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Commit 24fc7979 authored by Stefano Brivio's avatar Stefano Brivio Committed by Steffen Klassert
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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: default avatarStefano Brivio <sbrivio@redhat.com>
Acked-by: default avatarSabrina Dubroca <sd@queasysnail.net>
Signed-off-by: default avatarSteffen 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: