[Qt][WK2] Crash in drawUpdateChunkIntoBackingStore

• Component: WebKit2
• Status: RESOLVED FIXED

[Andreas Kling]

UpdateChunk images should be created using the QImage constructor that takes a bytesPerLine value, or the data length won't match UpdateChunk::size().

Crashiness is easily reproduced by manually resizing MiniBrowser.

[Andreas Kling]

Created attachment 72429 [details]
Proposed patch

[Andreas Kling]

Valgrind stack from such a crash (Invalid read of size 1):

memcpy (mc_replace_strmem.c:497)
qt_blend_rgb32_on_rgb32(unsigned char*, int, unsigned char const*, int, int, int, int) (string3.h:52)
QRasterPaintEngine::drawImage(QPointF const&, QImage const&) (qpaintengine_raster.cpp:2490)
QPainter::drawImage(QPointF const&, QImage const&) (qpainter.cpp:5618)
WebKit::ChunkedUpdateDrawingAreaProxy::drawUpdateChunkIntoBackingStore(WebKit::UpdateChunk*) (qpainter.h:923)
WebKit::ChunkedUpdateDrawingAreaProxy::didSetSize(WebKit::UpdateChunk*) (ChunkedUpdateDrawingAreaProxy.cpp:130)
WebKit::ChunkedUpdateDrawingAreaProxy::didReceiveMessage(CoreIPC::Connection*, CoreIPC::MessageID, CoreIPC::ArgumentDecoder*) (ChunkedUpdateDrawingAreaProxy.cpp:168)
WebKit::ChunkedUpdateDrawingAreaProxy::paint(WebCore::IntRect const&, QPainter*) (ChunkedUpdateDrawingAreaProxy.cpp:70)
QWKPagePrivate::paint(QPainter*, QRect) (qwkpage.cpp:149)
_q_paintItem(QGraphicsItem*, QPainter*, QStyleOptionGraphicsItem const*, QWidget*, bool, bool) (qgraphicsscene.cpp:4314)
QGraphicsScenePrivate::drawItemHelper(QGraphicsItem*, QPainter*, QStyleOptionGraphicsItem const*, QWidget*, bool) (qgraphicsscene.cpp:4427)
QGraphicsScenePrivate::draw(QGraphicsItem*, QPainter*, QTransform const*, QTransform const*, QRegion*, QWidget*, double, QTransform const*, bool, bool) (qgraphicsscene.cpp:4962)
QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem*, QPainter*, QTransform const*, QRegion*, QWidget*, double, QTransform const*) (qgraphicsscene.cpp:4853)
QGraphicsScenePrivate::drawItems(QPainter*, QTransform const*, QRegion*, QWidget*) (qgraphicsscene.cpp:4735)
QGraphicsView::paintEvent(QPaintEvent*) (qgraphicsview.cpp:3472)
QWidget::event(QEvent*) (qwidget.cpp:8407)
QFrame::event(QEvent*) (qframe.cpp:557)
QGraphicsView::viewportEvent(QEvent*) (qgraphicsview.cpp:2867)
QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) (qcoreapplication.cpp:870)
QApplicationPrivate::notify_helper(QObject*, QEvent*) (qapplication.cpp:4443)
QApplication::notify(QObject*, QEvent*) (qapplication.cpp:4326)
QCoreApplication::notifyInternal(QObject*, QEvent*) (qcoreapplication.cpp:760)
QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) (qcoreapplication.h:234)
QWidgetBackingStore::sync() (qbackingstore.cpp:1325)
QWidgetPrivate::syncBackingStore() (qwidget.cpp:1842)
QWidget::event(QEvent*) (qwidget.cpp:8554)
QMainWindow::event(QEvent*) (qmainwindow.cpp:1480)
QApplicationPrivate::notify_helper(QObject*, QEvent*) (qapplication.cpp:4447)
QApplication::notify(QObject*, QEvent*) (qapplication.cpp:4326)
QCoreApplication::notifyInternal(QObject*, QEvent*) (qcoreapplication.cpp:760)
QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (qcoreapplication.h:231)
QGraphicsScenePrivate::_q_processDirtyItems() (qgraphicsview_p.h:200)
QGraphicsScene::qt_metacall(QMetaObject::Call, int, void**) (moc_qgraphicsscene.cpp:130)
QObject::event(QEvent*) (qobject.cpp:1192)
QGraphicsScene::event(QEvent*) (qgraphicsscene.cpp:3545)
QApplicationPrivate::notify_helper(QObject*, QEvent*) (qapplication.cpp:4447)
QApplication::notify(QObject*, QEvent*) (qapplication.cpp:4326)
QCoreApplication::notifyInternal(QObject*, QEvent*) (qcoreapplication.cpp:760)
QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (qcoreapplication.h:231)
postEventSourceDispatch(_GSource*, int (*)(void*), void*) (qcoreapplication.h:236)
g_main_context_dispatch (in /lib/libglib-2.0.so.0.2600.0)
??? (in /lib/libglib-2.0.so.0.2600.0)
g_main_context_iteration (in /lib/libglib-2.0.so.0.2600.0)
QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (qeventdispatcher_glib.cpp:417)
QGuiEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (qguieventdispatcher_glib.cpp:204)
QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (qeventloop.cpp:149)
QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (qeventloop.cpp:201)
QCoreApplication::exec() (qcoreapplication.cpp:1032)
main (main.cpp:53)

[Kenneth Rohde Christiansen]

Comment on attachment 72429 [details]
Proposed patch

What size does it get by default?

[Andreas Kling]

(In reply to comment #3)
> What size does it get by default?

It would allocate width * height * 4 bytes, (UpdateChunk::size() returns this) but the default QImage ctor will prefer making every scanline 32-bit aligned.

[Andreas Kling]

Comment on attachment 72429 [details]
Proposed patch

Clearing flags on attachment: 72429

Committed r70981: <http://trac.webkit.org/changeset/70981>

[Andreas Kling]

All reviewed patches have been landed.  Closing bug.