int hns_nic_net_xmit_hw(struct net_device *ndev,
netdev_tx_t hns_nic_net_xmit_hw(struct net_device *ndev,
				struct sk_buff *skb,
				struct hns_nic_ring_data *ring_data)
 {
 	struct hns_nic_priv *priv = netdev_priv(ndev);
 	struct hnae_ring *ring = ring_data->ring;
	struct device *dev = ring_to_dev(ring);
	struct netdev_queue *dev_queue;
	struct skb_frag_struct *frag;
	int buf_num;
	int seg_num;
	dma_addr_t dma;
	int size, next_to_use;
	int i;

	switch (priv->ops.maybe_stop_tx(&skb, &buf_num, ring)) {
	case -EBUSY:
		ring->stats.tx_busy++;
		goto out_net_tx_busy;
	case -ENOMEM:
		ring->stats.sw_err_cnt++;
		netdev_err(ndev, "no memory to xmit!\n");
		goto out_err_tx_ok;
	default:
		break;
	}

	/* no. of segments (plus a header) */
	seg_num = skb_shinfo(skb)->nr_frags + 1;
	next_to_use = ring->next_to_use;

	/* fill the first part */
	size = skb_headlen(skb);
	dma = dma_map_single(dev, skb->data, size, DMA_TO_DEVICE);
	if (dma_mapping_error(dev, dma)) {
		netdev_err(ndev, "TX head DMA map failed\n");
		ring->stats.sw_err_cnt++;
		goto out_err_tx_ok;
	}
	priv->ops.fill_desc(ring, skb, size, dma, seg_num == 1 ? 1 : 0,
			    buf_num, DESC_TYPE_SKB, ndev->mtu);

	/* fill the fragments */
	for (i = 1; i < seg_num; i++) {
		frag = &skb_shinfo(skb)->frags[i - 1];
		size = skb_frag_size(frag);
		dma = skb_frag_dma_map(dev, frag, 0, size, DMA_TO_DEVICE);
		if (dma_mapping_error(dev, dma)) {
			netdev_err(ndev, "TX frag(%d) DMA map failed\n", i);
			ring->stats.sw_err_cnt++;
			goto out_map_frag_fail;
		}
		priv->ops.fill_desc(ring, skb_frag_page(frag), size, dma,
				    seg_num - 1 == i ? 1 : 0, buf_num,
				    DESC_TYPE_PAGE, ndev->mtu);
	}

	/*complete translate all packets*/
 	dev_queue = netdev_get_tx_queue(ndev, skb->queue_mapping);
 	netdev_tx_sent_queue(dev_queue, skb->len);
 
	netif_trans_update(ndev);
	ndev->stats.tx_bytes += skb->len;
	ndev->stats.tx_packets++;

 	wmb(); /* commit all data before submit */
 	assert(skb->queue_mapping < priv->ae_handle->q_num);
 	hnae_queue_xmit(priv->ae_handle->qs[skb->queue_mapping], buf_num);
	ring->stats.tx_pkts++;
	ring->stats.tx_bytes += skb->len;

	return NETDEV_TX_OK;

out_map_frag_fail:

	while (ring->next_to_use != next_to_use) {
		unfill_desc(ring);
		if (ring->next_to_use != next_to_use)
			dma_unmap_page(dev,
				       ring->desc_cb[ring->next_to_use].dma,
				       ring->desc_cb[ring->next_to_use].length,
				       DMA_TO_DEVICE);
		else
			dma_unmap_single(dev,
					 ring->desc_cb[next_to_use].dma,
					 ring->desc_cb[next_to_use].length,
					 DMA_TO_DEVICE);
	}

out_err_tx_ok:

	dev_kfree_skb_any(skb);
	return NETDEV_TX_OK;

out_net_tx_busy:

	netif_stop_subqueue(ndev, skb->queue_mapping);

	/* Herbert's original patch had:
	 *  smp_mb__after_netif_stop_queue();
	 * but since that doesn't exist yet, just open code it.
	 */
	smp_mb();
	return NETDEV_TX_BUSY;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.