linux-kernel - Re: [dm-devel] [PATCH 1/1] dm: add message command to disallow device open

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Date:   Tue, 19 Jul 2022 09:42:26 +1000
From:   Daniil Lunev <dlunev@...omium.org>
To:     Zdenek Kabelac <zdenek.kabelac@...il.com>
Cc:     Mikulas Patocka <mpatocka@...hat.com>, dm-devel@...hat.com,
        Mike Snitzer <snitzer@...nel.org>,
        Brian Geffon <bgeffon@...gle.com>,
        Alasdair Kergon <agk@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [dm-devel] [PATCH 1/1] dm: add message command to disallow device open

We understand that if someone acquires root it is a game over. The intent of
this mechanism is to reduce the attack surface. The exposure might be a
certain system daemon that is exploited into accessing a wrong node in
the filesystem. And exposing modifiable system memory is a pathway for
further escalation and leaks of secrets. This is a defense in depth mechanism,
that is intended to make attackers' lives harder even if they find an
exploitable
vulnerability.
We understand that in regular situations people may not want the behaviour,
that is why the mechanism is controlled via a side channel - if a message is
never sent - the behaviour is not altered.
--Daniil