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Date: Mon, 28 Nov 2011 10:12:50 -0800
From: Kees Cook <>
To: Vasiliy Kulikov <>
Cc: "Serge E. Hallyn" <>, Serge Hallyn <>,,,
Subject: Re: [RFC] Make Yama pid_ns aware

On Wed, Nov 23, 2011 at 8:55 AM, Vasiliy Kulikov <> wrote:
> On Wed, Nov 23, 2011 at 14:49 +0000, Serge E. Hallyn wrote:
>> Quoting Vasiliy Kulikov (
>> > Actually, what concerns me is not ptrace, but symlink/hardling
>> > protection.  There is no interaction between namespaces in case of
>> > containers via symlinks in the basic case.  In case of ptrace I don't
>> > think the child ns may weaken the parent ns - child ns may not access
>> > processes of the parent namespace and everything it may ptrace is
>> > already inside of this ns.
>> Oh, yes.  If you're saying the symlink protection shouldn't be
>> per-pidns, I agree it seems an odd fit.
>> How about a version of this patch leaving symlink protection
>> out of pidns (maybe in user ns), and just putting ptrace
>> protection per-pidns?
> I don't think moving symlink/hardling from pid ns to user ns is a good
> idea as user ns is not matured yet.  Also we (Openwall) want to use Yama
> almost as-is in our RHEL6 and RHEL5-based kernels with OpenVZ support
> which don't have user namespaces yet at all (yes, it is not a cause for
> mainline decisions :-) ).
> While user ns is not yet ready, I don't clearly see what is the division
> of security policies among namespaces including user namespace.  I had
> a view that all stuff related to processes (i.e. distinct processes in
> several ways) belongs to pid ns, all net stuff to net ns, etc.  If we
> differentiate user ns and pid ns, only strictly things handling pids
> (like kill(2), procfs, ptrace(2), etc.) belong to pid ns and all other
> process-related stuff (like credentials handling, these symlink/hardling
> things, etc.) belong to user namespaces.
> Can we probably leave them in pid ns for now and when user ns is matured
> just move it from pid ns to user ns?  Is it possible without breaking
> Yama's ABI (I think so)?

So it sounds like you'll send a new patch where only ptrace_scope is
tied to pidns?


Kees Cook
ChromeOS Security

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