Comment # 10 on bug 980521 from Egbert Eich

Werner, I've done so already. Point is, that this loop does not work:

        for suid in "${HOME}/.dbus/session-bus/"${mid}* ; do
            test -e "$suid" || break
            grep -q $guid "$suid" || continue
            dpid=$(grep -E '^DBUS_SESSION_BUS_PID=[[:digit:]]+' "$suid")
            test /proc/${dpid#*=}/exe -ef $dbusdaemon && continue
            unset DBUS_SESSION_BUS_ADDRESS
            break
        done

There is no file in ${HOME}/.dbus/session-bus/ containing $guid. In fact, there
isn't even a file in this directory that was created at or after the start of
the gdm session.
DBUS_SESSION_BUS_ADDRESS is set and gets unset due to the failure to verify it.

I don't know how it can be verified and frankly I think we have to give up the
idea that we need to and should instead trust DBUS_SESSION_BUS_ADDRESS.