From: Johannes Berg <johannes.berg@intel.com>

commit ad0e2b5a00dbec303e4682b403bb6703d11dcdb2
Author: Johannes Berg <johannes.berg@intel.com>
Date:   Tue Jun 1 10:19:19 2010 +0200

    mac80211: simplify key locking

removed the synchronization against RCU and thus
opened a race window where we can use a key for
TX while it is already freed. Put a synchronisation
into the right place to close that window.

Reported-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Cc: stable@kernel.org [2.6.36+]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -382,6 +382,12 @@ static void __ieee80211_key_destroy(stru
 	if (!key)
 		return;
 
+	/*
+	 * Synchronize so the TX path can no longer be using
+	 * this key before we free/remove it.
+	 */
+	synchronize_rcu();
+
 	if (key->local)
 		ieee80211_key_disable_hw_accel(key);