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From: Christian Brauner <brauner@kernel.org>
To: Florian Weimer <fweimer@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Tycho Andersen <tycho@tycho.pizza>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	Jan Kara <jack@suse.cz>,
	linux-fsdevel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: Re: [RFC 1/3] pidfd: allow pidfd_open() on non-thread-group leaders
Date: Fri, 8 Dec 2023 14:48:30 +0100	[thread overview]
Message-ID: <20231208-hitzig-charmant-6bbdc427bf7e@brauner> (raw)
In-Reply-To: <87wmtog7ht.fsf@oldenburg.str.redhat.com>

On Fri, Dec 08, 2023 at 02:15:58PM +0100, Florian Weimer wrote:
> * Christian Brauner:
> 
> > File descriptors are reachable for all processes/threads that share a
> > file descriptor table. Changing that means breaking core userspace
> > assumptions about how file descriptors work. That's not going to happen
> > as far as I'm concerned.
> 
> It already has happened, though?  Threads are free to call
> unshare(CLONE_FILES).  I'm sure that we have applications out there that

If you unshare a file descriptor table it will affect all file
descriptors of a given task. We don't allow hiding individual or ranges
of file descriptors from close/dup. That's akin to a partially shared
file descriptor table which is conceptually probably doable but just
plain weird and nasty to get right imho.

This really is either LSM territory to block such operations or use
stuff like io_uring gives you.

  reply	other threads:[~2023-12-08 13:48 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-30 16:39 [RFC 1/3] pidfd: allow pidfd_open() on non-thread-group leaders Tycho Andersen
2023-11-30 16:39 ` [RFC 2/3] selftests/pidfd: add non-thread-group leader tests Tycho Andersen
2023-11-30 16:39 ` [RFC 3/3] clone: allow CLONE_THREAD | CLONE_PIDFD together Tycho Andersen
2023-11-30 17:39 ` [RFC 1/3] pidfd: allow pidfd_open() on non-thread-group leaders Oleg Nesterov
2023-11-30 17:56   ` Tycho Andersen
2023-12-01 16:31     ` Tycho Andersen
2023-12-07 17:57       ` Christian Brauner
2023-12-07 21:25         ` Christian Brauner
2023-12-08 20:04           ` Tycho Andersen
2023-11-30 18:37 ` Florian Weimer
2023-11-30 18:54   ` Tycho Andersen
2023-11-30 19:00     ` Mathieu Desnoyers
2023-11-30 19:17       ` Tycho Andersen
2023-11-30 19:43       ` Florian Weimer
2023-12-06 15:27         ` Tycho Andersen
2023-12-07 22:58         ` Christian Brauner
2023-12-08  3:16           ` Jens Axboe
2023-12-08 13:15           ` Florian Weimer
2023-12-08 13:48             ` Christian Brauner [this message]
2023-12-08 13:58               ` Florian Weimer
2023-12-07 17:21 ` Christian Brauner
2023-12-07 17:52   ` Tycho Andersen
2023-12-08 17:47   ` Jan Kara

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