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

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>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>
This commit is contained in:
Linn Crosetto 2019-08-19 17:17:52 -07:00 committed by James Morris
parent 41fa1ee9c6
commit 6ea0e815fc
1 changed files with 6 additions and 0 deletions
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6
drivers/acpi/tables.c
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@ -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);