mac80211: add beacon configuration via cfg80211

This patch implements the cfg80211 hooks for configuring beaconing
on an access point interface in mac80211. While doing so, it fixes
a number of races that could badly crash the machine when the
beacon is changed while being requested by the driver.

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

1 files changed, 8 insertions, 1 deletions

diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index c9981701ef68..859682eee547 100644
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -321,10 +321,17 @@ static int ieee80211_stop(struct net_device *dev)
 
         dev_mc_unsync(local->mdev, dev);
 
-        /* down all dependent devices, that is VLANs */
+        /* APs need special treatment */
         if (sdata->vif.type == IEEE80211_IF_TYPE_AP) {
                 struct ieee80211_sub_if_data *vlan, *tmp;
+                struct beacon_data *old_beacon = sdata->u.ap.beacon;
 
+                /* remove beacon */
+                rcu_assign_pointer(sdata->u.ap.beacon, NULL);
+                synchronize_rcu();
+                kfree(old_beacon);
+
+                /* down all dependent devices, that is VLANs */
                 list_for_each_entry_safe(vlan, tmp, &sdata->u.ap.vlans,
                                          u.vlan.list)
                         dev_close(vlan->dev);