mac80211: Fix circular locking dependency in ARP filter handling

There is a circular locking dependency when configuring the
hardware ARP filters on association, occurring when flushing the mac80211
workqueue. This is what happens:

[   92.026800] =======================================================
[   92.030507] [ INFO: possible circular locking dependency detected ]
[   92.030507] 2.6.34-04781-g2b2c009e #85
[   92.030507] -------------------------------------------------------
[   92.030507] modprobe/5225 is trying to acquire lock:
[   92.030507]  ((wiphy_name(local->hw.wiphy))){+.+.+.}, at: [<ffffffff8105b5c0>] flush_workq
ueue+0x0/0xb0
[   92.030507]
[   92.030507] but task is already holding lock:
[   92.030507]  (rtnl_mutex){+.+.+.}, at: [<ffffffff812b9ce2>] rtnl_lock+0x12/0x20
[   92.030507]
[   92.030507] which lock already depends on the new lock.
[   92.030507]
[   92.030507]
[   92.030507] the existing dependency chain (in reverse order) is:
[   92.030507]
[   92.030507] -> #2 (rtnl_mutex){+.+.+.}:
[   92.030507]        [<ffffffff810761fb>] lock_acquire+0xdb/0x110
[   92.030507]        [<ffffffff81341754>] mutex_lock_nested+0x44/0x300
[   92.030507]        [<ffffffff812b9ce2>] rtnl_lock+0x12/0x20
[   92.030507]        [<ffffffffa022d47c>] ieee80211_assoc_done+0x6c/0xe0 [mac80211]
[   92.030507]        [<ffffffffa022f2ad>] ieee80211_work_work+0x31d/0x1280 [mac80211]

[   92.030507] -> #1 ((&local->work_work)){+.+.+.}:
[   92.030507]        [<ffffffff810761fb>] lock_acquire+0xdb/0x110
[   92.030507]        [<ffffffff8105a51a>] worker_thread+0x22a/0x370
[   92.030507]        [<ffffffff8105ecc6>] kthread+0x96/0xb0
[   92.030507]        [<ffffffff81003a94>] kernel_thread_helper+0x4/0x10
[   92.030507]
[   92.030507] -> #0 ((wiphy_name(local->hw.wiphy))){+.+.+.}:
[   92.030507]        [<ffffffff81075fdc>] __lock_acquire+0x1c0c/0x1d50
[   92.030507]        [<ffffffff810761fb>] lock_acquire+0xdb/0x110
[   92.030507]        [<ffffffff8105b60e>] flush_workqueue+0x4e/0xb0
[   92.030507]        [<ffffffffa023ff7b>] ieee80211_stop_device+0x2b/0xb0 [mac80211]
[   92.030507]        [<ffffffffa0231635>] ieee80211_stop+0x3e5/0x680 [mac80211]

The locking in this case is quite complex. Fix the problem by rewriting the
way the hardware ARP filter list is handled - i.e. make a copy of the address
list to the bss_conf struct, and provide that list to the hardware driver
when needed.

The current patch will enable filtering also in promiscuous mode. This may need
to be changed in the future.
Reported-by: NReinette Chatre <reinette.chatre@intel.com>
Signed-off-by: NJuuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -19,7 +19,6 @@
 #include <linux/wireless.h>
 #include <linux/device.h>
 #include <linux/ieee80211.h>
-#include <linux/inetdevice.h>
 #include <net/cfg80211.h>
 
 /**
@@ -147,6 +146,7 @@ struct ieee80211_low_level_stats {
  *	enabled/disabled (beaconing modes)
  * @BSS_CHANGED_CQM: Connection quality monitor config changed
  * @BSS_CHANGED_IBSS: IBSS join status changed
+ * @BSS_CHANGED_ARP_FILTER: Hardware ARP filter address list or state changed.
  */
 enum ieee80211_bss_change {
 	BSS_CHANGED_ASSOC		= 1<<0,
@@ -161,10 +161,18 @@ enum ieee80211_bss_change {
 	BSS_CHANGED_BEACON_ENABLED	= 1<<9,
 	BSS_CHANGED_CQM			= 1<<10,
 	BSS_CHANGED_IBSS		= 1<<11,
+	BSS_CHANGED_ARP_FILTER		= 1<<12,
 
