From: krw <krw@openbsd.org>
Date: Wed, 16 Jun 2021 15:40:47 +0000 (+0000)
Subject: Ensure that the '-i' command line option and the 'reinit [mbr]'
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=c94b0391c2425cf229f3d2fc83575cde3a9c2897;p=openbsd

Ensure that the '-i' command line option and the 'reinit [mbr]'
editing commnd completely remove any existing on-disk GPT header
when writing the MBR.

'-ig'/'reinit gpt' must be used to create GPT format.

Previous interactions between '-i', '-b' and overly clever
'reinit' produced surprising, inconsistent and incorrect
behaviour.

ok deraadt@ kettenis@
---

diff --git a/sbin/fdisk/cmd.c b/sbin/fdisk/cmd.c
index 542035dd986..fe7c21f871d 100644
--- a/sbin/fdisk/cmd.c
+++ b/sbin/fdisk/cmd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cmd.c,v 1.115 2021/06/14 17:34:06 krw Exp $	*/
+/*	$OpenBSD: cmd.c,v 1.116 2021/06/16 15:40:47 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -45,9 +45,9 @@ int
 Xreinit(char *args, struct mbr *mbr)
 {
 	struct dos_mbr dos_mbr;
-	int efi, dogpt;
+	int dogpt;
 
-	efi = MBR_protective_mbr(mbr);
+	dogpt = 0;
 
 	if (strncasecmp(args, "gpt", 3) == 0)
 		dogpt = 1;
@@ -56,10 +56,7 @@ Xreinit(char *args, struct mbr *mbr)
 	else if (strlen(args) > 0) {
 		printf("Unrecognized modifier '%s'\n", args);
 		return (CMD_CONT);
-	} else if (efi != -1)
-		dogpt = 1;
-	else
-		dogpt = 0;
+	}
 
 	MBR_make(&initial_mbr, &dos_mbr);
 	MBR_parse(&dos_mbr, mbr->offset, mbr->reloffset, mbr);
@@ -455,8 +452,7 @@ Xwrite(char *args, struct mbr *mbr)
 			return (CMD_CONT);
 		}
 	} else {
-		/* Ensure any on-disk GPT headers are zeroed. */
-		MBR_zapgpt(&dos_mbr, DL_GETDSIZE(&dl) - 1);
+		GPT_zap_headers();
 	}
 
 	/* Refresh in memory copy to reflect what was just written. */
diff --git a/sbin/fdisk/fdisk.8 b/sbin/fdisk/fdisk.8
index 45bc95ae954..fb083588556 100644
--- a/sbin/fdisk/fdisk.8
+++ b/sbin/fdisk/fdisk.8
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: fdisk.8,v 1.96 2021/01/30 15:15:20 naddy Exp $
+.\"	$OpenBSD: fdisk.8,v 1.97 2021/06/16 15:40:47 krw Exp $
 .\"
 .\"
 .\" Copyright (c) 1997 Tobias Weingartner
@@ -15,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: January 30 2021 $
+.Dd $Mdocdate: June 16 2021 $
 .Dt FDISK 8
 .Os
 .Sh NAME
@@ -371,19 +371,11 @@ Display this manual page.
 .It Cm reinit Op Cm gpt | Cm mbr
 Initialize the currently selected, in-memory copy of the
 boot block.
+.Pp
+By default an MBR is initialized.
 If
 .Cm gpt
 is specified a protective MBR and a GPT are initialized.
-If
-.Cm mbr
-is specified only an MBR is initialized.
-If neither
-.Cm mbr
-nor
-.Cm gpt
-are specified then a protective MBR and a GPT are initialized if a protective
-MBR already exists.
-Otherwise only an MBR is initialized.
 .It Cm disk
 Display the current drive geometry that
 .Nm
diff --git a/sbin/fdisk/gpt.c b/sbin/fdisk/gpt.c
index f123d876a48..b54e27f7d08 100644
--- a/sbin/fdisk/gpt.c
+++ b/sbin/fdisk/gpt.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: gpt.c,v 1.29 2021/06/14 12:46:47 krw Exp $	*/
+/*	$OpenBSD: gpt.c,v 1.30 2021/06/16 15:40:47 krw Exp $	*/
 /*
  * Copyright (c) 2015 Markus Muller <mmu@grummel.net>
  * Copyright (c) 2015 Kenneth R Westerback <krw@openbsd.org>
@@ -451,6 +451,35 @@ GPT_init(void)
 	return rslt;
 }
 
+void
+GPT_zap_headers(void)
+{
+	char *secbuf;
+	uint64_t sig;
+
+	secbuf = DISK_readsector(GPTSECTOR);
+	if (secbuf == NULL)
+		return;
+
+	memcpy(&sig, secbuf, sizeof(sig));
+	if (letoh64(sig) == GPTSIGNATURE) {
+		memset(secbuf, 0, dl.d_secsize);
+		DISK_writesector(secbuf, GPTSECTOR);
+	}
+	free(secbuf);
+
+	secbuf = DISK_readsector(DL_GETDSIZE(&dl) - 1);
+	if (secbuf == NULL)
+		return;
+
+	memcpy(&sig, secbuf, sizeof(sig));
+	if (letoh64(sig) == GPTSIGNATURE) {
+		memset(secbuf, 0, dl.d_secsize);
+		DISK_writesector(secbuf, DL_GETDSIZE(&dl) - 1);
+	}
+	free(secbuf);
+}
+
 int
 GPT_write(void)
 {
diff --git a/sbin/fdisk/gpt.h b/sbin/fdisk/gpt.h
index 93a8e4796f7..f349b81ba26 100644
--- a/sbin/fdisk/gpt.h
+++ b/sbin/fdisk/gpt.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: gpt.h,v 1.11 2021/06/12 17:19:13 krw Exp $	*/
+/*	$OpenBSD: gpt.h,v 1.12 2021/06/16 15:40:47 krw Exp $	*/
 /*
  * Copyright (c) 2015 Markus Muller <mmu@grummel.net>
  * Copyright (c) 2015 Kenneth R Westerback <krw@openbsd.org>
@@ -22,6 +22,7 @@ int		GPT_get_lba_end(unsigned int);
 
 int		GPT_init(void);
 int		GPT_write(void);
+void		GPT_zap_headers(void);
 void		GPT_print(char *, int);
 void		GPT_print_part(int, char *, int);
 void		GPT_print_parthdr(int);
diff --git a/sbin/fdisk/mbr.c b/sbin/fdisk/mbr.c
index 72382043e98..27fe2e4eff1 100644
--- a/sbin/fdisk/mbr.c
+++ b/sbin/fdisk/mbr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mbr.c,v 1.75 2021/06/10 15:30:49 krw Exp $	*/
+/*	$OpenBSD: mbr.c,v 1.76 2021/06/16 15:40:47 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -247,50 +247,6 @@ MBR_write(off_t where, struct dos_mbr *dos_mbr)
 	return (0);
 }
 
-/*
- * If *dos_mbr has a 0xee or 0xef partition, nothing needs to happen. If no
- * such partition is present but the first or last sector on the disk has a
- * GPT, zero the GPT to ensure the MBR takes priority and fewer BIOSes get
- * confused.
- */
-void
-MBR_zapgpt(struct dos_mbr *dos_mbr, uint64_t lastsec)
-{
-	struct dos_partition dos_parts[NDOSPART];
-	char *secbuf;
-	uint64_t sig;
-	int i;
-
-	memcpy(dos_parts, dos_mbr->dmbr_parts, sizeof(dos_parts));
-
-	for (i = 0; i < NDOSPART; i++)
-		if ((dos_parts[i].dp_typ == DOSPTYP_EFI) ||
-		    (dos_parts[i].dp_typ == DOSPTYP_EFISYS))
-			return;
-
-	secbuf = DISK_readsector(GPTSECTOR);
-	if (secbuf == NULL)
-		return;
-
-	memcpy(&sig, secbuf, sizeof(sig));
-	if (letoh64(sig) == GPTSIGNATURE) {
-		memset(secbuf, 0, sizeof(sig));
-		DISK_writesector(secbuf, GPTSECTOR);
-	}
-	free(secbuf);
-
-	secbuf = DISK_readsector(lastsec);
-	if (secbuf == NULL)
-		return;
-
-	memcpy(&sig, secbuf, sizeof(sig));
-	if (letoh64(sig) == GPTSIGNATURE) {
-		memset(secbuf, 0, sizeof(sig));
-		DISK_writesector(secbuf, lastsec);
-	}
-	free(secbuf);
-}
-
 /*
  * Return the index into dp[] of the EFI GPT (0xEE) partition, or -1 if no such
  * partition exists.
diff --git a/sbin/fdisk/mbr.h b/sbin/fdisk/mbr.h
index 29b704c6616..ccc55418bb4 100644
--- a/sbin/fdisk/mbr.h
+++ b/sbin/fdisk/mbr.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mbr.h,v 1.30 2021/05/20 14:27:14 krw Exp $	*/
+/*	$OpenBSD: mbr.h,v 1.31 2021/06/16 15:40:47 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -36,7 +36,6 @@ void MBR_init(struct mbr *);
 void MBR_init_GPT(struct mbr *);
 int MBR_read(off_t, struct dos_mbr *);
 int MBR_write(off_t, struct dos_mbr *);
-void MBR_zapgpt(struct dos_mbr *, uint64_t);
 int MBR_protective_mbr(struct mbr *);
 
 #endif /* _MBR_H */