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SubjectRe: [PATCH 16/27] acpi: Disable ACPI table override if the kernel is locked down
On Thu, Oct 19, 2017 at 03:52:34PM +0100, David Howells wrote:
> From: Linn Crosetto <linn@hpe.com>
>
> >From the kernel documentation (initrd_table_override.txt):
>
> If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible
> to override nearly any ACPI table provided by the BIOS with an
> instrumented, modified one.
>
> When securelevel is set, the kernel should disallow any unauthenticated
> changes to kernel space. ACPI tables contain code invoked by the kernel,
> so do not allow ACPI tables to be overridden if the kernel is locked down.
>
> Signed-off-by: Linn Crosetto <linn@hpe.com>
> Signed-off-by: David Howells <dhowells@redhat.com>

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

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

Thanks!
Joey Lee

> cc: linux-acpi@vger.kernel.org
> ---
>
> drivers/acpi/tables.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
> index 80ce2a7d224b..5cc13c42daf9 100644
> --- a/drivers/acpi/tables.c
> +++ b/drivers/acpi/tables.c
> @@ -526,6 +526,11 @@ void __init acpi_table_upgrade(void)
> if (table_nr == 0)
> return;
>
> + if (kernel_is_locked_down("ACPI table override")) {
> + pr_notice("kernel is locked down, ignoring table override\n");
> + return;
> + }
> +
> acpi_tables_addr =
> memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS,
> all_tables_size, PAGE_SIZE);
>
> --
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