Fix memory leak and random crash in windows playback backend

The leak is trivial, just not deleted object.

The crash is not trivial for reproducing; the fix is based on
the assumption that some events can be enqueued for an object
between deleteLater and real deleting.

Task-number: QTBUG-109149
Pick-to: 6.5 6.4 6.2
Change-Id: I256f29a03e7f01d27923b183b63d9a6b6a4f21b9
Reviewed-by: Lars Knoll <lars@knoll.priv.no>

1 files changed, 8 insertions, 3 deletions

diff --git a/src/plugins/multimedia/windows/player/mfplayersession.cpp b/src/plugins/multimedia/windows/player/mfplayersession.cpp
index 49b76e2a2..54df5ab90 100644
--- a/src/plugins/multimedia/windows/player/mfplayersession.cpp
+++ b/src/plugins/multimedia/windows/player/mfplayersession.cpp
@@ -77,7 +77,7 @@ MFPlayerSession::MFPlayerSession(MFPlayerControl *playerControl)
     m_request.rate = 1.0f;
 
     m_audioSampleGrabber = new AudioSampleGrabberCallback;
-    m_videoRendererControl = new MFVideoRendererControl;
+    m_videoRendererControl = new MFVideoRendererControl(this);
 }
 
 void MFPlayerSession::timeout()
@@ -1515,8 +1515,13 @@ ULONG MFPlayerSession::AddRef(void)
 ULONG MFPlayerSession::Release(void)
 {
     LONG cRef = InterlockedDecrement(&m_cRef);
-    if (cRef == 0)
-        this->deleteLater();
+    if (cRef == 0) {
+        deleteLater();
+
+        // In rare cases the session has queued events to be run between deleteLater and deleting,
+        // so we set the parent control to nullptr in order to prevent crashes in the cases.
+        m_playerControl = nullptr;
+    }
     return cRef;
 }