install_session_keyring_to_cred
extern int install_session_keyring_to_cred(struct cred *, struct key *);
ret = install_session_keyring_to_cred(new, keyring);
ret = install_session_keyring_to_cred(new, NULL);
ret = install_session_keyring_to_cred(new, keyring);
return install_session_keyring_to_cred(cred, keyring);