linux-kernel - Re: Really good idea to allow mmap(0, FIXED)?

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Date:	Sat, 7 Oct 2006 11:23:01 +0000
From:	Pavel Machek <pavel@....cz>
To:	Michael Buesch <mb@...sch.de>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Really good idea to allow mmap(0, FIXED)?

Hi!
> 
> > > Besides that, I currently don't see a valid reason to mmap address 0.
> > > 
> > > Comments?
> > 
> > User zero is not neccessarily mapped at kernel zero so your argument
> > isn't portable either.
> 
> Eh, so what about the following.
> We _have_ arches which map user zero to kernel zero. What about
> specialcasing that on a per-arch case. So remapping user zero to
> something else in kernel.

Just add some magic constant on architectures you care about... make
user 0 start at 4mb in kernel... and you get your security hardened
kernel w/o breaking dosemu. All you need is to create a patch :-)


-- 
Thanks for all the (sleeping) penguins.
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