wifi: mac80211: RCU-ify link/link_conf pointers

Since links can be added and removed dynamically, we need to
somehow protect the sdata->link[] and vif->link_conf[] array
pointers from disappearing when accessing them without locks.
RCU-ify the pointers to achieve this, which requires quite a
bit of rework.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
index 2eb3a409b70f..ea7ce87b7ec4 100644
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -140,12 +140,14 @@ bool ieee80211_ht_cap_ie_to_sta_ht_cap(struct ieee80211_sub_if_data *sdata,
 				       const struct ieee80211_ht_cap *ht_cap_ie,
 				       struct link_sta_info *link_sta)
 {
+	struct ieee80211_bss_conf *link_conf;
 	struct sta_info *sta = link_sta->sta;
 	struct ieee80211_sta_ht_cap ht_cap, own_cap;
 	u8 ampdu_info, tx_mcs_set_cap;
 	int i, max_tx_streams;
 	bool changed;
 	enum ieee80211_sta_rx_bandwidth bw;
+	enum nl80211_chan_width width;
 
 	memset(&ht_cap, 0, sizeof(ht_cap));
 
@@ -248,7 +250,14 @@ bool ieee80211_ht_cap_ie_to_sta_ht_cap(struct ieee80211_sub_if_data *sdata,
 
 	memcpy(&link_sta->pub->ht_cap, &ht_cap, sizeof(ht_cap));
 
-	switch (sdata->vif.link_conf[link_sta->link_id]->chandef.width) {
+	rcu_read_lock();
+	link_conf = rcu_dereference(sdata->vif.link_conf[link_sta->link_id]);
+	if (WARN_ON(!link_conf))
+		width = NL80211_CHAN_WIDTH_20_NOHT;
+	else
+		width = link_conf->chandef.width;
+
+	switch (width) {
 	default:
 		WARN_ON_ONCE(1);
 		fallthrough;
@@ -264,6 +273,7 @@ bool ieee80211_ht_cap_ie_to_sta_ht_cap(struct ieee80211_sub_if_data *sdata,
 				IEEE80211_STA_RX_BW_40 : IEEE80211_STA_RX_BW_20;
 		break;
 	}
+	rcu_read_unlock();
 
 	link_sta->pub->bandwidth = bw;
 
@@ -547,7 +557,7 @@ void ieee80211_request_smps_mgd_work(struct work_struct *work)
 			     u.mgd.request_smps_work);
 
 	sdata_lock(link->sdata);
-	__ieee80211_request_smps_mgd(link->sdata, link->link_id,
+	__ieee80211_request_smps_mgd(link->sdata, link,
 				     link->u.mgd.driver_smps_mode);
 	sdata_unlock(link->sdata);
 }
@@ -556,19 +566,23 @@ void ieee80211_request_smps(struct ieee80211_vif *vif, unsigned int link_id,
 			    enum ieee80211_smps_mode smps_mode)
 {
 	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
-	struct ieee80211_link_data *link = sdata->link[link_id];
+	struct ieee80211_link_data *link;
 
 	if (WARN_ON_ONCE(vif->type != NL80211_IFTYPE_STATION))
 		return;
 
+	rcu_read_lock();
+	link = rcu_dereference(sdata->link[link_id]);
 	if (WARN_ON(!link))
-		return;
+		goto out;
 
 	if (link->u.mgd.driver_smps_mode == smps_mode)
-		return;
+		goto out;
 
 	link->u.mgd.driver_smps_mode = smps_mode;
 	ieee80211_queue_work(&sdata->local->hw, &link->u.mgd.request_smps_work);
+out:
+	rcu_read_unlock();
 }
 /* this might change ... don't want non-open drivers using it */
 EXPORT_SYMBOL_GPL(ieee80211_request_smps);