ath6kl: add some bounds checking

The "ev->traffic_class" and "reply->ac" variables come from the network
and they're used as an offset into the wmi->stream_exist_for_ac[] array.
Those variables are u8 so they can be 0-255 but the stream_exist_for_ac[]
array only has WMM_NUM_AC (4) elements.  We need to add a couple bounds
checks to prevent array overflows.

I also modified one existing check from "if (traffic_class > 3) {" to
"if (traffic_class >= WMM_NUM_AC) {" just to make them all consistent.

Fixes: bdcd8170 (" Add ath6kl cleaned up driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ath/ath6kl/wmi.c

@@ -1176,6 +1176,10 @@ static int ath6kl_wmi_pstream_timeout_event_rx(struct wmi *wmi, u8 *datap,
 		return -EINVAL;
 
 	ev = (struct wmi_pstream_timeout_event *) datap;
+	if (ev->traffic_class >= WMM_NUM_AC) {
+		ath6kl_err("invalid traffic class: %d\n", ev->traffic_class);
+		return -EINVAL;
+	}
 
 	/*
 	 * When the pstream (fat pipe == AC) timesout, it means there were
@@ -1516,6 +1520,10 @@ static int ath6kl_wmi_cac_event_rx(struct wmi *wmi, u8 *datap, int len,
 		return -EINVAL;
 
 	reply = (struct wmi_cac_event *) datap;
+	if (reply->ac >= WMM_NUM_AC) {
+		ath6kl_err("invalid AC: %d\n", reply->ac);
+		return -EINVAL;
+	}
 
 	if ((reply->cac_indication == CAC_INDICATION_ADMISSION_RESP) &&
 	    (reply->status_code != IEEE80211_TSPEC_STATUS_ADMISS_ACCEPTED)) {
@@ -2632,7 +2640,7 @@ int ath6kl_wmi_delete_pstream_cmd(struct wmi *wmi, u8 if_idx, u8 traffic_class,
 	u16 active_tsids = 0;
 	int ret;
 
-	if (traffic_class > 3) {
+	if (traffic_class >= WMM_NUM_AC) {
 		ath6kl_err("invalid traffic class: %d\n", traffic_class);
 		return -EINVAL;
 	}