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Tue, 3 Apr 2018 19:48:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:56428 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753811AbeDCXsw (ORCPT ); Tue, 3 Apr 2018 19:48:52 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E4872183C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org X-Google-Smtp-Source: AIpwx4/b39fXYzOht989weLYQ5UOQ0WbHduVawi+VUE3G2XdGucZenmdtmbbfdxOhSAjeHimRVQqGbp+A6dsRQFECMI= MIME-Version: 1.0 In-Reply-To: <10718.1522798745@warthog.procyon.org.uk> References: <4136.1522452584@warthog.procyon.org.uk> <186aeb7e-1225-4bb8-3ff5-863a1cde86de@kernel.org> <30459.1522739219@warthog.procyon.org.uk> <9758.1522775763@warthog.procyon.org.uk> <13189.1522784944@warthog.procyon.org.uk> <9349.1522794769@warthog.procyon.org.uk> <10718.1522798745@warthog.procyon.org.uk> From: Andy Lutomirski Date: Tue, 3 Apr 2018 16:48:31 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] Kernel lockdown for secure boot To: David Howells Cc: Linus Torvalds , Andy Lutomirski , Matthew Garrett , Ard Biesheuvel , James Morris , Alan Cox , Greg Kroah-Hartman , Linux Kernel Mailing List , Justin Forbes , linux-man , joeyli , LSM List , Linux API , Kees Cook , linux-efi Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-security-module@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Tue, Apr 3, 2018 at 4:39 PM, David Howells wrote: > Linus Torvalds wrote: > >> The same thing is true of some lockdown patch. Maybe it's a good thing >> in general. But whether it's a good thing is _entirely_ independent of >> any secure boot issue. I can see using secure boot without it, but I >> can very much also see using lockdown without secure boot. >> >> The two things are simply entirely orthogonal. They have _zero_ >> overlap. I'm not seeing why they'd be linked at all in any way. > > I'm not sure I agree. Here's my reasoning: > > (1) Lockdown mode really needs to activated during kernel boot, before > userspace has a chance to run, otherwise there's a window of opportunity > in which the kernel *isn't* locked down. That's simply not true. A sensible verified boot chain (a la Chrome OS) is likely to load, as one verified chunk, a kernel and initramfs. Then initramfs can flip on lockdown all by itself before it enables networking or any other attack vectors.