static int nfs_idmap_init_keyring(void)
{
	struct cred *cred;
	struct key *keyring;
	int ret = 0;

	printk(KERN_NOTICE "NFS: Registering the %s key type\n",
		key_type_id_resolver.name);

	cred = prepare_kernel_cred(NULL);
	if (!cred)
		return -ENOMEM;

	keyring = keyring_alloc(".id_resolver",
				GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
				KEY_USR_VIEW | KEY_USR_READ,
				KEY_ALLOC_NOT_IN_QUOTA, NULL);
	if (IS_ERR(keyring)) {
		ret = PTR_ERR(keyring);
		goto failed_put_cred;
	}

	ret = register_key_type(&key_type_id_resolver);
	if (ret < 0)
		goto failed_put_key;

	ret = register_key_type(&key_type_id_resolver_legacy);
	if (ret < 0)
		goto failed_reg_legacy;

	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
	cred->thread_keyring = keyring;
	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
	id_resolver_cache = cred;
	return 0;

failed_reg_legacy:
	unregister_key_type(&key_type_id_resolver);
failed_put_key:
	key_put(keyring);
failed_put_cred:
	put_cred(cred);
	return ret;
}

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