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>
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 927cbde..eaf3603 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -643,7 +643,9 @@
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
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 8dc2c21..00562a8 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -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 @@
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 @@
{
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 @@
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);
}
}
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 210dfe3..a109c06 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -758,6 +758,7 @@
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 @@
{
struct ieee80211_local *local = hw_to_local(hw);
+ mutex_destroy(&local->iflist_mtx);
+
wiphy_free(local->hw.wiphy);
}
EXPORT_SYMBOL(ieee80211_free_hw);
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index fc30f29..73c7d73 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -468,7 +468,7 @@
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 @@
&sdata->vif);
}
- rtnl_unlock();
+ mutex_unlock(&local->iflist_mtx);
}
EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces);