[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>
diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index 4e345f8..ccf8463 100644
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -93,14 +93,13 @@
struct ieee80211_sub_if_data *sdata;
int res = -EOPNOTSUPP;
- read_lock(&local->sub_if_lock);
- list_for_each_entry(sdata, &local->sub_if_list, list) {
+ /* we hold the RTNL here so can safely walk the list */
+ list_for_each_entry(sdata, &local->interfaces, list) {
if (sdata->dev != dev && netif_running(sdata->dev)) {
res = 0;
break;
}
}
- read_unlock(&local->sub_if_lock);
return res;
}
@@ -109,11 +108,10 @@
struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
struct ieee80211_sub_if_data *sdata;
- read_lock(&local->sub_if_lock);
- list_for_each_entry(sdata, &local->sub_if_list, list)
+ /* we hold the RTNL here so can safely walk the list */
+ list_for_each_entry(sdata, &local->interfaces, list)
if (sdata->dev != dev && netif_running(sdata->dev))
dev_close(sdata->dev);
- read_unlock(&local->sub_if_lock);
return 0;
}
@@ -315,8 +313,8 @@
sdata = IEEE80211_DEV_TO_SUB_IF(dev);
- read_lock(&local->sub_if_lock);
- list_for_each_entry(nsdata, &local->sub_if_list, list) {
+ /* we hold the RTNL here so can safely walk the list */
+ list_for_each_entry(nsdata, &local->interfaces, list) {
struct net_device *ndev = nsdata->dev;
if (ndev != dev && ndev != local->mdev && netif_running(ndev) &&
@@ -325,10 +323,8 @@
* check whether it may have the same address
*/
if (!identical_mac_addr_allowed(sdata->type,
- nsdata->type)) {
- read_unlock(&local->sub_if_lock);
+ nsdata->type))
return -ENOTUNIQ;
- }
/*
* can only add VLANs to enabled APs
@@ -339,7 +335,6 @@
sdata->u.vlan.ap = nsdata;
}
}
- read_unlock(&local->sub_if_lock);
switch (sdata->type) {
case IEEE80211_IF_TYPE_WDS:
@@ -466,14 +461,13 @@
sdata->u.sta.state = IEEE80211_DISABLED;
del_timer_sync(&sdata->u.sta.timer);
/*
- * Holding the sub_if_lock for writing here blocks
- * out the receive path and makes sure it's not
- * currently processing a packet that may get
- * added to the queue.
+ * When we get here, the interface is marked down.
+ * Call synchronize_rcu() to wait for the RX path
+ * should it be using the interface and enqueuing
+ * frames at this very time on another CPU.
*/
- write_lock_bh(&local->sub_if_lock);
+ synchronize_rcu();
skb_queue_purge(&sdata->u.sta.skb_queue);
- write_unlock_bh(&local->sub_if_lock);
if (!local->ops->hw_scan &&
local->scan_dev == sdata->dev) {
@@ -1033,9 +1027,9 @@
rthdr->data_retries = status->retry_count;
- read_lock(&local->sub_if_lock);
+ rcu_read_lock();
monitors = local->monitors;
- list_for_each_entry(sdata, &local->sub_if_list, list) {
+ list_for_each_entry_rcu(sdata, &local->interfaces, list) {
/*
* Using the monitors counter is possibly racy, but
* if the value is wrong we simply either clone the skb
@@ -1051,7 +1045,7 @@
continue;
monitors--;
if (monitors)
- skb2 = skb_clone(skb, GFP_KERNEL);
+ skb2 = skb_clone(skb, GFP_ATOMIC);
else
skb2 = NULL;
skb->dev = sdata->dev;
@@ -1066,7 +1060,7 @@
}
}
out:
- read_unlock(&local->sub_if_lock);
+ rcu_read_unlock();
if (skb)
dev_kfree_skb(skb);
}
@@ -1154,8 +1148,7 @@
INIT_LIST_HEAD(&local->modes_list);
- rwlock_init(&local->sub_if_lock);
- INIT_LIST_HEAD(&local->sub_if_list);
+ INIT_LIST_HEAD(&local->interfaces);
INIT_DELAYED_WORK(&local->scan_work, ieee80211_sta_scan_work);
ieee80211_rx_bss_list_init(mdev);
@@ -1175,7 +1168,8 @@
sdata->u.ap.force_unicast_rateidx = -1;
sdata->u.ap.max_ratectrl_rateidx = -1;
ieee80211_if_sdata_init(sdata);
- list_add_tail(&sdata->list, &local->sub_if_list);
+ /* no RCU needed since we're still during init phase */
+ list_add_tail(&sdata->list, &local->interfaces);
tasklet_init(&local->tx_pending_tasklet, ieee80211_tx_pending,
(unsigned long)local);
@@ -1334,7 +1328,6 @@
{
struct ieee80211_local *local = hw_to_local(hw);
struct ieee80211_sub_if_data *sdata, *tmp;
- struct list_head tmp_list;
int i;
tasklet_kill(&local->tx_pending_tasklet);
@@ -1348,11 +1341,12 @@
if (local->apdev)
ieee80211_if_del_mgmt(local);
- write_lock_bh(&local->sub_if_lock);
- list_replace_init(&local->sub_if_list, &tmp_list);
- write_unlock_bh(&local->sub_if_lock);
-
- list_for_each_entry_safe(sdata, tmp, &tmp_list, list)
+ /*
+ * At this point, interface list manipulations are fine
+ * because the driver cannot be handing us frames any
+ * more and the tasklet is killed.
