Re: [PATCH -next] riscv: Implement thread_struct whitelist for hardened usercopy

[Palmer Dabbelt]

On Thu, 01 Jul 2021 21:54:21 PDT (-0700), tongtiangen@xxxxxxxxxx wrote:
> This whitelists the FPU register state portion of the thread_struct for
> copying to userspace, instead of the default entire struct.
>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> ---
>  arch/riscv/Kconfig                 | 1 +
>  arch/riscv/include/asm/processor.h | 8 ++++++++
>  2 files changed, 9 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 821081bdb8b8..5c26c0726944 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -70,6 +70,7 @@ config RISCV
>  	select HAVE_ARCH_MMAP_RND_BITS if MMU
>  	select HAVE_ARCH_SECCOMP_FILTER
>  	select HAVE_ARCH_TRACEHOOK
> +	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
>  	select HAVE_ASM_MODVERSIONS
>  	select HAVE_CONTEXT_TRACKING
>  	select HAVE_DEBUG_KMEMLEAK
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index 021ed64ee608..46b492c78cbb 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -37,6 +37,14 @@ struct thread_struct {
>  	unsigned long bad_cause;
>  };
>
> +/* Whitelist the fstate from the task_struct for hardened usercopy */
> +static inline void arch_thread_struct_whitelist(unsigned long *offset,
> +						unsigned long *size)
> +{
> +	*offset = offsetof(struct thread_struct, fstate);
> +	*size = sizeof_field(struct thread_struct, fstate);
> +}
> +
>  #define INIT_THREAD {					\
>  	.sp = sizeof(init_stack) + (long)&init_stack,	\
>  }

Thanks, this is on for-next.