Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759427AbcCVLL1 (ORCPT ); Tue, 22 Mar 2016 07:11:27 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56635 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758744AbcCVKmQ (ORCPT ); Tue, 22 Mar 2016 06:42:16 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Eric Dumazet , Jerry Chu , Yuchung Cheng , "David S. Miller" , Luis Henriques Subject: [PATCH 3.16.y-ckt 060/142] tcp: fix NULL deref in tcp_v4_send_ack() Date: Tue, 22 Mar 2016 10:39:49 +0000 Message-Id: <1458643271-4227-61-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1458643271-4227-1-git-send-email-luis.henriques@canonical.com> References: <1458643271-4227-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3843 Lines: 97 3.16.7-ckt26 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Eric Dumazet commit e62a123b8ef7c5dc4db2c16383d506860ad21b47 upstream. Neal reported crashes with this stack trace : RIP: 0010:[] tcp_v4_send_ack+0x41/0x20f ... CR2: 0000000000000018 CR3: 000000044005c000 CR4: 00000000001427e0 ... [] tcp_v4_reqsk_send_ack+0xa5/0xb4 [] tcp_check_req+0x2ea/0x3e0 [] tcp_rcv_state_process+0x850/0x2500 [] tcp_v4_do_rcv+0x141/0x330 [] sk_backlog_rcv+0x21/0x30 [] tcp_recvmsg+0x75d/0xf90 [] inet_recvmsg+0x80/0xa0 [] sock_aio_read+0xee/0x110 [] do_sync_read+0x6f/0xa0 [] SyS_read+0x1e1/0x290 [] system_call_fastpath+0x16/0x1b The problem here is the skb we provide to tcp_v4_send_ack() had to be parked in the backlog of a new TCP fastopen child because this child was owned by the user at the time an out of window packet arrived. Before queuing a packet, TCP has to set skb->dev to NULL as the device could disappear before packet is removed from the queue. Fix this issue by using the net pointer provided by the socket (being a timewait or a request socket). IPv6 is immune to the bug : tcp_v6_send_response() already gets the net pointer from the socket if provided. Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path") Reported-by: Neal Cardwell Signed-off-by: Eric Dumazet Cc: Jerry Chu Cc: Yuchung Cheng Acked-by: Neal Cardwell Signed-off-by: David S. Miller [ luis: backported to 3.16: adjusted context ] Signed-off-by: Luis Henriques --- net/ipv4/tcp_ipv4.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 0fd3c84ffaf8..6b4c3e3639bf 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -704,7 +704,8 @@ release_sk1: outside socket context is ugly, certainly. What can I do? */ -static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack, +static void tcp_v4_send_ack(struct net *net, + struct sk_buff *skb, u32 seq, u32 ack, u32 win, u32 tsval, u32 tsecr, int oif, struct tcp_md5sig_key *key, int reply_flags, u8 tos) @@ -719,7 +720,6 @@ static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack, ]; } rep; struct ip_reply_arg arg; - struct net *net = dev_net(skb_dst(skb)->dev); memset(&rep.th, 0, sizeof(struct tcphdr)); memset(&arg, 0, sizeof(arg)); @@ -780,7 +780,8 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb) struct inet_timewait_sock *tw = inet_twsk(sk); struct tcp_timewait_sock *tcptw = tcp_twsk(sk); - tcp_v4_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt, + tcp_v4_send_ack(sock_net(sk), skb, + tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt, tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale, tcp_time_stamp + tcptw->tw_ts_offset, tcptw->tw_ts_recent, @@ -799,8 +800,10 @@ static void tcp_v4_reqsk_send_ack(struct sock *sk, struct sk_buff *skb, /* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV * sk->sk_state == TCP_SYN_RECV -> for Fast Open. */ - tcp_v4_send_ack(skb, (sk->sk_state == TCP_LISTEN) ? - tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt, + u32 seq = (sk->sk_state == TCP_LISTEN) ? tcp_rsk(req)->snt_isn + 1 : + tcp_sk(sk)->snd_nxt; + + tcp_v4_send_ack(sock_net(sk), skb, seq, tcp_rsk(req)->rcv_nxt, req->rcv_wnd, tcp_time_stamp, req->ts_recent,