From 6253682e66578cbd757a77c704802b5d775a2096 Mon Sep 17 00:00:00 2001
From: Sergey Nikolaienkov <sergeynv@google.com>
Date: Fri, 18 Mar 2022 12:39:39 +0100
Subject: [PATCH] Fix NPE in CompanionDeviceServiceConnector

Null-check mListener CompanionDeviceServiceConnector.onBindingDied()
before invoking mListener.onBindingDied().

Bug: 225202799
Test: force-stop test companion app that declares multiple &
      CompanionDeviceServices while it "self-reports" companion device &
      as present.
Change-Id: I1ab3cc6d3d8c4f27997012e08b04e28475c9cfe0
---
 .../CompanionDeviceServiceConnector.java         | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/services/companion/java/com/android/server/companion/CompanionDeviceServiceConnector.java b/services/companion/java/com/android/server/companion/CompanionDeviceServiceConnector.java
index 4c7b9b80d5be1..a6bd48056e12d 100644
--- a/services/companion/java/com/android/server/companion/CompanionDeviceServiceConnector.java
+++ b/services/companion/java/com/android/server/companion/CompanionDeviceServiceConnector.java
@@ -51,12 +51,12 @@ class CompanionDeviceServiceConnector extends ServiceConnector.Impl<ICompanionDe
         void onBindingDied(@UserIdInt int userId, @NonNull String packageName);
     }
 
-    @UserIdInt
-    private final int mUserId;
-    @NonNull
-    private final ComponentName mComponentName;
-    @Nullable
-    private Listener mListener;
+    private final @UserIdInt int mUserId;
+    private final @NonNull ComponentName mComponentName;
+    // IMPORTANT: this can (and will!) be null (at the moment, CompanionApplicationController only
+    // installs a listener to the primary ServiceConnector), hence we should always null-check the
+    // reference before calling on it.
+    private @Nullable Listener mListener;
 
     /**
      * Create a CompanionDeviceServiceConnector instance.
@@ -125,7 +125,9 @@ class CompanionDeviceServiceConnector extends ServiceConnector.Impl<ICompanionDe
 
         if (DEBUG) Log.d(TAG, "onBindingDied() " + mComponentName.toShortString());
 
-        mListener.onBindingDied(mUserId, mComponentName.getPackageName());
+        if (mListener != null) {
+            mListener.onBindingDied(mUserId, mComponentName.getPackageName());
+        }
     }
 
     @Override