linux-kernel - Re: [PATCH] powerpc: Default to enabling STRICT_KERNEL

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Message-ID: <6e6bf9ba-d66c-0bcc-358e-fed97b2ca5cd@c-s.fr>
Date:   Thu, 5 Oct 2017 09:49:06 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Cc:     Paul Mackerras <paulus@...ba.org>, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc: Default to enabling STRICT_KERNEL_RWX



Le 05/10/2017 à 05:45, Kees Cook a écrit :
> 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@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>   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
>