ath9k: snprintf() returns largish values

The snprintf() function returns the number of characters that would have
been written (not counting the NUL character on the end).  It could
potentially be larger than the size of the buffer.
Signed-off-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

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

@@ -524,6 +524,9 @@ static ssize_t read_file_tgt_stats(struct file *file, char __user *user_buf,
 	len += snprintf(buf + len, sizeof(buf) - len,
 			"%19s : %10u\n", "TX Rate", priv->debug.txrate);
 
+	if (len > sizeof(buf))
+		len = sizeof(buf);
+
 	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
 }
 
@@ -569,6 +572,9 @@ static ssize_t read_file_xmit(struct file *file, char __user *user_buf,
 			"%20s : %10u\n", "VO queued",
 			priv->debug.tx_stats.queue_stats[WME_AC_VO]);
 
+	if (len > sizeof(buf))
+		len = sizeof(buf);
+
 	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
 }
 
@@ -595,6 +601,9 @@ static ssize_t read_file_recv(struct file *file, char __user *user_buf,
 			"%20s : %10u\n", "SKBs Dropped",
 			priv->debug.rx_stats.skb_dropped);
 
+	if (len > sizeof(buf))
+		len = sizeof(buf);
+
 	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
 }