Re: [PATCH V2] powerpc: Restore KUAP registers on syscall restart exit

[Sayali Patil <sayalip@linux.ibm.com>]

On 15/06/26 21:56, Mukesh Kumar Chaurasiya (IBM) wrote:
> During a syscall restart, block KUAP so that pending interrupts can be
> replayed. The original KUAP state is not restored before returning to
> userspace, causing subsequent userspace accesses to fault and eventually
> trigger bad_access_pkey(), crashing the kernel.
> 
> The original KUAP register values are already saved in
> arch_enter_from_user_mode(). Restore them on the syscall restart exit
> path before returning to userspace.
> 
> Fixes: bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature")
> Reported-by: Sayali Patil <sayalip@linux.ibm.com>
> Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
> ---
> V1 -> V2:
> - Commit message rephrased
> V1: https://lore.kernel.org/all/20260613123831.1510474-1-mkchauras@gmail.com
> 
>   arch/powerpc/kernel/interrupt.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
> index 89a999be1352..f04978080837 100644
> --- a/arch/powerpc/kernel/interrupt.c
> +++ b/arch/powerpc/kernel/interrupt.c
> @@ -166,6 +166,7 @@ notrace unsigned long syscall_exit_restart(unsigned long r3, struct pt_regs *reg
>   		goto again;
>   	}
>   
> +	kuap_user_restore(regs);
>   	regs->exit_result |= regs->exit_flags;
>   
>   	return regs->exit_result;

This fixes the reported issue.

Tested-by: Sayali Patil <sayalip@linux.ibm.com>