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Date: Mon, 15 Jun 2020 19:02:51 +0200
From: Jann Horn <jannh@...gle.com>
To: John Haxby <john.haxby@...cle.com>
Cc: oss-security@...ts.openwall.com, "Jason A. Donenfeld" <Jason@...c4.com>,
linux-security-module <linux-security-module@...r.kernel.org>, linux-acpi@...r.kernel.org,
Matthew Garrett <mjg59@...f.ucam.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Ubuntu Kernel Team <kernel-team@...ts.ubuntu.com>
Subject: Re: lockdown bypass on mainline kernel for loading
unsigned modules
On Mon, Jun 15, 2020 at 6:24 PM John Haxby <john.haxby@...cle.com> wrote:
> > On 15 Jun 2020, at 11:26, Jason A. Donenfeld <Jason@...c4.com> 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:
> >
> > https://git.zx2c4.com/american-unsigned-language/tree/american-unsigned-language-2.sh
> >
> > 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] https://www.openwall.com/lists/oss-security/2020/06/14/1
>
>
> 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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