From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+willy=40w.ods.org-S261246AbVFCMqw@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S261246AbVFCMqw (ORCPT <rfc822;willy@w.ods.org>);
	Fri, 3 Jun 2005 08:46:52 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261247AbVFCMqw
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Fri, 3 Jun 2005 08:46:52 -0400
Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:63909 "EHLO
	parcelfarce.linux.theplanet.co.uk") by vger.kernel.org with ESMTP
	id S261246AbVFCMqs (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 3 Jun 2005 08:46:48 -0400
Date: Fri, 3 Jun 2005 04:58:16 -0300
From: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
To: Greg KH <greg@kroah.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>, akpm@osdl.org,
       julien.tinnes@francetelecom.com, linux-kernel@vger.kernel.org
Subject: Re: potential-null-pointer-dereference-in-amiga-serial-driver.patch added to -mm tree
Message-ID: <20050603075816.GA9922@logos.cnet>
References: <200505310909.j4V98xBR008727@shell0.pdx.osdl.net> <200505311949.15449.adobriyan@gmail.com> <20050531122215.GA5108@logos.cnet> <20050602052108.GA8042@kroah.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20050602052108.GA8042@kroah.com>
User-Agent: Mutt/1.5.5.1i
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, Jun 01, 2005 at 10:21:08PM -0700, Greg KH wrote:
> On Tue, May 31, 2005 at 09:22:15AM -0300, Marcelo Tosatti wrote:
> > 
> > Hi Alexey,
> > 
> > On Tue, May 31, 2005 at 07:49:15PM +0400, Alexey Dobriyan wrote:
> > > On Tuesday 31 May 2005 13:08, akpm@osdl.org wrote:
> > > > A pointer is dereferenced before it is null-checked.
> > > 
> > > > --- 25/drivers/char/amiserial.c~potential-null-pointer-dereference-in-amiga-serial-driver
> > > > +++ 25-akpm/drivers/char/amiserial.c
> > > 
> > > >  static void rs_put_char(struct tty_struct *tty, unsigned char ch)
> > > >  {
> > > > -	struct async_struct *info = (struct async_struct *)tty->driver_data;
> > > > +	struct async_struct *info;
> > > >  	unsigned long flags;
> > > >  
> > > > +	if (!tty)
> > > > +		return;
> > > 
> > > Can ->put_char be ever called with tty being NULL? From my reading of
> > > drivers/char/n_tty.c it can't.
> > 
> > Nope it can't, but the change makes the code more readable IMO, while handling
> > a NULL "tty" argument properly (which the old version pretends to, but doesnt).
> 
> But unneeded checks like this are not encouraged in the kernel.  As the
> tty pointer can never be null, don't worry about it.

OK - so better just remove the check. Julien, care to follow Greg's 
recommendation and refresh the patch?