From: utzoo!decvax!duke!harpo!floyd!cmcl2!philabs!sdcsvax!stanonik Newsgroups: net.unix-wizards Title: root executing setuid programs Article-I.D.: sdcsvax.32 Posted: Fri Dec 31 19:37:48 1982 Received: Sun Jan 2 01:41:51 1983 Why shouldn't root change uid like any user when exec'ing a setuid program? In the procedure getxfile in sys1.c (4.1bsd) the following code appears: /* * set SUID/SGID protections, if no tracing */ if ((u.u_procp->p_flag&STRC)==0) { #ifndef MELB if(u.u_uid != 0) #endif { u.u_uid = uid; u.u_procp->p_uid = uid; } So, root processes are exempt from changing uid. Why? This can cause problems when a daemon which runs as root interacts with uucp. In particular, the arpanet daemons in bbn's tcp software. Thanks, Ron Stanonik ucbvax!sdcsvax!stanonik or stanonik@nprdc