void ap_queue_message(struct ap_device *ap_dev, struct ap_message *ap_msg)
{
	unsigned long flags;
	int rc;

	/* For asynchronous message handling a valid receive-callback
	 * is required. */
	BUG_ON(!ap_msg->receive);

	spin_lock_bh(&ap_dev->lock);
	if (!ap_dev->unregistered) {
		/* Make room on the queue by polling for finished requests. */
		rc = ap_poll_queue(ap_dev, &flags);
		if (!rc)
			rc = __ap_queue_message(ap_dev, ap_msg);
		if (!rc)
			wake_up(&ap_poll_wait);
		if (rc == -ENODEV)
			ap_dev->unregistered = 1;
	} else {
		ap_msg->receive(ap_dev, ap_msg, ERR_PTR(-ENODEV));
		rc = -ENODEV;
	}
	spin_unlock_bh(&ap_dev->lock);
	if (rc == -ENODEV)
		device_unregister(&ap_dev->device);
}

This category addresses vulnerabilities caused by flawed access control mechanisms, where incorrect permission settings allow unauthorized users to access restricted resources.