Initialize iface->sta_seen on allocation

Previously, struct hostapd_iface sta_seen list head was initialized only
when completing interface setup. This left a window for operation that
could potentially iterate through the list before the list head has been
initialized. While the existing code checked iface->num_sta_seen to
avoid this case, it is much cleaner to initialize the list when struct
hostapd_iface is allocated to avoid any accidental missing of the extra
checks before list iteration.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/ap/hostapd.c

@@ -1777,7 +1777,6 @@ static int hostapd_setup_interface_complete_sync(struct hostapd_iface *iface,
 	hostapd_tx_queue_params(iface);
 
 	ap_list_init(iface);
-	dl_list_init(&iface->sta_seen);
 
 	hostapd_set_acl(hapd);
 
@@ -2068,6 +2067,20 @@ void hostapd_interface_free(struct hostapd_iface *iface)
 }
 
 
+struct hostapd_iface * hostapd_alloc_iface(void)
+{
+	struct hostapd_iface *hapd_iface;
+
+	hapd_iface = os_zalloc(sizeof(*hapd_iface));
+	if (!hapd_iface)
+		return NULL;
+
+	dl_list_init(&hapd_iface->sta_seen);
+
+	return hapd_iface;
+}
+
+
 /**
  * hostapd_init - Allocate and initialize per-interface data
  * @config_file: Path to the configuration file
@@ -2085,7 +2098,7 @@ struct hostapd_iface * hostapd_init(struct hapd_interfaces *interfaces,
 	struct hostapd_data *hapd;
 	size_t i;
 
-	hapd_iface = os_zalloc(sizeof(*hapd_iface));
+	hapd_iface = hostapd_alloc_iface();
 	if (hapd_iface == NULL)
 		goto fail;
 
@@ -2421,7 +2434,7 @@ hostapd_iface_alloc(struct hapd_interfaces *interfaces)
 		return NULL;
 	interfaces->iface = iface;
 	hapd_iface = interfaces->iface[interfaces->count] =
-		os_zalloc(sizeof(*hapd_iface));
+		hostapd_alloc_iface();
 	if (hapd_iface == NULL) {
 		wpa_printf(MSG_ERROR, "%s: Failed to allocate memory for "
 			   "the interface", __func__);

src/ap/hostapd.h

@@ -471,6 +471,7 @@ int hostapd_setup_interface(struct hostapd_iface *iface);
 int hostapd_setup_interface_complete(struct hostapd_iface *iface, int err);
 void hostapd_interface_deinit(struct hostapd_iface *iface);
 void hostapd_interface_free(struct hostapd_iface *iface);
+struct hostapd_iface * hostapd_alloc_iface(void);
 struct hostapd_iface * hostapd_init(struct hapd_interfaces *interfaces,
 				    const char *config_file);
 struct hostapd_iface *

wpa_supplicant/ap.c

@@ -675,7 +675,7 @@ int wpa_supplicant_create_ap(struct wpa_supplicant *wpa_s,
 		return -1;
 	}
 
-	wpa_s->ap_iface = hapd_iface = os_zalloc(sizeof(*wpa_s->ap_iface));
+	wpa_s->ap_iface = hapd_iface = hostapd_alloc_iface();
 	if (hapd_iface == NULL)
 		return -1;
 	hapd_iface->owner = wpa_s;