Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752257AbdHPT31 (ORCPT ); Wed, 16 Aug 2017 15:29:27 -0400 Received: from mail-it0-f49.google.com ([209.85.214.49]:37133 "EHLO mail-it0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751678AbdHPT30 (ORCPT ); Wed, 16 Aug 2017 15:29:26 -0400 MIME-Version: 1.0 In-Reply-To: <20170816190906.11098-1-labbott@redhat.com> References: <20170816190906.11098-1-labbott@redhat.com> From: Kees Cook Date: Wed, 16 Aug 2017 12:29:24 -0700 X-Google-Sender-Auth: 7rPhzVh7mpMDiptjINGW-kJwpSM Message-ID: Subject: Re: [PATCH] init: Move stack canary initialization after setup_arch To: Laura Abbott Cc: Laura Abbott , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2194 Lines: 72 On Wed, Aug 16, 2017 at 12:09 PM, Laura Abbott wrote: > From: Laura Abbott > > Stack canary intialization involves getting a random number. > Getting this random number may involve accessing caches or other > architectural specific features which are not available until > after the architecture is setup. Move the stack canary initialization > later to accomodate this. > > Signed-off-by: Laura Abbott > Signed-off-by: Laura Abbott > --- > This was a patch I did a while ago as part of some out of tree work to make the > stack canary randomized on arm. The overall work didn't really go anywhere > but there is interest in this part for other approaches to adding randomeness. > > I can re-send with more Cc for anyone else who might have opinions. Combined with adding the kernel cmdline to entropy, this would be desirable. This should probably go via -mm (as far a CCs go). > --- > init/main.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/init/main.c b/init/main.c > index 052481fbe363..c71c4451094c 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -515,11 +515,7 @@ asmlinkage __visible void __init start_kernel(void) > smp_setup_processor_id(); > debug_objects_early_init(); > > - /* > - * Set up the initial canary ASAP: > - */ > add_latent_entropy(); > - boot_init_stack_canary(); Please move the entropy call too, since that should be just before the stack canary initialization (in an effort to gather as much as possible). > > cgroup_init_early(); > > @@ -534,6 +530,10 @@ asmlinkage __visible void __init start_kernel(void) > page_address_init(); > pr_notice("%s", linux_banner); > setup_arch(&command_line); > + /* > + * Set up the the initial canary ASAP: Maybe change "ASAP" to "after reasonable entropy has been gathered" > + */ > + boot_init_stack_canary(); > mm_init_cpumask(&init_mm); > setup_command_line(command_line); > setup_nr_cpu_ids(); > -- > 2.13.0 > Thanks! -Kees -- Kees Cook Pixel Security