linux-kernel - [PATCH V40 07/29] lockdown: Copy secure_boot flag in boot params across kexec reboot

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Message-Id: <20190820001805.241928-8-matthewgarrett@google.com>
Date:   Mon, 19 Aug 2019 17:17:43 -0700
From:   Matthew Garrett <matthewgarrett@...gle.com>
To:     jmorris@...ei.org
Cc:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Dave Young <dyoung@...hat.com>,
        David Howells <dhowells@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Kees Cook <keescook@...omium.org>, kexec@...ts.infradead.org
Subject: [PATCH V40 07/29] lockdown: Copy secure_boot flag in boot params
 across kexec reboot

From: Dave Young <dyoung@...hat.com>

Kexec reboot in case secure boot being enabled does not keep the secure
boot mode in new kernel, so later one can load unsigned kernel via legacy
kexec_load.  In this state, the system is missing the protections provided
by secure boot.

Adding a patch to fix this by retain the secure_boot flag in original
kernel.

secure_boot flag in boot_params is set in EFI stub, but kexec bypasses the
stub.  Fixing this issue by copying secure_boot flag across kexec reboot.

Signed-off-by: Dave Young <dyoung@...hat.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Matthew Garrett <mjg59@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
cc: kexec@...ts.infradead.org
Signed-off-by: James Morris <jmorris@...ei.org>
---
 arch/x86/kernel/kexec-bzimage64.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index f03237e3f192..5d64a22f99ce 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -180,6 +180,7 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
 	if (efi_enabled(EFI_OLD_MEMMAP))
 		return 0;
 
+	params->secure_boot = boot_params.secure_boot;
 	ei->efi_loader_signature = current_ei->efi_loader_signature;
 	ei->efi_systab = current_ei->efi_systab;
 	ei->efi_systab_hi = current_ei->efi_systab_hi;
-- 
2.23.0.rc1.153.gdeed80330f-goog