 	/* when adding here, make sure to change ieee80211_reconfig */
 };
 
+/*
+ * The maximum number of IPv4 addresses listed for ARP filtering. If the number
+ * of addresses for an interface increase beyond this value, hardware ARP
+ * filtering will be disabled.
+ */
+#define IEEE80211_BSS_ARP_ADDR_LIST_LEN 4
+
 /**
  * struct ieee80211_bss_conf - holds the BSS's changing parameters
  *
@@ -200,6 +208,15 @@ enum ieee80211_bss_change {
  * @cqm_rssi_thold: Connection quality monitor RSSI threshold, a zero value
  *	implies disabled
  * @cqm_rssi_hyst: Connection quality monitor RSSI hysteresis
+ * @arp_addr_list: List of IPv4 addresses for hardware ARP filtering. The
+ *	may filter ARP queries targeted for other addresses than listed here.
+ *	The driver must allow ARP queries targeted for all address listed here
+ *	to pass through. An empty list implies no ARP queries need to pass.
+ * @arp_addr_cnt: Number of addresses currently on the list.
+ * @arp_filter_enabled: Enable ARP filtering - if enabled, the hardware may
+ *	filter ARP queries based on the @arp_addr_list, if disabled, the
+ *	hardware must not perform any ARP filtering. Note, that the filter will
+ *	be enabled also in promiscuous mode.
  */
 struct ieee80211_bss_conf {
 	const u8 *bssid;
@@ -220,6 +237,9 @@ struct ieee80211_bss_conf {
 	s32 cqm_rssi_thold;
 	u32 cqm_rssi_hyst;
 	enum nl80211_channel_type channel_type;
+	__be32 arp_addr_list[IEEE80211_BSS_ARP_ADDR_LIST_LEN];
+	u8 arp_addr_cnt;
+	bool arp_filter_enabled;
 };
 
 /**
@@ -1529,16 +1549,6 @@ enum ieee80211_ampdu_mlme_action {
  *	of the bss parameters has changed when a call is made. The callback
  *	can sleep.
  *
- * @configure_arp_filter: Configuration function for hardware ARP query filter.
- *	This function is called with all the IP addresses configured to the
- *	interface as argument - all ARP queries targeted to any of these
- *	addresses must pass through. If the hardware filter does not support
- *	enought addresses, hardware filtering must be disabled. The ifa_list
- *	argument may be NULL, indicating that filtering must be disabled.
- *	This function is called upon association complete with current
- *	address(es), and while associated whenever the IP address(es) change.
- *	The callback can sleep.
- *
  * @prepare_multicast: Prepare for multicast filter configuration.
  *	This callback is optional, and its return value is passed
  *	to configure_filter(). This callback must be atomic.
@@ -1678,9 +1688,6 @@ struct ieee80211_ops {
 				 struct ieee80211_vif *vif,
 				 struct ieee80211_bss_conf *info,
 				 u32 changed);
-	int (*configure_arp_filter)(struct ieee80211_hw *hw,
-				    struct ieee80211_vif *vif,
-				    struct in_ifaddr *ifa_list);
 	u64 (*prepare_multicast)(struct ieee80211_hw *hw,
 				 struct netdev_hw_addr_list *mc_list);
 	void (*configure_filter)(struct ieee80211_hw *hw,

net/mac80211/driver-ops.h

@@ -89,23 +89,6 @@ static inline void drv_bss_info_changed(struct ieee80211_local *local,
 	trace_drv_return_void(local);
 }
 
-struct in_ifaddr;
-static inline int drv_configure_arp_filter(struct ieee80211_local *local,
-					   struct ieee80211_vif *vif,
-					   struct in_ifaddr *ifa_list)
-{
-	int ret = 0;
-
-	might_sleep();
-
-	trace_drv_configure_arp_filter(local, vif_to_sdata(vif));
-	if (local->ops->configure_arp_filter)
-		ret = local->ops->configure_arp_filter(&local->hw, vif,
-						       ifa_list);
-	trace_drv_return_int(local, ret);
-	return ret;
-}
-
 static inline u64 drv_prepare_multicast(struct ieee80211_local *local,
 					struct netdev_hw_addr_list *mc_list)
 {

net/mac80211/driver-trace.h

@@ -251,28 +251,6 @@ TRACE_EVENT(drv_bss_info_changed,
 	)
 );
 
