[PATCH] mac80211: avoid null ptr deref in ieee80211_ibss_add_sta

avoid sdata null pointer dereference in ieee80211_ibss_add_sta.
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/ieee80211_sta.c

@@ -2997,7 +2997,7 @@ struct sta_info * ieee80211_ibss_add_sta(struct net_device *dev,
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct sta_info *sta;
-	struct ieee80211_sub_if_data *sdata = NULL;
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
 	/* TODO: Could consider removing the least recently used entry and
 	 * allow new one to be added. */