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Date:      Wed, 27 May 1998 11:23:12 -0700
From:      Mike Smith <mike@smith.net.au>
To:        "Brian Feldman" <brianfeldman@hotmail.com>
Cc:        current@FreeBSD.ORG
Subject:   Re: current instabilities 
Message-ID:  <199805271823.LAA01163@dingo.cdrom.com>
In-Reply-To: Your message of "Wed, 27 May 1998 12:20:50 PDT." <19980527192053.7361.qmail@hotmail.com> 

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(Restored cc: to -current)

> Yes it was a graphical program, DOS so it was trying to manipulate the 
> memory regions of the graphics card. As I gather about vm86, supposedly 
> it allows low-level access to specific memory regions, does it not?

No.  Doscmd uses the standard FreeBSD mechanisms for low-level hardware 
access.

> And 
> this does seem to be a Denial of Service at the moment, considering a 
> valid MS-DOS program and a world-usable doscmd can currently be used to 
> lock the system completely. 

Doscmd is setgid kmem.  Arguably it shouldn't be.  To be really 
dangerous though, it has to be run as root.

> As of USER_LDT I want to know more too, so I 
> can understand concerns about it. Coincidentally, X was running, and 
> doscmd -b were my args. I'll see what -r is when I get home...

I would suggest learning more before rushing into print.  However,
please don't take that to mean that we aren't interested in hearing 
about these problems.


-- 
\\  Sometimes you're ahead,       \\  Mike Smith
\\  sometimes you're behind.      \\  mike@smith.net.au
\\  The race is long, and in the  \\  msmith@freebsd.org
\\  end it's only with yourself.  \\  msmith@cdrom.com



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