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>

diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
index 6def402bf5691f504292b88ff994b9a472fa2bc5..5da36e56b36a1cc29c971934559e5852bed0e7bc 100644 (file)
--- 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;
 }