From: krw <krw@openbsd.org>
Date: Fri, 12 Aug 2022 20:05:49 +0000 (+0000)
Subject: Revert to pre-r1.249 more laissez-faire checks for valid MBR
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=8e434e93737cb25921e442bcb5f2ae7ba3e6166e;p=openbsd

Revert to pre-r1.249 more laissez-faire checks for valid MBR
partitions.

miod@ (re)discovered an off-by-one in some device size
calculations. Whether the ancient misbehaviour of some devices to
confuse number of sectors with highest valid sector address or
something newer.

Should fix miod@'s octeon boot disk.
---

diff --git a/sys/kern/subr_disk.c b/sys/kern/subr_disk.c
index 7f65013eb8a..9e12d8a2c71 100644
--- a/sys/kern/subr_disk.c
+++ b/sys/kern/subr_disk.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: subr_disk.c,v 1.251 2022/08/12 00:32:59 krw Exp $	*/
+/*	$OpenBSD: subr_disk.c,v 1.252 2022/08/12 20:05:49 krw Exp $	*/
 /*	$NetBSD: subr_disk.c,v 1.17 1996/03/16 23:17:08 christos Exp $	*/
 
 /*
@@ -743,11 +743,16 @@ spoofmbr(struct buf *bp, void (*strat)(struct buf *), const uint8_t *dosbb,
 		}
 
 		for (i = 0; i < NDOSPART; i++) {
+			if (letoh32(dp[i].dp_start) > DL_GETDSIZE(lp))
+				continue;
+			if (letoh32(dp[i].dp_size) > DL_GETDSIZE(lp))
+				continue;
+			if (letoh32(dp[i].dp_size) == 0)
+				continue;
+
 			start = sector + letoh32(dp[i].dp_start);
 			end = start + letoh32(dp[i].dp_size);
 
-			if (start >= end || end > DL_GETDSIZE(lp))
-				continue;
 			parts++;
 			if (obsdfound == 0) {
 				labeloff = partoff + DOS_LABELSECTOR;