kern/43125: zyd(4) crashes with Buffalo WLI-U2-KG54L

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         43125
>Category:       kern
>Synopsis:       zyd(4) crashes with Buffalo WLI-U2-KG54L
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Apr 05 11:05:00 +0000 2010
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current as of roughly Feb 24, 2010
>Organization:
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

Connecting a Buffalo WLI-U2-KG54L USB WLAN dongle to a
NetBSD-current/i386 machine, it successfully attaches as "zyd0",
but attempting to ifconfig the interface consistently leads
to a kernel trap.  Even the command "ifconfig zyd0" (with no
further arguments) causes a crash.

Screenshot of trap message and backtrace:

   http://www.gson.org/netbsd/bugs/buffalo/backtrace.jpg

Photo of Buffalo WLI-U2-KG54L:

  http://www.gson.org/netbsd/bugs/buffalo/device.jpg

The screenshot is from a -current as of a couple of weeks ago,
but I have also reproduced the problem with a -current built
from 2010.04.04.23.38.55 sources.

>How-To-Repeat:

Connect a WLI-U2-KG54L.  Attempt to use it.

>Fix: