netdev - Re: [PATCH net] tcp: fastopen: tcp_connect() must refresh the route

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Date:   Tue, 08 Aug 2017 21:04:17 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org, weiwan@...gle.com, ycheng@...gle.com,
        dvyukov@...gle.com
Subject: Re: [PATCH net] tcp: fastopen: tcp_connect() must refresh the route

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

> From: Eric Dumazet <edumazet@...gle.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@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable.