mac80211: add deadlock fix patch

SVN-Revision: 17290

1 files changed, 108 insertions, 0 deletions

diff --git a/package/mac80211/patches/100-cfg80211-fix-deadlock.patch b/package/mac80211/patches/100-cfg80211-fix-deadlock.patch
new file mode 100644
index 0000000000..6e2a2b1d1f
--- /dev/null
+++ b/package/mac80211/patches/100-cfg80211-fix-deadlock.patch
@@ -0,0 +1,108 @@
+Subject: [PATCH] cfg80211: fix deadlock
+From:	Johannes Berg <johannes@sipsolutions.net>
+To:	John Linville <linville@tuxdriver.com>
+Cc:	linux-wireless <linux-wireless@vger.kernel.org>,
+	Christian Lamparter <chunkeey@web.de>
+Content-Type: text/plain
+Date:	Sun, 16 Aug 2009 13:32:38 +0200
+Message-Id: <1250422358.17522.0.camel@johannes.local>
+Mime-Version: 1.0
+X-Mailer: Evolution 2.27.90 
+Content-Transfer-Encoding: 7bit
+Sender:	linux-wireless-owner@vger.kernel.org
+Precedence: bulk
+List-ID: <linux-wireless.vger.kernel.org>
+X-Mailing-List:	linux-wireless@vger.kernel.org
+
+When removing an interface with nl80211, cfg80211 will
+deadlock in the netdev notifier because we're already
+holding rdev->mtx and try to acquire it again to verify
+the scan has been done.
+
+This bug was introduced by my patch
+"cfg80211: check for and abort dangling scan requests".
+
+To fix this, move the dangling scan request check into
+wiphy_unregister(). This will not be able to catch all
+cases right away, but if the scan problem happens with
+a manual ifdown or so it will be possible to remedy it
+by removing the module/device.
+
+Additionally, add comments about the deadlock scenario.
+
+Reported-by: Christian Lamparter <chunkeey@web.de>
+Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
+---
+ net/wireless/core.c |   32 +++++++++++++++++++-------------
+ 1 file changed, 19 insertions(+), 13 deletions(-)
+
+--- a/net/wireless/core.c
++++ b/net/wireless/core.c
+@@ -586,9 +586,15 @@ void wiphy_unregister(struct wiphy *wiph
+ 	 * get to lock contention here if userspace issues a command
+ 	 * that identified the hardware by wiphy index.
+ 	 */
+-	mutex_lock(&rdev->mtx);
+-	/* unlock again before freeing */
+-	mutex_unlock(&rdev->mtx);
++	cfg80211_lock_rdev(rdev);
++
++	if (WARN_ON(rdev->scan_req)) {
++		rdev->scan_req->aborted = true;
++		___cfg80211_scan_done(rdev);
++	}
++
++	cfg80211_unlock_rdev(rdev);
++	flush_work(&rdev->scan_done_wk);
+ 
+ 	cfg80211_debugfs_rdev_del(rdev);
+ 
+@@ -603,9 +609,7 @@ void wiphy_unregister(struct wiphy *wiph
+ 
+ 	mutex_unlock(&cfg80211_mutex);
+ 
+-	flush_work(&rdev->scan_done_wk);
+ 	cancel_work_sync(&rdev->conn_work);
+-	kfree(rdev->scan_req);
+ 	flush_work(&rdev->event_work);
+ }
+ EXPORT_SYMBOL(wiphy_unregister);
+@@ -653,6 +657,11 @@ static int cfg80211_netdev_notifier_call
+ 
+ 	switch (state) {
+ 	case NETDEV_REGISTER:
++		/*
++		 * NB: cannot take rdev->mtx here because this may be
++		 * called within code protected by it when interfaces
++		 * are added with nl80211.
++		 */
+ 		mutex_init(&wdev->mtx);
+ 		INIT_LIST_HEAD(&wdev->event_list);
+ 		spin_lock_init(&wdev->event_lock);
+@@ -730,13 +739,11 @@ static int cfg80211_netdev_notifier_call
+ #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);
+-		}
+-
++		/*
++		 * NB: cannot take rdev->mtx here because this may be
++		 * called within code protected by it when interfaces
++		 * are removed with nl80211.
++		 */
+ 		mutex_lock(&rdev->devlist_mtx);
+ 		/*
+ 		 * It is possible to get NETDEV_UNREGISTER
+@@ -755,7 +762,6 @@ static int cfg80211_netdev_notifier_call
+ #endif
+ 		}
+ 		mutex_unlock(&rdev->devlist_mtx);
+-		cfg80211_unlock_rdev(rdev);
+ 		break;
+ 	case NETDEV_PRE_UP:
+ 		if (!(wdev->wiphy->interface_modes & BIT(wdev->iftype)))