Re: [PATCH] userns/capability: Add user namespace capability

Am 18.10.2015 um 22:13 schrieb Tobias Markus:

On 17.10.2015 22:17, Richard Weinberger wrote:

quoted

On Sat, Oct 17, 2015 at 5:58 PM, Tobias Markus [off-list ref] wrote:

quoted

One question remains though: Does this break userspace executables that
expect being able to create user namespaces without priviledge? Since
creating user namespaces without CAP_SYS_ADMIN was not possible before
Linux 3.8, programs should already expect a potential EPERM upon calling
clone. Since creating a user namespace without CAP_SYS_USER_NS would
also cause EPERM, we should be on the safe side.

In case of doubt, yes it will break existing software.
Hiding user namespaces behind CAP_SYS_USER_NS will not magically
make them secure.

The goal is not to make user namespaces secure, but to limit access to
them somewhat in order to reduce the potential attack surface.

We have already a framework to reduce the attack surface, seccomp.
There is no need to invent new capabilities for every non-trivial
kernel feature.

I can understand the user namespaces seems scary and had bugs.
But which software didn't?

Are there any unfixed exploitable bugs in user namespaces in recent kerenls?

Thanks,
//richard

--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html