mac80211: add interface list lock

Using only the RTNL has a number of problems, most notably that
ieee80211_iterate_active_interfaces() and other interface list
traversals cannot be done from the internal workqueue because it
needs to be flushed under the RTNL.

This patch introduces a new mutex that protects the interface list
against modifications. A more detailed explanation is part of the
code change.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 210dfe3cf6c..a109c06e8e4 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -758,6 +758,7 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
 	local->hw.conf.radio_enabled = true;
 
 	INIT_LIST_HEAD(&local->interfaces);
+	mutex_init(&local->iflist_mtx);
 
 	spin_lock_init(&local->key_lock);
 
@@ -1008,6 +1009,8 @@ void ieee80211_free_hw(struct ieee80211_hw *hw)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 
+	mutex_destroy(&local->iflist_mtx);
+
 	wiphy_free(local->hw.wiphy);
 }
 EXPORT_SYMBOL(ieee80211_free_hw);