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

> From: Eric Dumazet <eduma...@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 <dvyu...@google.com>
> Signed-off-by: Eric Dumazet <eduma...@google.com>

Applied and queued up for -stable.

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