From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753876AbaENIVm (ORCPT ); Wed, 14 May 2014 04:21:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:9612 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753769AbaENIVd (ORCPT ); Wed, 14 May 2014 04:21:33 -0400 Date: Wed, 14 May 2014 16:23:00 +0800 From: Dave Young To: Mateusz Guzik Cc: keescook@chromium.org, hpa@zytor.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] x86: kaslr to avoid setup_data regions Message-ID: <20140514082300.GH2039@darkstar.nay.redhat.com> References: <20140514080201.GA18922@dhcp-16-198.nay.redhat.com> <20140514081325.GA8992@mguzik.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140514081325.GA8992@mguzik.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/14/14 at 10:13am, Mateusz Guzik wrote: > On Wed, May 14, 2014 at 04:02:01PM +0800, Dave Young wrote: > > X86 will pass setup_data region while necessary, these regions could be > > overwitten by kernel due to kaslr. > > > > Thus iterate and add setup regions to mem_avoid[] in this patch. > > Set max mem avoid entries 32, hopefully it will be enough. > > > > Signed-off-by: Dave Young > > --- > > arch/x86/boot/compressed/aslr.c | 30 ++++++++++++++++++++++++++++-- > > 1 file changed, 28 insertions(+), 2 deletions(-) > > > > Index: linux-2.6/arch/x86/boot/compressed/aslr.c > > =================================================================== > > --- linux-2.6.orig/arch/x86/boot/compressed/aslr.c > > +++ linux-2.6/arch/x86/boot/compressed/aslr.c > > @@ -110,8 +110,9 @@ struct mem_vector { > > unsigned long size; > > }; > > > > -#define MEM_AVOID_MAX 5 > > +#define MEM_AVOID_MAX 32 > > static struct mem_vector mem_avoid[MEM_AVOID_MAX]; > > +static int mem_avoid_nr; > > > > static bool mem_contains(struct mem_vector *region, struct mem_vector *item) > > { > > @@ -135,6 +136,28 @@ static bool mem_overlaps(struct mem_vect > > return true; > > } > > > > +static void mem_avoid_setup_data(void) > > +{ > > + struct setup_data *data; > > + u64 pa_data; > > + > > + if (mem_avoid_nr >= MEM_AVOID_MAX) { > > + debug_putstr("KASLR: too many setup_data ranges.\n"); > > + return; > > + } > > + > > + pa_data = real_mode->hdr.setup_data; > > + while (pa_data) { > > + data = (struct setup_data *)pa_data; > > + if (pa_data < CONFIG_RANDOMIZE_BASE_MAX_OFFSET) { > > + mem_avoid[mem_avoid_nr].start = pa_data; > > + mem_avoid[mem_avoid_nr].size = sizeof(*data) + data->len; > > + mem_avoid_nr++; > > + } > > + pa_data = data->next; > > + } > > +} > > + > > I have no idea if this real_mode->hdr.setup_data examination is correct, > so not commenting on that. > > What prevents the loop from overflowing the table? Ooooops, the checking should be in the loop instead of our of it. Will repost. Thanks for catching. Dave