static int __packet_snd_vnet_parse(struct virtio_net_hdr *vnet_hdr, size_t len)
{
	unsigned short gso_type = 0;

	if ((vnet_hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
	    (__virtio16_to_cpu(vio_le(), vnet_hdr->csum_start) +
	     __virtio16_to_cpu(vio_le(), vnet_hdr->csum_offset) + 2 >
	      __virtio16_to_cpu(vio_le(), vnet_hdr->hdr_len)))
		vnet_hdr->hdr_len = __cpu_to_virtio16(vio_le(),
			 __virtio16_to_cpu(vio_le(), vnet_hdr->csum_start) +
			__virtio16_to_cpu(vio_le(), vnet_hdr->csum_offset) + 2);

	if (__virtio16_to_cpu(vio_le(), vnet_hdr->hdr_len) > len)
		return -EINVAL;

	if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
		switch (vnet_hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
		case VIRTIO_NET_HDR_GSO_TCPV4:
			gso_type = SKB_GSO_TCPV4;
			break;
		case VIRTIO_NET_HDR_GSO_TCPV6:
			gso_type = SKB_GSO_TCPV6;
			break;
		case VIRTIO_NET_HDR_GSO_UDP:
			gso_type = SKB_GSO_UDP;
			break;
		default:
			return -EINVAL;
		}

		if (vnet_hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
			gso_type |= SKB_GSO_TCP_ECN;

		if (vnet_hdr->gso_size == 0)
			return -EINVAL;
	}

	vnet_hdr->gso_type = gso_type;	/* changes type, temporary storage */
	return 0;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.