Iterating over WDM device stack

[cross-posted to StackOverflow - http://stackoverflow.com/questions/5...-device-stack]

As I understand, one can iterate the device stack of WDM devices only
from the bottoms up, because DEVICE_OBJECT has an AttachedDevice
member (but not a LowerDevice member). Luckily, the AddDevice callback
receives the PhysicalDeviceObject so you one iterate over the entire
stack.

From within my filter driver I'm trying to determine whether I'm
already filtering a certain device object. (Let's say I have a legit
reason for this. Bear with me.) My idea was to go over every
DEVICE_OBJECT in the stack and compare its DriverObject member to
mine.

Judging from the existence of IoGetAttachedDeviceReference, I assume
just accessing AttachedDevice isn't a safe thing to do, for the risk
of the device suddenly going away. However,
IoGetAttachedDeviceReference brings me straight to the top of the
stack, which is no good for me.

So, is there a safe way to iterate over a device stack?

Thanks!