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Date:   Tue, 16 Apr 2019 05:59:11 +1000
From:   Aleksa Sarai <cyphar@cyphar.com>
To:     "Enrico Weigelt, metux IT consult" <lkml@metux.net>
Cc:     Christian Brauner <christian@brauner.io>,
        torvalds@linux-foundation.org, viro@zeniv.linux.org.uk,
        jannh@google.com, dhowells@redhat.com, linux-api@vger.kernel.org,
        linux-kernel@vger.kernel.org, serge@hallyn.com, luto@kernel.org,
        arnd@arndb.de, ebiederm@xmission.com, keescook@chromium.org,
        tglx@linutronix.de, mtk.manpages@gmail.com,
        akpm@linux-foundation.org, oleg@redhat.com, joel@joelfernandes.org,
        dancol@google.com
Subject: Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add
 CLONE_PIDFD]
Message-ID: <20190415195911.z7b7miwsj67ha54y@yavin>
References: <20190414201436.19502-1-christian@brauner.io>
 <dc05ffe3-c2ff-8b3e-d181-e0cc620bf91d@metux.net>
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On 2019-04-15, Enrico Weigelt, metux IT consult <lkml@metux.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.
>=20
> Sorry, for highjacking this thread, but I'm curious on what things to
> consider when introducing new CLONE_* flags.
>=20
> The reason I'm asking is:
>=20
> 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.

--=20
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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