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Date: Tue, 3 Apr 2018 17:08:30 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Matthew Garrett <mjg59@...gle.com>
Cc: Andrew Lutomirski <luto@...nel.org>,
David Howells <dhowells@...hat.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
James Morris <jmorris@...ei.org>,
Alan Cox <gnomes@...rguk.ukuu.org.uk>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Justin Forbes <jforbes@...hat.com>,
linux-man <linux-man@...r.kernel.org>, joeyli <jlee@...e.com>,
LSM List <linux-security-module@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>,
Kees Cook <keescook@...omium.org>,
linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [GIT PULL] Kernel lockdown for secure boot
On Tue, Apr 3, 2018 at 5:04 PM, Matthew Garrett <mjg59@...gle.com> wrote:
>
> How? When there are random DMA-capable PCI devices that are driven by
> userland tools that are mmap()ing the BARs out of sysfs, how do we
> simultaneously avoid breaking those devices while also preventing the
> majority of users from being vulnerable to an attacker just DMAing over the
> kernel?
.. if that ends up being a real problem, then you print a warning and
tell people to use the kernel command line to disable things.
And if it's a big and common problem, then the answer may be that
lockdown has to be entirely OFF by default, and you instead just tell
people to enable it manually with a kernel command line option.
Still better than telling them to disable/enable secure boot, which
they may or may not even be able to to.
Linus
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