Florian Weimer <fweimer@redhat.com>:

    dump_dir_accessible_by_uid() is fundamentally insecure because it
    opens up a classic time-of-check-time-of-use race between this
    function and and dd_opendir().  At least re-checking after
    dd_opendir() with the stored file descriptor is needed.

Related: #1214745

Signed-off-by: Jakub Filak <jfilak@redhat.com>