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, 6 insertions, 2 deletions

diff --git a/net/mac80211/wme.c b/net/mac80211/wme.c
index 8cc036decc82..4e94e4026e78 100644
--- a/net/mac80211/wme.c
+++ b/net/mac80211/wme.c
@@ -153,6 +153,7 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
 
         if (pkt_data->flags & IEEE80211_TXPD_REQUEUE) {
                 queue = pkt_data->queue;
+                rcu_read_lock();
                 sta = sta_info_get(local, hdr->addr1);
                 tid = skb->priority & QOS_CONTROL_TAG1D_MASK;
                 if (sta) {
@@ -164,8 +165,8 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
                         } else {
                                 pkt_data->flags &= ~IEEE80211_TXPD_AMPDU;
                         }
-                        sta_info_put(sta);
                 }
+                rcu_read_unlock();
                 skb_queue_tail(&q->requeued[queue], skb);
                 qd->q.qlen++;
                 return 0;
@@ -187,6 +188,8 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
                 p++;
                 *p = 0;
 
+                rcu_read_lock();
+
                 sta = sta_info_get(local, hdr->addr1);
                 if (sta) {
                         int ampdu_queue = sta->tid_to_tx_q[tid];
@@ -197,8 +200,9 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
                         } else {
                                 pkt_data->flags &= ~IEEE80211_TXPD_AMPDU;
                         }
-                        sta_info_put(sta);
                 }
+
+                rcu_read_unlock();
         }
 
         if (unlikely(queue >= local->hw.queues)) {