[PATCH] mac80211: fix virtual interface locking

Florian Lohoff noticed a bug in mac80211: when bringing the
master interface down while other virtual interfaces are up
we call dev_close() under a spinlock which is not allowed.
This patch removes the sub_if_lock used by mac80211 in favour
of using an RCU list. All list manipulations are already done
under rtnl so are well protected against each other, and the
read-side locks we took in the RX and TX code are already in
RCU read-side critical sections.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Florian Lohoff <flo@rfc822.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index 17455c6a5229..651aaba1add4 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -2676,8 +2676,8 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw)
         memset(&wrqu, 0, sizeof(wrqu));
         wireless_send_event(dev, SIOCGIWSCAN, &wrqu, NULL);
 
-        read_lock(&local->sub_if_lock);
-        list_for_each_entry(sdata, &local->sub_if_list, list) {
+        rcu_read_lock();
+        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
 
                 /* No need to wake the master device. */
                 if (sdata->dev == local->mdev)
@@ -2691,7 +2691,7 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw)
 
                 netif_wake_queue(sdata->dev);
         }
-        read_unlock(&local->sub_if_lock);
+        rcu_read_unlock();
 
         sdata = IEEE80211_DEV_TO_SUB_IF(dev);
         if (sdata->type == IEEE80211_IF_TYPE_IBSS) {
@@ -2828,8 +2828,8 @@ static int ieee80211_sta_start_scan(struct net_device *dev,
 
         local->sta_scanning = 1;
 
-        read_lock(&local->sub_if_lock);
-        list_for_each_entry(sdata, &local->sub_if_list, list) {
+        rcu_read_lock();
+        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
 
                 /* Don't stop the master interface, otherwise we can't transmit
                  * probes! */
@@ -2841,7 +2841,7 @@ static int ieee80211_sta_start_scan(struct net_device *dev,
                     (sdata->u.sta.flags & IEEE80211_STA_ASSOCIATED))
                         ieee80211_send_nullfunc(local, sdata, 1);
         }
-        read_unlock(&local->sub_if_lock);
+        rcu_read_unlock();
 
         if (ssid) {
                 local->scan_ssid_len = ssid_len;