iwlwifi: mvm: fix access to BSS elements

BSS elements are protected using RCU, so we need to use
RCU properly to access them, fix that.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210805130823.fd8b5791ab44.Iba26800a6301078d3782fb249c476dd8ac2bf3c6@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

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

@@ -2990,16 +2990,20 @@ static void iwl_mvm_check_he_obss_narrow_bw_ru_iter(struct wiphy *wiphy,
 						    void *_data)
 {
 	struct iwl_mvm_he_obss_narrow_bw_ru_data *data = _data;
+	const struct cfg80211_bss_ies *ies;
 	const struct element *elem;
 
-	elem = cfg80211_find_elem(WLAN_EID_EXT_CAPABILITY, bss->ies->data,
-				  bss->ies->len);
+	rcu_read_lock();
+	ies = rcu_dereference(bss->ies);
+	elem = cfg80211_find_elem(WLAN_EID_EXT_CAPABILITY, ies->data,
+				  ies->len);
 
 	if (!elem || elem->datalen < 10 ||
 	    !(elem->data[10] &
 	      WLAN_EXT_CAPA10_OBSS_NARROW_BW_RU_TOLERANCE_SUPPORT)) {
 		data->tolerated = false;
 	}
+	rcu_read_unlock();
 }
 
 static void iwl_mvm_check_he_obss_narrow_bw_ru(struct ieee80211_hw *hw,