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Commit c771c9d8 authored by Johannes Berg's avatar Johannes Berg Committed by John W. Linville
Browse files

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: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 506d03f9

include/net/mac80211.h

+2 −3
Original line number Diff line number Diff line
@@ -928,9 +928,8 @@ enum ieee80211_hw_flags { 
 * @workqueue: single threaded workqueue available for driver use,

 *	allocated by mac80211 on registration and flushed when an

 *	interface is removed.

 *	NOTICE: All work performed on this workqueue should NEVER

 *	acquire the RTNL lock (i.e. Don't use the function

 *	ieee80211_iterate_active_interfaces())

 *	NOTICE: All work performed on this workqueue must not

 *	acquire the RTNL lock.

 *

 * @priv: pointer to private area that was allocated for driver use

 *	along with this structure.

net/mac80211/ieee80211_i.h

+2 −0
Original line number Diff line number Diff line
@@ -643,7 +643,9 @@ struct ieee80211_local { 
	struct crypto_blkcipher *wep_rx_tfm;

	u32 wep_iv;



	/* see iface.c */

	struct list_head interfaces;

	struct mutex iflist_mtx;



	/*

	 * Key lock, protects sdata's key_list and sta_info's

net/mac80211/iface.c

+31 −0
Original line number Diff line number Diff line
@@ -21,6 +21,23 @@ 
#include "mesh.h"

#include "led.h"



/**

 * DOC: Interface list locking

 *

 * The interface list in each struct ieee80211_local is protected

 * three-fold:

 *

 * (1) modifications may only be done under the RTNL

 * (2) modifications and readers are protected against each other by

 *     the iflist_mtx.

 * (3) modifications are done in an RCU manner so atomic readers

 *     can traverse the list in RCU-safe blocks.

 *

 * As a consequence, reads (traversals) of the list can be protected

 * by either the RTNL, the iflist_mtx or RCU.

 */





static int ieee80211_change_mtu(struct net_device *dev, int new_mtu)

{

	int meshhdrlen;
@@ -800,7 +817,9 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name, 
					    params->mesh_id_len,

					    params->mesh_id);



	mutex_lock(&local->iflist_mtx);

	list_add_tail_rcu(&sdata->list, &local->interfaces);

	mutex_unlock(&local->iflist_mtx);



	if (new_dev)

		*new_dev = ndev;
@@ -816,7 +835,10 @@ void ieee80211_if_remove(struct ieee80211_sub_if_data *sdata) 
{

	ASSERT_RTNL();



	mutex_lock(&sdata->local->iflist_mtx);

	list_del_rcu(&sdata->list);

	mutex_unlock(&sdata->local->iflist_mtx);



	synchronize_rcu();

	unregister_netdevice(sdata->dev);

}
@@ -832,7 +854,16 @@ void ieee80211_remove_interfaces(struct ieee80211_local *local) 
	ASSERT_RTNL();



	list_for_each_entry_safe(sdata, tmp, &local->interfaces, list) {

		/*

		 * we cannot hold the iflist_mtx across unregister_netdevice,

		 * but we only need to hold it for list modifications to lock

		 * out readers since we're under the RTNL here as all other

		 * writers.

		 */

		mutex_lock(&local->iflist_mtx);

		list_del(&sdata->list);

		mutex_unlock(&local->iflist_mtx);



		unregister_netdevice(sdata->dev);

	}

}

net/mac80211/main.c

+3 −0
Original line number Diff line number Diff line
@@ -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);

net/mac80211/util.c

+2 −2
Original line number Diff line number Diff line
@@ -468,7 +468,7 @@ void ieee80211_iterate_active_interfaces( 
	struct ieee80211_local *local = hw_to_local(hw);

	struct ieee80211_sub_if_data *sdata;



	rtnl_lock();

	mutex_lock(&local->iflist_mtx);



	list_for_each_entry(sdata, &local->interfaces, list) {

		switch (sdata->vif.type) {
@@ -489,7 +489,7 @@ void ieee80211_iterate_active_interfaces( 
				 &sdata->vif);

	}



	rtnl_unlock();

	mutex_unlock(&local->iflist_mtx);

}

EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces);