wifi: cfg80211: ocb: don't leave if not joined

If there's no OCB state, don't ask the driver/mac80211 to
leave, since that's just confusing. Since set/clear the
chandef state, that's a simple check.

Reported-by: syzbot+09d1cd2f71e6dd3bfd2c@syzkaller.appspotmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/ocb.c

@@ -68,6 +68,9 @@ int __cfg80211_leave_ocb(struct cfg80211_registered_device *rdev,
 	if (!rdev->ops->leave_ocb)
 		return -EOPNOTSUPP;
 
+	if (!wdev->u.ocb.chandef.chan)
+		return -ENOTCONN;
+
 	err = rdev_leave_ocb(rdev, dev);
 	if (!err)
 		memset(&wdev->u.ocb.chandef, 0, sizeof(wdev->u.ocb.chandef));