Commit 24fc7979 authored Mar 15, 2018 by Stefano Brivio Committed by Steffen Klassert Mar 19, 2018

ip_tunnel: Clamp MTU to bounds on new link



Otherwise, it's possible to specify invalid MTU values directly
on creation of a link (via 'ip link add'). This is already
prevented on subsequent MTU changes by commit b96f9afe
("ipv4/6: use core net MTU range checking").

Fixes: c5441932 ("GRE: Refactor GRE tunneling code.")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Acked-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

parent dd1df247

net/ipv4/ip_tunnel.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -1108,8 +1108,14 @@ int ip_tunnel_newlink(struct net_device dev, struct nlattr tb[],
		eth_hw_addr_random(dev);

		mtu = ip_tunnel_bind_dev(dev);
		if (!tb[IFLA_MTU])
		if (tb[IFLA_MTU]) {
		unsigned int max = 0xfff8 - dev->hard_header_len - nt->hlen;

		dev->mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU,
		(unsigned int)(max - sizeof(struct iphdr)));
		} else {
		dev->mtu = mtu;
		}

		ip_tunnel_add(itn, nt);
		out:

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