linux-kernel - Re: [PATCH] userns,pidns: Verify the userns for new pid namespaces

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Date:   Sat, 29 Apr 2017 23:42:17 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     "Serge E. Hallyn" <serge@...lyn.com>
Cc:     Linux Containers <containers@...ts.linux-foundation.org>,
        agruenba@...hat.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, oleg@...hat.com, paul@...l-moore.com,
        viro@...iv.linux.org.uk, avagin@...nvz.org,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        mtk.manpages@...il.com, akpm@...ux-foundation.org,
        luto@...capital.net, gorcunov@...nvz.org, mingo@...nel.org,
        keescook@...omium.org, Kirill Tkhai <ktkhai@...tuozzo.com>
Subject: Re: [PATCH] userns,pidns: Verify the userns for new pid namespaces

ebiederm@...ssion.com (Eric W. Biederman) writes:

> "Serge E. Hallyn" <serge@...lyn.com> writes:
>
>> Quoting Eric W. Biederman (ebiederm@...ssion.com):
>>> 
>>> It is pointless and confusing to allow a pid namespace hierarchy and
>>> the user namespace hierarchy to get out of sync.  The owner of a child
>>> pid namespace should be the owner of the parent pid namespace or
>>> a descendant of the owner of the parent pid namespace.
>>> 
>>> Otherwise it is possible to construct scenarios where it is legal to
>>> do something in a parent pid namespace but in a child pid namespace.
>>
>> Hi,
>>
>> did you mean 'but not in a child...' above?
>
> Actually I believe I meant:
>
>>> Otherwise it is possible to construct scenarios where it is not legal
>>> to do something in a parent pid namespace but it is legal a child pid
>>> namespace.
>
> I definitely need to fix that wording thank you.

Looking at some more I mean:

Otherwise it is possible to construct scenarios where a process has a
capability in a over a parent pid namespace but does not have the
capability over a child pid namespace.  Which confusingly makes
permission checks non-transitive.


Eric