Fix crash caused by objects self-destructions during displacement animations

The root cause was that the QAbstractAnimationJob::finished() might delegate its
destruction to change.listener->animationFinished(this), and the original author
was aware of that and provided a RETURN_IF_DELETE macro to return early if itself
got deleted. In the bug's case, change.listener->animationFinished(this)
dispatched to QQuickItemViewPrivate::animationFinished() which called
QQuickItemViewPrivate::release() and deleted the QAbstractAnimationJob object
itself in the end.

However, any objects derived from QAbstractAnimationJob, or holding a pointer
to a QAbstractAnimationJob, may potentially fall into the code path calling
QAbstractAnimationJob::finished(). Any QAnimationJobChangeListener that directly
or indirectly deletes QAbstractAnimationJob should be very suspicious to this
kind of "heap-use-after-free" bug. Should ensure that the QAbstractAnimationJob
won't be referenced after deletion.

In the bug's case, within the code path triggered by ListView displacement
animation, the other affected classes by QAbstractAnimationJob are:
QQuickItemViewFxItem, QQuickItemViewTransitionableItem, QQuickTransitionManager.

To fix this, a new SelfDeletable class is factored out to simplify the self-deletion
test logic. Any affected classes are made to have a public member m_selfDeletable.
Any code paths that finally reach QAbstractAnimationJob::finished() are
wrapped with related util macro.

Change-Id: Idd33fc3f2d529fd7d8bb088c329101b1e70dd6c0
Task-number: QTBUG-44308
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
 

8 files changed, 22 insertions, 20 deletions

diff --git a/src/quick/items/qquickflickable.cpp b/src/quick/items/qquickflickable.cpp
index d6dddc3f1c..7e1f54f07e 100644
--- a/src/quick/items/qquickflickable.cpp
+++ b/src/quick/items/qquickflickable.cpp
@@ -206,8 +206,8 @@ public:
             axisData->move.setValue(-flickable->contentX());
         else
             axisData->move.setValue(-flickable->contentY());
-        cancel();
         active = false;
+        cancel();
     }
 
 protected:
diff --git a/src/quick/items/qquickitemview.cpp b/src/quick/items/qquickitemview.cpp
index 8dafc16cf4..2e1962bc7b 100644
--- a/src/quick/items/qquickitemview.cpp
+++ b/src/quick/items/qquickitemview.cpp
@@ -2225,7 +2225,10 @@ bool QQuickItemViewPrivate::prepareNonVisibleItemTransition(FxViewItem *item, co
     if (item->scheduledTransitionType() == QQuickItemViewTransitioner::MoveTransition)
         repositionItemAt(item, item->index, 0);
 
-    if (item->prepareTransition(transitioner, viewBounds)) {
+    bool success = false;
+    ACTION_IF_DELETED(item, success = item->prepareTransition(transitioner, viewBounds), return success);
+
+    if (success) {
         item->releaseAfterTransition = true;
         return true;
     }
diff --git a/src/quick/items/qquickitemviewfxitem.cpp b/src/quick/items/qquickitemviewfxitem.cpp
index f9c65967ea..16c2182962 100644
--- a/src/quick/items/qquickitemviewfxitem.cpp
+++ b/src/quick/items/qquickitemviewfxitem.cpp
@@ -56,6 +56,8 @@ QQuickItemViewFxItem::QQuickItemViewFxItem(QQuickItem *item, bool ownItem, QQuic
 QQuickItemViewFxItem::~QQuickItemViewFxItem()
 {
     delete transitionableItem;
+    transitionableItem = nullptr;
+
     if (ownItem && item) {
         trackGeometry(false);
         item->setParentItem(0);
diff --git a/src/quick/items/qquickitemviewfxitem_p_p.h b/src/quick/items/qquickitemviewfxitem_p_p.h
index 48ffe248bc..d10ebb9cdf 100644
--- a/src/quick/items/qquickitemviewfxitem_p_p.h
+++ b/src/quick/items/qquickitemviewfxitem_p_p.h
@@ -54,6 +54,7 @@
 #include <QtQuick/private/qtquickglobal_p.h>
 #include <QtQuick/private/qquickitem_p.h>
 #include <QtQuick/private/qquickitemviewtransition_p.h>
+#include <private/qanimationjobutil_p.h>
 
 QT_REQUIRE_CONFIG(quick_itemview);
 
@@ -94,6 +95,7 @@ public:
 
     virtual bool contains(qreal x, qreal y) const = 0;
 
+    SelfDeletable m_selfDeletable;
     int index = -1;
     QPointer<QQuickItem> item;
     bool ownItem;
diff --git a/src/quick/items/qquickitemviewtransition.cpp b/src/quick/items/qquickitemviewtransition.cpp
index 0fde0beb75..109851608b 100644
--- a/src/quick/items/qquickitemviewtransition.cpp
+++ b/src/quick/items/qquickitemviewtransition.cpp
@@ -61,7 +61,6 @@ public:
     QPointF m_toPos;
     QQuickItemViewTransitioner::TransitionType m_type;
     bool m_isTarget;
-    bool *m_wasDeleted;
 
 protected:
     void finished() override;
@@ -73,14 +72,11 @@ QQuickItemViewTransitionJob::QQuickItemViewTransitionJob()
     , m_item(nullptr)
     , m_type(QQuickItemViewTransitioner::NoTransition)
     , m_isTarget(false)
-    , m_wasDeleted(nullptr)
 {
 }
 
