SMB2_echo(struct TCP_Server_Info *server)
{
	struct smb2_echo_req *req;
	int rc = 0;
	struct kvec iov[1];
	struct smb_rqst rqst = { .rq_iov = iov,
				 .rq_nvec = 1 };
	unsigned int total_len;

	cifs_dbg(FYI, "In echo request\n");

	if (server->tcpStatus == CifsNeedNegotiate) {
		/* No need to send echo on newly established connections */
		queue_delayed_work(cifsiod_wq, &server->reconnect, 0);
		return rc;
	}

	rc = smb2_plain_req_init(SMB2_ECHO, NULL, (void **)&req, &total_len);
	if (rc)
		return rc;

	req->sync_hdr.CreditRequest = cpu_to_le16(1);

	iov[0].iov_len = total_len;
	iov[0].iov_base = (char *)req;

	rc = cifs_call_async(server, &rqst, NULL, smb2_echo_callback, NULL,
			     server, CIFS_ECHO_OP, NULL);
	if (rc)
		cifs_dbg(FYI, "Echo request failed: %d\n", rc);

	cifs_small_buf_release(req);
	return rc;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.