linux-kernel - Re: LockDown that allows read of /dev/mem ?

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Message-ID: <99e0ef5a-156f-c8e5-cfc3-7c50e5e15a98@metux.net>
Date:   Mon, 21 Jun 2021 12:27:41 +0200
From:   "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
To:     "David F." <df7729@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: LockDown that allows read of /dev/mem ?

On 20.06.21 01:55, David F. wrote:

> I'm finding that LockDown Integrity prevents blocks things like mdadm,
> Xvesa, and a couple of my specialized tools.    There should be an
> option to allow /dev/mem read access.  Is there?  There are no secrets
> to the boot disk booted environment it's all root.

Looks like conflict of goals. lockdown is used in scenarios where one
really doesn't take any chance that code running w/ root privileges can
do such things (there's a lot of security critical information one can
learn from reading the raw memory).

I wonder what your actual use case is.

* why are you using lockdown and also running everything as root ?
* why are you still using the old Xvesa instead of using KMS or
  framebuffer device ?
* why does mdadm want to access /dev/mem ?

--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@...ux.net -- +49-151-27565287