File grub2-verifiers-fix-system-freeze-if-verify-failed.patch of Package grub2.15778

From d0de8b37f651e13886ef0e0fda285a1294adafe8 Mon Sep 17 00:00:00 2001
From: Michael Chang <mchang@suse.com>
Date: Tue, 18 Feb 2020 18:08:18 +0800
Subject: [PATCH] verifiers: Fix calling uninitialized function pointer

The necessary check for NULL before use of function ver->close is not
taking place in the failure path. This patch simply adds the missing
check and fixes the problem that GRUB hangs indefinitely after booting
rogue image without valid signature if secure boot is turned on.

Now it displays like this for booting rogue UEFI image:

  error: bad shim signature
  error: you need to load the kernel first

  Press any key to continue...

and then you can go back to boot menu by pressing any key or after a few
seconds expired.

Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/commands/verifiers.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/grub-core/commands/verifiers.c b/grub-core/commands/verifiers.c
index 0dde48182..7b9297cd3 100644
--- a/grub-core/commands/verifiers.c
+++ b/grub-core/commands/verifiers.c
@@ -196,7 +196,8 @@ grub_verifiers_open (grub_file_t io, enum grub_file_type type)
   return ret;
 
  fail:
-  ver->close (context);
+  if (ver->close)
+    ver->close (context);
  fail_noclose:
   verified_free (verified);
   grub_free (ret);
-- 
2.16.4