Harden NsdManager against null-dereference crashes
Due to race conditions or programming errors, the NsdManager
can attempt to process an asynchronous status message (and issue
a callback to the listener) after the listener has already been
removed from the NsdManager state. This causes dereferencing of
null objects, and a crash.
Split out the three async-queue message cases: these are ones
in which message.arg2 does not hold an NsdManager array index
and the code should not interpret this field as if it were.
Add an explicit check for "null listener" (the array index in the
message has already been released), log a warning, and exit early.
Safeguard accesses to the "NSD service type" string from a (possibly
null) NsdServiceInfo object... return a constant "?" string rather
than crashing.
Bug: 9016259
Change-Id: I40aabdfc65d86fdd0eaac7a1e7e56e6ff69796cf
diff --git a/core/java/android/net/nsd/NsdManager.java b/core/java/android/net/nsd/NsdManager.java
index 9c3e405..7b2c623 100644
--- a/core/java/android/net/nsd/NsdManager.java
+++ b/core/java/android/net/nsd/NsdManager.java
@@ -301,27 +301,36 @@
@Override
public void handleMessage(Message message) {
- Object listener = getListener(message.arg2);
- boolean listenerRemove = true;
switch (message.what) {
case AsyncChannel.CMD_CHANNEL_HALF_CONNECTED:
mAsyncChannel.sendMessage(AsyncChannel.CMD_CHANNEL_FULL_CONNECTION);
- break;
+ return;
case AsyncChannel.CMD_CHANNEL_FULLY_CONNECTED:
mConnected.countDown();
- break;
+ return;
case AsyncChannel.CMD_CHANNEL_DISCONNECTED:
Log.e(TAG, "Channel lost");
+ return;
+ default:
break;
+ }
+ Object listener = getListener(message.arg2);
+ if (listener == null) {
+ Log.d(TAG, "Stale key " + message.arg2);
+ return;
+ }
+ boolean listenerRemove = true;
+ NsdServiceInfo ns = getNsdService(message.arg2);
+ switch (message.what) {
case DISCOVER_SERVICES_STARTED:
- String s = ((NsdServiceInfo) message.obj).getServiceType();
+ String s = getNsdServiceInfoType((NsdServiceInfo) message.obj);
((DiscoveryListener) listener).onDiscoveryStarted(s);
// Keep listener until stop discovery
listenerRemove = false;
break;
case DISCOVER_SERVICES_FAILED:
- ((DiscoveryListener) listener).onStartDiscoveryFailed(
- getNsdService(message.arg2).getServiceType(), message.arg1);
+ ((DiscoveryListener) listener).onStartDiscoveryFailed(getNsdServiceInfoType(ns),
+ message.arg1);
break;
case SERVICE_FOUND:
((DiscoveryListener) listener).onServiceFound((NsdServiceInfo) message.obj);
@@ -334,16 +343,14 @@
listenerRemove = false;
break;
case STOP_DISCOVERY_FAILED:
- ((DiscoveryListener) listener).onStopDiscoveryFailed(
- getNsdService(message.arg2).getServiceType(), message.arg1);
+ ((DiscoveryListener) listener).onStopDiscoveryFailed(getNsdServiceInfoType(ns),
+ message.arg1);
break;
case STOP_DISCOVERY_SUCCEEDED:
- ((DiscoveryListener) listener).onDiscoveryStopped(
- getNsdService(message.arg2).getServiceType());
+ ((DiscoveryListener) listener).onDiscoveryStopped(getNsdServiceInfoType(ns));
break;
case REGISTER_SERVICE_FAILED:
- ((RegistrationListener) listener).onRegistrationFailed(
- getNsdService(message.arg2), message.arg1);
+ ((RegistrationListener) listener).onRegistrationFailed(ns, message.arg1);
break;
case REGISTER_SERVICE_SUCCEEDED:
((RegistrationListener) listener).onServiceRegistered(
@@ -352,16 +359,13 @@
listenerRemove = false;
break;
case UNREGISTER_SERVICE_FAILED:
- ((RegistrationListener) listener).onUnregistrationFailed(
- getNsdService(message.arg2), message.arg1);
+ ((RegistrationListener) listener).onUnregistrationFailed(ns, message.arg1);
break;
case UNREGISTER_SERVICE_SUCCEEDED:
- ((RegistrationListener) listener).onServiceUnregistered(
- getNsdService(message.arg2));
+ ((RegistrationListener) listener).onServiceUnregistered(ns);
break;
case RESOLVE_SERVICE_FAILED:
- ((ResolveListener) listener).onResolveFailed(
- getNsdService(message.arg2), message.arg1);
+ ((ResolveListener) listener).onResolveFailed(ns, message.arg1);
break;
case RESOLVE_SERVICE_SUCCEEDED:
((ResolveListener) listener).onServiceResolved((NsdServiceInfo) message.obj);
@@ -421,6 +425,11 @@
}
+ private String getNsdServiceInfoType(NsdServiceInfo s) {
+ if (s == null) return "?";
+ return s.getServiceType();
+ }
+
/**
* Initialize AsyncChannel
*/
