Re: [patch 01/18] powerpc: Move stack randomization after syscall_enter_from_user_mode()

[Shrikanth Hegde]

On 7/8/26 12:35 AM, Thomas Gleixner wrote:
> add_random_kstack_offset() is invoked before syscall_enter_from_user_mode()
> establishes state. That's wrong because add_random_kstack_offset() calls
> into instrumentable code.

Thanks for fixing that.

> Move it after syscall_enter_from_user_mode() to ensure that state is
> correctly established.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> ---
>   arch/powerpc/kernel/syscall.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/arch/powerpc/kernel/syscall.c
> +++ b/arch/powerpc/kernel/syscall.c
> @@ -19,8 +19,8 @@ notrace long system_call_exception(struc
>   	long ret;
>   	syscall_fn f;
>   
> -	add_random_kstack_offset();
>   	r0 = syscall_enter_from_user_mode(regs, r0);
> +	add_random_kstack_offset();
>   
>   	if (unlikely(r0 >= NR_syscalls)) {
>   		if (unlikely(trap_is_unsupported_scv(regs))) {

Reviewed-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>