rt2x00: Fix for race condition while update beacon

The patch "Implement set_tim callback for all drivers" can cause kernel
oops in rt73usb_write_beacon. The oops is caused by one of the following
race conditions:
* In case of two near calls to set_tim: rt2x00lib_beacondone_iter is
cleaning the beacon skb, whereas rt73usb_write_beacon is still using it.
* In case of two near updates of beacon: first as the result of set_tim
and second as the result of a call from an application (e.g. hostapd).
This patch fixes the race condition by rearranging the update logic and
guarding rt2x00_intf->beacon->skb with a mutex.

Signed-off-by: Igor Perminov <igor.perminov@inbox.ru>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 0 insertions, 7 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c
index e0348cc22d16..b6676c6722fc 100644
--- a/drivers/net/wireless/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/rt2x00/rt2x00dev.c
@@ -186,7 +186,6 @@ static void rt2x00lib_intf_scheduled(struct work_struct *work)
 static void rt2x00lib_beacondone_iter(void *data, u8 *mac,
                                       struct ieee80211_vif *vif)
 {
-        struct rt2x00_dev *rt2x00dev = data;
         struct rt2x00_intf *intf = vif_to_intf(vif);
 
         if (vif->type != NL80211_IFTYPE_AP &&
@@ -195,12 +194,6 @@ static void rt2x00lib_beacondone_iter(void *data, u8 *mac,
             vif->type != NL80211_IFTYPE_WDS)
                 return;
 
-        /*
-         * Clean up the beacon skb.
-         */
-        rt2x00queue_free_skb(rt2x00dev, intf->beacon->skb);
-        intf->beacon->skb = NULL;
-
         spin_lock(&intf->lock);
         intf->delayed_flags |= DELAYED_UPDATE_BEACON;
         spin_unlock(&intf->lock);