Re: [PATCH] powerpc: Default to enabling STRICT_KERNEL_RWX

[Christophe LEROY]

Le 05/10/2017 Ã 05:45, Kees Cook a ÃcritÂ:
> 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.

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