Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964929AbdCJNXs (ORCPT ); Fri, 10 Mar 2017 08:23:48 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43782 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934667AbdCJLwg (ORCPT ); Fri, 10 Mar 2017 06:52:36 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Eric Dumazet" , "David S. Miller" Date: Fri, 10 Mar 2017 11:46:23 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 334/370] dccp: fix out of bound access in dccp_v4_err() In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2037 Lines: 56 3.16.42-rc1 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 [bwh: Backported to 3.16: use offsetof() + sizeof() instead of offsetofend()] Signed-off-by: Ben Hutchings --- net/dccp/ipv4.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -213,7 +213,7 @@ 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; @@ -223,11 +223,13 @@ 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_BH(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(offsetof(struct dccp_hdr, dccph_sport) + sizeof(dh->dccph_sport) > 8); + BUILD_BUG_ON(offsetof(struct dccp_hdr, dccph_dport) + sizeof(dh->dccph_dport) > 8); + dh = (struct dccp_hdr *)(skb->data + offset); sk = inet_lookup(net, &dccp_hashinfo, iph->daddr, dh->dccph_dport,