Fix crash due to racecondition in renderer on shutdown

Protects access to m_renderQueue using the m_renderQueue mutex on
shutdown. When a Qt3DWindow is deleted it signals the aspect thread to
do early cleanup, the aspect thread calls Renderer::shutdown which in
turn resets m_renderQueue. Meanwhile the render thread may be working on
m_renderQueue, this leads to a double free of the front render view in
m_renderQueue (and potentially other stuff).

Fixes: QTBUG-69877
Change-Id: Ifd018597dbdb2f1538494932c907c63e8db9c715
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/render/renderers/opengl/renderer/renderer.cpp b/src/render/renderers/opengl/renderer/renderer.cpp
index e1d237622..8039b6412 100644
--- a/src/render/renderers/opengl/renderer/renderer.cpp
+++ b/src/render/renderers/opengl/renderer/renderer.cpp
@@ -106,6 +106,7 @@
 #include <QSurface>
 #include <QElapsedTimer>
 #include <QLibraryInfo>
+#include <QMutexLocker>
 #include <QPluginLoader>
 #include <QDir>
 #include <QUrl>
@@ -444,8 +445,10 @@ void Renderer::shutdown()
 
     // We delete any renderqueue that we may not have had time to render
     // before the surface was destroyed
+    QMutexLocker lockRenderQueue(m_renderQueue->mutex());
     qDeleteAll(m_renderQueue->nextFrameQueue());
     m_renderQueue->reset();
+    lockRenderQueue.unlock();
 
     m_commandThread->shutdown();