Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Wed, 26 Oct 2011 19:53:10 +0400
From: Vasiliy Kulikov <>
Subject: Re: CVE Request -- kernel: sysctl: restrict write
 access to dmesg_restrict


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

Vasiliy Kulikov - bringing security into open computing environments

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.