crdup
new = crdup(p->p_ucred);
cred = crdup(cred);
p->p_ucred = crdup(p->p_ucred);
p->p_ucred = crdup(cred);
p->p_ucred = newcred = crdup(oldcred);
sp->s_cred = crdup(cnp->cn_cred);
struct ucred *crdup(struct ucred *cr);
sdp->swd_cred = crdup(p->p_ucred);