From: Vitaliy Makkoveev <mvs@openbsd.org>
Subject: Re: Move copyout() out of netlock within sysctl_ifnames()
To: Jonathan Matthew <jonathan@d14n.org>
Cc: Alexander Bluhm <bluhm@openbsd.org>, tech@openbsd.org
Date: Wed, 5 Nov 2025 11:23:13 +0300

On Wed, Nov 05, 2025 at 05:45:38PM +1000, Jonathan Matthew wrote:
> On Tue, Nov 04, 2025 at 12:16:26PM +0300, Vitaliy Makkoveev wrote:
> > Bump reference counter and link desired interface descriptors into
> > temporary `if_tmplist' while holding shared netlock. This temporary
> > list is protected by `if_tmplist_lock' rwlock so release of the
> > netlock is fine. Do copyout() while holding `if_tmplist_lock' and
> > then tear down temporary list.
> > 
> > We follow this way in if_getgroupmembers() and related paths.
> 
> This skips the tail of sysctl_rtable(), which is required for callers to
> determine how much space is required.  This breaks dhcpleased and
> probably more.
> 
> This gets things working again:
> 

Sorry, ok mvs.

> Index: rtsock.c
> ===================================================================
> RCS file: /cvs/src/sys/net/rtsock.c,v
> diff -u -p -r1.389 rtsock.c
> --- rtsock.c	4 Nov 2025 20:03:03 -0000	1.389
> +++ rtsock.c	5 Nov 2025 07:37:03 -0000
> @@ -2276,7 +2276,8 @@ sysctl_rtable(int *name, u_int namelen, 
>  		break;
>  
>  	case NET_RT_IFNAMES:
> -		return (sysctl_ifnames(&w));
> +		error = sysctl_ifnames(&w);
> +		break;
>  	}
>  	free(w.w_tmem, M_RTABLE, w.w_tmemsize);
>  	if (where) {