Shut down subscription clients when DeviceController shuts down.

Other clients get shut down due to their sessions going away, but subscription
clients can be in a state where they are not waiting on a response, and those
should get shut down too.

Also:

1) Fixes ReadClient::Close to release its exchange, so shutting down a
subscription while it's waiting for a response from the server actually shuts it
down, instead of delivering OnDone and then getting a message on the exchange
and possibly sending more notifications after OnDone.

2) Fixes potential use-after-free in the ShutdownSubscriptions functions.

Fixes project-chip#22319

src/app/InteractionModelEngine.cpp

@@ -253,24 +253,50 @@ CHIP_ERROR InteractionModelEngine::ShutdownSubscription(const ScopedNodeId & aPe
 
 void InteractionModelEngine::ShutdownSubscriptions(FabricIndex aFabricIndex, NodeId aPeerNodeId)
 {
-    for (auto * readClient = mpActiveReadClientList; readClient != nullptr; readClient = readClient->GetNextClient())
+    // This is assuming that ReadClient::Close will not affect any other
+    // ReadClients in the list.
+    for (auto * readClient = mpActiveReadClientList; readClient != nullptr;)
     {
+        // Grab the next client now, because we might be about to delete readClient.
+        auto * nextClient = readClient->GetNextClient();
         if (readClient->IsSubscriptionType() && readClient->GetFabricIndex() == aFabricIndex &&
             readClient->GetPeerNodeId() == aPeerNodeId)
         {
             readClient->Close(CHIP_NO_ERROR);
         }
+        readClient = nextClient;
+    }
+}
+
+void InteractionModelEngine::ShutdownSubscriptions(FabricIndex aFabricIndex)
+{
+    // This is assuming that ReadClient::Close will not affect any other
+    // ReadClients in the list.
+    for (auto * readClient = mpActiveReadClientList; readClient != nullptr;)
+    {
+        // Grab the next client now, because we might be about to delete readClient.
+        auto * nextClient = readClient->GetNextClient();
+        if (readClient->IsSubscriptionType() && readClient->GetFabricIndex() == aFabricIndex)
+        {
+            readClient->Close(CHIP_NO_ERROR);
+        }
+        readClient = nextClient;
     }
 }
 
 void InteractionModelEngine::ShutdownAllSubscriptions()
 {
-    for (auto * readClient = mpActiveReadClientList; readClient != nullptr; readClient = readClient->GetNextClient())
+    // This is assuming that ReadClient::Close will not affect any other
+    // ReadClients in the list.
+    for (auto * readClient = mpActiveReadClientList; readClient != nullptr;)
     {
+        // Grab the next client now, because we might be about to delete readClient.
+        auto * nextClient = readClient->GetNextClient();
         if (readClient->IsSubscriptionType())
         {
             readClient->Close(CHIP_NO_ERROR);
         }
+        readClient = nextClient;
     }
 }
 

src/app/InteractionModelEngine.h

@@ -139,6 +139,11 @@ class InteractionModelEngine : public Messaging::UnsolicitedMessageHandler,
      */
     void ShutdownSubscriptions(FabricIndex aFabricIndex, NodeId aPeerNodeId);
 
+    /**
+     * Tears down all active subscriptions for a given fabric.
+     */
+    void ShutdownSubscriptions(FabricIndex aFabricIndex);
+
     /**
      * Tears down all active subscriptions.
      */

src/app/ReadClient.cpp

@@ -194,6 +194,7 @@ void ReadClient::Close(CHIP_ERROR aError, bool allowResubscription, bool allowOn
     {
         mpCallback.OnDone(this);
     }
+    mExchange.Release();
 }
 
 const char * ReadClient::GetStateStr() const

src/controller/CHIPDeviceController.cpp

@@ -329,6 +329,9 @@ void DeviceController::Shutdown()
 
     if (mFabricIndex != kUndefinedFabricIndex)
     {
+        // Shut down any subscription clients for this fabric.
+        app::InteractionModelEngine::GetInstance()->ShutdownSubscriptions(mFabricIndex);
+
         // Shut down any ongoing CASE session activity we have.  We're going to
         // assume that all sessions for our fabric belong to us here.
         mSystemState->CASESessionMgr()->ReleaseSessionsForFabric(mFabricIndex);