linux-kernel - Re: [PATCH] AF_UNIX: Fix deadlock on connecting to shutdown socket

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Date:	Mon, 19 Oct 2009 11:57:13 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	alan@...rguk.ukuu.org.uk, davem@...emloft.net,
	satoshi.oshima.fk@...achi.com, hidehiro.kawai.ez@...achi.com,
	hideo.aoki.tk@...achi.com
Subject: Re: [PATCH] AF_UNIX: Fix deadlock on connecting to shutdown socket

On 19-10-2009 08:02, Tomoki Sekiyama wrote:
...
> Why this happens:
>  Error checks between unix_socket_connect() and unix_wait_for_peer() are
>  inconsistent. The former calls the latter to wait until the backlog is
>  processed. Despite the latter returns without doing anything when the
>  socket is shutdown, the former doesn't check the shutdown state and
>  just retries calling the latter forever.
> 
> Patch:
>  The patch below adds shutdown check into unix_socket_connect(), so
>  connect(2) to the shutdown socket will return -ECONREFUSED.
> 
> Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
> Signed-off-by: Masanori Yoshida <masanori.yoshida.tv@...achi.com>
> ---
>  net/unix/af_unix.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 51ab497..fc820cd 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -1074,6 +1074,8 @@ restart:
>  	err = -ECONNREFUSED;
>  	if (other->sk_state != TCP_LISTEN)
>  		goto out_unlock;
> +	if (other->sk_shutdown & RCV_SHUTDOWN)
> +		goto out_unlock;

Isn't the shutdown call expected to change sk_state to TCP_CLOSE?

Jarek P.
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