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Date: Wed, 13 Feb 2019 20:57:43 +1100
From: Aleksa Sarai <cyphar@...har.com>
To: EJ Campbell <ejc3@...izonmedia.com>
Cc: oss-security@...ts.openwall.com
Subject: Re: CVE-2019-5736: runc container breakout exploit
 code

On 2019-02-13, Aleksa Sarai <cyphar@...har.com> wrote:
> On 2019-02-13, EJ Campbell <ejc3@...izonmedia.com> wrote:
> > While fixing docker / runc is clearly the right fix, would using chattr -i
> > on runc be a quick mitigation for the issue? I believe that will prevent
> > the file from being overwritten by the exploit and Etienne Stalmans
> > verified that it helped:
> >  https://twitter.com/_staaldraad/status/1095354945073754112
> 
> The privileged user in the container could just un-set the immutable
> bit using "/proc/self/fd/..." and then open it for writing. A read-only
> filesystem would work much better.

Sorry, I forgot that CAP_LINUX_IMMUTABLE is dropped by default in
Docker. Yes that mitigation would also work.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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