Lookup layer handle when registering region sampling listener

We must do this in order to prevent clients from providing a bogus
handle when registering a region sampling listener. Fortunately, this
particular path required a permissions check so it cannot be accessed
from arbitrary apps on unrooted devices. But, we should not allow this
type of memory corruption to be reachable by the system.

Bug: 153467444
Test: libgui_test
Test: Repro steps in the bug no longer reproduce
Change-Id: I883506798574dfd0688371fdb6305cfad9d153fc

1 files changed, 1 insertions, 6 deletions

diff --git a/services/surfaceflinger/RegionSamplingThread.cpp b/services/surfaceflinger/RegionSamplingThread.cpp
index 68cd84f661..19c204cddb 100644
--- a/services/surfaceflinger/RegionSamplingThread.cpp
+++ b/services/surfaceflinger/RegionSamplingThread.cpp
@@ -199,13 +199,8 @@ RegionSamplingThread::~RegionSamplingThread() {
     }
 }
 
-void RegionSamplingThread::addListener(const Rect& samplingArea, const sp<IBinder>& stopLayerHandle,
+void RegionSamplingThread::addListener(const Rect& samplingArea, const wp<Layer>& stopLayer,
                                        const sp<IRegionSamplingListener>& listener) {
-    wp<Layer> stopLayer;
-    if (stopLayerHandle != nullptr && stopLayerHandle->localBinder() != nullptr) {
-        stopLayer = static_cast<Layer::Handle*>(stopLayerHandle.get())->owner;
-    }
-
     sp<IBinder> asBinder = IInterface::asBinder(listener);
     asBinder->linkToDeath(this);
     std::lock_guard lock(mSamplingMutex);