Only allow changing the domainname (from empty) before securelevel increase.

libc YP support has a couple of places where the domainname is cached, and
this results in wildly incoherent behaviour which could even be risky.
If you want to change the domainname, you will have to reboot.
ok beck miod

diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index f9d1f04..1be54b0 100644 (file)
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kern_sysctl.c,v 1.403 2022/07/05 15:06:16 visa Exp $  */
+/*     $OpenBSD: kern_sysctl.c,v 1.404 2022/07/26 14:53:45 deraadt Exp $       */
 /*     $NetBSD: kern_sysctl.c,v 1.17 1996/05/20 17:49:05 mrg Exp $     */
 
 /*-
@@ -486,8 +486,11 @@ kern_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp, void *newp,
                        hostnamelen = newlen;
                return (error);
        case KERN_DOMAINNAME:
-               error = sysctl_tstring(oldp, oldlenp, newp, newlen,
-                   domainname, sizeof(domainname));
+               if (securelevel >= 1 && domainnamelen && newp)
+                       error = EPERM;
+               else
+                       error = sysctl_tstring(oldp, oldlenp, newp, newlen,
+                           domainname, sizeof(domainname));
                if (newp && !error)
                        domainnamelen = newlen;
                return (error);