mac80211: handle failed scan requests in STA mode

If cfg80211 requests a scan it awaits either a return code != 0 from
the scan function or the cfg80211_scan_done to be called. In case of
a STA mac80211's scan function ever returns 0 and queues the scan request.
If ieee80211_sta_work is executed and ieee80211_start_scan fails for
some reason cfg80211_scan_done will never be called but cfg80211 still
thinks the scan was triggered successfully and will refuse any future
scan requests due to drv->scan_req not being cleaned up.

If a scan is triggered from within the MLME a similar problem appears. If
ieee80211_start_scan returns an error, local->scan_req will not be reset
and mac80211 will refuse any future scan requests.

Hence, in both cases call ieee80211_scan_failed (which notifies cfg80211
and resets local->scan_req) if ieee80211_start_scan returns an error.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index eeb6da8..841b845 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1720,7 +1720,10 @@ static int ieee80211_sta_config_auth(struct ieee80211_sub_if_data *sdata)
 				local->int_scan_req.ssids[0].ssid_len = 0;
 			else
 				local->int_scan_req.ssids[0].ssid_len = ifmgd->ssid_len;
-			ieee80211_start_scan(sdata, &local->int_scan_req);
+
+			if (ieee80211_start_scan(sdata, &local->int_scan_req))
+				ieee80211_scan_failed(local);
+
 			ifmgd->state = IEEE80211_STA_MLME_AUTHENTICATE;
 			set_bit(IEEE80211_STA_REQ_AUTH, &ifmgd->request);
 		} else {
@@ -1757,7 +1760,14 @@ static void ieee80211_sta_work(struct work_struct *work)
 	    ifmgd->state != IEEE80211_STA_MLME_AUTHENTICATE &&
 	    ifmgd->state != IEEE80211_STA_MLME_ASSOCIATE &&
 	    test_and_clear_bit(IEEE80211_STA_REQ_SCAN, &ifmgd->request)) {
-		ieee80211_start_scan(sdata, local->scan_req);
+		/*
+		 * The call to ieee80211_start_scan can fail but ieee80211_request_scan
+		 * (which queued ieee80211_sta_work) did not return an error. Thus, call
+		 * ieee80211_scan_failed here if ieee80211_start_scan fails in order to
+		 * notify the scan requester.
+		 */
+		if (ieee80211_start_scan(sdata, local->scan_req))
+			ieee80211_scan_failed(local);
 		return;
 	}