Crash at shutdown in ~QNetworkConfiguration

[Michael Sheldon]

After the recent landing for bug 1618590 the Ubuntu Download Manager tests frequently crash at shutdown with the following stack trace:

Thread 1 "test_mms_downlo" received signal SIGSEGV, Segmentation fault.
0x00007ffff7201b23 in QNetworkConfiguration::~QNetworkConfiguration() () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
(gdb) bt
#0 0x00007ffff7201b23 in QNetworkConfiguration::~QNetworkConfiguration() () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#1 0x00007ffff6f31169 in QMetaType::destroy(int, void*) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2 0x00007ffff6f46bf9 in QMetaCallEvent::~QMetaCallEvent() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3 0x00007ffff6f46c79 in QMetaCallEvent::~QMetaCallEvent() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4 0x00007ffff6f1c9a8 in QCoreApplicationPrivate::cleanupThreadData() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5 0x00007ffff6f1ca8a in QCoreApplicationPrivate::~QCoreApplicationPrivate() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#6 0x00007ffff6f1cba9 in QCoreApplicationPrivate::~QCoreApplicationPrivate() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#7 0x00007ffff6f510dc in QObject::~QObject() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#8 0x00007ffff6f1ed12 in QCoreApplication::~QCoreApplication() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#9 0x0000000000449bbc in main (argc=1, argv=<optimised out>) at /home/mike/src/udm/fix-1628635/tests/downloads/daemon/test_mms_download.cpp:97

This commit seems especially relevant: https://codereview.qt-project.org/#/c/172173/

Neither this test, nor UDM itself make any explicit use of QPluginLoader, so this is unlikely to be a case of UDM incorrectly unloading a plugin itself.

To reproduce simply run UDM's test_mms_download test a number of times (crashes only occur intermittently).

When tested with a silo without the three patches added for bug 1618590 this crash no-longer occurs.

A similar crash appears to be happening in webbrowser-app as well: https://bugs.launchpad.net/ubuntu/+source/webbrowser-app/+bug/1630765

Possibly another similar crash in ~QNetworkSession:
https://bugs.launchpad.net/ubuntu/+source/webbrowser-app/+bug/1630510

[Timo Jyrinki (timo-jyrinki)]

See bug #1630765 for updates.