static int tun_set_queue(struct file *file, struct ifreq *ifr)
{
	struct tun_file *tfile = file->private_data;
	struct tun_struct *tun;
	int ret = 0;

	rtnl_lock();

	if (ifr->ifr_flags & IFF_ATTACH_QUEUE) {
		tun = tfile->detached;
		if (!tun) {
			ret = -EINVAL;
			goto unlock;
		}
		ret = security_tun_dev_attach_queue(tun->security);
		if (ret < 0)
			goto unlock;
		ret = tun_attach(tun, file, false);
	} else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
		tun = rtnl_dereference(tfile->tun);
		if (!tun || !(tun->flags & IFF_MULTI_QUEUE) || tfile->detached)
			ret = -EINVAL;
		else
			__tun_detach(tfile, false);
	} else
		ret = -EINVAL;

unlock:
	rtnl_unlock();
	return ret;
}

The product dereferences a pointer that it expects to be valid but is NULL.