3.16.57-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Stefano Brivio <[email protected]> commit 24fc79798b8ddfd46f2dd363a8d29072c083b977 upstream. 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]> Signed-off-by: Steffen Klassert <[email protected]> [bwh: Backported to 3.16: Add definition of ETH_MIN_MTU] Signed-off-by: Ben Hutchings <[email protected]> --- net/ipv4/ip_tunnel.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -968,8 +968,14 @@ int ip_tunnel_newlink(struct net_device 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); --- a/include/uapi/linux/if_ether.h +++ b/include/uapi/linux/if_ether.h @@ -36,6 +36,8 @@ #define ETH_FRAME_LEN 1514 /* Max. octets in frame sans FCS */ #define ETH_FCS_LEN 4 /* Octets in the FCS */ +#define ETH_MIN_MTU 68 /* Min IPv4 MTU per RFC791 */ + /* * These are the defined Ethernet Protocol ID's. */
