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 7f65013..9e12d8a 100644 (file)
--- 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;