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Subject: Re: [V9fs-developer] [PATCH] /net/9p/trans_fd.c: fix race-condition
 by flushing workqueue before the kfree()
To:     Tomas Bortoli <tomasbortoli@gmail.com>, <ericvh@gmail.com>,
        <rminnich@sandia.gov>, <lucho@ionkov.net>
References: <20180719200607.30286-1-tomasbortoli@gmail.com>
CC:     <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <syzkaller@googlegroups.com>,
        <v9fs-developer@lists.sourceforge.net>, <davem@davemloft.net>
From:   jiangyiwen <jiangyiwen@huawei.com>
Message-ID: <5B519EB0.8000700@huawei.com>
Date:   Fri, 20 Jul 2018 16:34:56 +0800
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On 2018/7/20 4:06, Tomas Bortoli wrote:
> The patch adds the flush in p9_mux_poll_stop() as it the function used by
> p9_conn_destroy(), in turn called by p9_fd_close() to stop the async
> polling associated with the data regarding the connection.
> 
> Signed-off-by: Tomas Bortoli <tomasbortoli@gmail.com>
> Reported-by: syzbot+39749ed7d9ef6dfb23f6@syzkaller.appspotmail.com
> ---
> As shown by Syzbot, it is possible to provoke a race between p9_fd_close() 
> and p9_poll_workfn() that is called to take care of the async read/write work
> to do. To make sure p9_fd_close() frees "trans" when it is not used anymore, 
> it has to explicitly call flush_scheduled_work() before the kfree().
> 
>  net/9p/trans_fd.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
> index bf459ee0feab..76ae134c05d9 100644
> --- a/net/9p/trans_fd.c
> +++ b/net/9p/trans_fd.c
> @@ -185,6 +185,8 @@ static void p9_mux_poll_stop(struct p9_conn *m)
>  	spin_lock_irqsave(&p9_poll_lock, flags);
>  	list_del_init(&m->poll_pending_link);
>  	spin_unlock_irqrestore(&p9_poll_lock, flags);
> +
> +	flush_scheduled_work();

I suggest we should use flush_work(&p9_poll_work), flush_scheduled_work is not
suitable.

Thanks.

>  }
>  
>  /**
>