x86/ima: Check EFI_RUNTIME_SERVICES before using

Checking efi_enabled(EFI_BOOT) is not sufficient to ensure that
EFI runtime services are available, e.g. if efi=noruntime is used.

Without this, I get an oops on a PREEMPT_RT kernel where efi=noruntime is
the default.

Fixes: 399574c64eaf94e8 ("x86/ima: retry detecting secure boot mode")
Cc: stable@vger.kernel.org  (linux-5.0)
Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

diff --git a/arch/x86/kernel/ima_arch.c b/arch/x86/kernel/ima_arch.c
index 85de790..64b973f 100644 (file)
--- a/arch/x86/kernel/ima_arch.c
+++ b/arch/x86/kernel/ima_arch.c
@@ -18,6 +18,11 @@ static enum efi_secureboot_mode get_sb_mode(void)
 
        size = sizeof(secboot);
 
+       if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
+               pr_info("ima: secureboot mode unknown, no efi\n");
+               return efi_secureboot_mode_unknown;
+       }
+
        /* Get variable contents into buffer */
        status = efi.get_variable(efi_SecureBoot_name, &efi_variable_guid,
                                  NULL, &size, &secboot);