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 <[email protected]>
Acked-by: Sabrina Dubroca <[email protected]>
---
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:
--
2.15.1
