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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