Commit 6ea0e815 authored Aug 19, 2019 by Linn Crosetto Committed by James Morris Aug 19, 2019

acpi: Disable ACPI table override if the kernel is locked down



>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 lockdown is enabled, 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 <lcrosetto@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: linux-acpi@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>

parent 41fa1ee9

drivers/acpi/tables.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -20,6 +20,7 @@
		#include <linux/memblock.h>
		#include <linux/earlycpio.h>
		#include <linux/initrd.h>
		#include <linux/security.h>
		#include "internal.h"

		#ifdef CONFIG_ACPI_CUSTOM_DSDT
		@@ -577,6 +578,11 @@ void __init acpi_table_upgrade(void)
		if (table_nr == 0)
		return;

		if (security_locked_down(LOCKDOWN_ACPI_TABLES)) {
		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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