From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753876AbbJPJtn (ORCPT <rfc822;w@1wt.eu>);
	Fri, 16 Oct 2015 05:49:43 -0400
Received: from ozlabs.org ([103.22.144.67]:51613 "EHLO ozlabs.org"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1752034AbbJPJtm (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 16 Oct 2015 05:49:42 -0400
Message-ID: <1444988979.12954.1.camel@ellerman.id.au>
Subject: Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially
 freed memory
From: Michael Ellerman <mpe@ellerman.id.au>
To: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: benh@kernel.crashing.org, paulus@samba.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Date: Fri, 16 Oct 2015 20:49:39 +1100
In-Reply-To: <5620971D.8040103@wanadoo.fr>
References: <20151014040011.8AB1514110A@ozlabs.org>
	 <1444888580-12966-1-git-send-email-christophe.jaillet@wanadoo.fr>
	 <1444890977.5970.4.camel@ellerman.id.au> <5620971D.8040103@wanadoo.fr>
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.16.5-1ubuntu2 
Mime-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, 2015-10-16 at 08:20 +0200, Christophe JAILLET wrote:
> Le 15/10/2015 08:36, Michael Ellerman a écrit :
> > On Thu, 2015-10-15 at 07:56 +0200, Christophe JAILLET wrote:
> > > Use 'of_property_read_u32()' instead of
> > > 'of_get_property()'+pointer
> > > dereference in order to avoid access to potentially freed memory.
> > > 
> > > Use 'of_get_next_parent()' to simplify the while() loop and avoid
> > > the
> > > need of a temp variable.
> > > 
> > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > > ---
> > > v2: Use of_property_read_u32 instead of of_get_property+pointer
> > > dereference
> > > *** Untested ***
> > Thanks.
> > 
> > Can someone with an mpc5xxx test this?
> 
> Hi,
> I don't think it is an issue, but while looking at another similar 
> patch, I noticed that the proposed patch adds a call to
> be32_to_cpup() 
> (within of_property_read_u32).
> Apparently, powerPC is a BE architecture, so this call should be a no
> -op.
> 
> Just wanted to point it out, in case of.

Hi Christoph,

I'm not sure I follow.

The device tree is always big endian, but of_property_read_u32() does
the
conversion to CPU endian for you already. That is one of the advantages
of
using it.

cheers