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>
diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c
index e67e339..06af823 100644
--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
@@ -503,14 +503,25 @@
if (unlikely(!intf->beacon))
return -ENOBUFS;
+ mutex_lock(&intf->beacon_skb_mutex);
+
+ /*
+ * Clean up the beacon skb.
+ */
+ rt2x00queue_free_skb(rt2x00dev, intf->beacon->skb);
+ intf->beacon->skb = NULL;
+
if (!enable_beacon) {
rt2x00dev->ops->lib->kill_tx_queue(rt2x00dev, QID_BEACON);
+ mutex_unlock(&intf->beacon_skb_mutex);
return 0;
}
intf->beacon->skb = ieee80211_beacon_get(rt2x00dev->hw, vif);
- if (!intf->beacon->skb)
+ if (!intf->beacon->skb) {
+ mutex_unlock(&intf->beacon_skb_mutex);
return -ENOMEM;
+ }
/*
* Copy all TX descriptor information into txdesc,
@@ -548,6 +559,8 @@
rt2x00dev->ops->lib->write_beacon(intf->beacon);
rt2x00dev->ops->lib->kick_tx_queue(rt2x00dev, QID_BEACON);
+ mutex_unlock(&intf->beacon_skb_mutex);
+
return 0;
}