static netdev_tx_t catc_start_xmit(struct sk_buff *skb,
					 struct net_device *netdev)
{
	struct catc *catc = netdev_priv(netdev);
	unsigned long flags;
	int r = 0;
	char *tx_buf;

	spin_lock_irqsave(&catc->tx_lock, flags);

	catc->tx_ptr = (((catc->tx_ptr - 1) >> 6) + 1) << 6;
	tx_buf = catc->tx_buf[catc->tx_idx] + catc->tx_ptr;
	if (catc->is_f5u011)
		*(__be16 *)tx_buf = cpu_to_be16(skb->len);
	else
		*(__le16 *)tx_buf = cpu_to_le16(skb->len);
	skb_copy_from_linear_data(skb, tx_buf + 2, skb->len);
	catc->tx_ptr += skb->len + 2;

	if (!test_and_set_bit(TX_RUNNING, &catc->flags)) {
		r = catc_tx_run(catc);
		if (r < 0)
			clear_bit(TX_RUNNING, &catc->flags);
	}

	if ((catc->is_f5u011 && catc->tx_ptr) ||
	    (catc->tx_ptr >= ((TX_MAX_BURST - 1) * (PKT_SZ + 2))))
		netif_stop_queue(netdev);

	spin_unlock_irqrestore(&catc->tx_lock, flags);

	if (r >= 0) {
		catc->netdev->stats.tx_bytes += skb->len;
		catc->netdev->stats.tx_packets++;
	}

	dev_kfree_skb(skb);

	return NETDEV_TX_OK;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.