From: David Howells <dhowells@redhat.com>
Date: Wed, 8 Nov 2017 15:11:37 +0000
Subject: [29/29] efi: Lock down the kernel if booted in secure boot mode
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=a364bd945ffc141a7b17cb331bda0d8ad68f7e72

UEFI Secure Boot provides a mechanism for ensuring that the firmware will
only load signed bootloaders and kernels.  Certain use cases may also
require that all kernel modules also be signed.  Add a configuration option
that to lock down the kernel - which includes requiring validly signed
modules - if the kernel is secure-booted.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc: linux-efi@vger.kernel.org
---
 arch/x86/kernel/setup.c |  6 ++++--
 security/Kconfig        | 14 ++++++++++++++
 security/lock_down.c    |  1 +
 3 files changed, 19 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -65,6 +65,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/ctype.h>
 #include <linux/uaccess.h>
+#include <linux/security.h>
 
 #include <linux/percpu.h>
 #include <linux/crash_dump.h>
@@ -1005,6 +1006,9 @@ void __init setup_arch(char **cmdline_p)
 	if (efi_enabled(EFI_BOOT))
 		efi_init();
 
+	efi_set_secure_boot(boot_params.secure_boot);
+	init_lockdown();
+
 	dmi_scan_machine();
 	dmi_memdev_walk();
 	dmi_set_dump_stack_arch_desc();
@@ -1159,8 +1163,6 @@ void __init setup_arch(char **cmdline_p)
 	/* Allocate bigger log buffer */
 	setup_log_buf(1);
 
-	efi_set_secure_boot(boot_params.secure_boot);
-
 	reserve_initrd();
 
 	acpi_table_upgrade();
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -247,6 +247,21 @@ config LOCK_DOWN_KERNEL
 	  turns off various features that might otherwise allow access to the
 	  kernel image (eg. setting MSR registers).
 
+config LOCK_DOWN_IN_EFI_SECURE_BOOT
+	bool "Lock down the kernel in EFI Secure Boot mode"
+	default n
+	select LOCK_DOWN_KERNEL
+	depends on EFI
+	help
+	  UEFI Secure Boot provides a mechanism for ensuring that the firmware
+	  will only load signed bootloaders and kernels.  Secure boot mode may
+	  be determined from EFI variables provided by the system firmware if
+	  not indicated by the boot parameters.
+
+	  Enabling this option turns on results in kernel lockdown being
+	  triggered if EFI Secure Boot is set.
+
+
 source security/selinux/Kconfig
 source security/smack/Kconfig
 source security/tomoyo/Kconfig
--- a/security/lock_down.c
+++ b/security/lock_down.c
@@ -11,6 +11,7 @@
 
 #include <linux/security.h>
 #include <linux/export.h>
+#include <linux/efi.h>
 
 static __ro_after_init bool kernel_locked_down;
 
