User-Mode Debugging Internals

Alex Ionescu has posted some publications at his blog. I've only had an opportunity to go through the three-part series on Windows XP / 2003 User-Mode Debugging Internals, but I found them to be quite interesting and I hope to go through the rest of the publications which cover topics like Process Internals, VB File Format, NTFS ADS, and Subverting Windows 2003 SP1 Kernel Integrity Protection.

One thing (probably trivial) that I am curoius about in the User-Mode Debugging Internals papers is the analysis of NtDebugActiveProcess. Alex comments in his analysis in part 3 "Don't allow debugging the initial system process". The check for the initial system process is made, and STATUS_ACCESS_DENIED is returned if indeed it is the initial system process that is the subject of the debug attempt. I am curious as to why, prior to returning in this case, the process is not dereferenced (ObDereferenceObject(Process);)? Is it simply the nature of the system process that this is not required, though perhaps it might be considered good practice to call ObDereferenceObject(Process) in this case? Or is there some other reason?

Does anyone have any thoughts on the above?


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