Re: [PATCH] powerpc: Default to enabling STRICT_KERNEL_RWX

[christophe leroy]

Le 05/10/2017 Ã 19:30, Kees Cook a ÃcritÂ:
> On Thu, Oct 5, 2017 at 12:49 AM, Christophe LEROY
> <christophe.leroy@xxxxxx> wrote:
> > Le 05/10/2017 Ã 05:45, Kees Cook a Ãcrit :
> > > When available, CONFIG_KERNEL_RWX should be default-enabled.
> >
> >
> > On PPC32, this option implies deactivating BATs and/or LTLB mapping of the
> > linear kernel address space, hence a significant performance degradation.
> >
> > So at least on PPC32, it should remain unselected by default.
>
> Alright, sounds fine to me. Would this be okay?
>
> +       select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if !PPC64

You mean

select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if PPC64

Don't you ?

Christophe

> -Kees
>
> > Christophe
> >
> >
> > > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> > > Cc: Paul Mackerras <paulus@xxxxxxxxx>
> > > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > > ---
> > >    arch/powerpc/Kconfig | 1 +
> > >    1 file changed, 1 insertion(+)
> > >
> > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > > index 809c468edab1..9a549bbfc278 100644
> > > --- a/arch/powerpc/Kconfig
> > > +++ b/arch/powerpc/Kconfig
> > > @@ -178,6 +178,7 @@ config PPC
> > >          select HAVE_ARCH_TRACEHOOK
> > >          select ARCH_HAS_STRICT_KERNEL_RWX       if ((PPC_BOOK3S_64 ||
> > > PPC32) && !RELOCATABLE && !HIBERNATION)
> > >          select ARCH_OPTIONAL_KERNEL_RWX         if
> > > ARCH_HAS_STRICT_KERNEL_RWX
> > > +       select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> > >          select HAVE_CBPF_JIT                    if !PPC64
> > >          select HAVE_CONTEXT_TRACKING            if PPC64
> > >          select HAVE_DEBUG_KMEMLEAK

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