[PATCH 20/27] wifi: mac80211: add vif/sta link RCU dereference macros

[Johannes Berg <johannes@xxxxxxxxxxxxxxxx>]

From: Johannes Berg <johannes.berg@xxxxxxxxx>

Add macros (and an exported function) to allow checking some
link RCU protected accesses that are happening in callbacks
from mac80211 and are thus under the correct lock.

Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
 drivers/net/wireless/mac80211_hwsim.c |  3 +--
 include/net/mac80211.h                | 31 ++++++++++++++++++++++++---
 net/mac80211/sta_info.c               | 10 +++++++++
 3 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index f464d3507fe9..f044db1621dd 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -3069,8 +3069,7 @@ static int mac80211_hwsim_change_vif_links(struct ieee80211_hw *hw,
 	for_each_set_bit(i, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
 		struct ieee80211_bss_conf *link_conf;
 
-		/* FIXME: figure out how to get the locking here */
-		link_conf = rcu_dereference_protected(vif->link_conf[i], 1);
+		link_conf = link_conf_dereference_protected(vif, i);
 		if (WARN_ON(!link_conf))
 			continue;
 
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index bfa6a1625c5c..d9e7f62cc972 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -18,6 +18,7 @@
 #include <linux/if_ether.h>
 #include <linux/skbuff.h>
 #include <linux/ieee80211.h>
+#include <linux/lockdep.h>
 #include <net/cfg80211.h>
 #include <net/codel.h>
 #include <net/ieee80211_radiotap.h>
@@ -1901,6 +1902,19 @@ struct ieee80211_vif *wdev_to_ieee80211_vif(struct wireless_dev *wdev);
  */
 struct wireless_dev *ieee80211_vif_to_wdev(struct ieee80211_vif *vif);
 
+/**
+ * lockdep_vif_mutex_held - for lockdep checks on link poiners
+ * @vif: the interface to check
+ */
+static inline bool lockdep_vif_mutex_held(struct ieee80211_vif *vif)
+{
+	return lockdep_is_held(&ieee80211_vif_to_wdev(vif)->mtx);
+}
+
+#define link_conf_dereference_protected(vif, link_id)		\
+	rcu_dereference_protected((vif)->link_conf[link_id],	\
+				  lockdep_vif_mutex_held(vif))
+
 /**
  * enum ieee80211_key_flags - key flags
  *
@@ -2266,13 +2280,24 @@ struct ieee80211_sta {
 	u8 drv_priv[] __aligned(sizeof(void *));
 };
 
-/* FIXME: check the locking correctly */
+#ifdef CONFIG_LOCKDEP
+bool lockdep_sta_mutex_held(struct ieee80211_sta *pubsta);
+#else
+static inline bool lockdep_sta_mutex_held(struct ieee80211_sta *pubsta)
+{
+	return true;
+}
+#endif
+
+#define link_sta_dereference_protected(sta, link_id)		\
+	rcu_dereference_protected((sta)->link[link_id],		\
+				  lockdep_sta_mutex_held(sta))
+
 #define for_each_sta_active_link(vif, sta, link_sta, link_id)			\
 	for (link_id = 0; link_id < ARRAY_SIZE((sta)->link); link_id++)		\
 		if ((!(vif)->active_links ||					\
 		     (vif)->active_links & BIT(link_id)) &&			\
-		    ((link_sta) = rcu_dereference_protected((sta)->link[link_id],\
-							    1)))
+		    ((link_sta) = link_sta_dereference_protected(sta, link_id)))
 
 /**
  * enum sta_notify_cmd - sta notify command
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 1749c21e735c..baa55fbab0a2 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -2871,3 +2871,13 @@ void ieee80211_sta_set_max_amsdu_subframes(struct sta_info *sta,
 	if (val)
 		sta->sta.max_amsdu_subframes = 4 << val;
 }
+
+#ifdef CONFIG_LOCKDEP
+bool lockdep_sta_mutex_held(struct ieee80211_sta *pubsta)
+{
+	struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
+
+	return lockdep_is_held(&sta->local->sta_mtx);
+}
+EXPORT_SYMBOL(lockdep_sta_mutex_held);
+#endif
-- 
2.37.2