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Message-ID: <20111027193547.GH28067@dhcp-25-225.brq.redhat.com>
Date: Thu, 27 Oct 2011 21:35:47 +0200
From: Petr Matousek <pmatouse@...hat.com>
To: oss-security@...ts.openwall.com
Cc: kseifried@...hat.com
Subject: Re: CVE Request -- kernel: sysctl: restrict write
access to dmesg_restrict
On Wed, Oct 26, 2011 at 07:53:10PM +0400, Vasiliy Kulikov wrote:
> 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? :-)
Yes, you are right. I was aware of the procfs limitations, still it looked
to me that boundary explicitly defined in eaf06b2 is directly crossed in
this case.
Anyway I agree that it is useless to issue CVE for each procfs flaw of
this kind.
Kurt, could you please reject the CVE?
Sorry for the noise,
Petr
>
> 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
--
Petr Matousek / Red Hat Security Response Team
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