mac80211: holding sta_info for non associated stations

["Ron Rindjunsky" <ron.rindjunsky@intel.com>]

Hi folks

examining prints form the tear down of 11n session (see thread "Try to
stop Tx aggregation on non active TID messages"), i found an
interesting issue.
If i associate to a random AP "x" (what happened automatically as i
was configured by ifup scripts to do that), and then scan and
associate to my desired AP "y", i notice that AP "x" was not removed
from the mac80211 station table. Then, what happened was that during
ieee80211_stop, when we reach

list_for_each_entry_rcu(sta, &local->sta_list, list) {
    if (sta->sdata == sdata)
    ieee80211_sta_tear_down_BA_sessions(dev, sta->addr);
}

we try to tear down sessions to irrelevant stations (AP "x" in my
example), which leads to bugs.

did i miss something, or is there really a problem in the state
machine in the described scenario?

Thanks
Ron