linux-kernel - Re: [PATCH 1/3] Kconfig: Create "kernel hardening" config area

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Message-ID: <CAGXu5j+S1He+2sR+cvjV=2xAcCHQoRv942+OAEDprMmB=TF4Bw@mail.gmail.com>
Date:   Thu, 11 Apr 2019 09:59:04 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Sandeep Patil <sspatil@...roid.com>,
        Laura Abbott <labbott@...hat.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Alexander Popov <alpopov@...ecurity.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Emese Revfy <re.emese@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 1/3] Kconfig: Create "kernel hardening" config area

On Thu, Apr 11, 2019 at 1:51 AM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> On Thu, Apr 11, 2019 at 1:16 AM Kees Cook <keescook@...omium.org> wrote:
> > diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
> > index 74271dba4f94..01874ef0f883 100644
> > --- a/scripts/gcc-plugins/Kconfig
> > +++ b/scripts/gcc-plugins/Kconfig
> > @@ -13,10 +13,11 @@ config HAVE_GCC_PLUGINS
> >           An arch should select this symbol if it supports building with
> >           GCC plugins.
> >
> > -menuconfig GCC_PLUGINS
> > -       bool "GCC plugins"
> > +config GCC_PLUGINS
> > +       bool
>
>
> This will flatten the plugin config options.
>
> If you want to keep the current menu structure, you can do:
>
> menu "GCC plugins"
> ...
> endmenu

Ah, excellent point. I'll fix this.

> Another side-effect is Kbuild will descend into scripts/gcc-plugins/
> even when no plugin is selected.
> It is not a big build speed regression, though.

I suspect the plugins Kconfig may disppear eventually with the options
spread around other Kconfigs (since now the plugin capability is known
at config time).

> > diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> > new file mode 100644
> > index 000000000000..8223a8ab1a12
> > --- /dev/null
> > +++ b/security/Kconfig.hardening
> > @@ -0,0 +1,94 @@
> > +menu "Kernel hardening options"
> > +
> > +config GCC_PLUGIN_STRUCTLEAK
> > +       bool
> > +       depends on GCC_PLUGIN_STRUCTLEAK_USER || GCC_PLUGIN_STRUCTLEAK_BYREF || GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
>
>
> I think this 'depends on' is unnecessary.

Okay, I'll drop it.

>
>
> > +menu "Memory initialization"
> > +
> > +choice
> > +       prompt "Initialize kernel stack variables at function entry"
> > +       depends on CC_HAS_AUTO_VAR_INIT || GCC_PLUGINS
>
> Nit:
> CC_HAS_AUTO_VAR_INIT does not exist at this point.
> I will be added by 3/3.

Oops, yes, I split this chunk in the wrong place. I will fix it.

Thanks!

-- 
Kees Cook