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From:   Matthew Garrett <mjg59@google.com>
Date:   Thu, 18 Apr 2019 12:35:36 -0700
Message-ID: <CACdnJus9AhAAYs-R94BH7HDuuQfXjgdhdqUR6Pvk9mxbuPx1=Q@mail.gmail.com>
Subject: Re: [PATCH V32 01/27] Add the ability to lock down access to the
 running kernel image
To:     Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Cc:     James Morris <jmorris@namei.org>,
        LSM List <linux-security-module@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        David Howells <dhowells@redhat.com>,
        Linux API <linux-api@vger.kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Daniel Axtens <dja@axtens.net>, cmr <cmr@informatik.wtf>
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On Tue, Apr 16, 2019 at 1:40 AM Andrew Donnellan
<andrew.donnellan@au1.ibm.com> wrote:
> I'm thinking about whether we should lock down the powerpc xmon debug
> monitor - intuitively, I think the answer is yes if for no other reason
> than Least Astonishment, when lockdown is enabled you probably don't
> expect xmon to keep letting you access kernel memory.

The original patchset contained a sysrq hotkey to allow physically
present users to disable lockdown, so I'm not super concerned about
this case - I could definitely be convinced otherwise, though.