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Date:      Thu, 17 Sep 1998 17:41:19 -0400 (EDT)
From:      spork <spork@super-g.com>
To:        John Polstra <jdp@polstra.com>
Cc:        bwithrow@BayNetworks.COM, hackers@FreeBSD.ORG
Subject:   Re: GDB modifies shared libraries?
Message-ID:  <Pine.BSF.4.00.9809171739480.3886-100000@super-g.inch.com>
In-Reply-To: <199809171632.JAA11090@austin.polstra.com>

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Actually I see someone has just posted Mr. Withrow's message to Bugtraq.
Odd.  He's hinting that it's a security issue, which I don't quite see.
It could create some confusion though, I suppose.

---
Charles Sprickman
spork@super-g.com

On Thu, 17 Sep 1998, John Polstra wrote:

> In article <199809171409.KAA02717@tuva.engeast.baynetworks.com>,
> Robert Withrow  <bwithrow@BayNetworks.COM> wrote:
> > I was debugging a (large) program using GDB on an xterm (which
> > prevented me from getting the exact text, as you will see).  This
> > is on 2.2.6-RELEASE on a P6-200 with 128M ram.  I was running as
> > a normal user, not root.
> > 
> > I issued the "run" command and GDB said that /usr/lib/libc.so.3.1
> > had changed and it was re-loading it.  That was followed immediately
> > by X freezing, and then a spontaneous re-boot.  
> > 
> > After the system re-booted, sure enough the date on /usr/lib/libc.so.3.1
> > had been changed!
> > 
> > Now, with this program, GDB generally says that the *program* has changed
> > *every* time I issue the "run" command, but I thought that was just a
> > GDB problem.  But I don't understand how GDB can override protections
> > on /usr/lib/libc.so.3.1 in order to change its date.  This seems like
> > an OS bug.
> 
> Yes, it is a kernel bug.  As far as I know, it doesn't actually modify
> the file -- it just "updates" it with its original contents, changing
> the timestamp.
> 
> The problem is believed to be solved in -current (and hence in 3.0).
> At least, I haven't heard it reported there for a good long time.
> However, I don't think anybody (except possibly John Dyson) knows
> exactly what "the" fix was.
> --
>    John Polstra                                       jdp@polstra.com
>    John D. Polstra & Co., Inc.                Seattle, Washington USA
>    "Self-knowledge is always bad news."                 -- John Barth
> 
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> 


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