Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752235AbdLELrP (ORCPT ); Tue, 5 Dec 2017 06:47:15 -0500 Received: from mail.horus.com ([78.46.148.228]:50191 "EHLO mail.horus.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750855AbdLELrM (ORCPT ); Tue, 5 Dec 2017 06:47:12 -0500 Date: Tue, 5 Dec 2017 12:47:09 +0100 From: Matthias Reichl To: Steven Rostedt Cc: Kees Cook , LKML , Russell King , Eric Anholt , Stefan Wahren , Phil Elwell , linux-rpi-kernel@lists.infradead.org, "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] Arm: mm: ftrace: Only set text back to ro after kernel has been marked ro Message-ID: <20171205114709.f6aj6i426keq2cn5@camel2.lan> Mail-Followup-To: Matthias Reichl , Steven Rostedt , Kees Cook , LKML , Russell King , Eric Anholt , Stefan Wahren , Phil Elwell , linux-rpi-kernel@lists.infradead.org, "linux-arm-kernel@lists.infradead.org" References: <20170823135836.52fb44fc@gandalf.local.home> <20170823150351.606ba09f@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170823150351.606ba09f@gandalf.local.home> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2350 Lines: 85 On Wed, Aug 23, 2017 at 03:03:51PM -0400, Steven Rostedt wrote: > On Wed, 23 Aug 2017 11:48:13 -0700 > Kees Cook wrote: > > > > diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c > > > index ad80548..fd75f38 100644 > > > --- a/arch/arm/mm/init.c > > > +++ b/arch/arm/mm/init.c > > > @@ -745,19 +745,29 @@ static int __mark_rodata_ro(void *unused) > > > return 0; > > > } > > > > > > +static int kernel_set_to_readonly; > > > > Adding a comment here might be a good idea, something like: > > > > /* Has system boot-up reached mark_rodata_ro() yet? */ > > I don't mind adding a comment, but the above is rather self explanatory > (one can easily see that it is set in mark_rodata_ro() with a simple > search). > > If a comment is to be added, something a bit more descriptive of the > functionality of the variable would be appropriate: > > /* > * Ignore modifying kernel text permissions until the kernel core calls > * make_rodata_ro() at system start up. > */ > > I can resend with the comment, or whoever takes this could add it > themselves. Gentle ping: this patch doesn't seem to have landed in upstream trees yet. Is any more work required? It would be nice to have this fix added. Just tested next-20171205 on RPi B+, it oopses when the function tracer is enabled during boot. next-20171205 plus this patch boots up fine. so long, Hias > > -- Steve > > > > > > Otherwise: > > > > Acked-by: Kees Cook > > > > > + > > > void mark_rodata_ro(void) > > > { > > > + kernel_set_to_readonly = 1; > > > + > > > stop_machine(__mark_rodata_ro, NULL, NULL); > > > } > > > > > > void set_kernel_text_rw(void) > > > { > > > + if (!kernel_set_to_readonly) > > > + return; > > > + > > > set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), false, > > > current->active_mm); > > > } > > > > > > void set_kernel_text_ro(void) > > > { > > > + if (!kernel_set_to_readonly) > > > + return; > > > + > > > set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), true, > > > current->active_mm); > > > } > > > > Does arm64 suffer from a similar condition? (It looks like no, as text > > patching is done with a fixmap poke.) > > > > -Kees > > >