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Harden NsdManager against null-dereference crashes

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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

Manual cherrypick of commit b1fbb14122a99c62363a949dd634294f5e887ef,
change-ID I7a6ff6842cf035cefbafe2a023ae1fd43734081e in master.

Change-Id: I8d9b7a1763d47d061a0f46b3cb453de4bdb8c2ed
This commit is contained in:
Dave Platt
2014-03-13 17:27:03 -07:00
parent 4429e878fb
commit febcdae1ba
1 changed files with 28 additions and 19 deletions
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47
core/java/android/net/nsd/NsdManager.java
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@@ -301,27 +301,36 @@ public final class NsdManager {
@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 @@ public final class NsdManager {
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 @@ public final class NsdManager {
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 @@ public final class NsdManager {
}
private String getNsdServiceInfoType(NsdServiceInfo s) {
if (s == null) return "?";
return s.getServiceType();
}
/**
* Initialize AsyncChannel
*/