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

Dan Williams
2024-02-24T19:43:09Z

Borislav Petkov wrote:
> 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.

BTW, I am about to revert all the CXL GUIDs for v6.8 to try again for
v6.9: