mac80211: correctly close cancelled scans

commit a754055a1296fcbe6f32de3a5eaca6efb2fd1865 upstream.

__ieee80211_scan_completed is called from a worker. This
means that the following flow is possible.

 * driver calls ieee80211_scan_completed
 * mac80211 cancels the scan (that is already complete)
 * __ieee80211_scan_completed runs

When scan_work will finally run, it will see that the scan
hasn't been aborted and might even trigger another scan on
another band. This leads to a situation where cfg80211's
scan is not done and no further scan can be issued.

Fix this by setting a new flag when a HW scan is being
cancelled so that no other scan will be triggered.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 22 insertions, 0 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 9ca8e3278cc0..92ef04c72c51 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -842,6 +842,8 @@ struct tpt_led_trigger {
  *      that the scan completed.
  * @SCAN_ABORTED: Set for our scan work function when the driver reported
  *      a scan complete for an aborted scan.
+ * @SCAN_HW_CANCELLED: Set for our scan work function when the scan is being
+ *      cancelled.
  */
 enum {
         SCAN_SW_SCANNING,
@@ -849,6 +851,7 @@ enum {
         SCAN_ONCHANNEL_SCANNING,
         SCAN_COMPLETED,
         SCAN_ABORTED,
+        SCAN_HW_CANCELLED,
 };
 
 /**
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 99b103921a4b..eb03337b6545 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -202,6 +202,9 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
         enum ieee80211_band band;
         int i, ielen, n_chans;
 
+        if (test_bit(SCAN_HW_CANCELLED, &local->scanning))
+                return false;
+
         do {
                 if (local->hw_scan_band == IEEE80211_NUM_BANDS)
                         return false;
@@ -878,7 +881,23 @@ void ieee80211_scan_cancel(struct ieee80211_local *local)
         if (!local->scan_req)
                 goto out;
 
+        /*
+         * We have a scan running and the driver already reported completion,
+         * but the worker hasn't run yet or is stuck on the mutex - mark it as
+         * cancelled.
+         */
+        if (test_bit(SCAN_HW_SCANNING, &local->scanning) &&
+            test_bit(SCAN_COMPLETED, &local->scanning)) {
+                set_bit(SCAN_HW_CANCELLED, &local->scanning);
+                goto out;
+        }
+
         if (test_bit(SCAN_HW_SCANNING, &local->scanning)) {
+                /*
+                 * Make sure that __ieee80211_scan_completed doesn't trigger a
+                 * scan on another band.
+                 */
+                set_bit(SCAN_HW_CANCELLED, &local->scanning);
                 if (local->ops->cancel_hw_scan)
                         drv_cancel_hw_scan(local,
                                 rcu_dereference_protected(local->scan_sdata,