ipv4: better IP_MAX_MTU enforcement
authorEric Dumazet <edumazet@google.com>
Wed, 16 Aug 2017 18:09:12 +0000 (11:09 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 30 Aug 2017 08:21:40 +0000 (10:21 +0200)
commitf29c9f46af4ac2540713e43981ded8588e03ae3b
tree93fa568b95c657a95c6bbfeca2a35ce2e4bcec05
parent59af5b87695de8e2c772827798938d8e35b49d05
ipv4: better IP_MAX_MTU enforcement

[ Upstream commit c780a049f9bf442314335372c9abc4548bfe3e44 ]

While working on yet another syzkaller report, I found
that our IP_MAX_MTU enforcements were not properly done.

gcc seems to reload dev->mtu for min(dev->mtu, IP_MAX_MTU), and
final result can be bigger than IP_MAX_MTU :/

This is a problem because device mtu can be changed on other cpus or
threads.

While this patch does not fix the issue I am working on, it is
probably worth addressing it.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
include/net/ip.h
net/ipv4/route.c