From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net] tcp: fastopen: tcp_connect() must refresh the route
Date: Tue, 08 Aug 2017 21:04:17 -0700 (PDT)
Message-ID: <20170808.210417.1748836096752126270.davem@davemloft.net>
References: <1502181718.4487.9.camel@edumazet-glaptop3.roam.corp.google.com>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Cc: netdev@vger.kernel.org, weiwan@google.com, ycheng@google.com,
        dvyukov@google.com
To: eric.dumazet@gmail.com
Return-path: <netdev-owner@vger.kernel.org>
Received: from shards.monkeyblade.net ([184.105.139.130]:60254 "EHLO
        shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751957AbdHIEES (ORCPT
        <rfc822;netdev@vger.kernel.org>); Wed, 9 Aug 2017 00:04:18 -0400
In-Reply-To: <1502181718.4487.9.camel@edumazet-glaptop3.roam.corp.google.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 08 Aug 2017 01:41:58 -0700

> From: Eric Dumazet <edumazet@google.com>
> 
> With new TCP_FASTOPEN_CONNECT socket option, there is a possibility
> to call tcp_connect() while socket sk_dst_cache is either NULL
> or invalid.
> 
>  +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
>  +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
>  +0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
>  +0 connect(4, ..., ...) = 0
> 
> << sk->sk_dst_cache becomes obsolete, or even set to NULL >>
> 
>  +1 sendto(4, ..., 1000, MSG_FASTOPEN, ..., ...) = 1000
> 
> 
> We need to refresh the route otherwise bad things can happen,
> especially when syzkaller is running on the host :/
> 
> Fixes: 19f6d3f3c8422 ("net/tcp-fastopen: Add new API support")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied and queued up for -stable.