From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:42388 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1164055AbeE1KxJ (ORCPT ); Mon, 28 May 2018 06:53:09 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefano Brivio , Sabrina Dubroca , Steffen Klassert , Sasha Levin Subject: [PATCH 4.14 264/496] ip_tunnel: Clamp MTU to bounds on new link Date: Mon, 28 May 2018 12:00:49 +0200 Message-Id: <20180528100330.986219941@linuxfoundation.org> In-Reply-To: <20180528100319.498712256@linuxfoundation.org> References: <20180528100319.498712256@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stefano Brivio [ Upstream commit 24fc79798b8ddfd46f2dd363a8d29072c083b977 ] 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 Acked-by: Sabrina Dubroca Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- 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 @@ -1103,8 +1103,14 @@ 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); out: