[src/trunk]: src/sys/dev/dkwedge dk(4): Explain why dk_rawopens can't overflo...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9d2e1cd905d8
branches:  trunk
changeset: 374248:9d2e1cd905d8
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Thu Apr 13 08:30:40 2023 +0000

description:
dk(4): Explain why dk_rawopens can't overflow and assert it.

diffstat:

 sys/dev/dkwedge/dk.c |  10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diffs (32 lines):

diff -r 95d3bb202231 -r 9d2e1cd905d8 sys/dev/dkwedge/dk.c
--- a/sys/dev/dkwedge/dk.c      Thu Apr 13 07:03:31 2023 +0000
+++ b/sys/dev/dkwedge/dk.c      Thu Apr 13 08:30:40 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dk.c,v 1.124 2022/09/27 17:04:52 mlelstv Exp $ */
+/*     $NetBSD: dk.c,v 1.125 2023/04/13 08:30:40 riastradh Exp $       */
 
 /*-
  * Copyright (c) 2004, 2005, 2006, 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: dk.c,v 1.124 2022/09/27 17:04:52 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dk.c,v 1.125 2023/04/13 08:30:40 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_dkwedge.h"
@@ -1200,7 +1200,13 @@ dkfirstopen(struct dkwedge_softc *sc, in
        } else {
                /*
                 * Retrieve mode from an already opened wedge.
+                *
+                * At this point, dk_rawopens is bounded by the number
+                * of dkwedge devices in the system, which is limited
+                * by autoconf device numbering to INT_MAX.  Since
+                * dk_rawopens is unsigned, this can't overflow.
                 */
+               KASSERT(sc->sc_parent->dk_rawopens < UINT_MAX);
                mode = 0;
                LIST_FOREACH(nsc, &sc->sc_parent->dk_wedges, sc_plink) {
                        if (nsc == sc || nsc->sc_dk.dk_openmask == 0)