[tip:efi/urgent] efi/libstub: Treat missing SecureBoot variable as Secure Boot disabled

[tip-bot for Ard Biesheuvel <tipbot@zytor.com>]

Commit-ID:  52e51f16407b7b34e26affb500a21e250d9fce0b
Gitweb:     http://git.kernel.org/tip/52e51f16407b7b34e26affb500a21e250d9fce0b
Author:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
AuthorDate: Wed, 1 Mar 2017 19:04:35 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 2 Mar 2017 08:11:18 +0100

efi/libstub: Treat missing SecureBoot variable as Secure Boot disabled

The newly refactored code that infers the firmware's Secure Boot state
prints the following error when the EFI variable 'SecureBoot' does not
exist:

  EFI stub: ERROR: Could not determine UEFI Secure Boot status.

However, this variable is only guaranteed to be defined on a system that
is Secure Boot capable to begin with, and so it is not an error if it is
missing. So report Secure Boot as being disabled in this case, without
printing any error messages.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1488395076-29712-2-git-send-email-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 drivers/firmware/efi/libstub/secureboot.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
index 6def402..5da36e5 100644
--- a/drivers/firmware/efi/libstub/secureboot.c
+++ b/drivers/firmware/efi/libstub/secureboot.c
@@ -45,6 +45,8 @@ enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg)
 	size = sizeof(secboot);
 	status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
 			     NULL, &size, &secboot);
+	if (status == EFI_NOT_FOUND)
+		return efi_secureboot_mode_disabled;
 	if (status != EFI_SUCCESS)
 		goto out_efi_err;
 
@@ -78,7 +80,5 @@ secure_boot_enabled:
 
 out_efi_err:
 	pr_efi_err(sys_table_arg, "Could not determine UEFI Secure Boot status.\n");
-	if (status == EFI_NOT_FOUND)
-		return efi_secureboot_mode_disabled;
 	return efi_secureboot_mode_unknown;
 }