efi: Restrict efivar_ssdt_load when the kernel is locked down

efivar_ssdt_load allows the kernel to import arbitrary ACPI code from an
EFI variable, which gives arbitrary code execution in ring 0. Prevent
that when the kernel is locked down.

Signed-off-by: Matthew Garrett <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: [email protected]
Signed-off-by: James Morris <[email protected]>
This commit is contained in:
Matthew Garrett 2019-08-19 17:18:04 -07:00 • committed by James Morris
commit 1957a85b00

View file

@ -30,6 +30,7 @@
#include <linux/acpi.h>
#include <linux/ucs2_string.h>
#include <linux/memblock.h>
#include <linux/security.h>
#include <asm/early_ioremap.h>
@ -241,6 +242,11 @@ static void generic_ops_unregister(void)
static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;
static int __init efivar_ssdt_setup(char *str)
{
int ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
if (ret)
return ret;
if (strlen(str) < sizeof(efivar_ssdt))
memcpy(efivar_ssdt, str, strlen(str));
else