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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!xanth!ukma!tut.cis.ohio-state.edu!osu-cis!att!laidbak!stevea
From: stevea@laidbak.UUCP (Steve Alexander)
Newsgroups: comp.unix.wizards,comp.bugs.sys5
Subject: Re: setuid (euid) after setuid (uid) on System 5
Message-ID: <2162@laidbak.UUCP>
Date: 21 Mar 89 22:50:45 GMT
References: <123@cat.Fulcrum.BT.CO.UK> <822@pedsga.UUCP>
Reply-To: stevea@laidbak.UUCP (Steve Alexander)
Followup-To: comp.bugs.sys5
Organization: Lachman Associates, Inc. Naperville, IL
Lines: 18

In article <822@pedsga.UUCP> jeffj@pedsga.UUCP writes:
>Perhaps the saved-uid was erroneously set to the real UID?

I believe that if the current effective id is root, the saved set-uid is set to
the new uid along with the effective uid and the real uid when the setuid() is 
done.  Thus, the following will not work:

	root -> user -> root

This is only true for effective uid 0.  Otherwise, the saved set-uid is
left alone.

For non-zero uid's, the setuid() proceeds if the new uid is equal to
either the real uid or the saved set-uid.

-- 
Steve Alexander, TCP/IP Development | stevea%laidbak@sun.com
Lachman Associates, Inc.            | ...!sun!laidbak!stevea