linux-kernel - Re: [PATCH V31 19/25] x86/mmiotrace: Lock down the testmmiotrace module

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACdnJuv82qUnVhtZXHaHAJH0x9edS=j5X8awhhJmFfGAz5Ayzg@mail.gmail.com>
Date:   Wed, 27 Mar 2019 09:55:20 -0700
From:   Matthew Garrett <mjg59@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     James Morris <jmorris@...ei.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        Linux API <linux-api@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH V31 19/25] x86/mmiotrace: Lock down the testmmiotrace module

On Wed, Mar 27, 2019 at 8:57 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 26 Mar 2019 11:27:35 -0700
> Matthew Garrett <matthewgarrett@...gle.com> wrote:
>
> > From: David Howells <dhowells@...hat.com>
> >
> > The testmmiotrace module shouldn't be permitted when the kernel is locked
> > down as it can be used to arbitrarily read and write MMIO space. This is
> > a runtime check rather than buildtime in order to allow configurations
> > where the same kernel may be run in both locked down or permissive modes
> > depending on local policy.
> >
>
> Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
>
> I'm curious. Should there be a mode to lockdown the tracefs directory
> too? As that can expose addresses.

That sounds like a reasonable thing to do in the confidentiality mode,
I don't think it'd be necessary in the integrity mode.