Print warning when a GPT partition start or end is outside the

usable LBA area of the device the GPT is currently inhabiting.

Makes GPT display as informative as MBR display.

In passing, eliminate possible underflow in partition size
calculation.

ok deraadt@

1 files changed, 13 insertions, 6 deletions

diff --git a/sbin/fdisk/gpt.c b/sbin/fdisk/gpt.c
index fac7ed873a1..247c7d2699c 100644
--- a/sbin/fdisk/gpt.c
+++ b/sbin/fdisk/gpt.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: gpt.c,v 1.79 2022/06/28 15:35:24 krw Exp $	*/
+/*	$OpenBSD: gpt.c,v 1.80 2022/08/29 19:39:10 krw Exp $	*/
 /*
  * Copyright (c) 2015 Markus Muller <mmu@grummel.net>
  * Copyright (c) 2015 Kenneth R Westerback <krw@openbsd.org>
@@ -437,15 +437,16 @@ GPT_print_part(const unsigned int pn, const char *units, const int verbosity)
 	const struct unit_type	*ut;
 	char			*guidstr = NULL;
 	double			 size;
-	uint64_t		 sectors;
+	uint64_t		 end, start;
 	uint32_t		 status;
 
-	sectors = gp[pn].gp_lba_end - gp[pn].gp_lba_start + 1;
-	size = units_size(units, sectors, &ut);
+	start = gp[pn].gp_lba_start;
+	end = gp[pn].gp_lba_end;
+	size = units_size(units, (start > end) ? 0 : end - start + 1, &ut);
+
 	printf("%c%3u: %-36s [%12lld: %12.0f%s]\n",
 	    gp[pn].gp_attrs & GPTDOSACTIVE ? '*' : ' ', pn,
-	    PRT_uuid_to_sname(&gp[pn].gp_type), gp[pn].gp_lba_start,
-	    size, ut->ut_abbr);
+	    PRT_uuid_to_sname(&gp[pn].gp_type), start, size, ut->ut_abbr);
 
 	if (verbosity == VERBOSE) {
 		uuid_to_string(&gp[pn].gp_guid, &guidstr, &status);
@@ -456,6 +457,12 @@ GPT_print_part(const unsigned int pn, const char *units, const int verbosity)
 		printf("%-36s\n", name_to_string(pn));
 		free(guidstr);
 	}
+
+	if (start > end)
+		printf("partition %u first LBA is > last LBA\n", pn);
+	if (start < gh.gh_lba_start || end > gh.gh_lba_end)
+		printf("partition %u extends beyond usable LBA range of %s\n",
+		    pn, disk.dk_name);
 }
 
 int