mac80211: fix handling of 4-address-mode in ieee80211_change_iface

commit f7917af9 upstream.

A misplaced interface type check bails out too early if the interface
is not in monitor mode. This patch moves it to the right place, so that
it only covers changes to the monitor flags.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

net/mac80211/cfg.c

@@ -97,9 +97,6 @@ static int ieee80211_change_iface(struct wiphy *wiphy,
 					    params->mesh_id_len,
 					    params->mesh_id);
 
-	if (sdata->vif.type != NL80211_IFTYPE_MONITOR || !flags)
-		return 0;
-
 	if (type == NL80211_IFTYPE_AP_VLAN &&
 	    params && params->use_4addr == 0)
 		rcu_assign_pointer(sdata->u.vlan.sta, NULL);
@@ -107,7 +104,9 @@ static int ieee80211_change_iface(struct wiphy *wiphy,
 		 params && params->use_4addr >= 0)
 		sdata->u.mgd.use_4addr = params->use_4addr;
 
-	sdata->u.mntr_flags = *flags;
+	if (sdata->vif.type == NL80211_IFTYPE_MONITOR && flags)
+		sdata->u.mntr_flags = *flags;
+
 	return 0;
 }