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Date: Sun, 4 Apr 2004 23:20:10 -0500
From: Alan Cox <alc@cs.rice.edu>
To: Alexander Kabaev <ak03@gte.com>
Message-ID: <20040405042010.GQ15786@cs.rice.edu>
References: <20040402191254.GK26131@elvis.mu.org>
	<35917.1080933274@critter.freebsd.dk> <20040402195957.GN26131@elvis.mu.org>
	<20040404201251.GP15786@cs.rice.edu> <20040405041147.GA39962@kanpc.gte.com>
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cc: alc@freebsd.org
cc: kan@freebsd.org
cc: Poul-Henning Kamp <phk@phk.freebsd.dk>
cc: Alfred Perlstein <alfred@freebsd.org>
cc: current@freebsd.org
Subject: Re: mmap breakage?
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On Mon, Apr 05, 2004 at 12:11:47AM -0400, Alexander Kabaev wrote:
> On Sun, Apr 04, 2004 at 03:12:51PM -0500, Alan Cox wrote:
> > Alfred,
> > 
> > Please try the attached patch.  This problems appears to be a
> > consequence of vm/vm_mmap.c revision 1.180, where as part of a much
> > needed code reorganization for locking the check for the /dev/zero
> > special case got placed after the permissions check for the general
> > case.  This patch simply delays the permissions check for devices
> > until you have the necessary lock to also check for /dev/zero.
> > 
> > Since kan@ authored the reorganization, I'm cc:'ing him on this
> > message for purposes of obtaining a review.  (At least one comment
> > should be updated to reflect my code changes.)
> > 
> > Regards,
> > Alan
> > 
> > 
> Alan, Alfred,
> 
> I had the following patch which is currently pending a review by
> Peter Wemm. I meant to commit it on Friday, but ran out of time:
> 
> 
>  http://perforce.freebsd.org/chv.cgi?CH=50213
> 

I believe that there is a problem with this patch.  Specifically, if
maxprot is set to VM_PROT_ALL for devices in mmap(), then the security
check in vm_mmap_vnode() has no effect.  Please take a look at the
entirety of the changes that I propose to mmap().

Regards,
Alan