Don't allow dangerous operations on shared handlers

Test: Boot, tree hugger
Fix: 235594693
Change-Id: I1c14bc2e4dd22623cecbd166ea20cd62f6a8d790

core/java/android/os/Handler.java

@@ -230,6 +230,7 @@ public class Handler {
         mQueue = mLooper.mQueue;
         mCallback = callback;
         mAsynchronous = async;
+        mIsShared = false;
     }
 
     /**
@@ -253,10 +254,17 @@ public class Handler {
      */
     @UnsupportedAppUsage
     public Handler(@NonNull Looper looper, @Nullable Callback callback, boolean async) {
+        this(looper, callback, async, /* shared= */ false);
+    }
+
+    /** @hide */
+    public Handler(@NonNull Looper looper, @Nullable Callback callback, boolean async,
+            boolean shared) {
         mLooper = looper;
         mQueue = looper.mQueue;
         mCallback = callback;
         mAsynchronous = async;
+        mIsShared = shared;
     }
 
     /**
@@ -778,6 +786,14 @@ public class Handler {
         return queue.enqueueMessage(msg, uptimeMillis);
     }
 
+    private Object disallowNullArgumentIfShared(@Nullable Object arg) {
+        if (mIsShared && arg == null) {
+            throw new IllegalArgumentException("Null argument disallowed for shared handler."
+                    + " Consider creating your own Handler instance.");
+        }
+        return arg;
+    }
+
     /**
      * Remove any pending posts of messages with code 'what' that are in the
      * message queue.
@@ -792,7 +808,7 @@ public class Handler {
      * all messages will be removed.
      */
     public final void removeMessages(int what, @Nullable Object object) {
-        mQueue.removeMessages(this, what, object);
+        mQueue.removeMessages(this, what, disallowNullArgumentIfShared(object));
     }
 
     /**
@@ -807,7 +823,7 @@ public class Handler {
      *@hide
      */
     public final void removeEqualMessages(int what, @Nullable Object object) {
-        mQueue.removeEqualMessages(this, what, object);
+        mQueue.removeEqualMessages(this, what, disallowNullArgumentIfShared(object));
     }
 
     /**
@@ -816,7 +832,7 @@ public class Handler {
      * all callbacks and messages will be removed.
      */
     public final void removeCallbacksAndMessages(@Nullable Object token) {
-        mQueue.removeCallbacksAndMessages(this, token);
+        mQueue.removeCallbacksAndMessages(this, disallowNullArgumentIfShared(token));
     }
 
     /**
@@ -827,7 +843,7 @@ public class Handler {
      *@hide
      */
     public final void removeCallbacksAndEqualMessages(@Nullable Object token) {
-        mQueue.removeCallbacksAndEqualMessages(this, token);
+        mQueue.removeCallbacksAndEqualMessages(this, disallowNullArgumentIfShared(token));
     }
     /**
      * Check if there are any pending posts of messages with code 'what' in
@@ -951,6 +967,9 @@ public class Handler {
     @UnsupportedAppUsage
     IMessenger mMessenger;
 
+    /** If it's a shared handler, we disallow certain dangeraous operations. */
+    private final boolean mIsShared;
+
     private static final class BlockingRunnable implements Runnable {
         private final Runnable mTask;
         private boolean mDone;

core/java/com/android/internal/os/BackgroundThread.java

@@ -46,7 +46,8 @@ public final class BackgroundThread extends HandlerThread {
             looper.setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
             looper.setSlowLogThresholdMs(
                     SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);
-            sHandler = new Handler(sInstance.getLooper());
+            sHandler = new Handler(sInstance.getLooper(), /*callback=*/ null, /* async=*/ false,
+                    /* shared=*/ true);
             sHandlerExecutor = new HandlerExecutor(sHandler);
         }
     }

services/core/java/com/android/server/DisplayThread.java

@@ -43,7 +43,7 @@ public final class DisplayThread extends ServiceThread {
             sInstance = new DisplayThread();
             sInstance.start();
             sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
-            sHandler = new Handler(sInstance.getLooper());
+            sHandler = makeSharedHandler(sInstance.getLooper());
         }
     }
 

services/core/java/com/android/server/FgThread.java

@@ -51,7 +51,7 @@ public final class FgThread extends ServiceThread {
             looper.setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
             looper.setSlowLogThresholdMs(
                     SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);
-            sHandler = new Handler(sInstance.getLooper());
+            sHandler = makeSharedHandler(sInstance.getLooper());
             sHandlerExecutor = new HandlerExecutor(sHandler);
         }
     }

services/core/java/com/android/server/IoThread.java

@@ -41,7 +41,7 @@ public final class IoThread extends ServiceThread {
             sInstance = new IoThread();
             sInstance.start();
             sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
-            sHandler = new Handler(sInstance.getLooper());
+            sHandler = makeSharedHandler(sInstance.getLooper());
             sHandlerExecutor = new HandlerExecutor(sHandler);
         }
     }

services/core/java/com/android/server/ServiceThread.java

@@ -16,7 +16,9 @@
 
 package com.android.server;
 
+import android.os.Handler;
 import android.os.HandlerThread;
+import android.os.Looper;
 import android.os.Process;
 import android.os.StrictMode;
 
@@ -43,4 +45,8 @@ public class ServiceThread extends HandlerThread {
 
         super.run();
     }
+
+    protected static Handler makeSharedHandler(Looper looper) {
+        return new Handler(looper, /*callback=*/ null, /* async=*/ false, /* shared=*/ true);
+    }
 }

services/core/java/com/android/server/UiThread.java

@@ -53,7 +53,7 @@ public final class UiThread extends ServiceThread {
             looper.setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
             looper.setSlowLogThresholdMs(
                     SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);
-            sHandler = new Handler(sInstance.getLooper());
+            sHandler = makeSharedHandler(sInstance.getLooper());
         }
     }