cfg80211: check for and abort dangling scan requests
Johannes Berg [Wed, 12 Aug 2009 20:21:21 +0000 (22:21 +0200)]
If you trigger a scan request on an interface and then
take it down, or rmmod the module or unplug the device
the driver might "forget" to cancel the scan request.
That is a bug in the driver, but the current behaviour
is that we just hang endlessly waiting for the netdev
refcount to become 0 which it never will. To improve
robustness, check for this situation in cfg80211, warn
about it and clean up behind the driver. I don't just
clean up silently because it's likely that the driver
also has some internal state it has now leaked.

Additionally, this fixes a locking bug, clearing the
scan_req pointer should be done under the rdev lock.

Finally, we also need to _wait_ for the scan work and
not just abort it since it might be pending and wanting
to do a cleanup.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/core.c
net/wireless/core.h
net/wireless/scan.c

index e630648..35d83be 100644 (file)
@@ -601,8 +601,8 @@ void wiphy_unregister(struct wiphy *wiphy)
 
        mutex_unlock(&cfg80211_mutex);
 
+       flush_work(&rdev->scan_done_wk);
        cancel_work_sync(&rdev->conn_work);
-       cancel_work_sync(&rdev->scan_done_wk);
        kfree(rdev->scan_req);
        flush_work(&rdev->event_work);
 }
@@ -728,6 +728,13 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb,
 #endif
                break;
        case NETDEV_UNREGISTER:
+               cfg80211_lock_rdev(rdev);
+
+               if (WARN_ON(rdev->scan_req && rdev->scan_req->dev == dev)) {
+                       rdev->scan_req->aborted = true;
+                       ___cfg80211_scan_done(rdev);
+               }
+
                mutex_lock(&rdev->devlist_mtx);
                /*
                 * It is possible to get NETDEV_UNREGISTER
@@ -746,6 +753,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb,
 #endif
                }
                mutex_unlock(&rdev->devlist_mtx);
+               cfg80211_unlock_rdev(rdev);
                break;
        case NETDEV_PRE_UP:
                if (!(wdev->wiphy->interface_modes & BIT(wdev->iftype)))
index f7be3a9..c603f52 100644 (file)
@@ -368,6 +368,7 @@ void cfg80211_sme_scan_done(struct net_device *dev);
 void cfg80211_sme_rx_auth(struct net_device *dev, const u8 *buf, size_t len);
 void cfg80211_sme_disassoc(struct net_device *dev, int idx);
 void __cfg80211_scan_done(struct work_struct *wk);
+void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev);
 void cfg80211_upload_connect_keys(struct wireless_dev *wdev);
 
 struct ieee80211_channel *
index e6c1f11..fe575a2 100644 (file)
 
 #define IEEE80211_SCAN_RESULT_EXPIRE   (15 * HZ)
 
-void __cfg80211_scan_done(struct work_struct *wk)
+void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev)
 {
-       struct cfg80211_registered_device *rdev;
        struct cfg80211_scan_request *request;
        struct net_device *dev;
 #ifdef CONFIG_WIRELESS_EXT
        union iwreq_data wrqu;
 #endif
 
-       rdev = container_of(wk, struct cfg80211_registered_device,
-                           scan_done_wk);
-
-       mutex_lock(&rdev->mtx);
        request = rdev->scan_req;
 
        dev = request->dev;
@@ -43,9 +38,9 @@ void __cfg80211_scan_done(struct work_struct *wk)
        cfg80211_sme_scan_done(dev);
 
        if (request->aborted)
-               nl80211_send_scan_aborted(wiphy_to_dev(request->wiphy), dev);
+               nl80211_send_scan_aborted(rdev, dev);
        else
-               nl80211_send_scan_done(wiphy_to_dev(request->wiphy), dev);
+               nl80211_send_scan_done(rdev, dev);
 
 #ifdef CONFIG_WIRELESS_EXT
        if (!request->aborted) {
@@ -57,11 +52,22 @@ void __cfg80211_scan_done(struct work_struct *wk)
 
        dev_put(dev);
 
-       cfg80211_unlock_rdev(rdev);
-       wiphy_to_dev(request->wiphy)->scan_req = NULL;
+       rdev->scan_req = NULL;
        kfree(request);
 }
 
+void __cfg80211_scan_done(struct work_struct *wk)
+{
+       struct cfg80211_registered_device *rdev;
+
+       rdev = container_of(wk, struct cfg80211_registered_device,
+                           scan_done_wk);
+
+       cfg80211_lock_rdev(rdev);
+       ___cfg80211_scan_done(rdev);
+       cfg80211_unlock_rdev(rdev);
+}
+
 void cfg80211_scan_done(struct cfg80211_scan_request *request, bool aborted)
 {
        WARN_ON(request != wiphy_to_dev(request->wiphy)->scan_req);