From: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
To: linux-kernel@vger.kernel.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Yue Haibing <yuehaibing@huawei.com>,
Tanya Agarwal <tanyaagarwal25699@gmail.com>,
Kees Cook <kees@kernel.org>,
linux-efi@vger.kernel.org, linux-security-module@vger.kernel.org,
Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
Subject: [PATCH 2/2] efi: introduce EFI_KERNEL_LOCK_DOWN_IN_SECURE_BOOT
Date: Thu, 26 Jun 2025 15:10:39 -0700 [thread overview]
Message-ID: <1750975839-32463-3-git-send-email-hamzamahfooz@linux.microsoft.com> (raw)
In-Reply-To: <1750975839-32463-1-git-send-email-hamzamahfooz@linux.microsoft.com>
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@linux.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
next prev parent reply other threads:[~2025-06-26 22:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-26 22:10 [PATCH 0/2] Secure Boot lock down Hamza Mahfooz
2025-06-26 22:10 ` [PATCH 1/2] security: introduce security_lock_kernel_down() Hamza Mahfooz
2025-06-26 22:10 ` Hamza Mahfooz [this message]
2025-07-16 21:29 ` [PATCH 0/2] Secure Boot lock down Hamza Mahfooz
2025-07-17 18:22 ` Paul Moore
2025-07-24 12:59 ` Nicolas Bouchinet
2025-07-24 14:13 ` sergeh
2025-07-24 15:03 ` Nicolas Bouchinet
2025-07-25 2:43 ` Paul Moore
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1750975839-32463-3-git-send-email-hamzamahfooz@linux.microsoft.com \
--to=hamzamahfooz@linux.microsoft.com \
--cc=ardb@kernel.org \
--cc=jmorris@namei.org \
--cc=kees@kernel.org \
--cc=linux-efi@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=paul@paul-moore.com \
--cc=serge@hallyn.com \
--cc=tanyaagarwal25699@gmail.com \
--cc=yuehaibing@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®