[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <1750975839-32463-3-git-send-email-hamzamahfooz@linux.microsoft.com>
Date: Thu, 26 Jun 2025 15:10:39 -0700
From: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>,
Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Yue Haibing <yuehaibing@...wei.com>,
Tanya Agarwal <tanyaagarwal25699@...il.com>,
Kees Cook <kees@...nel.org>,
linux-efi@...r.kernel.org,
linux-security-module@...r.kernel.org,
Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>
Subject: [PATCH 2/2] efi: introduce EFI_KERNEL_LOCK_DOWN_IN_SECURE_BOOT
Add a kernel configuration option to lock down the kernel, to restrict
userspace's ability to modify the running kernel when Secure Boot is
enabled.
Signed-off-by: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>
---
drivers/firmware/efi/Kconfig | 10 ++++++++++
drivers/firmware/efi/efi.c | 9 +++++++++
2 files changed, 19 insertions(+)
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 5fe61b9ab5f9..4e827354e919 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -248,6 +248,16 @@ config EFI_DISABLE_RUNTIME
This default can be overridden by using the efi=runtime option.
+config EFI_KERNEL_LOCK_DOWN_IN_SECURE_BOOT
+ bool "Lock down the kernel in EFI Secure Boot mode"
+ default n
+ depends on EFI
+ depends on SECURITY_LOCKDOWN_LSM
+ select SECURITY_LOCKDOWN_LSM_EARLY
+ help
+ Enabling this option results in kernel lockdown being
+ set in integrity mode if EFI Secure Boot is enabled.
+
config EFI_COCO_SECRET
bool "EFI Confidential Computing Secret Area Support"
help
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 7309394b8fc9..b7a5fc79b065 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -427,6 +427,15 @@ static int __init efisubsys_init(void)
}
}
+#ifdef CONFIG_EFI_KERNEL_LOCK_DOWN_IN_SECURE_BOOT
+ if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
+ if (efi_get_secureboot_mode(efi.get_variable) ==
+ efi_secureboot_mode_enabled)
+ security_lock_kernel_down("EFI Secure Boot",
+ LOCKDOWN_INTEGRITY_MAX);
+ }
+#endif
+
if (efi_rt_services_supported(EFI_RT_SUPPORTED_TIME_SERVICES))
platform_device_register_simple("rtc-efi", 0, NULL, 0);
--
2.49.0
Powered by blists - more mailing lists