From fd53e5766e34f79c33674c4d7443b66f34c185c1 Mon Sep 17 00:00:00 2001
From: Ashok Mutyala <quic_c_nmutya@quicinc.com>
Date: Thu, 12 Aug 2021 12:36:21 +0000
Subject: [PATCH] Avoid the scenario where Contexts list filled with null value
 in ShowAnrDialogs()

Problem: Framework Reboot i.e., NullPointer Exception in android.ui Thread
E AndroidRuntime: FATAL EXCEPTION IN SYSTEM PROCESS: android.ui
E AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method
'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference

E AndroidRuntime: **at android.app.Dialog.<init>(Dialog.java:199)
E AndroidRuntime: **at android.app.AlertDialog.<init>(AlertDialog.java:204)
E AndroidRuntime: **at android.app.AlertDialog.<init>(AlertDialog.java:200)
E AndroidRuntime: **at com.android.server.am.BaseErrorDialog.<init>(BaseErrorDialog.java:39)
E AndroidRuntime: **at com.android.server.am.AppNotRespondingDialog.<init>(AppNotRespondingDialog.java:53)
E AndroidRuntime: **at com.android.server.am.ErrorDialogController.showAnrDialogs(ErrorDialogController.java:183)
E AndroidRuntime: **at com.android.server.am.AppErrors.handleShowAnrUi(AppErrors.java:1077)

Analysis:
As Context Object is passed from showAnrDialogs method and will be retrieved from getDisplayContextWithErrorDialogs
And list of context objects will be filled by querying from RootWindowContainer.getDisplayUiContext and this method is
Annotated with Nullable. So, the possibility could be null value filled in the context object List.

Bug: 196189977
Bug: 200337305
Test: Stability Test

Original Change-Id: Ib944fc5ffc8bcca999c75f99d462d441e555fcda
Change-Id: I28bf8de72b4f6bce9210bb29fde2b3d989911c0e
(cherry picked from commit 25b5d20adf26a0a402d81d49ff948bf96b79cea5)
---
 .../java/com/android/server/wm/WindowProcessController.java     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/services/core/java/com/android/server/wm/WindowProcessController.java b/services/core/java/com/android/server/wm/WindowProcessController.java
index 719d52c892097..af386419d4552 100644
--- a/services/core/java/com/android/server/wm/WindowProcessController.java
+++ b/services/core/java/com/android/server/wm/WindowProcessController.java
@@ -952,7 +952,7 @@ public class WindowProcessController extends ConfigurationContainer<Configuratio
                 final int displayId = r.getDisplayId();
                 final Context c = root.getDisplayUiContext(displayId);
 
-                if (r.mVisibleRequested && !displayContexts.contains(c)) {
+                if (c != null && r.mVisibleRequested && !displayContexts.contains(c)) {
                     displayContexts.add(c);
                 }
             }