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

Philippe Mathieu-Daudé <[email protected]> Thu, 9 Jul 2026 13:12:57 +0200

Newsgroups	gmane.linux.ports.alpha,gmane.linux.kernel,gmane.linux.ports.ppc64.devel,gmane.linux.ports.riscv,gmane.linux.ports.arm.kernel,gmane.linux.ports.mips,gmane.linux.ports.parisc,gmane.linux.ports.sh.devel,gmane.linux.uml.devel,gmane.linux.kernel.arc,gmane.linux.ports.hexagon,gmane.linux.ports.sparc,gmane.linux.kernel.cross-arch,gmane.linux.documentation
Message-ID	<[email protected]>

On 7/7/26 21:05, 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.
> 
> Move it after syscall_enter_from_user_mode() to ensure that state is
> correctly established.
> 
> Signed-off-by: Thomas Gleixner <[email protected]>
> Cc: Michael Ellerman <[email protected]>
> Cc: Shrikanth Hegde <[email protected]>
> Cc: [email protected]
> ---
>   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: Philippe Mathieu-Daudé <[email protected]>