Comment 8 for bug 415766

From the text of the error it looks like AppArmor rather than selinux, but the issue is the same. I think what is needed is to stash credentials at startup and always use these when dealing with cache files rather than using the current process' credentials. This should not be difficult to do with the credentials API changes from David Howells - just haven't managed to configure selinux locally to be able to reproduce it.