mac80211: check that ieee80211_set_power_mgmt only handles STA interfaces.

ieee80211_set_power_mgmt is meant for STA interfaces only. Moreover,
since sdata->u.mgd.mtx is only initialized for STA interfaces, using
this code for any other type of interface (like creating a monitor
interface) will result in a oops.

Cc: stable@kernel.org
Signed-off-by: Benoit Papillault <benoit.papillault@free.fr>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/cfg.c

@@ -1331,6 +1331,9 @@ static int ieee80211_set_power_mgmt(struct wiphy *wiphy, struct net_device *dev,
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct ieee80211_conf *conf = &local->hw.conf;
 
+	if (sdata->vif.type != NL80211_IFTYPE_STATION)
+		return -EOPNOTSUPP;
+
 	if (!(local->hw.flags & IEEE80211_HW_SUPPORTS_PS))
 		return -EOPNOTSUPP;