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>

1 files changed, 19 insertions, 16 deletions

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 1b7fec3b53cd..019952d4fc7d 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -918,7 +918,7 @@ void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev,
 	union iwreq_data wrqu;
 #endif
 
-	ASSERT_RTNL();
+	lockdep_assert_held(&rdev->wiphy.mtx);
 
 	if (rdev->scan_msg) {
 		nl80211_send_scan_msg(rdev, rdev->scan_msg);
@@ -987,9 +987,9 @@ void __cfg80211_scan_done(struct work_struct *wk)
 	rdev = container_of(wk, struct cfg80211_registered_device,
 			    scan_done_wk);
 
-	rtnl_lock();
+	wiphy_lock(&rdev->wiphy);
 	___cfg80211_scan_done(rdev, true);
-	rtnl_unlock();
+	wiphy_unlock(&rdev->wiphy);
 }
 
 void cfg80211_scan_done(struct cfg80211_scan_request *request,
@@ -1022,7 +1022,7 @@ EXPORT_SYMBOL(cfg80211_scan_done);
 void cfg80211_add_sched_scan_req(struct cfg80211_registered_device *rdev,
 				 struct cfg80211_sched_scan_request *req)
 {
-	ASSERT_RTNL();
+	lockdep_assert_held(&rdev->wiphy.mtx);
 
 	list_add_rcu(&req->list, &rdev->sched_scan_req_list);
 }
@@ -1030,7 +1030,7 @@ void cfg80211_add_sched_scan_req(struct cfg80211_registered_device *rdev,
 static void cfg80211_del_sched_scan_req(struct cfg80211_registered_device *rdev,
 					struct cfg80211_sched_scan_request *req)
 {
-	ASSERT_RTNL();
+	lockdep_assert_held(&rdev->wiphy.mtx);
 
 	list_del_rcu(&req->list);
 	kfree_rcu(req, rcu_head);
@@ -1042,7 +1042,7 @@ cfg80211_find_sched_scan_req(struct cfg80211_registered_device *rdev, u64 reqid)
 	struct cfg80211_sched_scan_request *pos;
 
 	list_for_each_entry_rcu(pos, &rdev->sched_scan_req_list, list,
-				lockdep_rtnl_is_held()) {
+				lockdep_is_held(&rdev->wiphy.mtx)) {
 		if (pos->reqid == reqid)
 			return pos;
 	}
@@ -1090,7 +1090,7 @@ void cfg80211_sched_scan_results_wk(struct work_struct *work)
 	rdev = container_of(work, struct cfg80211_registered_device,
 			   sched_scan_res_wk);
 
-	rtnl_lock();
+	wiphy_lock(&rdev->wiphy);
 	list_for_each_entry_safe(req, tmp, &rdev->sched_scan_req_list, list) {
 		if (req->report_results) {
 			req->report_results = false;
@@ -1105,7 +1105,7 @@ void cfg80211_sched_scan_results_wk(struct work_struct *work)
 						NL80211_CMD_SCHED_SCAN_RESULTS);
 		}
 	}
-	rtnl_unlock();
+	wiphy_unlock(&rdev->wiphy);
 }
 
 void cfg80211_sched_scan_results(struct wiphy *wiphy, u64 reqid)
@@ -1126,23 +1126,23 @@ void cfg80211_sched_scan_results(struct wiphy *wiphy, u64 reqid)
 }
 EXPORT_SYMBOL(cfg80211_sched_scan_results);
 
-void cfg80211_sched_scan_stopped_rtnl(struct wiphy *wiphy, u64 reqid)
+void cfg80211_sched_scan_stopped_locked(struct wiphy *wiphy, u64 reqid)
 {
 	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
 
-	ASSERT_RTNL();
+	lockdep_assert_held(&wiphy->mtx);
 
 	trace_cfg80211_sched_scan_stopped(wiphy, reqid);
 
 	__cfg80211_stop_sched_scan(rdev, reqid, true);
 }
-EXPORT_SYMBOL(cfg80211_sched_scan_stopped_rtnl);
+EXPORT_SYMBOL(cfg80211_sched_scan_stopped_locked);
 
 void cfg80211_sched_scan_stopped(struct wiphy *wiphy, u64 reqid)
 {
-	rtnl_lock();
-	cfg80211_sched_scan_stopped_rtnl(wiphy, reqid);
-	rtnl_unlock();
+	wiphy_lock(wiphy);
+	cfg80211_sched_scan_stopped_locked(wiphy, reqid);
+	wiphy_unlock(wiphy);
 }
 EXPORT_SYMBOL(cfg80211_sched_scan_stopped);
 
@@ -1150,7 +1150,7 @@ int cfg80211_stop_sched_scan_req(struct cfg80211_registered_device *rdev,
 				 struct cfg80211_sched_scan_request *req,
 				 bool driver_initiated)
 {
-	ASSERT_RTNL();
+	lockdep_assert_held(&rdev->wiphy.mtx);
 
 	if (!driver_initiated) {
 		int err = rdev_sched_scan_stop(rdev, req->dev, req->reqid);
@@ -1170,7 +1170,7 @@ int __cfg80211_stop_sched_scan(struct cfg80211_registered_device *rdev,
 {
 	struct cfg80211_sched_scan_request *sched_scan_req;
 
-	ASSERT_RTNL();
+	lockdep_assert_held(&rdev->wiphy.mtx);
 
 	sched_scan_req = cfg80211_find_sched_scan_req(rdev, reqid);
 	if (!sched_scan_req)
@@ -2774,6 +2774,8 @@ int cfg80211_wext_siwscan(struct net_device *dev,
 
 	eth_broadcast_addr(creq->bssid);
 
+	wiphy_lock(&rdev->wiphy);
+
 	rdev->scan_req = creq;
 	err = rdev_scan(rdev, creq);
 	if (err) {
@@ -2785,6 +2787,7 @@ int cfg80211_wext_siwscan(struct net_device *dev,
 		creq = NULL;
 		dev_hold(dev);
 	}
+	wiphy_unlock(&rdev->wiphy);
  out:
 	kfree(creq);
 	return err;