From: David Howells <dhowells@redhat.com>
Date: Tue, 27 Feb 2018 10:04:55 +0000 (+0000)
Subject: efi: Lock down the kernel if booted in secure boot mode
X-Git-Tag: archive/raspbian/5.2.17-1+rpi1^2~32
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=4fab3d9954ee50dd672c2260ca5e712237a0f631;p=linux.git

efi: Lock down the kernel if booted in secure boot mode

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

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0029-efi-Lock-down-the-kernel-if-booted-in-secure-boot-mo.patch
---

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 76e8602c551..56095b3b33f 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -66,6 +66,7 @@
 #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>
@@ -1012,6 +1013,9 @@ 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_setup();
 
 	/*
@@ -1164,8 +1168,6 @@ 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();
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 6a1d90c8088..77af4256ff5 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -40,7 +40,7 @@ static bool debugfs_registered;
 static int debugfs_setattr(struct dentry *dentry, struct iattr *ia)
 {
 	if ((ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) &&
-	    kernel_is_locked_down("debugfs"))
+	    kernel_is_locked_down("changing perms in debugfs"))
 		return -EPERM;
 	return simple_setattr(dentry, ia);
 }
diff --git a/security/Kconfig b/security/Kconfig
index 6428f7d1ed6..c3f9907d98a 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -256,6 +256,20 @@ config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
 	  Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
 	  combination on a wired keyboard.
 
+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"
diff --git a/security/lock_down.c b/security/lock_down.c
index 2c6b00f0c22..527f7e51dc8 100644
--- a/security/lock_down.c
+++ b/security/lock_down.c
@@ -12,6 +12,7 @@
 #include <linux/security.h>
 #include <linux/export.h>
 #include <linux/sysrq.h>
+#include <linux/efi.h>
 #include <asm/setup.h>
 
 #ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