-TRACE_EVENT(drv_configure_arp_filter,
-	TP_PROTO(struct ieee80211_local *local,
-		 struct ieee80211_sub_if_data *sdata),
-
-	TP_ARGS(local, sdata),
-
-	TP_STRUCT__entry(
-		LOCAL_ENTRY
-		VIF_ENTRY
-	),
-
-	TP_fast_assign(
-		LOCAL_ASSIGN;
-		VIF_ASSIGN;
-	),
-
-	TP_printk(
-		VIF_PR_FMT LOCAL_PR_FMT,
-		VIF_PR_ARG, LOCAL_PR_ARG
-	)
-);
-
 TRACE_EVENT(drv_prepare_multicast,
 	TP_PROTO(struct ieee80211_local *local, int mc_count),
 

net/mac80211/ieee80211_i.h

@@ -514,6 +514,8 @@ struct ieee80211_sub_if_data {
 	struct work_struct work;
 	struct sk_buff_head skb_queue;
 
+	bool arp_filter_state;
+
 	/*
 	 * AP this belongs to: self in AP mode and
 	 * corresponding AP in VLAN mode, NULL for

net/mac80211/iface.c

@@ -1076,6 +1076,9 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 	sdata->wdev.wiphy = local->hw.wiphy;
 	sdata->local = local;
 	sdata->dev = ndev;
+#ifdef CONFIG_INET
+	sdata->arp_filter_state = true;
+#endif
 
 	for (i = 0; i < IEEE80211_FRAGMENT_MAX; i++)
 		skb_queue_head_init(&sdata->fragments[i].skb_list);

net/mac80211/main.c

@@ -20,6 +20,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/bitmap.h>
 #include <linux/pm_qos_params.h>
+#include <linux/inetdevice.h>
 #include <net/net_namespace.h>
 #include <net/cfg80211.h>
 
@@ -317,23 +318,6 @@ static void ieee80211_recalc_smps_work(struct work_struct *work)
 }
 
 #ifdef CONFIG_INET
-int ieee80211_set_arp_filter(struct ieee80211_sub_if_data *sdata)
-{
-	struct in_device *idev;
-	int ret = 0;
-
-	BUG_ON(!sdata);
-	ASSERT_RTNL();
-
-	idev = sdata->dev->ip_ptr;
-	if (!idev)
-		return 0;
-
-	ret = drv_configure_arp_filter(sdata->local, &sdata->vif,
-				       idev->ifa_list);
-	return ret;
-}
-
 static int ieee80211_ifa_changed(struct notifier_block *nb,
 				 unsigned long data, void *arg)
 {
@@ -343,8 +327,11 @@ static int ieee80211_ifa_changed(struct notifier_block *nb,
 			     ifa_notifier);
 	struct net_device *ndev = ifa->ifa_dev->dev;
 	struct wireless_dev *wdev = ndev->ieee80211_ptr;
+	struct in_device *idev;
 	struct ieee80211_sub_if_data *sdata;
+	struct ieee80211_bss_conf *bss_conf;
 	struct ieee80211_if_managed *ifmgd;
+	int c = 0;
 
 	if (!netif_running(ndev))
 		return NOTIFY_DONE;
@@ -356,17 +343,44 @@ static int ieee80211_ifa_changed(struct notifier_block *nb,
 	if (wdev->wiphy != local->hw.wiphy)
 		return NOTIFY_DONE;
 
-	/* We are concerned about IP addresses only when associated */
 	sdata = IEEE80211_DEV_TO_SUB_IF(ndev);
+	bss_conf = &sdata->vif.bss_conf;
 
 	/* ARP filtering is only supported in managed mode */
 	if (sdata->vif.type != NL80211_IFTYPE_STATION)
 		return NOTIFY_DONE;
 
+	idev = sdata->dev->ip_ptr;
+	if (!idev)
+		return NOTIFY_DONE;
+
 	ifmgd = &sdata->u.mgd;
 	mutex_lock(&ifmgd->mtx);
-	if (ifmgd->associated)
-		ieee80211_set_arp_filter(sdata);
+
+	/* Copy the addresses to the bss_conf list */
+	ifa = idev->ifa_list;
+	while (c < IEEE80211_BSS_ARP_ADDR_LIST_LEN && ifa) {
+		bss_conf->arp_addr_list[c] = ifa->ifa_address;
+		ifa = ifa->ifa_next;
+		c++;
+	}
+
+	/* If not all addresses fit the list, disable filtering */
+	if (ifa) {
+		sdata->arp_filter_state = false;
+		c = 0;
+	} else {
+		sdata->arp_filter_state = true;
+	}
+	bss_conf->arp_addr_cnt = c;
+
+	/* Configure driver only if associated */
+	if (ifmgd->associated) {
+		bss_conf->arp_filter_enabled = sdata->arp_filter_state;
+		ieee80211_bss_info_change_notify(sdata,
+						 BSS_CHANGED_ARP_FILTER);
+	}
+
 	mutex_unlock(&ifmgd->mtx);
 
 	return NOTIFY_DONE;

net/mac80211/mlme.c

@@ -806,11 +806,12 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
 {
 	struct ieee80211_bss *bss = (void *)cbss->priv;
 	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_bss_conf *bss_conf = &sdata->vif.bss_conf;
 
 	bss_info_changed |= BSS_CHANGED_ASSOC;
 	/* set timing information */
-	sdata->vif.bss_conf.beacon_int = cbss->beacon_interval;
-	sdata->vif.bss_conf.timestamp = cbss->tsf;
+	bss_conf->beacon_int = cbss->beacon_interval;
+	bss_conf->timestamp = cbss->tsf;
 
 	bss_info_changed |= BSS_CHANGED_BEACON_INT;
 	bss_info_changed |= ieee80211_handle_bss_capability(sdata,
@@ -835,7 +836,7 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
 
 	ieee80211_led_assoc(local, 1);
 
-	sdata->vif.bss_conf.assoc = 1;
+	bss_conf->assoc = 1;
 	/*
 	 * For now just always ask the driver to update the basic rateset
 	 * when we have associated, we aren't checking whether it actually
@@ -848,9 +849,15 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
 
 	/* Tell the driver to monitor connection quality (if supported) */
 	if ((local->hw.flags & IEEE80211_HW_SUPPORTS_CQM_RSSI) &&
-	    sdata->vif.bss_conf.cqm_rssi_thold)
+	    bss_conf->cqm_rssi_thold)
 		bss_info_changed |= BSS_CHANGED_CQM;
 
+	/* Enable ARP filtering */
+	if (bss_conf->arp_filter_enabled != sdata->arp_filter_state) {
+		bss_conf->arp_filter_enabled = sdata->arp_filter_state;
+		bss_info_changed |= BSS_CHANGED_ARP_FILTER;
+	}
+
 	ieee80211_bss_info_change_notify(sdata, bss_info_changed);
 
 	mutex_lock(&local->iflist_mtx);
@@ -932,6 +939,12 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata,
 
 	ieee80211_hw_config(local, config_changed);
 
+	/* Disable ARP filtering */
+	if (sdata->vif.bss_conf.arp_filter_enabled) {
+		sdata->vif.bss_conf.arp_filter_enabled = false;
+		changed |= BSS_CHANGED_ARP_FILTER;
+	}
+
 	/* The BSSID (not really interesting) and HT changed */
 	changed |= BSS_CHANGED_BSSID | BSS_CHANGED_HT;
 	ieee80211_bss_info_change_notify(sdata, changed);
@@ -2018,18 +2031,9 @@ static enum work_done_result ieee80211_assoc_done(struct ieee80211_work *wk,
 			cfg80211_send_assoc_timeout(wk->sdata->dev,
 						    wk->filter_ta);
 			return WORK_DONE_DESTROY;
-		} else {
-			mutex_unlock(&wk->sdata->u.mgd.mtx);
-#ifdef CONFIG_INET
-			/*
-			 * configure ARP filter IP addresses to the driver,
-			 * intentionally outside the mgd mutex.
-			 */
-			rtnl_lock();
-			ieee80211_set_arp_filter(wk->sdata);
-			rtnl_unlock();
-#endif
 		}
+
+		mutex_unlock(&wk->sdata->u.mgd.mtx);
 	}
 
 	cfg80211_send_rx_assoc(wk->sdata->dev, skb->data, skb->len);