ath9k: always set common->macaddr to the MAC adress of a virtual interface

In some cases it can be useful to change the MAC address of a virtual
interface to something that's completely different from the EEPROM
stored MAC address. In this case it is a bad idea to use the EEPROM MAC
address for calculating the BSSID mask, as that would make it too wide.

In one case a few devices have been observed to send ACKs for many
packets on the channel not directed at them, which results in a neat
Denial of Service attack on the channel.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ath9k.h

@@ -658,11 +658,10 @@ enum sc_op_flags {
 struct ath_rate_table;
 
 struct ath9k_vif_iter_data {
-	const u8 *hw_macaddr; /* phy's hardware address, set
-			       * before starting iteration for
-			       * valid bssid mask.
-			       */
+	u8 hw_macaddr[ETH_ALEN]; /* address of the first vif */
 	u8 mask[ETH_ALEN]; /* bssid mask */
+	bool has_hw_macaddr;
+
 	int naps;      /* number of AP vifs */
 	int nmeshes;   /* number of mesh vifs */
 	int nstations; /* number of station vifs */

drivers/net/wireless/ath/ath9k/main.c

@@ -839,10 +839,14 @@ static void ath9k_vif_iter(void *data, u8 *mac, struct ieee80211_vif *vif)
 	struct ath9k_vif_iter_data *iter_data = data;
 	int i;
 
-	if (iter_data->hw_macaddr)
+	if (iter_data->has_hw_macaddr) {
 		for (i = 0; i < ETH_ALEN; i++)
 			iter_data->mask[i] &=
 				~(iter_data->hw_macaddr[i] ^ mac[i]);
+	} else {
+		memcpy(iter_data->hw_macaddr, mac, ETH_ALEN);
+		iter_data->has_hw_macaddr = true;
+	}
 
 	switch (vif->type) {
 	case NL80211_IFTYPE_AP:
@@ -891,7 +895,6 @@ void ath9k_calculate_iter_data(struct ieee80211_hw *hw,
 	 * together with the BSSID mask when matching addresses.
 	 */
 	memset(iter_data, 0, sizeof(*iter_data));
-	iter_data->hw_macaddr = common->macaddr;
 	memset(&iter_data->mask, 0xff, ETH_ALEN);
 
 	if (vif)
@@ -901,6 +904,8 @@ void ath9k_calculate_iter_data(struct ieee80211_hw *hw,
 	ieee80211_iterate_active_interfaces_atomic(
 		sc->hw, IEEE80211_IFACE_ITER_RESUME_ALL,
 		ath9k_vif_iter, iter_data);
+
+	memcpy(common->macaddr, iter_data->hw_macaddr, ETH_ALEN);
 }
 
 /* Called with sc->mutex held. */