cfg80211: fix locking and lockdep complaints

To call cfg80211_get_chan_state() we need to lock
the wdev, so we need to lock the wdev_iter mutex
in cfg80211_can_use_iftype_chan(). This needs to
use nested locking for lockdep.

Also, cfg80211_get_chan_state() doesn't actually
use the rdev, so remove that completely including
the lock assertion that isn't needed.

Reported-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/chan.c

@@ -103,15 +103,13 @@ int cfg80211_set_monitor_channel(struct cfg80211_registered_device *rdev,
 }
 
 void
-cfg80211_get_chan_state(struct cfg80211_registered_device *rdev,
-		        struct wireless_dev *wdev,
+cfg80211_get_chan_state(struct wireless_dev *wdev,
 		        struct ieee80211_channel **chan,
 		        enum cfg80211_chan_mode *chanmode)
 {
 	*chan = NULL;
 	*chanmode = CHAN_MODE_UNDEFINED;
 
-	ASSERT_RDEV_LOCK(rdev);
 	ASSERT_WDEV_LOCK(wdev);
 
 	if (!netif_running(wdev->netdev))

net/wireless/core.h

@@ -463,8 +463,7 @@ cfg80211_can_use_chan(struct cfg80211_registered_device *rdev,
 }
 
 void
-cfg80211_get_chan_state(struct cfg80211_registered_device *rdev,
-		        struct wireless_dev *wdev,
+cfg80211_get_chan_state(struct wireless_dev *wdev,
 		        struct ieee80211_channel **chan,
 		        enum cfg80211_chan_mode *chanmode);
 

net/wireless/util.c

@@ -1059,7 +1059,16 @@ int cfg80211_can_use_iftype_chan(struct cfg80211_registered_device *rdev,
 		if (rdev->wiphy.software_iftypes & BIT(wdev_iter->iftype))
 			continue;
 
-		cfg80211_get_chan_state(rdev, wdev_iter, &ch, &chmode);
+		/*
+		 * We may be holding the "wdev" mutex, but now need to lock
+		 * wdev_iter. This is OK because once we get here wdev_iter
+		 * is not wdev (tested above), but we need to use the nested
+		 * locking for lockdep.
+		 */
+		mutex_lock_nested(&wdev_iter->mtx, 1);
+		__acquire(wdev_iter->mtx);
+		cfg80211_get_chan_state(wdev_iter, &ch, &chmode);
+		wdev_unlock(wdev_iter);
 
 		switch (chmode) {
 		case CHAN_MODE_UNDEFINED: