[RESEND PATCH v18 1/2] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

[Hanjun Guo]

On 2025/4/4 19:20, Shuai Xue wrote:
> Synchronous error was detected as a result of user-space process accessing
> a 2-bit uncorrected error. The CPU will take a synchronous error exception
> such as Synchronous External Abort (SEA) on Arm64. The kernel will queue a
> memory_failure() work which poisons the related page, unmaps the page, and
> then sends a SIGBUS to the process, so that a system wide panic can be
> avoided.
> 
> However, no memory_failure() work will be queued when abnormal synchronous
> errors occur. These errors can include situations such as invalid PA,
> unexpected severity, no memory failure config support, invalid GUID
> section, etc. In such case, the user-space process will trigger SEA again.
> This loop can potentially exceed the platform firmware threshold or even
> trigger a kernel hard lockup, leading to a system reboot.
> 
> Fix it by performing a force kill if no memory_failure() work is queued
> for synchronous errors.
> 
> Signed-off-by: Shuai Xue <xueshuai at linux.alibaba.com>
> Reviewed-by: Jarkko Sakkinen <jarkko at kernel.org>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron at huawei.com>
> Reviewed-by: Yazen Ghannam <yazen.ghannam at amd.com>
> Reviewed-by: Jane Chu <jane.chu at oracle.com>
> ---
>   drivers/acpi/apei/ghes.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index b72772494655..50e4d924aa8b 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -799,6 +799,17 @@ static bool ghes_do_proc(struct ghes *ghes,
>   		}
>   	}
>   
> +	/*
> +	 * If no memory failure work is queued for abnormal synchronous
> +	 * errors, do a force kill.
> +	 */
> +	if (sync && !queued) {
> +		dev_err(ghes->dev,
> +			HW_ERR GHES_PFX "%s:%d: synchronous unrecoverable error (SIGBUS)\n",
> +			current->comm, task_pid_nr(current));
> +		force_sig(SIGBUS);
> +	}

I think it's reasonable to send a force kill to the task when the
synchronous memory error is not recovered.

But I hope this code will not trigger some legacy firmware issues,
let's be careful for this, so can we just introduce arch specific
callbacks for this?

Thanks
Hanjun