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Date: Mon, 15 Jun 2020 19:02:51 +0200
From: Jann Horn <>
To: John Haxby <>
Cc:, "Jason A. Donenfeld" <>, 
	linux-security-module <>,, 
	Matthew Garrett <>, 
	Kernel Hardening <>, 
	Ubuntu Kernel Team <>
Subject: Re: [oss-security] lockdown bypass on mainline kernel for loading
 unsigned modules

On Mon, Jun 15, 2020 at 6:24 PM John Haxby <> wrote:
> > On 15 Jun 2020, at 11:26, Jason A. Donenfeld <> wrote:
> > Yesterday, I found a lockdown bypass in Ubuntu 18.04's kernel using
> > ACPI table tricks via the efi ssdt variable [1]. Today I found another
> > one that's a bit easier to exploit and appears to be unpatched on
> > mainline, using acpi_configfs to inject an ACPI table. The tricks are
> > basically the same as the first one, but this one appears to be
> > unpatched, at least on my test machine. Explanation is in the header
> > of the PoC:
> >
> >
> >
> > I need to get some sleep, but if nobody posts a patch in the
> > meanwhile, I'll try to post a fix tomorrow.
> >
> > Jason
> >
> > [1]
> This looks CVE-worthy.   Are you going to ask for a CVE for it?

Does it really make sense to dole out CVEs for individual lockdown
bypasses when various areas of the kernel (such as filesystems and
BPF) don't see root->kernel privilege escalation issues as a problem?
It's not like applying the fix for this one issue is going to make
systems meaningfully safer.

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