Re: [PATCH] Allow /dev/{,k}mem to be disabled to prevent kernel from being modified easily

From: bert hubert <ahu@ds9a.nl>
To: David Lang <david.lang@digitalinsight.com>
Cc: Andrew Morton <akpm@osdl.org>,
	linux-kernel@vger.kernel.org, devik@cdi.cz, aebr@win.tue.nl
Subject: Re: [PATCH] Allow /dev/{,k}mem to be disabled to prevent kernel from being modified easily
Date: Sun, 3 Aug 2003 23:47:38 +0200	[thread overview]
Message-ID: <20030803214738.GA16129@outpost.ds9a.nl> (raw)
In-Reply-To: <Pine.LNX.4.44.0308031425100.24695-100000@dlang.diginsite.com>

On Sun, Aug 03, 2003 at 02:33:01PM -0700, David Lang wrote:

> we already have the option to not support modules (as Alan Cox points out
> every time that subject comes up it can be bypassed by people who have
> access to /dev/*mem) so it would seem that adding the option to bar access
> to /dev/*mem as well would make exisitng config options mean what they
> appear to mean.

This was also on my mind, yes. As Wichert said, not all holes are closed
then, there is also /dev/microcode, iopl() and more.

However, perhaps we could all sweep them under the "don't allow userspace to
touch kernel memory easily" banner?

We can leave more finegrained tools to outside patchsets then.

I think root will always be able to figure out a way to get into the
kernel's innards, but we can raise the bar quite a lot easily without too
much infrastructure.

As to what Alan said about LSM, I've yet to see how to do that in a
reasonable way. But I didn't look too hard.

As to what Andries said, how about '/proc/sys/raw_memory_access'?

Thanks.

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