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Date:      Fri, 26 Nov 1999 21:22:41 -0600
From:      Dan Nelson <dnelson@emsphone.com>
To:        rjk191@psu.edu
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: That telnetd bug
Message-ID:  <19991126212241.B74868@dan.emsphone.com>
In-Reply-To: <Pine.BSF.4.21.9911262209170.30222-100000@rjk191.rh.psu.edu>; from "Ray Kohler" on Fri Nov 26 22:14:24 GMT 1999
References:  <Pine.BSF.4.21.9911262209170.30222-100000@rjk191.rh.psu.edu>

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In the last episode (Nov 26), Ray Kohler said:
> Today I did something stupid and got hit by that well-known bug
> wherein one runs a program under telnet and then kills telnetd,
> causing the second program to go berserk. I was completely locked out
> (due to lack of memory) for about 30 minutes, but then was able to
> get back on and kill the offending program (cvsup). My question is:
> How was it that I was able to get some RAM back without doing
> anything first? After all, no programs had died, they had just
> "quieted down". I very pleased at this surprise, but still... Why did
> it happen?

Note that this isn't a telnet bug; it's a bug in the application.  You
should always check the result of a read() for failure.  I seem to
remember tin and pine being the major problems, but they have long
since been fixed.  I've never seen this happen with cvsup, and loss of
telnetd shouldn't even affect cvsup since it is not an interactive
application anyway.

As for the out of memeory issue, whenever the system runs out of RAM
and swap, it will start killing processes.  Usually the first process
to die is the memory hog itself, which fixes the problem.

-- 
	Dan Nelson
	dnelson@emsphone.com


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