mac80211: correctly close cancelled scans
Emmanuel Grumbach [Mon, 16 Sep 2013 08:12:07 +0000 (11:12 +0300)]
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>

net/mac80211/ieee80211_i.h
net/mac80211/scan.c

index 9ca8e32..92ef04c 100644 (file)
@@ -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,
 };
 
 /**
index 99b1039..eb03337 100644 (file)
@@ -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,