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Date: Thu, 27 Oct 2011 16:04:53 -0600
From: Kurt Seifried <>
Subject: Re: CVE Request -- kernel: sysctl: restrict write
 access to dmesg_restrict

Please revoke


On 10/27/2011 01:35 PM, Petr Matousek wrote:
> 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
>> - bringing security into open computing environments


-Kurt Seifried / Red Hat Security Response Team

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