mac80211: correctly close cancelled scans

__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.

Cc: stable@vger.kernel.org
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 08afe74b98f4..d2d17a449224 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -238,6 +238,9 @@ 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;
@@ -940,7 +943,23 @@ 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,