mac80211: fix scan abort sanity checks

Since sometimes mac80211 queues up a scan request
to only act on it later, it must be allowed to
(internally) cancel a not-yet-running scan, e.g.
when the interface is taken down. This condition
was missing since we always checked only the
local->scanning variable which isn't yet set in
that situation.
Reported-by: Luis R. Rodriguez <mcgrof@gmail.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/scan.c

@@ -288,10 +288,14 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 
 	mutex_lock(&local->scan_mtx);
 
-	if (WARN_ON(!local->scanning)) {
-		mutex_unlock(&local->scan_mtx);
-		return;
-	}
+	/*
+	 * It's ok to abort a not-yet-running scan (that
+	 * we have one at all will be verified by checking
+	 * local->scan_req next), but not to complete it
+	 * successfully.
+	 */
+	if (WARN_ON(!local->scanning && !aborted))
+		aborted = true;
 
 	if (WARN_ON(!local->scan_req)) {
 		mutex_unlock(&local->scan_mtx);