From mboxrd@z Thu Jan  1 00:00:00 1970
From: Heorhi Valakhanovich <valahanovich@tut.by>
Subject: Re: [PATCH] tty: Only hangup once
Date: Tue, 19 Nov 2013 20:19:52 +0300
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To: Peter Hurley <peter@hurleysoftware.com>
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On Tue, 19 Nov 2013 08:46:27 -0500
Peter Hurley <peter@hurleysoftware.com> wrote:

> Would you please test the patch below and confirm the fix?
> 
> --->%---
> Subject: [PATCH] tty: Reset hupped state on open
> 
> A common security idiom is to hangup the current tty (via vhangup())
> after forking but before execing a root shell. This hangs up any
> existing opens which other processes may have and ensures subsequent
> opens have the necessary permissions to open the root shell tty/pty.
> 
> Reset the TTY_HUPPED state after the driver has successfully
> returned the opened tty (perform the reset while the tty is locked
> to avoid racing with concurrent hangups).
> 
> Reported-by: Heorhi Valakhanovich <valahanovich@tut.by>
> Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
> ---
>   drivers/tty/tty_io.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 3a1a01a..c74a00a 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -2086,6 +2086,7 @@ retry_open:
>   			filp->f_op = &tty_fops;
>   		goto retry_open;
>   	}
> +	clear_bit(TTY_HUPPED, &tty->flags);
>   	tty_unlock(tty);
> 
> 

It looks like this patch works. It solves my problem. Thanks.
Will wait for such fix in mainline.

Heorhi.