FltGetFileNameInformation does not return full file path in PFLT_FILE_NAME_INFORMATION::Name

NTFSD
1

The environment is Azure Virtual Desktop (AVD). The file (test.txt) is kept in Remote Desktop Virtual Drive on RDWebClient. In our minifilterā€™s PostCreateCallBack function, we try to retrieve the full file path with the help of FltGetFileNameInformation() and FltParseFileNameInformation(). We are observing below value in ā€˜FileNameInformation::Nameā€™ variable:
\Device\Mup\tsclient\Remote Desktop Virtual Drive\Uploads

As per the documentation, these APIs should return full file path e.g. \Device\Mup\tsclient\Remote Desktop Virtual Drive\Uploads\test.txt
The input flag Data->Iopb->OperationFlags is 0x0. Hence SL_OPEN_TARGET_DIRECTORY is not set.

The interesting observation is that values of below nameInfo variables are as expected:
FileNameInformation::FinalComponent: test.txt
FileNameInformation::Stream: test.txt

FinalComponent should be part of FileNameInformation::Name but somehow for this directory location, it is getting trimmed.
Please let me know if somebody knows how to retrieve the full file path on Remote Desktop Virtual Drive on AVD.

2

Does it happen for other files?
What about file names with the exact same length?

3

This happens for files in Remote Desktop virtual drive only. For all other files in local drives of the Azure Virtual Desktop, this behaviour is not observed and we get the complete file path.

4

File a bug for the API. And you will have to work around it in your code.
It is not strange for FGFNI to have issues :frowning: I have seen at least 50 (by
the time I stopped counting), luckily most are related to pre-Win7.

5

Thanks Dejan. Yes I will file a bug on Microsoft.

6

Moved to NTFSD.