We have a scenario where some groups need to have reporting info that is not visible to other users on the Report Server instance.  I can assign permission limiting access to report categories and data connections, but I don't see a way to limit shared data sources. 

Imagine, for example, a scenario where payroll wants to include an ADP data feed in their reports and they want to save it as SDSX to use in multiple places.  As far as I can tell, all other report editors on the server can now load and use that SDS.

I should be able to determine what SDSX files each user can access in the same way that I can for specific reports.