netdev - Re: net/ipv4: division by 0 in tcp_select

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Date:   Fri, 03 Mar 2017 12:56:01 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Cong Wang <xiyou.wangcong@...il.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net/ipv4: division by 0 in tcp_select_window

On Fri, 2017-03-03 at 10:25 -0800, Eric Dumazet wrote:
> On Fri, Mar 3, 2017 at 10:10 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> > Hello,
> >
> > The following program triggers division by 0 in tcp_select_window:
> >
> > https://gist.githubusercontent.com/dvyukov/ef28c0fd2ab57a655508ef7621b12e6c/raw/079011e2a9523a390b0621cbc1e5d9d5e637fd6d/gistfile1.txt
> 
> Yeah, tcp_disconnect() should never have existed in the first place.
> 
> We'll send a patch, unless you take care of this before us .

Could you try this first patch ?

Probably others will also be needed.

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 40d893556e6701ace6a02903e53c45822d6fa56d..2187ebf1f270d19e6dd019b8f9df5eef8d018e03 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -552,7 +552,8 @@ void tcp_write_timer_handler(struct sock *sk)
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	int event;
 
-	if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
+	if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
+	    !icsk->icsk_pending)
 		goto out;
 
 	if (time_after(icsk->icsk_timeout, jiffies)) {