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>

1 files changed, 5 insertions, 3 deletions

diff --git a/net/mac80211/ieee80211_rate.c b/net/mac80211/ieee80211_rate.c
index ebe29b716b27..4de06f128d90 100644
--- a/net/mac80211/ieee80211_rate.c
+++ b/net/mac80211/ieee80211_rate.c
@@ -170,9 +170,12 @@ void rate_control_get_rate(struct net_device *dev,
         struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
         struct rate_control_ref *ref = local->rate_ctrl;
         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
-        struct sta_info *sta = sta_info_get(local, hdr->addr1);
+        struct sta_info *sta;
         int i;
 
+        rcu_read_lock();
+        sta = sta_info_get(local, hdr->addr1);
+
         memset(sel, 0, sizeof(struct rate_selection));
 
         ref->ops->get_rate(ref->priv, dev, sband, skb, sel);
@@ -190,8 +193,7 @@ void rate_control_get_rate(struct net_device *dev,
                 }
         }
 
-        if (sta)
-                sta_info_put(sta);
+        rcu_read_unlock();
 }
 
 struct rate_control_ref *rate_control_get(struct rate_control_ref *ref)