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, 37 insertions, 35 deletions

diff --git a/framework/java/android/bluetooth/BluetoothSap.java b/framework/java/android/bluetooth/BluetoothSap.java
index bcdf4938fe..48481620c9 100644
--- a/framework/java/android/bluetooth/BluetoothSap.java
+++ b/framework/java/android/bluetooth/BluetoothSap.java
@@ -68,7 +68,7 @@ public final class BluetoothSap implements BluetoothProfile {
     public static final String ACTION_CONNECTION_STATE_CHANGED =
             "android.bluetooth.sap.profile.action.CONNECTION_STATE_CHANGED";
 
-    private IBluetoothSap mService;
+    private volatile IBluetoothSap mService;
     private final Context mContext;
     private ServiceListener mServiceListener;
     private BluetoothAdapter mAdapter;
@@ -202,9 +202,10 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public int getState() {
         if (VDBG) log("getState()");
-        if (mService != null) {
+        final IBluetoothSap service = mService;
+        if (service != null) {
             try {
-                return mService.getState();
+                return service.getState();
             } catch (RemoteException e) {
                 Log.e(TAG, e.toString());
             }
@@ -224,9 +225,10 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public BluetoothDevice getClient() {
         if (VDBG) log("getClient()");
-        if (mService != null) {
+        final IBluetoothSap service = mService;
+        if (service != null) {
             try {
-                return mService.getClient();
+                return service.getClient();
             } catch (RemoteException e) {
                 Log.e(TAG, e.toString());
             }
@@ -246,9 +248,10 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public boolean isConnected(BluetoothDevice device) {
         if (VDBG) log("isConnected(" + device + ")");
-        if (mService != null) {
+        final IBluetoothSap service = mService;
+        if (service != null) {
             try {
-                return mService.isConnected(device);
+                return service.isConnected(device);
             } catch (RemoteException e) {
                 Log.e(TAG, e.toString());
             }
@@ -279,15 +282,16 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public boolean disconnect(BluetoothDevice device) {
         if (DBG) log("disconnect(" + device + ")");
-        if (mService != null && isEnabled() && isValidDevice(device)) {
+        final IBluetoothSap service = mService;
+        if (service != null && isEnabled() && isValidDevice(device)) {
             try {
-                return mService.disconnect(device);
+                return service.disconnect(device);
             } catch (RemoteException e) {
                 Log.e(TAG, Log.getStackTraceString(new Throwable()));
                 return false;
             }
         }
-        if (mService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return false;
     }
 
@@ -299,15 +303,16 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public List<BluetoothDevice> getConnectedDevices() {
         if (DBG) log("getConnectedDevices()");
-        if (mService != null && isEnabled()) {
+        final IBluetoothSap service = mService;
+        if (service != null && isEnabled()) {
             try {
-                return mService.getConnectedDevices();
+                return service.getConnectedDevices();
             } catch (RemoteException e) {
                 Log.e(TAG, Log.getStackTraceString(new Throwable()));
                 return new ArrayList<BluetoothDevice>();
             }
         }
-        if (mService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return new ArrayList<BluetoothDevice>();
     }
 
@@ -319,15 +324,16 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public List<BluetoothDevice> getDevicesMatchingConnectionStates(int[] states) {
         if (DBG) log("getDevicesMatchingStates()");
-        if (mService != null && isEnabled()) {
+        final IBluetoothSap service = mService;
+        if (service != null && isEnabled()) {
             try {
-                return mService.getDevicesMatchingConnectionStates(states);
+                return service.getDevicesMatchingConnectionStates(states);
             } catch (RemoteException e) {
                 Log.e(TAG, Log.getStackTraceString(new Throwable()));
                 return new ArrayList<BluetoothDevice>();
             }
         }
-        if (mService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return new ArrayList<BluetoothDevice>();
     }
 
@@ -339,15 +345,16 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public int getConnectionState(BluetoothDevice device) {
         if (DBG) log("getConnectionState(" + device + ")");
-        if (mService != null && isEnabled() && isValidDevice(device)) {
+        final IBluetoothSap service = mService;
+        if (service != null && isEnabled() && isValidDevice(device)) {
             try {
-                return mService.getConnectionState(device);
+                return service.getConnectionState(device);
             } catch (RemoteException e) {
                 Log.e(TAG, Log.getStackTraceString(new Throwable()));
                 return BluetoothProfile.STATE_DISCONNECTED;
             }
         }
-        if (mService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return BluetoothProfile.STATE_DISCONNECTED;
     }
 
@@ -363,19 +370,20 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public boolean setPriority(BluetoothDevice device, int priority) {
         if (DBG) log("setPriority(" + device + ", " + priority + ")");
-        if (mService != null && isEnabled() && isValidDevice(device)) {
+        final IBluetoothSap service = mService;
+        if (service != null && isEnabled() && isValidDevice(device)) {
             if (priority != BluetoothProfile.PRIORITY_OFF
                     && priority != BluetoothProfile.PRIORITY_ON) {
                 return false;
             }
             try {
-                return mService.setPriority(device, priority);
+                return service.setPriority(device, priority);
             } catch (RemoteException e) {
                 Log.e(TAG, Log.getStackTraceString(new Throwable()));
                 return false;
             }
         }
-        if (mService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return false;
     }
 
@@ -388,19 +396,20 @@ public final class BluetoothSap implements BluetoothProfile {
      */
     public int getPriority(BluetoothDevice device) {
         if (VDBG) log("getPriority(" + device + ")");
-        if (mService != null && isEnabled() && isValidDevice(device)) {
+        final IBluetoothSap service = mService;
+        if (service != null && isEnabled() && isValidDevice(device)) {
             try {
-                return mService.getPriority(device);
+                return service.getPriority(device);
             } catch (RemoteException e) {
                 Log.e(TAG, Log.getStackTraceString(new Throwable()));
                 return PRIORITY_OFF;
             }
         }
-        if (mService == null) Log.w(TAG, "Proxy not attached to service");
+        if (service == null) Log.w(TAG, "Proxy not attached to service");
         return PRIORITY_OFF;
     }
 
-    private ServiceConnection mConnection = new ServiceConnection() {
+    private final ServiceConnection mConnection = new ServiceConnection() {
         public void onServiceConnected(ComponentName className, IBinder service) {
             if (DBG) log("Proxy object connected");
             mService = IBluetoothSap.Stub.asInterface(Binder.allowBlocking(service));
@@ -432,15 +441,8 @@ public final class BluetoothSap implements BluetoothProfile {
         return false;
     }
 
-    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());
     }
 
 }