mac80211: return if IBSS chandef can not be used

This was originally designed to fail when a 40+/40- mode can not be
used, but basic modes (such as 5/10/20 MHz) must be handled
with an error.
Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

net/mac80211/ibss.c

@@ -85,6 +85,14 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 
 	chandef = ifibss->chandef;
 	if (!cfg80211_reg_can_beacon(local->hw.wiphy, &chandef)) {
+		if (chandef.width == NL80211_CHAN_WIDTH_5 ||
+		    chandef.width == NL80211_CHAN_WIDTH_10 ||
+		    chandef.width == NL80211_CHAN_WIDTH_20_NOHT ||
+		    chandef.width == NL80211_CHAN_WIDTH_20) {
+			sdata_info(sdata,
+				   "Failed to join IBSS, beacons forbidden\n");
+			return;
+		}
 		chandef.width = NL80211_CHAN_WIDTH_20;
 		chandef.center_freq1 = chan->center_freq;
 	}