static void construct_get_dest_keyring(struct key **_dest_keyring)
{
	struct request_key_auth *rka;
	const struct cred *cred = current_cred();
	struct key *dest_keyring = *_dest_keyring, *authkey;

	kenter("%p", dest_keyring);

	/* find the appropriate keyring */
	if (dest_keyring) {
		/* the caller supplied one */
		key_get(dest_keyring);
	} else {
		/* use a default keyring; falling through the cases until we
		 * find one that we actually have */
		switch (cred->jit_keyring) {
		case KEY_REQKEY_DEFL_DEFAULT:
		case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
			if (cred->request_key_auth) {
				authkey = cred->request_key_auth;
				down_read(&authkey->sem);
				rka = authkey->payload.data[0];
				if (!test_bit(KEY_FLAG_REVOKED,
					      &authkey->flags))
					dest_keyring =
						key_get(rka->dest_keyring);
				up_read(&authkey->sem);
				if (dest_keyring)
					break;
			}

		case KEY_REQKEY_DEFL_THREAD_KEYRING:
			dest_keyring = key_get(cred->thread_keyring);
			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_PROCESS_KEYRING:
			dest_keyring = key_get(cred->process_keyring);
			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_SESSION_KEYRING:
			rcu_read_lock();
			dest_keyring = key_get(
				rcu_dereference(cred->session_keyring));
			rcu_read_unlock();

			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
			dest_keyring =
				key_get(cred->user->session_keyring);
			break;

		case KEY_REQKEY_DEFL_USER_KEYRING:
			dest_keyring = key_get(cred->user->uid_keyring);
			break;

		case KEY_REQKEY_DEFL_GROUP_KEYRING:
		default:
			BUG();
		}
	}

	*_dest_keyring = dest_keyring;
	kleave(" [dk %d]", key_serial(dest_keyring));
	return;
}
The software does not perform an authorization check when an actor attempts to access a resource or perform an action.