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From: Andy Lutomirski <luto@kernel.org>
To: Daniel Colascione <dancol@google.com>
Cc: Andrew Lutomirski <luto@kernel.org>,
	Christian Brauner <christian@brauner.io>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Jann Horn <jannh@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>, Aleksa Sarai <cyphar@cyphar.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	Tim Murray <timmurray@google.com>,
	Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] proc: allow killing processes via file descriptors
Date: Sun, 18 Nov 2018 08:17:55 -0800	[thread overview]
Message-ID: <CALCETrVLP_mudJTW6EQpRr5GZ7kfuGci+QCT1uPrOVDTWcod-A@mail.gmail.com> (raw)
In-Reply-To: <CAKOZuev1JUGFWuwsKqS6rXcFMqpCHT1VAG2kwB4O=FHo6DAFiQ@mail.gmail.com>

On Sun, Nov 18, 2018 at 7:53 AM Daniel Colascione <dancol@google.com> wrote:
>
> On Sun, Nov 18, 2018 at 7:38 AM, Andy Lutomirski <luto@kernel.org> wrote:
> > I fully agree that a more comprehensive, less expensive API for
> > managing processes would be nice.  But I also think that this patch
> > (using the directory fd and ioctl) is better from a security
> > perspective than using a new file in /proc.
>
> That's an assertion, not an argument. And I'm not opposed to an
> operation on the directory FD, now that it's clear Linus has banned
> "write(2)-as-a-command" APIs. I just insist that we implement the API
> with a system call instead of a less-reliable ioctl due to the
> inherent namespace collision issues in ioctl command names.

Linus banned it because of bugs iike the ones in the patch.

>
> > I have an old patch to make proc directory fds pollable:
> >
> > https://lore.kernel.org/patchwork/patch/345098/
> >
> > That patch plus the one in this thread might make a nice addition to
> > the kernel even if we expect something much better to come along
> > later.
>
> I've always commented on that patch. You never addressed my technical
> objections. Why are you bringing up this patch again as if that
> discussion had never happened? To review, that patch has various race
> conditions

I don't think I ever saw that review.

> and even if it were technically correct, it'd be an abuse
> of directory objects (in what other circumstance do we poll
> directories?) and not logically generalizable to a model in which we
> expose process exit status via the exit-monitoring API.

I agree it's weird.  It might be better to have /proc/PID/exit_status
and make *that* pollable.

  reply	other threads:[~2018-11-18 16:18 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-18 11:17 Christian Brauner
2018-11-18 13:59 ` Daniel Colascione
2018-11-18 15:38   ` Andy Lutomirski
2018-11-18 15:53     ` Daniel Colascione
2018-11-18 16:17       ` Andy Lutomirski [this message]
2018-11-18 16:29         ` Daniel Colascione
2018-11-18 17:13           ` Andy Lutomirski
2018-11-18 17:17             ` Daniel Colascione
2018-11-18 17:43               ` Eric W. Biederman
2018-11-18 17:45                 ` Andy Lutomirski
2018-11-18 17:56                 ` Daniel Colascione
2018-11-18 16:33         ` Randy Dunlap
2018-11-18 16:48           ` Daniel Colascione
2018-11-18 17:09             ` Andy Lutomirski
2018-11-18 17:24               ` Daniel Colascione
2018-11-18 17:42                 ` Andy Lutomirski
2018-11-18 17:51                   ` Daniel Colascione
2018-11-18 18:28                     ` Andy Lutomirski
2018-11-18 18:43                       ` Daniel Colascione
2018-11-18 19:05                         ` Aleksa Sarai
2018-11-18 19:44                           ` Daniel Colascione
2018-11-18 20:15                             ` Christian Brauner
2018-11-18 20:21                               ` Daniel Colascione
2018-11-18 20:28                             ` Andy Lutomirski
2018-11-18 20:32                               ` Daniel Colascione
2018-11-19  1:43                                 ` Andy Lutomirski
2018-11-18 20:43                               ` Christian Brauner
2018-11-18 20:54                                 ` Daniel Colascione
2018-11-18 21:23                                   ` Christian Brauner
2018-11-18 21:30                                     ` Christian Brauner
2018-11-19  0:31                                       ` Daniel Colascione
2018-11-19  0:40                                         ` Christian Brauner
2018-11-19  0:09                             ` Aleksa Sarai
2018-11-19  0:53                               ` Daniel Colascione
2018-11-19  1:16                                 ` Daniel Colascione
2018-11-19 16:13                       ` Dmitry Safonov
2018-11-19 16:26                         ` [PATCH] proc: allow killing processes via file descriptors (Larger pids) Eric W. Biederman
2018-11-19 16:27                         ` [PATCH] proc: allow killing processes via file descriptors Daniel Colascione
2018-11-19 20:21                           ` Aleksa Sarai
2018-11-19  2:47                   ` Al Viro
2018-11-19  3:01                     ` Andy Lutomirski
2018-11-18 17:41     ` Christian Brauner
2018-11-18 17:44       ` Andy Lutomirski
2018-11-18 18:07       ` Daniel Colascione
2018-11-18 18:15         ` Andy Lutomirski
2018-11-18 18:31           ` Daniel Colascione
2018-11-18 19:24         ` Christian Brauner
2018-11-19  0:08         ` Aleksa Sarai
2018-11-19  1:14           ` Daniel Colascione
2018-11-18 16:03 ` Daniel Colascione
2018-11-19 10:56 ` kbuild test robot
2018-11-19 14:15 ` David Laight
2018-11-19 15:49 ` Dave Martin

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