kern/60127: some drivers leak memory on detatch

["yamt%netbsd.org@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60127
>Category:       kern
>Synopsis:       some drivers leak memory on detatch
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Mar 25 12:40:00 +0000 2026
>Originator:     YAMAMOTO Takashi
>Release:        -current
>Organization:
	
>Environment:
	
	
>Description:

	some drivers attaches a device on open and detach it on close.
	eg. vnd, fss, cgd, pad, ... (i only confirmed vnd)

	typically they do:

	    open:
		cfdata_t cf = kmem_zalloc(sizeof(*cf), KM_SLEEP);
		  :
		  :
		config_attach_pseudo(cf);

	    close:
		config_detach(...);
		kmem_free(cf, sizeof(*cf));

	if they are detached by the other means, (eg. drvctl -d)
	cfdata_t leaks.

>How-To-Repeat:

	eg.
	```
	#! /bin/sh

	t=$(mktemp)
	dd if=/dev/zero of=$t bs=1m count=1

	while :; do
	    vnconfig vnd0 $t
	    drvctl -d vnd0
	done
	```

	
>Fix:
	

>Unformatted: