Make dl_list_first() and dl_list_last() uses easier for static analyzers

The previous check for dl_list_len() or having an entry from the list is
sufficient, but some static analyzers cannot figure out that
dl_list_first() and dl_list_last() will return non-NULL in this type of
cases. Avoid invalid reports by explicitly checking for NULL.

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

src/drivers/driver_test.c

@@ -1906,7 +1906,7 @@ static void wpa_driver_test_scan_cmd(struct wpa_driver_test_data *drv,
 
 	/* data: optional [ STA-addr | ' ' | IEs(hex) ] */
 
-	if (!drv->ibss)
+	if (bss == NULL || !drv->ibss)
 		return;
 
 	pos = buf;

src/p2p/p2p.c

@@ -4210,7 +4210,7 @@ p2p_get_peer_found(struct p2p_data *p2p, const u8 *addr, int next)
 				dev = dl_list_first(&dev->list,
 						    struct p2p_device,
 						    list);
-				if (&dev->list == &p2p->devices)
+				if (!dev || &dev->list == &p2p->devices)
 					return NULL;
 			} while (dev->flags & P2P_DEV_PROBE_REQ_ONLY);
 		}
@@ -4222,7 +4222,7 @@ p2p_get_peer_found(struct p2p_data *p2p, const u8 *addr, int next)
 			dev = dl_list_first(&dev->list,
 					    struct p2p_device,
 					    list);
-			if (&dev->list == &p2p->devices)
+			if (!dev || &dev->list == &p2p->devices)
 				return NULL;
 		}
 	}

src/wps/wps_upnp_ssdp.c

@@ -134,6 +134,8 @@ next_advertisement(struct upnp_wps_device_sm *sm,
 	*islast = 0;
 	iface = dl_list_first(&sm->interfaces,
 			      struct upnp_wps_device_interface, list);
+	if (!iface)
+		return NULL;
 	uuid_bin2str(iface->wps->uuid, uuid_string, sizeof(uuid_string));
 	msg = wpabuf_alloc(800); /* more than big enough */
 	if (msg == NULL)
@@ -587,6 +589,8 @@ static void ssdp_parse_msearch(struct upnp_wps_device_sm *sm,
 					&sm->interfaces,
 					struct upnp_wps_device_interface,
 					list);
+				if (!iface)
+					continue;
 				data += os_strlen("uuid:");
 				uuid_bin2str(iface->wps->uuid, uuid_string,
 					     sizeof(uuid_string));

src/wps/wps_upnp_web.c

@@ -179,15 +179,12 @@ static const char *wps_device_xml_postfix =
 /* format_wps_device_xml -- produce content of "file" wps_device.xml
  * (UPNP_WPS_DEVICE_XML_FILE)
  */
-static void format_wps_device_xml(struct upnp_wps_device_sm *sm,
+static void format_wps_device_xml(struct upnp_wps_device_interface *iface,
+				  struct upnp_wps_device_sm *sm,
 				  struct wpabuf *buf)
 {
 	const char *s;
 	char uuid_string[80];
-	struct upnp_wps_device_interface *iface;
-
-	iface = dl_list_first(&sm->interfaces,
-			      struct upnp_wps_device_interface, list);
 
 	wpabuf_put_str(buf, wps_device_xml_prefix);
 
@@ -319,6 +316,10 @@ static void web_connection_parse_get(struct upnp_wps_device_sm *sm,
 
 	iface = dl_list_first(&sm->interfaces,
 			      struct upnp_wps_device_interface, list);
+	if (iface == NULL) {
+		http_request_deinit(hreq);
+		return;
+	}
 
 	/*
 	 * It is not required that filenames be case insensitive but it is
@@ -391,7 +392,7 @@ static void web_connection_parse_get(struct upnp_wps_device_sm *sm,
 
 	switch (req) {
 	case GET_DEVICE_XML_FILE:
-		format_wps_device_xml(sm, buf);
+		format_wps_device_xml(iface, sm, buf);
 		break;
 	case GET_SCPD_XML_FILE:
 		wpabuf_put_str(buf, wps_scpd_xml);
@@ -419,13 +420,14 @@ web_process_get_device_info(struct upnp_wps_device_sm *sm,
 
 	iface = dl_list_first(&sm->interfaces,
 			      struct upnp_wps_device_interface, list);
-	peer = &iface->peer;
 
 	wpa_printf(MSG_DEBUG, "WPS UPnP: GetDeviceInfo");
 
-	if (iface->ctx->ap_pin == NULL)
+	if (!iface || iface->ctx->ap_pin == NULL)
 		return HTTP_INTERNAL_SERVER_ERROR;
 
+	peer = &iface->peer;
+
 	/*
 	 * Request for DeviceInfo, i.e., M1 TLVs. This is a start of WPS
 	 * registration over UPnP with the AP acting as an Enrollee. It should
@@ -473,6 +475,8 @@ web_process_put_message(struct upnp_wps_device_sm *sm, char *data,
 
 	iface = dl_list_first(&sm->interfaces,
 			      struct upnp_wps_device_interface, list);
+	if (!iface)
+		return HTTP_INTERNAL_SERVER_ERROR;
 
 	/*
 	 * PutMessage is used by external UPnP-based Registrar to perform WPS

wpa_supplicant/p2p_supplicant.c

@@ -6781,7 +6781,7 @@ void wpas_p2p_new_psk_cb(struct wpa_supplicant *wpa_s, const u8 *mac_addr,
 {
 	struct wpa_ssid *ssid = wpa_s->current_ssid;
 	struct wpa_ssid *persistent;
-	struct psk_list_entry *p;
+	struct psk_list_entry *p, *last;
 
 	if (psk_len != sizeof(p->psk))
 		return;
@@ -6841,10 +6841,9 @@ void wpas_p2p_new_psk_cb(struct wpa_supplicant *wpa_s, const u8 *mac_addr,
 	}
 	os_memcpy(p->psk, psk, psk_len);
 
-	if (dl_list_len(&persistent->psk_list) > P2P_MAX_STORED_CLIENTS) {
-		struct psk_list_entry *last;
-		last = dl_list_last(&persistent->psk_list,
-				    struct psk_list_entry, list);
+	if (dl_list_len(&persistent->psk_list) > P2P_MAX_STORED_CLIENTS &&
+	    (last = dl_list_last(&persistent->psk_list,
+				 struct psk_list_entry, list))) {
 		wpa_dbg(wpa_s, MSG_DEBUG, "P2P: Remove oldest PSK entry for "
 			MACSTR " (p2p=%u) to make room for a new one",
 			MAC2STR(last->addr), last->p2p);