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>

1 files changed, 10 insertions, 1 deletions

diff --git a/net/wireless/util.c b/net/wireless/util.c
index f7a0647bde9a..26f8cd30f712 100644
--- a/net/wireless/util.c
+++ b/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: