cfg80211: avoid holding the RTNL when calling the driver

Currently, _everything_ in cfg80211 holds the RTNL, and if you
have a slow USB device (or a few) you can get some bad lock
contention on that.

Fix that by re-adding a mutex to each wiphy/rdev as we had at
some point, so we have locking for the wireless_dev lists and
all the other things in there, and also so that drivers still
don't have to worry too much about it (they still won't get
parallel calls for a single device).

Then, we can restrict the RTNL to a few cases where we add or
remove interfaces and really need the added protection. Some
of the global list management still also uses the RTNL, since
we need to have it anyway for netdev management, but we only
hold the RTNL for very short periods of time here.

Link: https://lore.kernel.org/r/20210122161942.81df9f5e047a.I4a8e1a60b18863ea8c5e6d3a0faeafb2d45b2f40@changeid
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> [marvell driver issues]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

6 files changed, 33 insertions, 16 deletions

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index fcaf4d20cabf..4bc350cf4eee 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -357,11 +357,14 @@ static int ieee80211_open(struct net_device *dev)
 	if (err)
 		return err;
 
-	return ieee80211_do_open(&sdata->wdev, true);
+	wiphy_lock(sdata->local->hw.wiphy);
+	err = ieee80211_do_open(&sdata->wdev, true);
+	wiphy_unlock(sdata->local->hw.wiphy);
+
+	return err;
 }
 
-static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
-			      bool going_down)
+static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_down)
 {
 	struct ieee80211_local *local = sdata->local;
 	unsigned long flags;
@@ -637,7 +640,9 @@ static int ieee80211_stop(struct net_device *dev)
 {
 	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
+	wiphy_lock(sdata->local->hw.wiphy);
 	ieee80211_do_stop(sdata, true);
+	wiphy_unlock(sdata->local->hw.wiphy);
 
 	return 0;
 }
@@ -2057,13 +2062,16 @@ void ieee80211_remove_interfaces(struct ieee80211_local *local)
 			list_add(&sdata->list, &wdev_list);
 	}
 	mutex_unlock(&local->iflist_mtx);
+
 	unregister_netdevice_many(&unreg_list);
 
+	wiphy_lock(local->hw.wiphy);
 	list_for_each_entry_safe(sdata, tmp, &wdev_list, list) {
 		list_del(&sdata->list);
 		cfg80211_unregister_wdev(&sdata->wdev);
 		kfree(sdata);
 	}
+	wiphy_unlock(local->hw.wiphy);
 }
 
 static int netdev_notify(struct notifier_block *nb,
diff --git a/net/mac80211/key.c b/net/mac80211/key.c
index a4817aa4b171..56c068cb49c4 100644
--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -887,7 +887,7 @@ void ieee80211_reenable_keys(struct ieee80211_sub_if_data *sdata)
 	struct ieee80211_key *key;
 	struct ieee80211_sub_if_data *vlan;
 
-	ASSERT_RTNL();
+	lockdep_assert_wiphy(sdata->local->hw.wiphy);
 
 	mutex_lock(&sdata->local->key_mtx);
 
@@ -924,7 +924,7 @@ void ieee80211_iter_keys(struct ieee80211_hw *hw,
 	struct ieee80211_key *key, *tmp;
 	struct ieee80211_sub_if_data *sdata;
 
-	ASSERT_RTNL();
+	lockdep_assert_wiphy(hw->wiphy);
 
 	mutex_lock(&local->key_mtx);
 	if (vif) {
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index dee88ec566ad..4f3f8bb58e76 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -261,7 +261,9 @@ static void ieee80211_restart_work(struct work_struct *work)
 	     "%s called with hardware scan in progress\n", __func__);
 
 	flush_work(&local->radar_detected_work);
+	/* we might do interface manipulations, so need both */
 	rtnl_lock();
+	wiphy_lock(local->hw.wiphy);
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		/*
 		 * XXX: there may be more work for other vif types and even
@@ -293,6 +295,7 @@ static void ieee80211_restart_work(struct work_struct *work)
 	synchronize_net();
 
 	ieee80211_reconfig(local);
+	wiphy_unlock(local->hw.wiphy);
 	rtnl_unlock();
 }
 
@@ -1272,6 +1275,7 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 	rate_control_add_debugfs(local);
 
 	rtnl_lock();
+	wiphy_lock(hw->wiphy);
 
 	/* add one default STA interface if supported */
 	if (local->hw.wiphy->interface_modes & BIT(NL80211_IFTYPE_STATION) &&
@@ -1285,6 +1289,7 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 				   "Failed to add default virtual iface\n");
 	}
 
+	wiphy_unlock(hw->wiphy);
 	rtnl_unlock();
 
 #ifdef CONFIG_INET
diff --git a/net/mac80211/pm.c b/net/mac80211/pm.c
index ae378a41c927..7809a906d7fe 100644
--- a/net/mac80211/pm.c
+++ b/net/mac80211/pm.c
@@ -1,4 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
+/*
+ * Portions
+ * Copyright (C) 2020-2021 Intel Corporation
+ */
 #include <net/mac80211.h>
 #include <net/rtnetlink.h>
 
@@ -11,7 +15,7 @@ static void ieee80211_sched_scan_cancel(struct ieee80211_local *local)
 {
 	if (ieee80211_request_sched_scan_stop(local))
 		return;
-	cfg80211_sched_scan_stopped_rtnl(local->hw.wiphy, 0);
+	cfg80211_sched_scan_stopped_locked(local->hw.wiphy, 0);
 }
 
 int __ieee80211_suspend(struct ieee80211_hw *hw, struct cfg80211_wowlan *wowlan)
diff --git a/net/mac80211/tdls.c b/net/mac80211/tdls.c
index e01e4daeb8cd..f91d02b81b92 100644
--- a/net/mac80211/tdls.c
+++ b/net/mac80211/tdls.c
@@ -1927,7 +1927,7 @@ ieee80211_process_tdls_channel_switch(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_tdls_data *tf = (void *)skb->data;
 	struct wiphy *wiphy = sdata->local->hw.wiphy;
 
-	ASSERT_RTNL();
+	lockdep_assert_wiphy(wiphy);
 
 	/* make sure the driver supports it */
 	if (!(wiphy->features & NL80211_FEATURE_TDLS_CHANNEL_SWITCH))
@@ -1979,7 +1979,7 @@ void ieee80211_tdls_chsw_work(struct work_struct *wk)
 	struct sk_buff *skb;
 	struct ieee80211_tdls_data *tf;
 
-	rtnl_lock();
+	wiphy_lock(local->hw.wiphy);
 	while ((skb = skb_dequeue(&local->skb_queue_tdls_chsw))) {
 		tf = (struct ieee80211_tdls_data *)skb->data;
 		list_for_each_entry(sdata, &local->interfaces, list) {
@@ -1994,7 +1994,7 @@ void ieee80211_tdls_chsw_work(struct work_struct *wk)
 
 		kfree_skb(skb);
 	}
-	rtnl_unlock();
+	wiphy_unlock(local->hw.wiphy);
 }
 
 void ieee80211_tdls_handle_disconnect(struct ieee80211_sub_if_data *sdata,
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 8d3ae6b2f95f..f080fcf60e45 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -832,7 +832,7 @@ void ieee80211_iterate_active_interfaces_atomic(
 }
 EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_atomic);
 
-void ieee80211_iterate_active_interfaces_rtnl(
+void ieee80211_iterate_active_interfaces_mtx(
 	struct ieee80211_hw *hw, u32 iter_flags,
 	void (*iterator)(void *data, u8 *mac,
 			 struct ieee80211_vif *vif),
@@ -840,12 +840,12 @@ void ieee80211_iterate_active_interfaces_rtnl(
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 
-	ASSERT_RTNL();
+	lockdep_assert_wiphy(hw->wiphy);
 
 	__iterate_interfaces(local, iter_flags | IEEE80211_IFACE_ITER_ACTIVE,
 			     iterator, data);
 }
-EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_rtnl);
+EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_mtx);
 
 static void __iterate_stations(struct ieee80211_local *local,
 			       void (*iterator)(void *data,
@@ -2595,7 +2595,7 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 	mutex_unlock(&local->mtx);
 
 	if (sched_scan_stopped)
-		cfg80211_sched_scan_stopped_rtnl(local->hw.wiphy, 0);
+		cfg80211_sched_scan_stopped_locked(local->hw.wiphy, 0);
 
  wake_up:
 
@@ -3811,7 +3811,7 @@ void ieee80211_dfs_cac_cancel(struct ieee80211_local *local)
 	struct cfg80211_chan_def chandef;
 
 	/* for interface list, to avoid linking iflist_mtx and chanctx_mtx */
-	ASSERT_RTNL();
+	lockdep_assert_wiphy(local->hw.wiphy);
 
 	mutex_lock(&local->mtx);
 	list_for_each_entry(sdata, &local->interfaces, list) {
@@ -3851,9 +3851,9 @@ void ieee80211_dfs_radar_detected_work(struct work_struct *work)
 	}
 	mutex_unlock(&local->chanctx_mtx);
 
-	rtnl_lock();
+	wiphy_lock(local->hw.wiphy);
 	ieee80211_dfs_cac_cancel(local);
-	rtnl_unlock();
+	wiphy_unlock(local->hw.wiphy);
 
 	if (num_chanctx > 1)
 		/* XXX: multi-channel is not supported yet */