ath9k_htc: fix potential out of bounds access with invalid rxstatus->rs_keyix

The "rxstatus->rs_keyix" eventually gets passed to test_bit() so we need to
ensure that it is within the bitmap.

drivers/net/wireless/ath/ath9k/common.c:46 ath9k_cmn_rx_accept()
error: passing untrusted data 'rx_stats->rs_keyix' to 'test_bit()'

Fixes: 4ed1a8d4 ("ath9k_htc: use ath9k_cmn_rx_accept")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220409061225.GA5447@kili

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

@@ -1016,6 +1016,14 @@ static bool ath9k_rx_prepare(struct ath9k_htc_priv *priv,
 		goto rx_next;
 	}
 
+	if (rxstatus->rs_keyix >= ATH_KEYMAX &&
+	    rxstatus->rs_keyix != ATH9K_RXKEYIX_INVALID) {
+		ath_dbg(common, ANY,
+			"Invalid keyix, dropping (keyix: %d)\n",
+			rxstatus->rs_keyix);
+		goto rx_next;
+	}
+
 	/* Get the RX status information */
 
 	memset(rx_status, 0, sizeof(struct ieee80211_rx_status));