Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932069AbdCFJbm (ORCPT ); Mon, 6 Mar 2017 04:31:42 -0500 Received: from mx2.suse.de ([195.135.220.15]:37197 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752778AbdCFJNI (ORCPT ); Mon, 6 Mar 2017 04:13:08 -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, Eric Dumazet , "David S . Miller" , Jiri Slaby Subject: [PATCH 3.12 054/113] ipv4: keep skb->dst around in presence of IP options Date: Mon, 6 Mar 2017 10:11:18 +0100 Message-Id: X-Mailer: git-send-email 2.12.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1565 Lines: 50 From: Eric Dumazet 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ Upstream commit 34b2cef20f19c87999fff3da4071e66937db9644 ] Andrey Konovalov got crashes in __ip_options_echo() when a NULL skb->dst is accessed. ipv4_pktinfo_prepare() should not drop the dst if (evil) IP options are present. We could refine the test to the presence of ts_needtime or srr, but IP options are not often used, so let's be conservative. Thanks to syzkaller team for finding this bug. Fixes: d826eb14ecef ("ipv4: PKTINFO doesnt need dst reference") Signed-off-by: Eric Dumazet Reported-by: Andrey Konovalov Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- net/ipv4/ip_sockglue.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 9e4f832aaf13..5a7bb6cb22bb 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1044,7 +1044,14 @@ void ipv4_pktinfo_prepare(struct sk_buff *skb) pktinfo->ipi_ifindex = 0; pktinfo->ipi_spec_dst.s_addr = 0; } - skb_dst_drop(skb); + /* We need to keep the dst for __ip_options_echo() + * We could restrict the test to opt.ts_needtime || opt.srr, + * but the following is good enough as IP options are not often used. + */ + if (unlikely(IPCB(skb)->opt.optlen)) + skb_dst_force(skb); + else + skb_dst_drop(skb); } int ip_setsockopt(struct sock *sk, int level, -- 2.12.0