static int ipgre_tunnel_bind_dev(struct net_device *dev)
{
	struct net_device *tdev = NULL;
	struct ip_tunnel *tunnel;
	struct iphdr *iph;
	int hlen = LL_MAX_HEADER;
	int mtu = ETH_DATA_LEN;
	int addend = sizeof(struct iphdr) + 4;

	tunnel = netdev_priv(dev);
	iph = &tunnel->parms.iph;

	/* Guess output device to choose reasonable mtu and needed_headroom */

	if (iph->daddr) {
		struct flowi fl = {
			.oif = tunnel->parms.link,
			.fl4_dst = iph->daddr,
			.fl4_src = iph->saddr,
			.fl4_tos = RT_TOS(iph->tos),
			.proto = IPPROTO_GRE,
			.fl_gre_key = tunnel->parms.o_key
		};
		struct rtable *rt;

		if (!ip_route_output_key(dev_net(dev), &rt, &fl)) {
			tdev = rt->dst.dev;
			ip_rt_put(rt);
		}

		if (dev->type != ARPHRD_ETHER)
			dev->flags |= IFF_POINTOPOINT;
	}

	if (!tdev && tunnel->parms.link)
		tdev = __dev_get_by_index(dev_net(dev), tunnel->parms.link);

	if (tdev) {
		hlen = tdev->hard_header_len + tdev->needed_headroom;
		mtu = tdev->mtu;
	}
	dev->iflink = tunnel->parms.link;

	/* Precalculate GRE options length */
	if (tunnel->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) {
		if (tunnel->parms.o_flags&GRE_CSUM)
			addend += 4;
		if (tunnel->parms.o_flags&GRE_KEY)
			addend += 4;
		if (tunnel->parms.o_flags&GRE_SEQ)
			addend += 4;
	}
	dev->needed_headroom = addend + hlen;
	mtu -= dev->hard_header_len + addend;

	if (mtu < 68)
		mtu = 68;

	tunnel->hlen = addend;

	return mtu;
}

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