linux-kernel - Re: [043/127] TTY: ldisc, fix open flag handling

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Date:	Wed, 08 Dec 2010 07:24:46 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Greg KH <gregkh@...e.de>
CC:	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Alan Cox <alan@...ux.intel.com>
Subject: Re: [043/127] TTY: ldisc, fix open flag handling

On 12/08/2010 01:43 AM, Greg KH wrote:
> 2.6.32-stable review patch.  If anyone has any objections, please let us know.
> 
> ------------------
> 
> From: Jiri Slaby <jslaby@...e.cz>
> 
> commit 7f90cfc505d613f4faf096e0d84ffe99208057d9 upstream.
> 
> When a concrete ldisc open fails in tty_ldisc_open, we forget to clear
> TTY_LDISC_OPEN. This causes a false warning on the next ldisc open:
> WARNING: at drivers/char/tty_ldisc.c:445 tty_ldisc_open+0x26/0x38()
> Hardware name: System Product Name
> Modules linked in: ...
> Pid: 5251, comm: a.out Tainted: G        W  2.6.32-5-686 #1
> Call Trace:
>  [<c1030321>] ? warn_slowpath_common+0x5e/0x8a
>  [<c1030357>] ? warn_slowpath_null+0xa/0xc
>  [<c119311c>] ? tty_ldisc_open+0x26/0x38
>  [<c11936c5>] ? tty_set_ldisc+0x218/0x304
> ...
> 
> So clear the bit when failing...
> 
> Introduced in c65c9bc3efa (tty: rewrite the ldisc locking) back in
> 2.6.31-rc1.
> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Alan Cox <alan@...ux.intel.com>
> Reported-by: Sergey Lapin <slapin@...fans.org>
> Tested-by: Sergey Lapin <slapin@...fans.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> 
> ---
>  drivers/char/tty_ldisc.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> --- a/drivers/char/tty_ldisc.c
> +++ b/drivers/char/tty_ldisc.c
> @@ -444,9 +444,14 @@ static void tty_set_termios_ldisc(struct
>  
>  static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
>  {
> +	int ret;
> +
>  	WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
> -	if (ld->ops->open)
> -		return ld->ops->open(tty);
> +	if (ld->ops->open) {
> +		ret = ld->ops->open(tty);
> +		if (ret)
> +			clear_bit(TTY_LDISC_OPEN, &tty->flags);
> +	}
>  	return 0;

Whoops, this should write return ret; (with int ret = 0;)

Do you want me to send the patch against rebased on .32?

thanks,
-- 
js
suse labs
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