Path: utzoo!mnetor!uunet!husc6!bloom-beacon!mgm.mit.edu!wolfgang
From: wolfgang@mgm.mit.edu (Wolfgang Rupprecht)
Newsgroups: comp.unix.wizards
Subject: Re: Lingering LCK..cua0 files (tip)
Message-ID: <2282@bloom-beacon.MIT.EDU>
Date: 15 Jan 88 18:59:49 GMT
References: <523@srs.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: wolfgang@mgm.mit.edu (Wolfgang Rupprecht)
Organization: Freelance Software Consultant, Cambridge, Ma.
Lines: 29

In article <523@srs.UUCP> matt@srs.UUCP (Matt Goheen) writes:
> For some reason, the "tip" program here refuses to remove the device
> lock files when it exits.

I just had occasion to look at tip in great detail. (I added the
acucntrl dialin-dialout code to it, to allow all modems to be both
dialins and dialouts.)

What you observed is one of several BSD4.3 tip bugs concerning
setuid/setgid confusion. Tip gets confused about swapping the real and
effective uids/gids in the appropriate places. In your case, tip does
infact try to remove the lock file with the wrong uid
(uid=<users-real-uid>) if you break a tip connection with "~."
(however, tip gets it right in the case where you logout of the remote
host, and the remote host drops the carrier.)

Tip also reads your private $REMOTE/$PHONES file with uid=uucp
gid=daemon (or whatever you set the setuid/setgid to). This is a bug
that hits you if you have a mode 600 phones file.

What did I do to fix these bugs? Hell, I'm not paranoid. I made the
/usr/spool/uucp/LCK/ mode 777. (Playing swap the uids in tip just got
too confusing too quickly.) 

-wolfgang
---
Wolfgang Rupprecht 	ARPA: wolfgang@mgm.mit.edu (IP 18.82.0.114)
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