static void tun_get_iff(struct net *net, struct tun_struct *tun,
		       struct ifreq *ifr)
{
	tun_debug(KERN_INFO, tun, "tun_get_iff\n");

	strcpy(ifr->ifr_name, tun->dev->name);

	ifr->ifr_flags = tun_flags(tun);

}

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