static int __init ppp_init(void)
{
	int err;

	pr_info("PPP generic driver version " PPP_VERSION "\n");

	err = register_pernet_device(&ppp_net_ops);
	if (err) {
		pr_err("failed to register PPP pernet device (%d)\n", err);
		goto out;
	}

	err = register_chrdev(PPP_MAJOR, "ppp", &ppp_device_fops);
	if (err) {
		pr_err("failed to register PPP device (%d)\n", err);
		goto out_net;
	}

	ppp_class = class_create(THIS_MODULE, "ppp");
	if (IS_ERR(ppp_class)) {
		err = PTR_ERR(ppp_class);
		goto out_chrdev;
	}

	/* not a big deal if we fail here :-) */
	device_create(ppp_class, NULL, MKDEV(PPP_MAJOR, 0), NULL, "ppp");

	return 0;

out_chrdev:
	unregister_chrdev(PPP_MAJOR, "ppp");
out_net:
	unregister_pernet_device(&ppp_net_ops);
out:
	return err;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.