iwlwifi: mvm: Protect mvm->csa_vif with RCU

Currently mvm->csa_vif is protected with mvm mutex. The RCU protection
is required for "iwlwifi: mvm: Reflect GO channel switch in NoA" patch.
Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/mac-ctxt.c

@@ -1206,6 +1206,7 @@ int iwl_mvm_rx_beacon_notif(struct iwl_mvm *mvm,
 {
 	struct iwl_rx_packet *pkt = rxb_addr(rxb);
 	struct iwl_mvm_tx_resp *beacon_notify_hdr;
+	struct ieee80211_vif *csa_vif;
 	u64 tsf;
 
 	lockdep_assert_held(&mvm->mutex);
@@ -1231,13 +1232,15 @@ int iwl_mvm_rx_beacon_notif(struct iwl_mvm *mvm,
 		     mvm->ap_last_beacon_gp2,
 		     le32_to_cpu(beacon_notify_hdr->initial_rate));
 
-	if (unlikely(mvm->csa_vif && mvm->csa_vif->csa_active)) {
-		if (!ieee80211_csa_is_complete(mvm->csa_vif)) {
-			ieee80211_csa_update_counter(mvm->csa_vif);
-			iwl_mvm_mac_ctxt_beacon_changed(mvm, mvm->csa_vif);
+	csa_vif = rcu_dereference_protected(mvm->csa_vif,
+					    lockdep_is_held(&mvm->mutex));
+	if (unlikely(csa_vif && csa_vif->csa_active)) {
+		if (!ieee80211_csa_is_complete(csa_vif)) {
+			ieee80211_csa_update_counter(csa_vif);
+			iwl_mvm_mac_ctxt_beacon_changed(mvm, csa_vif);
 		} else {
-			ieee80211_csa_finish(mvm->csa_vif);
-			mvm->csa_vif = NULL;
+			ieee80211_csa_finish(csa_vif);
+			RCU_INIT_POINTER(mvm->csa_vif, NULL);
 		}
 	}
 

drivers/net/wireless/iwlwifi/mvm/mac80211.c

@@ -1607,6 +1607,10 @@ static void iwl_mvm_stop_ap_ibss(struct ieee80211_hw *hw,
 
 	mutex_lock(&mvm->mutex);
 
+	/* Handle AP stop while in CSA */
+	if (rcu_access_pointer(mvm->csa_vif) == vif)
+		RCU_INIT_POINTER(mvm->csa_vif, NULL);
+
 	mvmvif->ap_ibss_active = false;
 	mvm->ap_last_beacon_gp2 = 0;
 
@@ -2664,15 +2668,19 @@ static void iwl_mvm_channel_switch_beacon(struct ieee80211_hw *hw,
 					  struct cfg80211_chan_def *chandef)
 {
 	struct iwl_mvm *mvm = IWL_MAC80211_GET_MVM(hw);
+	struct ieee80211_vif *csa_vif;
 
 	mutex_lock(&mvm->mutex);
-	if (WARN(mvm->csa_vif && mvm->csa_vif->csa_active,
+
+	csa_vif = rcu_dereference_protected(mvm->csa_vif,
+					    lockdep_is_held(&mvm->mutex));
+	if (WARN(csa_vif && csa_vif->csa_active,
 		 "Another CSA is already in progress"))
 		goto out_unlock;
 
 	IWL_DEBUG_MAC80211(mvm, "CSA started to freq %d\n",
 			   chandef->center_freq1);
-	mvm->csa_vif = vif;
+	rcu_assign_pointer(mvm->csa_vif, vif);
 
 out_unlock:
 	mutex_unlock(&mvm->mutex);

drivers/net/wireless/iwlwifi/mvm/mvm.h

@@ -658,7 +658,7 @@ struct iwl_mvm {
 	/* Indicate if device power save is allowed */
 	bool ps_disabled;
 
-	struct ieee80211_vif *csa_vif;
+	struct ieee80211_vif __rcu *csa_vif;
 
 	/* system time of last beacon (for AP/GO interface) */
 	u32 ap_last_beacon_gp2;