[PATCH v2] riscv: define ILLEGAL_POINTER_VALUE for 64bit

[Jisheng Zhang]

On Sat, Jul 06, 2024 at 01:02:10AM +0800, Jisheng Zhang wrote:
> This is used in poison.h for poison pointer offset. Based on current
> SV39, SV48 and SV57 vm layout, 0xdead000000000000 is a proper value
> that is not mappable, this can avoid potentially turning an oops to
> an expolit.

Maybe I also need to cc stable? This is a secure hole fix patch.

> 
> Signed-off-by: Jisheng Zhang <jszhang at kernel.org>
> ---
> 
> Since v1:
>  - fix typo:s/SV59/SV57
> 
>  arch/riscv/Kconfig | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index c51b32a8ddff..c992eabbd002 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -313,6 +313,11 @@ config GENERIC_HWEIGHT
>  config FIX_EARLYCON_MEM
>  	def_bool MMU
>  
> +config ILLEGAL_POINTER_VALUE
> +	hex
> +	default 0 if 32BIT
> +	default 0xdead000000000000 if 64BIT
> +
>  config PGTABLE_LEVELS
>  	int
>  	default 5 if 64BIT
> -- 
> 2.43.0
> 
> 
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