mac80211: RCU-ify STA info structure access

This makes access to the STA hash table/list use RCU to protect
against freeing of items. However, it's not a true RCU, the
copy step is missing: whenever somebody changes a STA item it
is simply updated. This is an existing race condition that is
now somewhat understandable.

This patch also fixes the race key freeing vs. STA destruction
by making sure that sta_info_destroy() is always called under
RTNL and frees the key.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index ed7c9f3..73cfb4d 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -51,7 +51,7 @@
 		STA_OPS(name)
 
 STA_FILE(aid, aid, D);
-STA_FILE(dev, dev->name, S);
+STA_FILE(dev, sdata->dev->name, S);
 STA_FILE(rx_packets, rx_packets, LU);
 STA_FILE(tx_packets, tx_packets, LU);
 STA_FILE(rx_bytes, rx_bytes, LU);
@@ -200,7 +200,7 @@
 		const char __user *user_buf, size_t count, loff_t *ppos)
 {
 	struct sta_info *sta = file->private_data;
-	struct net_device *dev = sta->dev;
+	struct net_device *dev = sta->sdata->dev;
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct ieee80211_hw *hw = &local->hw;
 	u8 *da = sta->addr;