Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755946AbcJZAqt (ORCPT ); Tue, 25 Oct 2016 20:46:49 -0400 Received: from ozlabs.org ([103.22.144.67]:48563 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753777AbcJZAqq (ORCPT ); Tue, 25 Oct 2016 20:46:46 -0400 From: Rusty Russell To: AKASHI Takahiro , Kees Cook Cc: "kernel-hardening\@lists.openwall.com" , LKML , "Jessica Yu" Subject: Re: [kernel-hardening] [PATCH] module: extend 'rodata=off' boot cmdline parameter to module mappings In-Reply-To: <20161021011210.GT19531@linaro.org> References: <20161020062458.14014-1-takahiro.akashi@linaro.org> <20161021011210.GT19531@linaro.org> User-Agent: Notmuch/0.21 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Wed, 26 Oct 2016 10:43:32 +1030 Message-ID: <87wpgw3r2r.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2817 Lines: 83 AKASHI Takahiro writes: > On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote: >> On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro >> wrote: >> > The current "rodata=off" parameter disables read-only kernel mappings >> > under CONFIG_DEBUG_RODATA: >> > commit d2aa1acad22f ("mm/init: Add 'rodata=off' boot cmdline parameter >> > to disable read-only kernel mappings") >> > >> > This patch is a logical extension to module mappings ie. read-only mappings >> > at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX >> > (mainly for debug use). Please note, however, that it only affects RO/RW >> > permissions, keeping NX set. This patch looks good (except the minor issues noted by Kees); please CC the followup version to Jessica as new module maintainer. Thanks! Rusty. >> > >> > This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory >> > (always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64. >> > >> > Suggested-by: Mark Rutland >> > Signed-off-by: AKASHI Takahiro >> > Cc: Rusty Russell >> > --- >> > v1: >> > * remove RFC's "module_ronx=" and merge it with "rodata=" >> > * always keep NX set if CONFIG_SET_MODULE_RONX >> > >> > include/linux/init.h | 3 ++- >> > init/main.c | 2 +- >> > kernel/module.c | 21 ++++++++++++++++++--- >> > 3 files changed, 21 insertions(+), 5 deletions(-) >> > >> > diff --git a/include/linux/init.h b/include/linux/init.h >> > index e30104c..20aa2eb 100644 >> > --- a/include/linux/init.h >> > +++ b/include/linux/init.h >> > @@ -126,7 +126,8 @@ void prepare_namespace(void); >> > void __init load_default_modules(void); >> > int __init init_rootfs(void); >> > >> > -#ifdef CONFIG_DEBUG_RODATA >> > +#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX) >> > +extern bool rodata_enabled; >> > void mark_rodata_ro(void); >> > #endif >> > >> > diff --git a/init/main.c b/init/main.c >> > index 2858be7..92db2f3 100644 >> > --- a/init/main.c >> > +++ b/init/main.c >> > @@ -915,7 +915,7 @@ static int try_to_run_init_process(const char *init_filename) >> > static noinline void __init kernel_init_freeable(void); >> > >> > #ifdef CONFIG_DEBUG_RODATA >> > -static bool rodata_enabled = true; >> > +bool rodata_enabled = true; >> >> Is there a mismatch here between the extern ifdef and the bool ifdef? >> I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too? > > Yes. > >> Also, can you mark this as __ro_after_init, since nothing changes it >> after the kernel command line is parsed? > > Yes, yes. > > Thanks, > -Takahiro AKASHI > >> Otherwise, this looks fine to me. >> >> -Kees >> >> >> -- >> Kees Cook >> Nexus Security