kern/60665: run: hot-plugging USB wifi crashes due to use of if_attach

["coypu%sdf.org@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60665
>Category:       kern
>Synopsis:       run: hot-plugging USB wifi crashes due to use of if_attach
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 29 01:10:01 +0000 2026
>Originator:     coypu
>Release:        NetBSD 11.0_BETA
>Organization:
>Environment:
NetBSD  11.0_BETA NetBSD 11.0_BETA (GENERIC) #0: Mon Oct 20 14:11:07 UTC 2025  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

>Description:
Note: this is clearly an issue that affects multiple USB wifi adapters.
I have plugged a run(4) device after booting, with wpa_supplicant/dhcpcd already running.
It attempted to use the driver immediately as it was published, before some structs were initialized, causing a null deref crash with the following backtrace:

mutex_enter() at netbsd:mutex_enter+0xc
run_ioctl() at netbsd:run_ioctl+0x87
doifioctl() at netbsd:doifioctl+0xad3
sys_ioctl() at netbsd;sys_ioctl+0x1fa
syscall() at netbsd:syscall+0x9d
--- syscall (number 54) ---
netbsd:syscall+0x9d:

hot-pluggable wifi probably can't get away with the use of if_attach at all.
Drivers that don't have this issue (e.g. urtwn) split the calls:

if_initialize
ieee80211_ifattach
... finish initializing ...
if_register
>How-To-Repeat:
Hot plug a run(4) with wpa_supplicant running.
>Fix: