From 9619265f8ac53c7eff18236937a7b7673dc76cbf Mon Sep 17 00:00:00 2001
From: krw <krw@openbsd.org>
Date: Fri, 2 Sep 2022 14:18:47 +0000
Subject: [PATCH] Don't ignore an OpenBSD GPT partition just because the GPT
 says it extends beyond the edge of the disk the GPT currently inhabits. We
 only care if enough of it is addressable that a disklabel is accessible.

Brings GPT handling of 'OpenBSD partitions extending too far'
into line with the MBR handling of the same situation.
---
 sys/kern/subr_disk.c | 60 ++++++++++++++++++++++++--------------------
 1 file changed, 33 insertions(+), 27 deletions(-)

diff --git a/sys/kern/subr_disk.c b/sys/kern/subr_disk.c
index 5f06c010aec..483cd7cb95a 100644
--- a/sys/kern/subr_disk.c
+++ b/sys/kern/subr_disk.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: subr_disk.c,v 1.257 2022/09/02 12:28:12 krw Exp $	*/
+/*	$OpenBSD: subr_disk.c,v 1.258 2022/09/02 14:18:47 krw Exp $	*/
 /*	$NetBSD: subr_disk.c,v 1.17 1996/03/16 23:17:08 christos Exp $	*/
 
 /*
@@ -590,17 +590,16 @@ int
 spoofgpt(struct buf *bp, void (*strat)(struct buf *), const uint8_t *dosbb,
     struct disklabel *lp, daddr_t *partoffp)
 {
-	static const uint8_t	 gpt_uuid_openbsd[] = GPT_UUID_OPENBSD;
 	struct dos_partition	 dp[NDOSPART];
 	struct gpt_header	 gh;
-	struct uuid		 gptype, uuid_openbsd;
+	struct uuid		 gptype;
 	struct gpt_partition	*gp;
 	struct partition	*pp;
-	uint64_t		 lbaend, lbastart;
+	uint64_t		 lbaend, lbastart, labelsec;
 	uint64_t		 gpbytes, end, start;
-	daddr_t			 labeloff, partoff;
+	daddr_t			 partoff;
 	unsigned int		 i, n;
-	int			 error, obsdfound;
+	int			 error, fstype, obsdfound;
 	uint32_t		 partnum;
 	uint16_t		 sig;
 
@@ -634,7 +633,6 @@ spoofgpt(struct buf *bp, void (*strat)(struct buf *), const uint8_t *dosbb,
 	partnum = letoh32(gh.gh_part_num);
 
 	n = 'i' - 'a';	/* Start spoofing at 'i', a.k.a. 8. */
-	uuid_dec_be(gpt_uuid_openbsd, &uuid_openbsd);
 
 	DL_SETBSTART(lp, lbastart);
 	DL_SETBEND(lp, lbaend + 1);
@@ -642,33 +640,41 @@ spoofgpt(struct buf *bp, void (*strat)(struct buf *), const uint8_t *dosbb,
 	obsdfound = 0;
 	for (i = 0; i < partnum; i++) {
 		start = letoh64(gp[i].gp_lba_start);
-		end = letoh64(gp[i].gp_lba_end) + 1;
-		if (start >= end || start < lbastart || end > lbaend + 1)
+		if (start > lbaend || start < lbastart)
+			continue;
+
+		end = letoh64(gp[i].gp_lba_end);
+		if (start > end)
+			continue;
+
+		uuid_dec_le(&gp[i].gp_type, &gptype);
+		fstype = gpt_get_fstype(&gptype);
+		if (obsdfound && fstype == FS_BSDFFS)
 			continue;
-		if (obsdfound == 0) {
-			labeloff = partoff + DOS_LABELSECTOR;
-			if (labeloff >= DL_SECTOBLK(lp, start) &&
-			    labeloff < DL_SECTOBLK(lp, end))
+
+		if (fstype == FS_BSDFFS) {
+			obsdfound = 1;
+			partoff = DL_SECTOBLK(lp, start);
+			labelsec = DL_BLKTOSEC(lp, partoff + DOS_LABELSECTOR);
+			if (labelsec > ((end < lbaend) ? end : lbaend))
 				partoff = -1;
+			DL_SETBSTART(lp, start);
+			DL_SETBEND(lp, end + 1);
+			continue;
 		}
 
-		uuid_dec_le(&gp[i].gp_type, &gptype);
-		if (memcmp(&gptype, &uuid_openbsd, sizeof(gptype)) == 0) {
-			if (obsdfound == 0) {
-				obsdfound = 1;
-				partoff = DL_SECTOBLK(lp, start);
-				labeloff = partoff + DOS_LABELSECTOR;
-				if (labeloff >= DL_SECTOBLK(lp, end))
-					partoff = -1;
-				DL_SETBSTART(lp, start);
-				DL_SETBEND(lp, end);
-			}
-		} else if (n < MAXPARTITIONS) {
+		if (partoff != -1) {
+			labelsec = DL_BLKTOSEC(lp, partoff + DOS_LABELSECTOR);
+			if (labelsec >= start && labelsec <= end)
+				partoff = -1;
+		}
+
+		if (n < MAXPARTITIONS && end <= lbaend) {
 			pp = &lp->d_partitions[n];
 			n++;
-			pp->p_fstype = gpt_get_fstype(&gptype);
+			pp->p_fstype = fstype;
 			DL_SETPOFFSET(pp, start);
-			DL_SETPSIZE(pp, end - start);
+			DL_SETPSIZE(pp, end - start + 1);
 		}
 	}
 
-- 
2.20.1