mac80211: ibss should not purge clients it is not responsible for

The IBSS merge code calls ieee80211_sta_expire() with a relatively
short expire timeout that purges other clients prematurely. The
expire function has to check that only the clients belonging to
the vif in question are purged.
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/sta_info.c

@@ -946,6 +946,9 @@ void ieee80211_sta_expire(struct ieee80211_sub_if_data *sdata,
 
 	mutex_lock(&local->sta_mtx);
 	list_for_each_entry_safe(sta, tmp, &local->sta_list, list)
+		if (sdata != sta->sdata)
+			continue;
+
 		if (time_after(jiffies, sta->last_rx + exp_time)) {
 #ifdef CONFIG_MAC80211_IBSS_DEBUG
 			printk(KERN_DEBUG "%s: expiring inactive STA %pM\n",