iwlagn: fix dangling scan request

If iwl_scan_initiate() fails for any reason,
priv->scan_request and priv->scan_vif are left
dangling. This can lead to a crash later when
iwl_bg_scan_completed() tries to run a pending
scan request.

In practice, this seems to be very rare due to
the STATUS_SCANNING check earlier. That check,
however, is wrong -- it should allow a scan to
be queued when a reset/roc scan is going on.
When a normal scan is already going on, a new
one can't be issued by mac80211, so that code
can be removed completely. I introduced this
bug when adding off-channel support in commit
266af4c745952e9bebf687dd68af58df553cb59d.

Cc: stable@kernel.org [3.0]
Reported-by: Peng Yan <peng.yan@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 16 insertions, 14 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-scan.c b/drivers/net/wireless/iwlwifi/iwl-scan.c
index dd6937e97055..77e528f5db88 100644
--- a/drivers/net/wireless/iwlwifi/iwl-scan.c
+++ b/drivers/net/wireless/iwlwifi/iwl-scan.c
@@ -405,31 +405,33 @@ int iwl_mac_hw_scan(struct ieee80211_hw *hw,
 
         mutex_lock(&priv->mutex);
 
-        if (test_bit(STATUS_SCANNING, &priv->status) &&
-            priv->scan_type != IWL_SCAN_NORMAL) {
-                IWL_DEBUG_SCAN(priv, "Scan already in progress.\n");
-                ret = -EAGAIN;
-                goto out_unlock;
-        }
-
-        /* mac80211 will only ask for one band at a time */
-        priv->scan_request = req;
-        priv->scan_vif = vif;
-
         /*
          * If an internal scan is in progress, just set
          * up the scan_request as per above.
          */
         if (priv->scan_type != IWL_SCAN_NORMAL) {
-                IWL_DEBUG_SCAN(priv, "SCAN request during internal scan\n");
+                IWL_DEBUG_SCAN(priv,
+                               "SCAN request during internal scan - defer\n");
+                priv->scan_request = req;
+                priv->scan_vif = vif;
                 ret = 0;
-        } else
+        } else {
+                priv->scan_request = req;
+                priv->scan_vif = vif;
+                /*
+                 * mac80211 will only ask for one band at a time
+                 * so using channels[0] here is ok
+                 */
                 ret = iwl_scan_initiate(priv, vif, IWL_SCAN_NORMAL,
                                         req->channels[0]->band);
+                if (ret) {
+                        priv->scan_request = NULL;
+                        priv->scan_vif = NULL;
+                }
+        }
 
         IWL_DEBUG_MAC80211(priv, "leave\n");
 
-out_unlock:
         mutex_unlock(&priv->mutex);
 
         return ret;