Fix security vulnerability allowing apps to start from background

Bug: 317048338
Test: Using the steps in b/317048338#comment12
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:c5fc8ea92c0aabbb2fdccc23b743c18a8bf62e64)
Merged-In: Ia91199fdb23beed27bde687fdca8fe5d3a5a4759
Change-Id: Ia91199fdb23beed27bde687fdca8fe5d3a5a4759

2 files changed, 19 insertions, 8 deletions

diff --git a/media/java/android/media/session/ParcelableListBinder.java b/media/java/android/media/session/ParcelableListBinder.java
index bbf1e0889b68..d78828462b1e 100644
--- a/media/java/android/media/session/ParcelableListBinder.java
+++ b/media/java/android/media/session/ParcelableListBinder.java
@@ -45,6 +45,7 @@ public class ParcelableListBinder<T extends Parcelable> extends Binder {
     private static final int END_OF_PARCEL = 0;
     private static final int ITEM_CONTINUED = 1;
 
+    private final Class<T> mListElementsClass;
     private final Consumer<List<T>> mConsumer;
 
     private final Object mLock = new Object();
@@ -61,9 +62,11 @@ public class ParcelableListBinder<T extends Parcelable> extends Binder {
     /**
      * Creates an instance.
      *
+     * @param listElementsClass the class of the list elements.
      * @param consumer a consumer that consumes the list received
      */
-    public ParcelableListBinder(@NonNull Consumer<List<T>> consumer) {
+    public ParcelableListBinder(Class<T> listElementsClass, @NonNull Consumer<List<T>> consumer) {
+        mListElementsClass = listElementsClass;
         mConsumer = consumer;
     }
 
@@ -83,7 +86,13 @@ public class ParcelableListBinder<T extends Parcelable> extends Binder {
                 mCount = data.readInt();
             }
             while (i < mCount && data.readInt() != END_OF_PARCEL) {
-                mList.add(data.readParcelable(null));
+                Object object = data.readParcelable(null);
+                if (mListElementsClass.isAssignableFrom(object.getClass())) {
+                    // Checking list items are of compaitible types to validate against malicious
+                    // apps calling it directly via reflection with non compilable items.
+                    // See b/317048338 for more details
+                    mList.add((T) object);
+                }
                 i++;
             }
             if (i >= mCount) {
diff --git a/services/core/java/com/android/server/media/MediaSessionRecord.java b/services/core/java/com/android/server/media/MediaSessionRecord.java
index a9a82725223d..e2e0d834d6d1 100644
--- a/services/core/java/com/android/server/media/MediaSessionRecord.java
+++ b/services/core/java/com/android/server/media/MediaSessionRecord.java
@@ -1329,12 +1329,14 @@ public class MediaSessionRecord extends MediaSessionRecordImpl implements IBinde
 
         @Override
         public IBinder getBinderForSetQueue() throws RemoteException {
-            return new ParcelableListBinder<QueueItem>((list) -> {
-                synchronized (mLock) {
-                    mQueue = list;
-                }
-                mHandler.post(MessageHandler.MSG_UPDATE_QUEUE);
-            });
+            return new ParcelableListBinder<QueueItem>(
+                    QueueItem.class,
+                    (list) -> {
+                        synchronized (mLock) {
+                            mQueue = list;
+                        }
+                        mHandler.post(MessageHandler.MSG_UPDATE_QUEUE);
+                    });
         }
 
         @Override