From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932927Ab2JSQDP (ORCPT ); Fri, 19 Oct 2012 12:03:15 -0400 Received: from mail-vb0-f46.google.com ([209.85.212.46]:45598 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932191Ab2JSQDN (ORCPT ); Fri, 19 Oct 2012 12:03:13 -0400 MIME-Version: 1.0 In-Reply-To: <1350647942-5260-1-git-send-email-ffainelli@freebox.fr> References: <1350647942-5260-1-git-send-email-ffainelli@freebox.fr> Date: Fri, 19 Oct 2012 09:03:12 -0700 X-Google-Sender-Auth: 9bzmEP9Yzgcom05tF17DuCsobKg Message-ID: Subject: Re: [PATCH] pstore/ram: fix undefined usage of rounddown_pow_of_two. From: Kees Cook To: Florian Fainelli Cc: cbouatmailru@gmail.com, ccross@android.com, tony.luck@intel.com, linux-kernel@vger.kernel.org, Maxime Bizon , stable@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 19, 2012 at 4:59 AM, Florian Fainelli wrote: > From: Maxime Bizon > > record_size / console_size / ftrace_size can be 0 (this is how you > disable the feature), but rounddown_pow_of_two(0) is undefined. This problem > has been present since commit 1894a253 (ramoops: Move to fs/pstore/ram.c). > > Signed-off-by: Maxime Bizon > Signed-off-by: Florian Fainelli > CC: stable@vger.kernel.org > --- > fs/pstore/ram.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c > index 1a4f6da..0c2ae26 100644 > --- a/fs/pstore/ram.c > +++ b/fs/pstore/ram.c > @@ -374,10 +374,14 @@ static int __devinit ramoops_probe(struct platform_device *pdev) > goto fail_out; > } > > - pdata->mem_size = rounddown_pow_of_two(pdata->mem_size); > - pdata->record_size = rounddown_pow_of_two(pdata->record_size); > - pdata->console_size = rounddown_pow_of_two(pdata->console_size); > - pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size); > + if (pdata->mem_size) > + pdata->mem_size = rounddown_pow_of_two(pdata->mem_size); Nice catch! Instead of the == 0 check, what about using !is_power_of_2(size) ? -Kees -- Kees Cook Chrome OS Security