3.16.57-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Stefano Brivio <sbrivio@xxxxxxxxxx>
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 <sbrivio@xxxxxxxxxx>
Acked-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
[bwh: Backported to 3.16: Add definition of ETH_MIN_MTU]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
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.
*/
