Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754766AbbKWNNQ (ORCPT ); Mon, 23 Nov 2015 08:13:16 -0500 Received: from mx2.suse.de ([195.135.220.15]:59805 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754729AbbKWNMs (ORCPT ); Mon, 23 Nov 2015 08:12:48 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Marcelo Leitner , Sabrina Dubroca , "David S . Miller" , Jiri Slaby Subject: [PATCH 3.12 70/72] ipv6: addrconf: validate new MTU before applying it Date: Mon, 23 Nov 2015 14:12:31 +0100 Message-Id: <49f9add06964fe16997aa34099e7bb31c39b0314.1448283890.git.jslaby@suse.cz> X-Mailer: git-send-email 2.6.3 In-Reply-To: <09f041d02b9d5407d544d6fd5a9026072c44956f.1448283890.git.jslaby@suse.cz> References: <09f041d02b9d5407d544d6fd5a9026072c44956f.1448283890.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2432 Lines: 75 From: Marcelo Leitner 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 77751427a1ff25b27d47a4c36b12c3c8667855ac upstream. Currently we don't check if the new MTU is valid or not and this allows one to configure a smaller than minimum allowed by RFCs or even bigger than interface own MTU, which is a problem as it may lead to packet drops. If you have a daemon like NetworkManager running, this may be exploited by remote attackers by forging RA packets with an invalid MTU, possibly leading to a DoS. (NetworkManager currently only validates for values too small, but not for too big ones.) The fix is just to make sure the new value is valid. That is, between IPV6_MIN_MTU and interface's MTU. Note that similar check is already performed at ndisc_router_discovery(), for when kernel itself parses the RA. Signed-off-by: Marcelo Ricardo Leitner Signed-off-by: Sabrina Dubroca Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- net/ipv6/addrconf.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 87f1a70bd234..38540a3ed92f 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -4656,6 +4656,21 @@ int addrconf_sysctl_forward(struct ctl_table *ctl, int write, return ret; } +static +int addrconf_sysctl_mtu(struct ctl_table *ctl, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + struct inet6_dev *idev = ctl->extra1; + int min_mtu = IPV6_MIN_MTU; + struct ctl_table lctl; + + lctl = *ctl; + lctl.extra1 = &min_mtu; + lctl.extra2 = idev ? &idev->dev->mtu : NULL; + + return proc_dointvec_minmax(&lctl, write, buffer, lenp, ppos); +} + static void dev_disable_change(struct inet6_dev *idev) { struct netdev_notifier_info info; @@ -4767,7 +4782,7 @@ static struct addrconf_sysctl_table .data = &ipv6_devconf.mtu6, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = addrconf_sysctl_mtu, }, { .procname = "accept_ra", -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/