init_cifs_idmap(void)
{
	struct cred *cred;
	struct key *keyring;
	int ret;

	cifs_dbg(FYI, "Registering the %s key type\n",
		 cifs_idmap_key_type.name);

	/* create an override credential set with a special thread keyring in
	 * which requests are cached
	 *
	 * this is used to prevent malicious redirections from being installed
	 * with add_key().
	 */
	cred = prepare_kernel_cred(NULL);
	if (!cred)
		return -ENOMEM;

	keyring = keyring_alloc(".cifs_idmap",
				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(&cifs_idmap_key_type);
	if (ret < 0)
		goto failed_put_key;

	/* instruct request_key() to use this special keyring as a cache for
	 * the results it looks up */
	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
	cred->thread_keyring = keyring;
	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
	root_cred = cred;

	cifs_dbg(FYI, "cifs idmap keyring: %d\n", key_serial(keyring));
	return 0;

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.