+ */
+ list_for_each_entry_safe(sdata, tmp, &local->interfaces, list)
__ieee80211_if_del(local, sdata);
rtnl_unlock();
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 1a43f3e..a5961f1 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -475,9 +475,8 @@
ieee80211_rx_handler *rx_handlers;
ieee80211_tx_handler *tx_handlers;
- rwlock_t sub_if_lock; /* Protects sub_if_list. Cannot be taken under
- * sta_bss_lock or sta_lock. */
- struct list_head sub_if_list;
+ struct list_head interfaces;
+
int sta_scanning;
int scan_channel_idx;
enum { SCAN_SET_CHANNEL, SCAN_SEND_PROBE } scan_state;
diff --git a/net/mac80211/ieee80211_iface.c b/net/mac80211/ieee80211_iface.c
index 4590205f..2ba24ef 100644
--- a/net/mac80211/ieee80211_iface.c
+++ b/net/mac80211/ieee80211_iface.c
@@ -79,16 +79,15 @@
ieee80211_debugfs_add_netdev(sdata);
ieee80211_if_set_type(ndev, type);
- write_lock_bh(&local->sub_if_lock);
+ /* we're under RTNL so all this is fine */
if (unlikely(local->reg_state == IEEE80211_DEV_UNREGISTERED)) {
- write_unlock_bh(&local->sub_if_lock);
__ieee80211_if_del(local, sdata);
return -ENODEV;
}
- list_add(&sdata->list, &local->sub_if_list);
+ list_add_tail_rcu(&sdata->list, &local->interfaces);
+
if (new_dev)
*new_dev = ndev;
- write_unlock_bh(&local->sub_if_lock);
return 0;
@@ -226,22 +225,22 @@
/* Remove all virtual interfaces that use this BSS
* as their sdata->bss */
struct ieee80211_sub_if_data *tsdata, *n;
- LIST_HEAD(tmp_list);
- write_lock_bh(&local->sub_if_lock);
- list_for_each_entry_safe(tsdata, n, &local->sub_if_list, list) {
+ list_for_each_entry_safe(tsdata, n, &local->interfaces, list) {
if (tsdata != sdata && tsdata->bss == &sdata->u.ap) {
printk(KERN_DEBUG "%s: removing virtual "
"interface %s because its BSS interface"
" is being removed\n",
sdata->dev->name, tsdata->dev->name);
- list_move_tail(&tsdata->list, &tmp_list);
+ list_del_rcu(&tsdata->list);
+ /*
+ * We have lots of time and can afford
+ * to sync for each interface
+ */
+ synchronize_rcu();
+ __ieee80211_if_del(local, tsdata);
}
}
- write_unlock_bh(&local->sub_if_lock);
-
- list_for_each_entry_safe(tsdata, n, &tmp_list, list)
- __ieee80211_if_del(local, tsdata);
kfree(sdata->u.ap.beacon_head);
kfree(sdata->u.ap.beacon_tail);
@@ -318,18 +317,16 @@
ASSERT_RTNL();
- write_lock_bh(&local->sub_if_lock);
- list_for_each_entry_safe(sdata, n, &local->sub_if_list, list) {
+ list_for_each_entry_safe(sdata, n, &local->interfaces, list) {
if ((sdata->type == id || id == -1) &&
strcmp(name, sdata->dev->name) == 0 &&
sdata->dev != local->mdev) {
- list_del(&sdata->list);
- write_unlock_bh(&local->sub_if_lock);
+ list_del_rcu(&sdata->list);
+ synchronize_rcu();
__ieee80211_if_del(local, sdata);
return 0;
}
}
- write_unlock_bh(&local->sub_if_lock);
return -ENODEV;
}
diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index 17455c6..651aaba 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -2676,8 +2676,8 @@
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 @@
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 @@
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 @@
(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;
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 2535d8d..cb44a9d 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1383,8 +1383,9 @@
}
/*
- * key references are protected using RCU and this requires that
- * we are in a read-site RCU section during receive processing
+ * key references and virtual interfaces are protected using RCU
+ * and this requires that we are in a read-side RCU section during
+ * receive processing
*/
rcu_read_lock();
@@ -1439,8 +1440,7 @@
bssid = ieee80211_get_bssid(hdr, skb->len - radiotap_len);
- read_lock(&local->sub_if_lock);
- list_for_each_entry(sdata, &local->sub_if_list, list) {
+ list_for_each_entry_rcu(sdata, &local->interfaces, list) {
rx.flags |= IEEE80211_TXRXD_RXRA_MATCH;
if (!netif_running(sdata->dev))
@@ -1493,7 +1493,6 @@
&rx, sta);
} else
dev_kfree_skb(skb);
- read_unlock(&local->sub_if_lock);
end:
rcu_read_unlock();
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 38394c4..244c80d 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -295,8 +295,12 @@
struct ieee80211_sub_if_data *sdata;
struct sta_info *sta;
- read_lock(&local->sub_if_lock);
- list_for_each_entry(sdata, &local->sub_if_list, list) {
+ /*
+ * virtual interfaces are protected by RCU
+ */
+ rcu_read_lock();
+
+ list_for_each_entry_rcu(sdata, &local->interfaces, list) {
struct ieee80211_if_ap *ap;
if (sdata->dev == local->mdev ||
sdata->type != IEEE80211_IF_TYPE_AP)
@@ -309,7 +313,7 @@
}
total += skb_queue_len(&ap->ps_bc_buf);
}
- read_unlock(&local->sub_if_lock);
+ rcu_read_unlock();
read_lock_bh(&local->sta_lock);
list_for_each_entry(sta, &local->sta_list, list) {