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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 b96f9afee4
("ipv4/6: use core net MTU range checking").

Fixes: c544193214 ("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>
zero-colors
Stefano Brivio 2018-03-15 17:16:28 +01:00 committed by Steffen Klassert
parent dd1df24737
commit 24fc79798b
1 changed files with 7 additions and 1 deletions
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8
net/ipv4/ip_tunnel.c
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@ -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: