Re: [PATCH v11 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

Borislav Petkov
2024-02-19T09:26:16Z

On Sun, Feb 04, 2024 at 04:01:42PM +0800, 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@linux.alibaba.com>
> ---
> drivers/acpi/apei/ghes.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 7b7c605166e0..0892550732d4 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -806,6 +806,15 @@ 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) {
> + pr_err("Sending SIGBUS to current task due to memory error not recovered");
> + force_sig(SIGBUS);
> + }

Except that there are a bunch of CXL GUIDs being handled there too and
this will sigbus those processes now automatically.

Lemme add the whole bunch from

671a794c33c6 ("acpi/ghes: Process CXL Component Events")

for comment to Cc.

--
Regards/Gruss,
Boris.