Panic on post-freeze current with ucom

[M. Warner Losh]

In message: <46790374.8040903 at yandex.ru>
            "R.Mahmatkhanov" <cvs-src at yandex.ru> writes:
: Good Day.
: 
: I just move to latest -current/i386 after the code freeze. And i catch
: 100% reproduceble panic condition. It happens when i plug my mobile
: phone to USB port. How it does:
: 
: ucom0: <CURITEL Incorporated CURITEL HX-550C USB Modem, class 2/0, rev
: 1.10/0.00, addr 2> on uhub1
: Fatal trap 12: page fault while in kernel mode cpuid = 0; apic id = 00
: fault virtual address = 0x4
: fault code = supervisor read, page not present
: instruction pointer = 0x20: 0xc06ca396
: stack pointer = 0x28: 0xdd30a760
: frame pointer = 0x28: 0xdd30a760
: code segment = base 0x0, limit 0xfffff, type = 0x1b, DPL 0, pres 1,
:              = def32 1, gran 1
: processor eflags = interrupt enabled, resume; IOPL = 0
: current process = 28 (usb1)
: [thread pid 28 tid 100023]
: Stopped at usb_get_interface_descruptor+0x6: movl 0x4(%eax), %eax

This looks like a null modem dereference.  Which driver is causing
this?

Warner