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Subject: Re: LockDown that allows read of /dev/mem ?
To:     "David F." <df7729@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <CAGRSmLvaZ7av7ne-XKfZGrij1x9i5v1aH=t0ufL=Ad1193G0vA@mail.gmail.com>
From:   "Enrico Weigelt, metux IT consult" <lkml@metux.net>
Message-ID: <99e0ef5a-156f-c8e5-cfc3-7c50e5e15a98@metux.net>
Date:   Mon, 21 Jun 2021 12:27:41 +0200
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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@metux.net -- +49-151-27565287