Re: [RFC 17/17] arm64: compile the kernel with ptrauth -msign-return-address

[Ramana Radhakrishnan]

On 05/10/2018 09:47, Kristina Martsenko wrote:
> Compile all functions with two ptrauth instructions: paciasp in the
> prologue to sign the return address, and autiasp in the epilogue to
> authenticate the return address. This should help protect the kernel
> against attacks using return-oriented programming.
>
> CONFIG_ARM64_PTR_AUTH enables pointer auth for both userspace and the
> kernel.
>
> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> Signed-off-by: Kristina Martsenko <kristina.martsenko@xxxxxxx>
> ---
>   arch/arm64/Makefile | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 106039d25e2f..dbcd43ea99d8 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -56,6 +56,10 @@ KBUILD_AFLAGS	+= $(lseinstr) $(brokengasinst)
>   KBUILD_CFLAGS	+= $(call cc-option,-mabi=lp64)
>   KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)
>   
> +ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
> +KBUILD_CFLAGS	+= -msign-return-address=all

Glad to see this being done and being proposed for mainline.

I can see why you would prefer this though have you guys experimented at 
all with -msign-return-address=non-leaf as well ?

Orthogonally and just fair warning - the command lines for this are also 
being revised to provide ROP and JOP protection using BTI from v8.5-a 
during the GCC-9 timeframe but I suspect that's a different option.

regards
Ramana

Reviewed-by: Ramana Radhakrishnan  <ramana.radhakrishnan@xxxxxxx>