Date: Sun, 9 Mar 1997 18:43:37 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Paul Derbyshire <ao950 AT FreeNet DOT Carleton DOT CA>
cc: djgpp AT delorie DOT com
Subject: Re: Ring 0?
In-Reply-To: <5fte3k$h5h@freenet-news.carleton.ca>
Message-ID: <Pine.SUN.3.91.970309184119.26812c-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


On 9 Mar 1997, Paul Derbyshire wrote:

> As for a ring 3 program being unable to currupt the kernel, I'm not sure
> this is entirely correct. I discovered that a DOS program running in a DOS
> box under Win 95 (and DOS boxes presumably run in ring 3) can crash the
> machine with a bad memory write.

It's harder, but if you really want it, you can do it.  Windows 95 is not 
protected enough (presumably, because it still wants to let you run 
legacy DOS code which played some notoriously nasty tricks).  Even DJGPP 
has enough potential to let you overwrite the entire memory with a bad 
pointer, especially when you are using `nearptr' or `_dos_ds'.