Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756739AbdGCPEV (ORCPT ); Mon, 3 Jul 2017 11:04:21 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34924 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754395AbdGCNiu (ORCPT ); Mon, 3 Jul 2017 09:38:50 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Denys Fedoryshchenko , Pablo Neira Ayuso Subject: [PATCH 4.4 017/101] netfilter: xt_TCPMSS: add more sanity tests on tcph->doff Date: Mon, 3 Jul 2017 15:34:17 +0200 Message-Id: <20170703133337.299501784@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170703133334.237346187@linuxfoundation.org> References: <20170703133334.237346187@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: 1365 Lines: 47 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit 2638fd0f92d4397884fd991d8f4925cb3f081901 upstream. Denys provided an awesome KASAN report pointing to an use after free in xt_TCPMSS I have provided three patches to fix this issue, either in xt_TCPMSS or in xt_tcpudp.c. It seems xt_TCPMSS patch has the smallest possible impact. Signed-off-by: Eric Dumazet Reported-by: Denys Fedoryshchenko Signed-off-by: Pablo Neira Ayuso Signed-off-by: Greg Kroah-Hartman --- net/netfilter/xt_TCPMSS.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/net/netfilter/xt_TCPMSS.c +++ b/net/netfilter/xt_TCPMSS.c @@ -104,7 +104,7 @@ tcpmss_mangle_packet(struct sk_buff *skb tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); tcp_hdrlen = tcph->doff * 4; - if (len < tcp_hdrlen) + if (len < tcp_hdrlen || tcp_hdrlen < sizeof(struct tcphdr)) return -1; if (info->mss == XT_TCPMSS_CLAMP_PMTU) { @@ -156,6 +156,10 @@ tcpmss_mangle_packet(struct sk_buff *skb if (len > tcp_hdrlen) return 0; + /* tcph->doff has 4 bits, do not wrap it to 0 */ + if (tcp_hdrlen >= 15 * 4) + return 0; + /* * MSS Option not found ?! add it.. */