From: Aleksa Sarai <cyphar@cyphar.com>
To: Daniel Colascione <dancol@google.com>
Cc: linux-kernel@vger.kernel.org, timmurray@google.com,
joelaf@google.com, surenb@google.com
Subject: Re: [RFC PATCH] Implement /proc/pid/kill
Date: Tue, 30 Oct 2018 16:00:12 +1100 [thread overview]
Message-ID: <20181030050012.u43lcvydy6nom3ul@yavin> (raw)
In-Reply-To: <20181029221037.87724-1-dancol@google.com>
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On 2018-10-29, Daniel Colascione <dancol@google.com> wrote:
> Add a simple proc-based kill interface. To use /proc/pid/kill, just
> write the signal number in base-10 ASCII to the kill file of the
> process to be killed: for example, 'echo 9 > /proc/$$/kill'.
>
> Semantically, /proc/pid/kill works like kill(2), except that the
> process ID comes from the proc filesystem context instead of from an
> explicit system call parameter. This way, it's possible to avoid races
> between inspecting some aspect of a process and that process's PID
> being reused for some other process.
(Aside from any UX concerns other folks might have.)
I think it would be a good idea to (at least temporarily) restrict this
so that only processes that are in the same PID namespace as the /proc
being resolved through may use this interface. Otherwise you might have
cases where partial container breakouts can start sending signals to
PIDs they wouldn't normally be able to address.
> With /proc/pid/kill, it's possible to write a proper race-free and
> safe pkill(1). An approximation follows. A real program might use
> openat(2), having opened a process's /proc/pid directory explicitly,
> with the directory file descriptor serving as a sort of "process
> handle".
I do like the idea of holding a dirfd to /proc/$pid to address
processes, and it something I considered doing in runc. (Unfortunately
there are lots of things that make it a bit difficult to use /proc/$pid
exclusively for introspection of a process -- especially in the context
of containers.)
--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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next prev parent reply other threads:[~2018-10-30 5:00 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-29 22:10 [RFC PATCH] Implement /proc/pid/kill Daniel Colascione
2018-10-30 3:21 ` Joel Fernandes
2018-10-30 8:50 ` Daniel Colascione
2018-10-30 10:39 ` Christian Brauner
2018-10-30 10:40 ` Christian Brauner
2018-10-30 10:48 ` Daniel Colascione
2018-10-30 11:04 ` Christian Brauner
2018-10-30 11:12 ` Daniel Colascione
2018-10-30 11:19 ` Christian Brauner
2018-10-31 5:00 ` Eric W. Biederman
2018-10-30 17:01 ` Joel Fernandes
2018-10-30 5:00 ` Aleksa Sarai [this message]
2018-10-30 9:05 ` Daniel Colascione
2018-10-30 20:45 ` Aleksa Sarai
2018-10-30 21:42 ` Joel Fernandes
2018-10-30 22:23 ` Aleksa Sarai
2018-10-30 22:33 ` Joel Fernandes
2018-10-30 22:49 ` Aleksa Sarai
2018-10-31 0:42 ` Joel Fernandes
2018-10-31 1:59 ` Daniel Colascione
2018-10-30 23:10 ` Daniel Colascione
2018-10-30 23:23 ` Christian Brauner
2018-10-30 23:55 ` Daniel Colascione
2018-10-31 2:56 ` Aleksa Sarai
2018-10-31 4:24 ` Joel Fernandes
2018-11-01 20:40 ` Joel Fernandes
2018-11-02 9:46 ` Christian Brauner
2018-11-02 14:34 ` Serge E. Hallyn
2018-10-31 0:57 ` Joel Fernandes
2018-10-31 1:56 ` Daniel Colascione
2018-10-31 4:47 ` Eric W. Biederman
2018-10-31 4:44 ` Eric W. Biederman
2018-10-31 12:44 ` Oleg Nesterov
2018-10-31 13:27 ` Daniel Colascione
2018-10-31 15:10 ` Oleg Nesterov
2018-10-31 15:16 ` Daniel Colascione
2018-10-31 15:49 ` Oleg Nesterov
2018-11-01 11:53 ` David Laight
2018-11-01 15:50 ` Daniel Colascione
2018-10-31 14:37 ` [PATCH v2] " Daniel Colascione
2018-10-31 15:05 ` Joel Fernandes
2018-10-31 17:33 ` Aleksa Sarai
2018-10-31 21:47 ` Joel Fernandes
2018-10-31 15:59 ` [PATCH v3] " Daniel Colascione
2018-10-31 17:54 ` Tycho Andersen
2018-10-31 18:00 ` Daniel Colascione
2018-10-31 18:17 ` Tycho Andersen
2018-10-31 19:33 ` Daniel Colascione
2018-10-31 20:06 ` Tycho Andersen
2018-11-01 11:33 ` David Laight
2018-11-12 1:19 ` Eric W. Biederman
2018-10-31 16:22 ` [RFC PATCH] " Jann Horn
2018-11-01 4:53 ` Andy Lutomirski
2018-11-12 23:13 ` Pavel Machek
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