x000000000034b643 in LmmsCore::deleteHelper(Mixer**) (ptr=0x6fefb0 LmmsCore::s_mixer) at /home/johannes/cprogs/lmms/lv2/include/Engine.h:137

#9  0x000000000034b01a in LmmsCore::destroy() () at /home/johannes/cprogs/lmms/lv2/src/core/Engine.cpp:101

#10 0x00000000004411d1 in MainWindow::~MainWindow() (this=0x1947f790, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/gui/MainWindow.cpp:276

#11 0x0000000000441246 in MainWindow::~MainWindow() (this=0x1947f790, __in_chrg=) at /home/johannes/cprogs/lmms/lv2/src/gui/MainWindow.cpp:277

#12 0x00000000061245a0 in QObject::event(QEvent*) () at /usr/lib/libQt5Core.so.5

#13 0x0000000004a07752 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/libQt5Widgets.so.5

#14 0x00000000060f7cda in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/libQt5Core.so.5

#15 0x00000000060fa7d3 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /usr/lib/libQt5Core.so.5

#16 0x0000000006151304 in  () at /usr/lib/libQt5Core.so.5

#17 0x0000000007208914 in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0

#18 0x000000000725c7d1 in  () at /usr/lib/libglib-2.0.so.0

#19 0x0000000007207121 in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0

#20 0x0000000006150941 in QEventDispatcherGlib::processEvents(QFlagsQEventLoop::ProcessEventsFlag) () at /usr/lib/libQt5Core.so.5

#21 0x00000000060f665c in QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) () at /usr/lib/libQt5Core.so.5

#22 0x00000000060feaf4 in QCoreApplication::exec() () at /usr/lib/libQt5Core.so.5

#23 0x00000000002e6219 in main(int, char**) (argc=1, argv=0x1ffefffbf8) at /home/johannes/cprogs/lmms/lv2/src/core/main.cpp:988

[PhysSong]

It looks like a regression in #5452. You should have added a check for m_jackAudio before calling removeMidiClient().

lmms/src/core/midi/MidiJack.cpp

Lines 119 to 122 in b701e82

	if(jackClient())
	{
	// remove ourselves first (atomically), so we will not get called again
	m_jackAudio->removeMidiClient();

[JohannesLorenz]

I'll mark this as a good first issue. @PhysSong 's analysis explains how to solve it, and it's alsmost a one-liner.

[salilra]

#5907

I've started this PR. Can someone review?