linux-kernel - [PATCH V2] x86/boot: Fix regression--secure boot info loss from bootparam sanitizing

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Date:   Mon, 2 Sep 2019 00:00:54 +0200
From:   John S Gruber <JohnSGruber@...il.com>
To:     john.hubbard@...il.com
Cc:     "John S. Gruber" <JohnSGruber@...il.com>, bp@...en8.de,
        hpa@...or.com, jhubbard@...dia.com, linux-kernel@...r.kernel.org,
        mingo@...hat.com, tglx@...utronix.de, x86@...nel.org,
        stable@...r.kernel.org
Subject: [PATCH V2] x86/boot: Fix regression--secure boot info loss from
 bootparam sanitizing

From: "John S. Gruber" <JohnSGruber@...il.com>

commit a90118c445cc ("x86/boot: Save fields explicitly, zero out everything
else") now zeros the secure boot information passed by the boot loader or
by the kernel's efi handover mechanism.  Include boot-params.secure_boot
in the preserve field list.

I noted a change in my computers between running signed 5.3-rc4 and 5.3-rc6
with signed kernels using the efi handoff protocol with grub. The kernel
log message "Secure boot enabled" becomes "Secure boot could not be
determined". The efi_main function in arch/x86/boot/compressed/eboot.c sets
this field early but it is subsequently zeroed by the above referenced
commit in the file arch/x86/include/asm/bootparam_utils.h

Fixes: commit a90118c445cc ("x86/boot: Save fields explicitly, zero
out everything else")
Signed-off-by: John S. Gruber <JohnSGruber@...il.com>
---

Adjusted the patch for John Hubbard's comments.

 arch/x86/include/asm/bootparam_utils.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/bootparam_utils.h
b/arch/x86/include/asm/bootparam_utils.h
index 9e5f3c7..981fe92 100644
--- a/arch/x86/include/asm/bootparam_utils.h
+++ b/arch/x86/include/asm/bootparam_utils.h
@@ -70,6 +70,7 @@ static void sanitize_boot_params(struct boot_params
*boot_params)
 			BOOT_PARAM_PRESERVE(eddbuf_entries),
 			BOOT_PARAM_PRESERVE(edd_mbr_sig_buf_entries),
 			BOOT_PARAM_PRESERVE(edd_mbr_sig_buffer),
+			BOOT_PARAM_PRESERVE(secure_boot),
 			BOOT_PARAM_PRESERVE(hdr),
 			BOOT_PARAM_PRESERVE(e820_table),
 			BOOT_PARAM_PRESERVE(eddbuf),
-- 
2.7.4