 QQuickItemViewTransitionJob::~QQuickItemViewTransitionJob()
 {
-    if (m_wasDeleted)
-        *m_wasDeleted = true;
     if (m_transitioner)
         m_transitioner->runningJobs.remove(this);
 }
@@ -138,13 +134,7 @@ void QQuickItemViewTransitionJob::finished()
     QQuickTransitionManager::finished();
 
     if (m_transitioner) {
-        bool deleted = false;
-        m_wasDeleted = &deleted;
-        m_transitioner->finishedTransition(this, m_item);
-        if (deleted)
-            return;
-        m_wasDeleted = nullptr;
-
+        RETURN_IF_DELETED(m_transitioner->finishedTransition(this, m_item));
         m_transitioner = nullptr;
     }
 
@@ -482,7 +472,7 @@ bool QQuickItemViewTransitionableItem::prepareTransition(QQuickItemViewTransitio
         // if transition type is not valid, the previous transition still has to be
         // canceled so that the item can move immediately to the right position
         item->setPosition(nextTransitionTo);
-        stopTransition();
+        ACTION_IF_DELETED(this, stopTransition(), return false);
     }
 
     prepared = true;
@@ -501,12 +491,12 @@ void QQuickItemViewTransitionableItem::startTransition(QQuickItemViewTransitione
 
     if (!transition || transition->m_type != nextTransitionType || transition->m_isTarget != isTransitionTarget) {
         if (transition)
-            transition->cancel();
+            RETURN_IF_DELETED(transition->cancel());
         delete transition;
         transition = new QQuickItemViewTransitionJob;
     }
 
-    transition->startTransition(this, index, transitioner, nextTransitionType, nextTransitionTo, isTransitionTarget);
+    RETURN_IF_DELETED(transition->startTransition(this, index, transitioner, nextTransitionType, nextTransitionTo, isTransitionTarget));
     clearCurrentScheduledTransition();
 }
 
@@ -558,7 +548,7 @@ void QQuickItemViewTransitionableItem::clearCurrentScheduledTransition()
 void QQuickItemViewTransitionableItem::stopTransition()
 {
     if (transition)
-        transition->cancel();
+        RETURN_IF_DELETED(transition->cancel());
     clearCurrentScheduledTransition();
     resetNextTransitionPos();
 }
diff --git a/src/quick/items/qquickitemviewtransition_p.h b/src/quick/items/qquickitemviewtransition_p.h
index 29a62f7f10..0c7a9cad75 100644
--- a/src/quick/items/qquickitemviewtransition_p.h
+++ b/src/quick/items/qquickitemviewtransition_p.h
@@ -60,6 +60,7 @@ QT_REQUIRE_CONFIG(quick_viewtransitions);
 #include <QtQml/qqml.h>
 #include <private/qqmlguard_p.h>
 #include <private/qquicktransition_p.h>
+#include <private/qanimationjobutil_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -157,6 +158,7 @@ public:
     bool prepareTransition(QQuickItemViewTransitioner *transitioner, int index, const QRectF &viewBounds);
     void startTransition(QQuickItemViewTransitioner *transitioner, int index);
 
+    SelfDeletable m_selfDeletable;
     QPointF nextTransitionTo;
     QPointF lastMovedTo;
     QPointF nextTransitionFrom;
diff --git a/src/quick/util/qquicktransitionmanager.cpp b/src/quick/util/qquicktransitionmanager.cpp
index e51de1a02a..0ee7e57997 100644
--- a/src/quick/util/qquicktransitionmanager.cpp
+++ b/src/quick/util/qquicktransitionmanager.cpp
@@ -47,6 +47,7 @@
 #include <private/qqmlproperty_p.h>
 
 #include <QtCore/qdebug.h>
+#include <private/qanimationjobutil_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -79,6 +80,7 @@ void QQuickTransitionManager::setState(QQuickState *s)
 QQuickTransitionManager::~QQuickTransitionManager()
 {
     delete d->transitionInstance;
+    d->transitionInstance = nullptr;
     delete d; d = nullptr;
 }
 
@@ -129,7 +131,7 @@ void QQuickTransitionManager::transition(const QList<QQuickStateAction> &list,
                                       QQuickTransition *transition,
                                       QObject *defaultTarget)
 {
-    cancel();
+    RETURN_IF_DELETED(cancel());
 
     // The copy below is ON PURPOSE, because firing actions might involve scripts that modify the list.
     QQuickStateOperation::ActionList applyList = list;
@@ -154,7 +156,6 @@ void QQuickTransitionManager::transition(const QList<QQuickStateAction> &list,
     //
     // This doesn't catch everything, and it might be a little fragile in
     // some cases - but whatcha going to do?
-
     if (transition && !d->bindingsList.isEmpty()) {
 
         // Apply all the property and binding changes
@@ -258,7 +259,7 @@ void QQuickTransitionManager::transition(const QList<QQuickStateAction> &list,
 void QQuickTransitionManager::cancel()
 {
     if (d->transitionInstance && d->transitionInstance->isRunning())
-        d->transitionInstance->stop();
+        RETURN_IF_DELETED(d->transitionInstance->stop());
 
     for (const QQuickStateAction &action : qAsConst(d->bindingsList)) {
         if (action.toBinding && action.deletableToBinding) {
diff --git a/src/quick/util/qquicktransitionmanager_p_p.h b/src/quick/util/qquicktransitionmanager_p_p.h
index 89317e1e07..fc00ec8a52 100644
--- a/src/quick/util/qquicktransitionmanager_p_p.h
+++ b/src/quick/util/qquicktransitionmanager_p_p.h
@@ -52,6 +52,7 @@
 //
 
 #include "qquickanimation_p.h"
+#include <private/qanimationjobutil_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -70,6 +71,7 @@ public:
 
     void cancel();
 
+    SelfDeletable m_selfDeletable;
 protected:
     virtual void finished();