IRP buffer access in XENHID

[Paul Durrant <xadimgnik@xxxxxxxxx>]

Hi Owen,

  In testing Troy's power state handling patch I got a crash, which appears to 
be because XENHID is directly accessing user memory
in IRP handling (particularly UserBuffer in the hid callback) without probing 
for access. Is that just an oversight, or is there a
reason not to call ProbeForRead/Write() on the buffers?

  Paul