linux-kernel - Re: [PATCH 17/27] acpi: Disable APEI error injection if the kernel is locked down

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Date:   Fri, 20 Oct 2017 14:47:05 +0800
From:   joeyli <jlee@...e.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-security-module@...r.kernel.org, gnomes@...rguk.ukuu.org.uk,
        linux-efi@...r.kernel.org, matthew.garrett@...ula.com,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        jforbes@...hat.com
Subject: Re: [PATCH 17/27] acpi: Disable APEI error injection if the kernel
 is locked down

On Thu, Oct 19, 2017 at 03:52:41PM +0100, David Howells wrote:
> From: Linn Crosetto <linn@....com>
> 
> ACPI provides an error injection mechanism, EINJ, for debugging and testing
> the ACPI Platform Error Interface (APEI) and other RAS features.  If
> supported by the firmware, ACPI specification 5.0 and later provide for a
> way to specify a physical memory address to which to inject the error.
> 
> Injecting errors through EINJ can produce errors which to the platform are
> indistinguishable from real hardware errors.  This can have undesirable
> side-effects, such as causing the platform to mark hardware as needing
> replacement.
> 
> While it does not provide a method to load unauthenticated privileged code,
> the effect of these errors may persist across reboots and affect trust in
> the underlying hardware, so disable error injection through EINJ if
> the kernel is locked down.
> 
> Signed-off-by: Linn Crosetto <linn@....com>
> Signed-off-by: David Howells <dhowells@...hat.com>

I have reviewed this patch. Please feel free to add:

Reviewed-by: "Lee, Chun-Yi" <jlee@...e.com>

Thanks!
Joey Lee

> cc: linux-acpi@...r.kernel.org
> ---
> 
>  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 b38737c83a24..6d71e1e97b20 100644
> --- a/drivers/acpi/apei/einj.c
> +++ b/drivers/acpi/apei/einj.c
> @@ -518,6 +518,9 @@ static int einj_error_inject(u32 type, u32 flags, u64 param1, u64 param2,
>  	int rc;
>  	u64 base_addr, size;
>  
> +	if (kernel_is_locked_down("ACPI error injection"))
> +		return -EPERM;
> +
>  	/* If user manually set "flags", make sure it is legal */
>  	if (flags && (flags &
>  		~(SETWA_FLAGS_APICID|SETWA_FLAGS_MEM|SETWA_FLAGS_PCIE_SBDF)))
> 
> --
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