Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752983AbdFGX0D (ORCPT ); Wed, 7 Jun 2017 19:26:03 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:50766 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753378AbdFGXFe (ORCPT ); Wed, 7 Jun 2017 19:05:34 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Eric Dumazet , "David S . Miller" , Willy Tarreau Subject: [PATCH 3.10 118/250] ipv4: keep skb->dst around in presence of IP options Date: Thu, 8 Jun 2017 00:58:24 +0200 Message-Id: <1496876436-32402-119-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1496876436-32402-1-git-send-email-w@1wt.eu> References: <1496876436-32402-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1468 Lines: 46 From: Eric Dumazet commit 34b2cef20f19c87999fff3da4071e66937db9644 upstream. 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: Willy Tarreau --- 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 f660314..3d009e1 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1042,7 +1042,14 @@ 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, -- 2.8.0.rc2.1.gbe9624a