Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756705AbdDPKxA (ORCPT ); Sun, 16 Apr 2017 06:53:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59180 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756650AbdDPKws (ORCPT ); Sun, 16 Apr 2017 06:52:48 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Andrey Konovalov , "David S. Miller" Subject: [PATCH 3.18 007/145] ipv4: keep skb->dst around in presence of IP options Date: Sun, 16 Apr 2017 12:48:20 +0200 Message-Id: <20170416080200.571313397@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170416080200.205458595@linuxfoundation.org> References: <20170416080200.205458595@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1538 Lines: 49 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ 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: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- net/ipv4/ip_sockglue.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1066,7 +1066,14 @@ void ipv4_pktinfo_prepare(const struct s 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,