From 47ac14766773b81f636592b71b7817e345b4679b Mon Sep 17 00:00:00 2001
From: Austin Delgado <austindelgado@google.com>
Date: Thu, 11 Aug 2022 18:21:57 +0000
Subject: [PATCH] Added subscription to binder death which removes dead
 callbacks

Test: atest BiometricStateCallbackTest
Bug: 237439972
Change-Id: I4fad4c5f1042edb27e20c9f916f999092afed0e0
---
 .../sensors/BiometricStateCallback.java       | 26 +++++++++++++++++--
 .../BiometricStateCallbackTest.java           | 10 +++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/services/core/java/com/android/server/biometrics/sensors/BiometricStateCallback.java b/services/core/java/com/android/server/biometrics/sensors/BiometricStateCallback.java
index f8543162f95e7..2263e80039bd4 100644
--- a/services/core/java/com/android/server/biometrics/sensors/BiometricStateCallback.java
+++ b/services/core/java/com/android/server/biometrics/sensors/BiometricStateCallback.java
@@ -28,6 +28,7 @@ import android.content.pm.UserInfo;
 import android.hardware.biometrics.BiometricStateListener;
 import android.hardware.biometrics.IBiometricStateListener;
 import android.hardware.biometrics.SensorPropertiesInternal;
+import android.os.IBinder;
 import android.os.RemoteException;
 import android.os.UserManager;
 import android.util.Slog;
@@ -45,7 +46,8 @@ import java.util.concurrent.CopyOnWriteArrayList;
  * @param <P> internal property type
  */
 public class BiometricStateCallback<T extends BiometricServiceProvider<P>,
-        P extends SensorPropertiesInternal> implements ClientMonitorCallback {
+        P extends SensorPropertiesInternal>
+        implements ClientMonitorCallback, IBinder.DeathRecipient {
 
     private static final String TAG = "BiometricStateCallback";
 
@@ -161,6 +163,11 @@ public class BiometricStateCallback<T extends BiometricServiceProvider<P>,
             @NonNull IBiometricStateListener listener) {
         mBiometricStateListeners.add(listener);
         broadcastCurrentEnrollmentState(listener);
+        try {
+            listener.asBinder().linkToDeath(this, 0 /* flags */);
+        } catch (RemoteException e) {
+            Slog.e(TAG, "Failed to link to death", e);
+        }
     }
 
     private synchronized void broadcastCurrentEnrollmentState(
@@ -196,4 +203,19 @@ public class BiometricStateCallback<T extends BiometricServiceProvider<P>,
             Slog.e(TAG, "Remote exception", e);
         }
     }
-}
+
+    @Override
+    public void binderDied() {
+        // Do nothing, handled below
+    }
+
+    @Override
+    public void binderDied(IBinder who) {
+        Slog.w(TAG, "Callback binder died: " + who);
+        if (mBiometricStateListeners.removeIf(listener -> listener.asBinder().equals(who))) {
+            Slog.w(TAG, "Removed dead listener for " + who);
+        } else {
+            Slog.w(TAG, "No dead listeners found");
+        }
+    }
+}
\ No newline at end of file
diff --git a/services/tests/servicestests/src/com/android/server/biometrics/sensors/fingerprint/BiometricStateCallbackTest.java b/services/tests/servicestests/src/com/android/server/biometrics/sensors/fingerprint/BiometricStateCallbackTest.java
index 0e30782eaece9..3b66eaba6129e 100644
--- a/services/tests/servicestests/src/com/android/server/biometrics/sensors/fingerprint/BiometricStateCallbackTest.java
+++ b/services/tests/servicestests/src/com/android/server/biometrics/sensors/fingerprint/BiometricStateCallbackTest.java
@@ -80,6 +80,8 @@ public class BiometricStateCallbackTest {
         when(mFakeProvider.hasEnrollments(eq(SENSOR_ID), eq(USER_ID))).thenReturn(true);
         when(mUserManager.getAliveUsers()).thenReturn(
                 List.of(new UserInfo(USER_ID, "name", 0)));
+        when(mBiometricStateListener.asBinder()).thenReturn(mBiometricStateListener);
+
 
         mCallback = new BiometricStateCallback<>(mUserManager);
         mCallback.registerBiometricStateListener(mBiometricStateListener);
@@ -110,6 +112,14 @@ public class BiometricStateCallbackTest {
                 false /* expectCallback */, false /* expectedCallbackValue */);
     }
 
+    @Test
+    public void testBinderDeath() {
+        mCallback.binderDied(mBiometricStateListener.asBinder());
+
+        testEnrollmentCallback(true /* changed */, false /* isNowEnrolled */,
+                false /* expectCallback */, false /* expectedCallbackValue */);
+    }
+
     private void testEnrollmentCallback(boolean changed, boolean isNowEnrolled,
             boolean expectCallback, boolean expectedCallbackValue) {
         EnrollClient<?> client = mock(EnrollClient.class);