cfg80211: avoid mem leak on driver hint set

commit 34f05f54 upstream.

In the already-set and intersect case of a driver-hint, the previous
wiphy regdomain was not freed before being reset with a copy of the
cfg80211 regdomain.
Signed-off-by: Arik Nemtsov <arikx.nemtsov@intel.com>
Acked-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

net/wireless/reg.c

@@ -1720,7 +1720,7 @@ static enum reg_request_treatment
 reg_process_hint_driver(struct wiphy *wiphy,
 			struct regulatory_request *driver_request)
 {
-	const struct ieee80211_regdomain *regd;
+	const struct ieee80211_regdomain *regd, *tmp;
 	enum reg_request_treatment treatment;
 
 	treatment = __reg_process_hint_driver(driver_request);
@@ -1740,7 +1740,10 @@ reg_process_hint_driver(struct wiphy *wiphy,
 			reg_free_request(driver_request);
 			return REG_REQ_IGNORE;
 		}
+
+		tmp = get_wiphy_regdom(wiphy);
 		rcu_assign_pointer(wiphy->regd, regd);
+		rcu_free_regdom(tmp);
 	}