From d7e4e1b3e68f6a250474eacb622f384a3b6140d2 Mon Sep 17 00:00:00 2001
From: krw <krw@openbsd.org>
Date: Thu, 12 May 2022 11:04:27 +0000
Subject: [PATCH] Prevent '-u' when operating on GPT formatted disks, as the
 equivalent 'update' editing command already is.

Avoids the destruction of the GPT when the preventative MBR
is overwritten with the default MBR.

ok deraadt@
---
 sbin/fdisk/fdisk.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sbin/fdisk/fdisk.c b/sbin/fdisk/fdisk.c
index c9b58c78c53..2dd0704c238 100644
--- a/sbin/fdisk/fdisk.c
+++ b/sbin/fdisk/fdisk.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: fdisk.c,v 1.144 2022/04/24 12:13:37 krw Exp $	*/
+/*	$OpenBSD: fdisk.c,v 1.145 2022/05/12 11:04:27 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -187,6 +187,8 @@ main(int argc, char *argv[])
 			Xwrite(NULL, &mbr);
 		break;
 	case INIT_MBRBOOTCODE:
+		if (GPT_read(ANYGPT) == 0)
+			errx(1, "-u not available for GPT");
 		if (MBR_read(0, 0, &mbr))
 			errx(1, "Can't read MBR!");
 		memcpy(mbr.mbr_code, default_dmbr.dmbr_boot,
-- 
2.20.1