mac80211: release the channel in error path in start_ap

When the driver cannot start the AP or when the assignement
of the beacon goes wrong, we need to unassign the vif.

Cc: stable@vger.kernel.org
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1021,8 +1021,10 @@ static int ieee80211_start_ap(struct wiphy *wiphy, struct net_device *dev,
 					IEEE80211_P2P_OPPPS_ENABLE_BIT;
 
 	err = ieee80211_assign_beacon(sdata, &params->beacon);
-	if (err < 0)
+	if (err < 0) {
+		ieee80211_vif_release_channel(sdata);
 		return err;
+	}
 	changed |= err;
 
 	err = drv_start_ap(sdata->local, sdata);
@@ -1032,6 +1034,7 @@ static int ieee80211_start_ap(struct wiphy *wiphy, struct net_device *dev,
 		if (old)
 			kfree_rcu(old, rcu_head);
 		RCU_INIT_POINTER(sdata->u.ap.beacon, NULL);
+		ieee80211_vif_release_channel(sdata);
 		return err;
 	}