From 24fc79798b8ddfd46f2dd363a8d29072c083b977 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Thu, 15 Mar 2018 17:16:28 +0100 Subject: 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 b96f9afee4eb ("ipv4/6: use core net MTU range checking"). Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.") Signed-off-by: Stefano Brivio Acked-by: Sabrina Dubroca Signed-off-by: Steffen Klassert --- net/ipv4/ip_tunnel.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c index 6d21068f9b55..7c76dd17b6b9 100644 --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -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: -- cgit