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>
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@ -928,9 +928,8 @@ enum ieee80211_hw_flags {
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* @workqueue: single threaded workqueue available for driver use,
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* allocated by mac80211 on registration and flushed when an
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* interface is removed.
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* NOTICE: All work performed on this workqueue should NEVER
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* acquire the RTNL lock (i.e. Don't use the function
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* ieee80211_iterate_active_interfaces())
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* NOTICE: All work performed on this workqueue must not
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* acquire the RTNL lock.
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*
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* @priv: pointer to private area that was allocated for driver use
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* along with this structure.
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@ -643,7 +643,9 @@ struct ieee80211_local {
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struct crypto_blkcipher *wep_rx_tfm;
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u32 wep_iv;
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/* see iface.c */
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struct list_head interfaces;
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struct mutex iflist_mtx;
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/*
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* Key lock, protects sdata's key_list and sta_info's
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@ -21,6 +21,23 @@
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#include "mesh.h"
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#include "led.h"
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/**
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* DOC: Interface list locking
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*
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* The interface list in each struct ieee80211_local is protected
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* three-fold:
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*
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* (1) modifications may only be done under the RTNL
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* (2) modifications and readers are protected against each other by
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* the iflist_mtx.
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* (3) modifications are done in an RCU manner so atomic readers
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* can traverse the list in RCU-safe blocks.
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*
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* As a consequence, reads (traversals) of the list can be protected
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* by either the RTNL, the iflist_mtx or RCU.
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*/
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static int ieee80211_change_mtu(struct net_device *dev, int new_mtu)
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{
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int meshhdrlen;
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@ -800,7 +817,9 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
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params->mesh_id_len,
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params->mesh_id);
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mutex_lock(&local->iflist_mtx);
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list_add_tail_rcu(&sdata->list, &local->interfaces);
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mutex_unlock(&local->iflist_mtx);
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if (new_dev)
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*new_dev = ndev;
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@ -816,7 +835,10 @@ void ieee80211_if_remove(struct ieee80211_sub_if_data *sdata)
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{
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ASSERT_RTNL();
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mutex_lock(&sdata->local->iflist_mtx);
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list_del_rcu(&sdata->list);
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mutex_unlock(&sdata->local->iflist_mtx);
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synchronize_rcu();
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unregister_netdevice(sdata->dev);
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}
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@ -832,7 +854,16 @@ void ieee80211_remove_interfaces(struct ieee80211_local *local)
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ASSERT_RTNL();
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list_for_each_entry_safe(sdata, tmp, &local->interfaces, list) {
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/*
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* we cannot hold the iflist_mtx across unregister_netdevice,
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* but we only need to hold it for list modifications to lock
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* out readers since we're under the RTNL here as all other
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* writers.
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*/
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mutex_lock(&local->iflist_mtx);
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list_del(&sdata->list);
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mutex_unlock(&local->iflist_mtx);
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unregister_netdevice(sdata->dev);
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}
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}
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@ -758,6 +758,7 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
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local->hw.conf.radio_enabled = true;
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INIT_LIST_HEAD(&local->interfaces);
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mutex_init(&local->iflist_mtx);
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spin_lock_init(&local->key_lock);
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@ -1008,6 +1009,8 @@ void ieee80211_free_hw(struct ieee80211_hw *hw)
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{
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struct ieee80211_local *local = hw_to_local(hw);
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mutex_destroy(&local->iflist_mtx);
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wiphy_free(local->hw.wiphy);
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}
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EXPORT_SYMBOL(ieee80211_free_hw);
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@ -468,7 +468,7 @@ void ieee80211_iterate_active_interfaces(
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struct ieee80211_local *local = hw_to_local(hw);
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struct ieee80211_sub_if_data *sdata;
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rtnl_lock();
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mutex_lock(&local->iflist_mtx);
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list_for_each_entry(sdata, &local->interfaces, list) {
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switch (sdata->vif.type) {
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@ -489,7 +489,7 @@ void ieee80211_iterate_active_interfaces(
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&sdata->vif);
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}
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rtnl_unlock();
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mutex_unlock(&local->iflist_mtx);
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}
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EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces);
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