Re: [RFC PATCH v2 1/2] ARM/mm/fault: always goto bad_area when handling with page faults of kernel address

Xie Yuanbin
2025-11-29T02:34:29Z

On Fri, 28 Nov 2025 13:03:59 +0100, Sebastian Andrzej Siewior wrote:
> what about this:
> diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> index ad58c1e22a5f9..b6b3cd893c808 100644
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -282,10 +282,10 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
> }
>
> /*
> - * If we're in an interrupt or have no user
> - * context, we must not take the fault..
> + * If we're in an interrupt or have no user context, we must not take
> + * the fault. Kernel addresses are handled in do_translation_fault().
> */
> - if (faulthandler_disabled() || !mm)
> + if (faulthandler_disabled() || !mm || addr >= TASK_SIZE)
> goto no_context;
>
> if (user_mode(regs))
>
> We shouldn't be getting here. Above TASK_SIZE there are just fix
> mappings which don't fault and the VMALLOC array which should be handled
> by do_translation_fault(). So this should be only the exception table.
>
> This should also not clash with the previous patches. Would that work
> for everyone?

When it is user_mode(), it should be goto __do_user_fault(), but
no_context goto __do_kernel_fault(). So I think it is not ok.

> Sebastian

Xie Yuanbin