Pass P_SUGID on to the child of a fork(). It was possible to get rlogin

to coredump previously since it (somewhat uniquely) is setuid and forks
without execing, and thus without passing P_SUGID the child could
coredump and possibly divulge sensitive information (such as encrypted
passwords from the passwd database).

sys/kern/kern_fork.c

@@ -275,6 +275,10 @@ fork1(p1, flags, retval)
 		p2->p_limit->p_refcnt++;
 	}
 
+	/*
+	 * Preserve some flags in subprocess.
+	 */
+	p2->p_flag |= p1->p_flag & P_SUGID;
 	if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
 		p2->p_flag |= P_CONTROLT;
 	if (flags & RFPPWAIT)