From d6054cd7feb9efd1218d54e03c14096628f86813 Mon Sep 17 00:00:00 2001
From: mvs <mvs@openbsd.org>
Date: Thu, 8 Aug 2024 10:25:00 +0000
Subject: [PATCH] Unlock KERN_MSGBUFSIZE and KERN_CONSBUFSIZE.

`msgbufp' and `consbufp' are immutable, such as `msg_magic' and
`msg_bufs'. initmsgbuf() and initconsbuf() which initialize this buffers
are called during kernel bootstrap, when concurrent sysctl(2) is
impossible, so they don't need to be reordered or use barriers.

ok bluhm
---
 sys/kern/kern_sysctl.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index cc0d4537ee9..3ac262a25a2 100644
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_sysctl.c,v 1.434 2024/08/06 12:36:54 mvs Exp $	*/
+/*	$OpenBSD: kern_sysctl.c,v 1.435 2024/08/08 10:25:00 mvs Exp $	*/
 /*	$NetBSD: kern_sysctl.c,v 1.17 1996/05/20 17:49:05 mrg Exp $	*/
 
 /*-
@@ -533,6 +533,18 @@ kern_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp, void *newp,
 		return (sysctl_rdstruct(oldp, oldlenp, newp,
 		    &mbs, sizeof(mbs)));
 	}
+	case KERN_MSGBUFSIZE:
+	case KERN_CONSBUFSIZE: {
+		struct msgbuf *mp;
+		mp = (name[0] == KERN_MSGBUFSIZE) ? msgbufp : consbufp;
+		/*
+		 * deal with cases where the message buffer has
+		 * become corrupted.
+		 */
+		if (!mp || mp->msg_magic != MSG_MAGIC)
+			return (ENXIO);
+		return (sysctl_rdint(oldp, oldlenp, newp, mp->msg_bufs));
+	}
 	case KERN_OSREV:
 	case KERN_NFILES:
 	case KERN_TTYCOUNT:
@@ -616,18 +628,6 @@ kern_sysctl_locked(int *name, u_int namelen, void *oldp, size_t *oldlenp,
 		error =  sysctl_int(oldp, oldlenp, newp, newlen, &inthostid);
 		hostid = inthostid;
 		return (error);
-	case KERN_MSGBUFSIZE:
-	case KERN_CONSBUFSIZE: {
-		struct msgbuf *mp;
-		mp = (name[0] == KERN_MSGBUFSIZE) ? msgbufp : consbufp;
-		/*
-		 * deal with cases where the message buffer has
-		 * become corrupted.
-		 */
-		if (!mp || mp->msg_magic != MSG_MAGIC)
-			return (ENXIO);
-		return (sysctl_rdint(oldp, oldlenp, newp, mp->msg_bufs));
-	}
 	case KERN_CONSBUF:
 		if ((error = suser(p)))
 			return (error);
@@ -635,7 +635,10 @@ kern_sysctl_locked(int *name, u_int namelen, void *oldp, size_t *oldlenp,
 	case KERN_MSGBUF: {
 		struct msgbuf *mp;
 		mp = (name[0] == KERN_MSGBUF) ? msgbufp : consbufp;
-		/* see note above */
+		/*
+		 * deal with cases where the message buffer has
+		 * become corrupted.
+		 */
 		if (!mp || mp->msg_magic != MSG_MAGIC)
 			return (ENXIO);
 		return (sysctl_rdstruct(oldp, oldlenp, newp, mp,
-- 
2.20.1