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Message-ID: <20161021011210.GT19531@linaro.org> Date: Fri, 21 Oct 2016 10:12:11 +0900 From: AKASHI Takahiro <takahiro.akashi@...aro.org> To: Kees Cook <keescook@...omium.org> Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Rusty Russell <rusty@...tcorp.com.au>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] module: extend 'rodata=off' boot cmdline parameter to module mappings On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote: > On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro > <takahiro.akashi@...aro.org> 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 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 <mark.rutland@....com> > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org> > > Cc: Rusty Russell <rusty@...tcorp.com.au> > > --- > > 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
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