Bluetooth: Thread-safe binder invocation

* Binder object may become null between null check and actual invocation
  if using a instance private variable assignable by service connection
  callbacks
* The solution to this problem without locking is to assign existing
  binder variable to a local final variable before the null check
* Any further invocation to a disconnected binder object will result in
  RemoteException that is caught by the try-catch block
* Read and write to volatile variable is always atomic and hence thread-safe
* Removed unnecessary synchronization in BluetoothAdapter constructor
* Private mConnection objects should be final
* Simplfied several return statements where booleans can be returned
  directly
* Removed unnecessary catches for NPE since there won't be any

Bug: 64724692
Test: make, pair and use devices, no functional change
Change-Id: Ifc9d6337c0d451a01484b61243230725d5314f8e

1 files changed, 30 insertions, 31 deletions

diff --git a/framework/java/android/bluetooth/BluetoothPan.java b/framework/java/android/bluetooth/BluetoothPan.java
index 63e83d2217..866b063083 100644
--- a/framework/java/android/bluetooth/BluetoothPan.java
+++ b/framework/java/android/bluetooth/BluetoothPan.java
@@ -123,7 +123,7 @@ public final class BluetoothPan implements BluetoothProfile {
     private Context mContext;
     private ServiceListener mServiceListener;
     private BluetoothAdapter mAdapter;
-    private IBluetoothPan mPanService;
+    private volatile IBluetoothPan mPanService;
 
     /**
      * Create a BluetoothPan proxy object for interacting with the local
@@ -238,15 +238,16 @@ public final class BluetoothPan implements BluetoothProfile {
      */
     public boolean connect(BluetoothDevice device) {
         if (DBG) log("connect(" + device + ")");
-        if (mPanService != null && isEnabled() && isValidDevice(device)) {
+        final IBluetoothPan service = mPanService;
+        if (service != null && isEnabled() && isValidDevice(device)) {
             try {
-                return mPanService.connect(device);
+                return service.connect(device);
             } catch (RemoteException e) {
                 Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
                 return false;
             }
         }
-        if (mPanService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return false;
     }
 
@@ -277,15 +278,16 @@ public final class BluetoothPan implements BluetoothProfile {
      */
     public boolean disconnect(BluetoothDevice device) {
         if (DBG) log("disconnect(" + device + ")");
-        if (mPanService != null && isEnabled() && isValidDevice(device)) {
+        final IBluetoothPan service = mPanService;
+        if (service != null && isEnabled() && isValidDevice(device)) {
             try {
-                return mPanService.disconnect(device);
+                return service.disconnect(device);
             } catch (RemoteException e) {
                 Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
                 return false;
             }
         }
-        if (mPanService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return false;
     }
 
@@ -295,15 +297,16 @@ public final class BluetoothPan implements BluetoothProfile {
     @Override
     public List<BluetoothDevice> getConnectedDevices() {
         if (VDBG) log("getConnectedDevices()");
-        if (mPanService != null && isEnabled()) {
+        final IBluetoothPan service = mPanService;
+        if (service != null && isEnabled()) {
             try {
-                return mPanService.getConnectedDevices();
+                return service.getConnectedDevices();
             } catch (RemoteException e) {
                 Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
                 return new ArrayList<BluetoothDevice>();
             }
         }
-        if (mPanService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return new ArrayList<BluetoothDevice>();
     }
 
@@ -313,15 +316,16 @@ public final class BluetoothPan implements BluetoothProfile {
     @Override
     public List<BluetoothDevice> getDevicesMatchingConnectionStates(int[] states) {
         if (VDBG) log("getDevicesMatchingStates()");
-        if (mPanService != null && isEnabled()) {
+        final IBluetoothPan service = mPanService;
+        if (service != null && isEnabled()) {
             try {
-                return mPanService.getDevicesMatchingConnectionStates(states);
+                return service.getDevicesMatchingConnectionStates(states);
             } catch (RemoteException e) {
                 Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
                 return new ArrayList<BluetoothDevice>();
             }
         }
-        if (mPanService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return new ArrayList<BluetoothDevice>();
     }
 
@@ -331,25 +335,25 @@ public final class BluetoothPan implements BluetoothProfile {
     @Override
     public int getConnectionState(BluetoothDevice device) {
         if (VDBG) log("getState(" + device + ")");
-        if (mPanService != null && isEnabled()
-                && isValidDevice(device)) {
+        final IBluetoothPan service = mPanService;
+        if (service != null && isEnabled() && isValidDevice(device)) {
             try {
-                return mPanService.getConnectionState(device);
+                return service.getConnectionState(device);
             } catch (RemoteException e) {
                 Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
                 return BluetoothProfile.STATE_DISCONNECTED;
             }
         }
-        if (mPanService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return BluetoothProfile.STATE_DISCONNECTED;
     }
 
     public void setBluetoothTethering(boolean value) {
         if (DBG) log("setBluetoothTethering(" + value + ")");
-
-        if (mPanService != null && isEnabled()) {
+        final IBluetoothPan service = mPanService;
+        if (service != null && isEnabled()) {
             try {
-                mPanService.setBluetoothTethering(value);
+                service.setBluetoothTethering(value);
             } catch (RemoteException e) {
                 Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
             }
@@ -358,10 +362,10 @@ public final class BluetoothPan implements BluetoothProfile {
 
     public boolean isTetheringOn() {
         if (VDBG) log("isTetheringOn()");
-
-        if (mPanService != null && isEnabled()) {
+        final IBluetoothPan service = mPanService;
+        if (service != null && isEnabled()) {
             try {
-                return mPanService.isTetheringOn();
+                return service.isTetheringOn();
             } catch (RemoteException e) {
                 Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
             }
@@ -373,7 +377,6 @@ public final class BluetoothPan implements BluetoothProfile {
         public void onServiceConnected(ComponentName className, IBinder service) {
             if (DBG) Log.d(TAG, "BluetoothPAN Proxy object connected");
             mPanService = IBluetoothPan.Stub.asInterface(Binder.allowBlocking(service));
-
             if (mServiceListener != null) {
                 mServiceListener.onServiceConnected(BluetoothProfile.PAN,
                         BluetoothPan.this);
@@ -390,15 +393,11 @@ public final class BluetoothPan implements BluetoothProfile {
     };
 
     private boolean isEnabled() {
-        if (mAdapter.getState() == BluetoothAdapter.STATE_ON) return true;
-        return false;
+        return mAdapter.getState() == BluetoothAdapter.STATE_ON;
     }
 
-    private boolean isValidDevice(BluetoothDevice device) {
-        if (device == null) return false;
-
-        if (BluetoothAdapter.checkBluetoothAddress(device.getAddress())) return true;
-        return false;
+    private static boolean isValidDevice(BluetoothDevice device) {
+        return device != null && BluetoothAdapter.checkBluetoothAddress(device.getAddress());
     }
 
     private static void log(String msg) {