[PATCH] mac80211: fix virtual interface locking

[deliverable/linux.git] / net / mac80211 / ieee80211.c

diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index 4e345f82f044e059df1849699f13f2d864cd86c0..ccf84634f15692c89a6b2a20644e99df0695fb43 100644 (file)
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -93,14 +93,13 @@ static int ieee80211_master_open(struct net_device *dev)
        struct ieee80211_sub_if_data *sdata;
        int res = -EOPNOTSUPP;
 
-       read_lock(&local->sub_if_lock);
-       list_for_each_entry(sdata, &local->sub_if_list, list) {
+       /* we hold the RTNL here so can safely walk the list */
+       list_for_each_entry(sdata, &local->interfaces, list) {
                if (sdata->dev != dev && netif_running(sdata->dev)) {
                        res = 0;
                        break;
                }
        }
-       read_unlock(&local->sub_if_lock);
        return res;
 }
 
@@ -109,11 +108,10 @@ static int ieee80211_master_stop(struct net_device *dev)
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct ieee80211_sub_if_data *sdata;
 
-       read_lock(&local->sub_if_lock);
-       list_for_each_entry(sdata, &local->sub_if_list, list)
+       /* we hold the RTNL here so can safely walk the list */
+       list_for_each_entry(sdata, &local->interfaces, list)
                if (sdata->dev != dev && netif_running(sdata->dev))
                        dev_close(sdata->dev);
-       read_unlock(&local->sub_if_lock);
 
        return 0;
 }
@@ -315,8 +313,8 @@ static int ieee80211_open(struct net_device *dev)
 
        sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
-       read_lock(&local->sub_if_lock);
-       list_for_each_entry(nsdata, &local->sub_if_list, list) {
+       /* we hold the RTNL here so can safely walk the list */
+       list_for_each_entry(nsdata, &local->interfaces, list) {
                struct net_device *ndev = nsdata->dev;
 
                if (ndev != dev && ndev != local->mdev && netif_running(ndev) &&
@@ -325,10 +323,8 @@ static int ieee80211_open(struct net_device *dev)
                         * check whether it may have the same address
                         */
                        if (!identical_mac_addr_allowed(sdata->type,
-                                                       nsdata->type)) {
-                               read_unlock(&local->sub_if_lock);
+                                                       nsdata->type))
                                return -ENOTUNIQ;
-                       }
 
                        /*
                         * can only add VLANs to enabled APs
@@ -339,7 +335,6 @@ static int ieee80211_open(struct net_device *dev)
                                sdata->u.vlan.ap = nsdata;
                }
        }
-       read_unlock(&local->sub_if_lock);
 
        switch (sdata->type) {
        case IEEE80211_IF_TYPE_WDS:
@@ -466,14 +461,13 @@ static int ieee80211_stop(struct net_device *dev)
                sdata->u.sta.state = IEEE80211_DISABLED;
                del_timer_sync(&sdata->u.sta.timer);
                /*
-                * Holding the sub_if_lock for writing here blocks
-                * out the receive path and makes sure it's not
-                * currently processing a packet that may get
-                * added to the queue.
+                * When we get here, the interface is marked down.
+                * Call synchronize_rcu() to wait for the RX path
+                * should it be using the interface and enqueuing
+                * frames at this very time on another CPU.
                 */
-               write_lock_bh(&local->sub_if_lock);
+               synchronize_rcu();
                skb_queue_purge(&sdata->u.sta.skb_queue);
-               write_unlock_bh(&local->sub_if_lock);
 
                if (!local->ops->hw_scan &&
                    local->scan_dev == sdata->dev) {
@@ -1033,9 +1027,9 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
 
        rthdr->data_retries = status->retry_count;
 
-       read_lock(&local->sub_if_lock);
+       rcu_read_lock();
        monitors = local->monitors;
-       list_for_each_entry(sdata, &local->sub_if_list, list) {
+       list_for_each_entry_rcu(sdata, &local->interfaces, list) {
                /*
                 * Using the monitors counter is possibly racy, but
                 * if the value is wrong we simply either clone the skb
@@ -1051,7 +1045,7 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
                                continue;
                        monitors--;
                        if (monitors)
-                               skb2 = skb_clone(skb, GFP_KERNEL);
+                               skb2 = skb_clone(skb, GFP_ATOMIC);
                        else
                                skb2 = NULL;
                        skb->dev = sdata->dev;
@@ -1066,7 +1060,7 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
                }
        }
  out:
-       read_unlock(&local->sub_if_lock);
+       rcu_read_unlock();
        if (skb)
                dev_kfree_skb(skb);
 }
@@ -1154,8 +1148,7 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
 
        INIT_LIST_HEAD(&local->modes_list);
 
-       rwlock_init(&local->sub_if_lock);
-       INIT_LIST_HEAD(&local->sub_if_list);
+       INIT_LIST_HEAD(&local->interfaces);
 
        INIT_DELAYED_WORK(&local->scan_work, ieee80211_sta_scan_work);
        ieee80211_rx_bss_list_init(mdev);
@@ -1175,7 +1168,8 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
        sdata->u.ap.force_unicast_rateidx = -1;
        sdata->u.ap.max_ratectrl_rateidx = -1;
        ieee80211_if_sdata_init(sdata);
-       list_add_tail(&sdata->list, &local->sub_if_list);
+       /* no RCU needed since we're still during init phase */
+       list_add_tail(&sdata->list, &local->interfaces);
 
        tasklet_init(&local->tx_pending_tasklet, ieee80211_tx_pending,
                     (unsigned long)local);
@@ -1334,7 +1328,6 @@ void ieee80211_unregister_hw(struct ieee80211_hw *hw)
 {
        struct ieee80211_local *local = hw_to_local(hw);
        struct ieee80211_sub_if_data *sdata, *tmp;
-       struct list_head tmp_list;
        int i;
 
        tasklet_kill(&local->tx_pending_tasklet);
@@ -1348,11 +1341,12 @@ void ieee80211_unregister_hw(struct ieee80211_hw *hw)
        if (local->apdev)
                ieee80211_if_del_mgmt(local);
 
-       write_lock_bh(&local->sub_if_lock);
-       list_replace_init(&local->sub_if_list, &tmp_list);
-       write_unlock_bh(&local->sub_if_lock);
-
-       list_for_each_entry_safe(sdata, tmp, &tmp_list, list)
+       /*
+        * At this point, interface list manipulations are fine
+        * because the driver cannot be handing us frames any
+        * more and the tasklet is killed.
+        */
+       list_for_each_entry_safe(sdata, tmp, &local->interfaces, list)
                __ieee80211_if_del(local, sdata);
 
        rtnl_unlock();