mac80211: handle drv_add_interface failures properly during reconfig

If any interface fails to be added to the driver in during reconfig,
we should remove all the successfully added interfaces and report
reconfig failure, so things can be cleaned up properly.  Failing to do
so can lead to subsequent failures and leave the drivers in a messed
up state.
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/util.c

@@ -1811,8 +1811,25 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (sdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
 		    sdata->vif.type != NL80211_IFTYPE_MONITOR &&
-		    ieee80211_sdata_running(sdata))
+		    ieee80211_sdata_running(sdata)) {
 			res = drv_add_interface(local, sdata);
+			if (WARN_ON(res))
+				break;
+		}
+	}
+
+	/* If adding any of the interfaces failed above, roll back and
+	 * report failure.
+	 */
+	if (res) {
+		list_for_each_entry_continue_reverse(sdata, &local->interfaces,
+						     list)
+			if (sdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
+			    sdata->vif.type != NL80211_IFTYPE_MONITOR &&
+			    ieee80211_sdata_running(sdata))
+				drv_remove_interface(local, sdata);
+		ieee80211_handle_reconfig_failure(local);
+		return res;
 	}
 
 	/* add channel contexts */