commit a820057ae00dba322b10d47b3711b04519324690
author Ady Abraham <adyabr@google.com> Mon Jun 06 15:16:06 2022 -0700
committer Ady Abraham <adyabr@google.com> Tue Jun 07 00:19:42 2022 +0000
tree 9b5c733535da3ea8a8c3ba1ad9d1fb1893007f08
parent cbe9c105fcdeba79f1722616e8b576c1d45c93a6

RESTRICT AUTOMERGE SurfaceFlinger: fix a potential race condition in stealReceiveChannel

Add a mutex to prevent a potential race condition.

Bug: 232541124
Test: See bug for details
Change-Id: Ia338f124c786bf12d6adba10a67b9048fe9c34a5

services/surfaceflinger/Scheduler/EventThread.cpp

diff --git a/services/surfaceflinger/Scheduler/EventThread.cpp b/services/surfaceflinger/Scheduler/EventThread.cpp
index cee36a1..cf57664 100644
--- a/services/surfaceflinger/Scheduler/EventThread.cpp
+++ b/services/surfaceflinger/Scheduler/EventThread.cpp
@@ -138,6 +138,11 @@
 }
 
 status_t EventThreadConnection::stealReceiveChannel(gui::BitTube* outChannel) {
+    std::scoped_lock lock(mLock);
+    if (mChannel.initCheck() != NO_ERROR) {
+        return NAME_NOT_FOUND;
+    }
+
     outChannel->setReceiveFd(mChannel.moveReceiveFd());
     return NO_ERROR;
 }

services/surfaceflinger/Scheduler/EventThread.h

diff --git a/services/surfaceflinger/Scheduler/EventThread.h b/services/surfaceflinger/Scheduler/EventThread.h
index 64acbd7..831bf7b 100644
--- a/services/surfaceflinger/Scheduler/EventThread.h
+++ b/services/surfaceflinger/Scheduler/EventThread.h
@@ -98,7 +98,8 @@
 private:
     virtual void onFirstRef();
     EventThread* const mEventThread;
-    gui::BitTube mChannel;
+    std::mutex mLock;
+    gui::BitTube mChannel GUARDED_BY(mLock);
 };
 
 class EventThread {