On Mon, Jan 25, 2016 at 10:51 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > On Sun, Jan 24, 2016 at 2:22 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: >> On Fri, Jan 22, 2016 at 7:02 PM, Eric W. Biederman >> <ebiederm@xxxxxxxxxxxx> wrote: >>> Kees Cook <keescook@xxxxxxxxxxxx> writes: >>> >>>> There continues to be unexpected side-effects and security exposures >>>> via CLONE_NEWUSER. For many end-users running distro kernels with >>>> CONFIG_USER_NS enabled, there is no way to disable this feature when >>>> desired. As such, this creates a sysctl to restrict CLONE_NEWUSER so >>>> admins not running containers or Chrome can avoid the risks of this >>>> feature. >>> >>> I don't actually think there do continue to be unexpected side-effects >>> and security exposures with CLONE_NEWUSER. It takes a while for all of >>> the fixes to trickle out to distros. At most what I have seen recently >>> are problems with other kernel interfaces being amplified with user >>> namespaces. AKA the current mess with devpts, and the unexpected >>> issues with bind mounts in mount namespaces. >>> >> >>> >>> So to keep this productive. Please tell me about the threat model >>> you envision, and how you envision knobs in the kernel being used to >>> counter those threats. >> >> I consider the ability to use CLONE_NEWUSER to acquire CAP_NET_ADMIN >> over /any/ network namespace and to thus access the network >> configuration API to be a huge risk. For example, unprivileged users >> can program iptables. I'll eat my hat if there are no privilege >> escalations in there. (They can't request module loading, but still.) > > Should I consider this an Ack for the patch? :) Only if you explain why you need the CAP_SYS_ADMIN check. :) IOW, I think you could change that one line of code and have a less weird version of the patch that would work just fine. --Andy -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
