Re: [PATCH] powerpc: Default to enabling STRICT_KERNEL_RWX

[Kees Cook]

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

-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
>>
>



-- 
Kees Cook
Pixel Security