Hi Ivan,
I just want to give notice that we implemented an interim fix for the problem you reported. It the fix is included in the Genode 12.02 release. The relevant commit is:
https://github.com/genodelabs/genode/commit/41eaff2cc656942e1b6a1665ade99f09...
The problem is also covered in the release notes:
http://genode.org/documentation/release-notes/12.02#Fiasco.OC_microkernel
Please note that this is not the actual solution for the underlying problem of proper lifetime management of capability selectors. Stefan is working on that. In the meantime, we hope that the current fix of the annoying capability-selector leak accommodates you well.
Best regards Norman