linux-kernel - Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add CLONE

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Date:   Tue, 16 Apr 2019 05:59:11 +1000
From:   Aleksa Sarai <cyphar@...har.com>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
Cc:     Christian Brauner <christian@...uner.io>,
        torvalds@...ux-foundation.org, viro@...iv.linux.org.uk,
        jannh@...gle.com, dhowells@...hat.com, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org, serge@...lyn.com, luto@...nel.org,
        arnd@...db.de, ebiederm@...ssion.com, keescook@...omium.org,
        tglx@...utronix.de, mtk.manpages@...il.com,
        akpm@...ux-foundation.org, oleg@...hat.com, joel@...lfernandes.org,
        dancol@...gle.com
Subject: Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add
 CLONE_PIDFD]

On 2019-04-15, Enrico Weigelt, metux IT consult <lkml@...ux.net> wrote:
> > This patchset makes it possible to retrieve pid file descriptors at
> > process creation time by introducing the new flag CLONE_PIDFD to the
> > clone() system call as previously discussed.
> 
> Sorry, for highjacking this thread, but I'm curious on what things to
> consider when introducing new CLONE_* flags.
> 
> The reason I'm asking is:
> 
> I'm working on implementing plan9-like fs namespaces, where unprivileged
> processes can change their own namespace at will. For that, certain
> traditional unix'ish things have to be disabled, most notably suid.
> As forbidding suid can be helpful in other scenarios, too, I thought
> about making this its own feature. Doing that switch on clone() seems
> a nice place for that, IMHO.

Just spit-balling -- is no_new_privs not sufficient for this usecase?
Not granting privileges such as setuid during execve(2) is the main
point of that flag.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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