Drivers: hv: vmbus: Fix a bug in channel rescind code

Rescind of subchannels were not being correctly handled. Fix the bug.
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Cc: <stable@vger.kernel.org>        [3.11+]
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/channel_mgmt.c

@@ -203,7 +203,8 @@ static void vmbus_process_rescind_offer(struct work_struct *work)
 	struct vmbus_channel *primary_channel;
 	struct vmbus_channel_relid_released msg;
 
-	vmbus_device_unregister(channel->device_obj);
+	if (channel->device_obj)
+		vmbus_device_unregister(channel->device_obj);
 	memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
 	msg.child_relid = channel->offermsg.child_relid;
 	msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
@@ -213,11 +214,6 @@ static void vmbus_process_rescind_offer(struct work_struct *work)
 		spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
 		list_del(&channel->listentry);
 		spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
-	} else {
-		primary_channel = channel->primary_channel;
-		spin_lock_irqsave(&primary_channel->sc_lock, flags);
-		list_del(&channel->listentry);
-		spin_unlock_irqrestore(&primary_channel->sc_lock, flags);
 	}
 	free_channel(channel);
 }