media: rc: do not access device via sysfs after rc_unregister_device()

Device drivers do not expect to have change_protocol or wakeup
re-programming to be accesed after rc_unregister_device(). This can
cause the device driver to access deallocated resources.

Cc: <[e-mail]> # 4.16+
Signed-off-by: Sean Young <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/rc/rc-main.c

···
 	}
 
 	mutex_lock(&dev->lock);
+	if (!dev->registered) {
+		mutex_unlock(&dev->lock);
+		return -ENODEV;
+	}
 
 	old_protocols = *current_protocols;
 	new_protocols = old_protocols;
···
 		return -EINVAL;
 
 	mutex_lock(&dev->lock);
+	if (!dev->registered) {
+		mutex_unlock(&dev->lock);
+		return -ENODEV;
+	}
 
 	new_filter = *filter;
 	if (fattr->mask)
···
 	int i;
 
 	mutex_lock(&dev->lock);
+	if (!dev->registered) {
+		mutex_unlock(&dev->lock);
+		return -ENODEV;
+	}
 
 	allowed = dev->allowed_wakeup_protocols;