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

[David Miller <davem@davemloft.net>]

From: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Date: Mon, 19 Oct 2009 15:02:52 +0900

> I found a deadlock bug in UNIX domain socket, which makes able to DoS
> attack against the local machine by non-root users.
 ...
> 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@hitachi.com>
> Signed-off-by: Masanori Yoshida <masanori.yoshida.tv@hitachi.com>

Looks good, applied, thank you!