Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753986AbcKSJfi (ORCPT ); Sat, 19 Nov 2016 04:35:38 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58176 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753866AbcKSJXq (ORCPT ); Sat, 19 Nov 2016 04:23:46 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , "David S. Miller" Subject: [PATCH 4.8 11/49] dccp: fix out of bound access in dccp_v4_err() Date: Sat, 19 Nov 2016 10:23:03 +0100 Message-Id: <20161119092038.462343915@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161119092036.698705716@linuxfoundation.org> References: <20161119092036.698705716@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: 1948 Lines: 56 4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 6706a97fec963d6cb3f7fc2978ec1427b4651214 ] dccp_v4_err() does not use pskb_may_pull() and might access garbage. We only need 4 bytes at the beginning of the DCCP header, like TCP, so the 8 bytes pulled in icmp_socket_deliver() are more than enough. This patch might allow to process more ICMP messages, as some routers are still limiting the size of reflected bytes to 28 (RFC 792), instead of extended lengths (RFC 1812 4.3.2.3) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/dccp/ipv4.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -235,7 +235,7 @@ static void dccp_v4_err(struct sk_buff * { const struct iphdr *iph = (struct iphdr *)skb->data; const u8 offset = iph->ihl << 2; - const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset); + const struct dccp_hdr *dh; struct dccp_sock *dp; struct inet_sock *inet; const int type = icmp_hdr(skb)->type; @@ -245,11 +245,13 @@ static void dccp_v4_err(struct sk_buff * int err; struct net *net = dev_net(skb->dev); - if (skb->len < offset + sizeof(*dh) || - skb->len < offset + __dccp_basic_hdr_len(dh)) { - __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); - return; - } + /* Only need dccph_dport & dccph_sport which are the first + * 4 bytes in dccp header. + * Our caller (icmp_socket_deliver()) already pulled 8 bytes for us. + */ + BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8); + BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8); + dh = (struct dccp_hdr *)(skb->data + offset); sk = __inet_lookup_established(net, &dccp_hashinfo, iph->daddr, dh->dccph_dport,