linux-kernel - Re: [PATCH] ACPI, APEI, EINJ: Refuse to inject into the zero page

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Date:   Fri, 22 Apr 2022 16:53:49 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Tony Luck <tony.luck@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, James Morse <james.morse@....com>,
        Borislav Petkov <bp@...en8.de>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        patches@...ts.linux.dev
Subject: Re: [PATCH] ACPI, APEI, EINJ: Refuse to inject into the zero page

On Tue, Apr 19, 2022 at 11:19 PM Tony Luck <tony.luck@...el.com> wrote:
>
> Some validation tests dynamically inject errors into memory used by
> applications to check that the system can recover from a variety of
> poison consumption sceenarios.
>
> But sometimes the virtual address picked by these tests is mapped to
> the zero page.
>
> This causes additional unexpected machine checks as other processes that
> map the zero page also consume the poison.
>
> Disallow injection to the zero page.
>
> Signed-off-by: Tony Luck <tony.luck@...el.com>
>
> ---
> I picked -EADDRINUSE as a somewhat descriptive error code distinct
> fromm -EINVAL used elsewhere in EINJ, but I'm not strongly attached
> to it. Any other non -EINVAL value would be as good an indicator to
> the validation tests that they shouldn't inject to this address.
> ---
>  drivers/acpi/apei/einj.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
> index 95cc2a9f3e05..d4326ec12d29 100644
> --- a/drivers/acpi/apei/einj.c
> +++ b/drivers/acpi/apei/einj.c
> @@ -549,6 +549,9 @@ static int einj_error_inject(u32 type, u32 flags, u64 param1, u64 param2,
>              !arch_is_platform_page(base_addr)))
>                 return -EINVAL;
>
> +       if (is_zero_pfn(base_addr >> PAGE_SHIFT))
> +               return -EADDRINUSE;
> +
>  inject:
>         mutex_lock(&einj_mutex);
>         rc = __einj_error_inject(type, flags, param1, param2, param3, param4);
> --

Applied as 5.19 material, thanks!