Path: utzoo!attcan!uunet!vsi!friedl
From: friedl@vsi.UUCP (Stephen J. Friedl)
Newsgroups: comp.unix.questions
Subject: Re: C - development under UNIX - XENIX
Summary: Almost
Message-ID: <666@vsi.UUCP>
Date: 16 May 88 14:49:57 GMT
References: <14827@jplgodo.UUCP> <7774@ncoast.UUCP>
Distribution: na
Organization: V-Systems, Inc. -- Santa Ana, CA
Lines: 22

In article <7774@ncoast.UUCP>, allbery@ncoast.UUCP (Brandon S. Allbery) writes:
< As quoted from <14827@jplgodo.UUCP> by deutsch@jplgodo.UUCP (Michael Deutsch ):
< +---------------
< | 2. A programm running with "setuid" privilege, i.e.: -rwsr-xr-x
< |    tries to create directory and fails when executed by non-root,
< |    however, it works when executed by root, why???
< +---------------
< 
< Since /bin/mkdir is setuid, it runs as root/ORIGINAL USER.  The setuid on
< mkdir overrides the setuid on the calling program.  Thus, the ORIGINAL user
< must have permission to create the directory.  The mkdir() system call doesn't
< have this problem.

A brief note here: mkdir does not always work properly if called from
a setgid program.  If the real user+group does *not* have permission to
see the file but the effective group *does*, mkdir permission is denied.
This is because mkdir(1) does not reset the effective group to real group
before the access(2) call.  As indicated, mkdir(2) should work OK.

-- 
Steve Friedl    V-Systems, Inc. (714) 545-6442    3B2-kind-of-guy
friedl@vsi.com    {backbones}!vsi.com!friedl   attmail!vsi!friedl