Interworking: Avoid busy loop in scan result mismatch corner cases

It was possible for interworking_find_network_match() to find a possible
BSS match in a case where more thorough checks in
wpa_supplicant_select_bss() reject network. This itself is fine, in
general, but when combined with wpa_supplicant_fast_associate()
optimization and auto_interworking=1, this resulted in a busy loop of up
to five seconds and a possible stack overflow due to recursion in that
loop.

Fix this by limiting the Interworking wpa_supplicant_fast_associate()
call to be used only once per scan iteration, so that new scan
operations can be completed before going through the scan results again.

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

wpa_supplicant/interworking.c

@@ -73,6 +73,8 @@ static int cred_prio_cmp(const struct wpa_cred *a, const struct wpa_cred *b)
 
 static void interworking_reconnect(struct wpa_supplicant *wpa_s)
 {
+	unsigned int tried;
+
 	if (wpa_s->wpa_state >= WPA_AUTHENTICATING) {
 		wpa_supplicant_cancel_sched_scan(wpa_s);
 		wpa_supplicant_deauthenticate(wpa_s,
@@ -80,10 +82,13 @@ static void interworking_reconnect(struct wpa_supplicant *wpa_s)
 	}
 	wpa_s->disconnected = 0;
 	wpa_s->reassociate = 1;
+	tried = wpa_s->interworking_fast_assoc_tried;
+	wpa_s->interworking_fast_assoc_tried = 1;
 
-	if (wpa_supplicant_fast_associate(wpa_s) >= 0)
+	if (!tried && wpa_supplicant_fast_associate(wpa_s) >= 0)
 		return;
 
+	wpa_s->interworking_fast_assoc_tried = 0;
 	wpa_supplicant_req_scan(wpa_s, 0, 0);
 }
 

wpa_supplicant/scan.c

@@ -1002,6 +1002,9 @@ scan:
 		wpa_supplicant_req_scan(wpa_s, 1, 0);
 	} else {
 		wpa_s->scan_for_connection = 0;
+#ifdef CONFIG_INTERWORKING
+		wpa_s->interworking_fast_assoc_tried = 0;
+#endif /* CONFIG_INTERWORKING */
 	}
 }
 

wpa_supplicant/wpa_supplicant_i.h

@@ -857,6 +857,7 @@ struct wpa_supplicant {
 	unsigned int network_select:1;
 	unsigned int auto_select:1;
 	unsigned int auto_network_select:1;
+	unsigned int interworking_fast_assoc_tried:1;
 	unsigned int fetch_all_anqp:1;
 	unsigned int fetch_osu_info:1;
 	unsigned int fetch_osu_waiting_scan:1;