linux-kernel - Re: Turn CONFIG_STRICT_DEVMEM in sysctl dev.mem.restricted

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Message-ID: <20081116080342.3d6c6976@infradead.org>
Date:	Sun, 16 Nov 2008 08:03:42 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Bernhard Walle <bwalle@...e.de>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	crash-utility@...hat.com
Subject: Re: Turn CONFIG_STRICT_DEVMEM in sysctl dev.mem.restricted

On Sun, 16 Nov 2008 15:45:41 +0000
Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
ules that circumvent that
> > protection.
> 
> With your patch I get crap in the kernel I don't need. In every kernel
> including those on memory tight devices like wireless routers that
> don't need it.
> 
> You are turd polishing, and what is needed is a shovel.
> 
> Even if you want to turd polish there are cleaner solutions. A process
> with CAP_SYS_RAWIO can cheerfully bypass any restriction you try and
> place

because it can load kernel modules?
or because it can bypass the iommu?

the point of the /dev/mem restrictions is to not allow things you know
you don't need, while still allowing X to function where it can access
the crap it does. Now in Bernhard's case he DOES need them, so he
shouldn't use the restrictions.

> There are proper ways to deal with X, modern video cards and modern
> security models. They involve using framebuffer mappings off the PCI
> device node itself and DRI.
> 
when X has this for all hw that matters /dev/mem could go away for the
people who then no longer have any need for it.


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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