linux-kernel - Re: [PATCH 02/24] Add a SysRq option to lift kernel lockdown

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Date:   Wed, 11 Apr 2018 19:05:56 +0200
From:   Jann Horn <jannh@...gle.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-man <linux-man@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 02/24] Add a SysRq option to lift kernel lockdown

On Wed, Apr 11, 2018 at 6:24 PM, David Howells <dhowells@...hat.com> wrote:
> From: Kyle McMartin <kyle@...hat.com>
>
> Make an option to provide a sysrq key that will lift the kernel lockdown,
> thereby allowing the running kernel image to be accessed and modified.
>
> On x86 this is triggered with SysRq+x, but this key may not be available on
> all arches, so it is set by setting LOCKDOWN_LIFT_KEY in asm/setup.h.
> Since this macro must be defined in an arch to be able to use this facility
> for that arch, the Kconfig option is restricted to arches that support it.

In the current form, this is probably incompatible with USB/IP (which
Debian seems to be shipping as a module by default), right? And
perhaps also with dummy_hcd (if I understand correctly what it's
doing)?