static int pkcs7_preparse(struct key_preparsed_payload *prep)
{
	struct pkcs7_message *pkcs7;
	const void *data, *saved_prep_data;
	size_t datalen, saved_prep_datalen;
	bool trusted;
	int ret;

	kenter("");

	saved_prep_data = prep->data;
	saved_prep_datalen = prep->datalen;
	pkcs7 = pkcs7_parse_message(saved_prep_data, saved_prep_datalen);
	if (IS_ERR(pkcs7)) {
		ret = PTR_ERR(pkcs7);
		goto error;
	}

	ret = pkcs7_verify(pkcs7);
	if (ret < 0)
		goto error_free;

	ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
	if (ret < 0)
		goto error_free;
	if (!trusted)
		pr_warn("PKCS#7 message doesn't chain back to a trusted key\n");

	ret = pkcs7_get_content_data(pkcs7, &data, &datalen, false);
	if (ret < 0)
		goto error_free;

	prep->data = data;
	prep->datalen = datalen;
	ret = user_preparse(prep);
	prep->data = saved_prep_data;
	prep->datalen = saved_prep_datalen;

error_free:
	pkcs7_free_message(pkcs7);
error:
	kleave(" = %d", ret);
	return ret;
}

The product dereferences a pointer that it expects to be valid but is NULL.