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From: Daniel Colascione <dancol@google.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: 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 09:17:31 -0800	[thread overview]
Message-ID: <CAKOZues3_uh1mnQr=VPCxoWiY0wfiUq0oFXcVuiHF7rPmUXsuw@mail.gmail.com> (raw)
In-Reply-To: <CALCETrXNBNcASRtxTL_aO-KSj4ahPRpXKLUdHaWG3sPjsWx3CQ@mail.gmail.com>

On Sun, Nov 18, 2018 at 9:13 AM, Andy Lutomirski <luto@kernel.org> wrote:
> On Sun, Nov 18, 2018 at 8:29 AM Daniel Colascione <dancol@google.com> wrote:
>>
>> On Sun, Nov 18, 2018 at 8:17 AM, Andy Lutomirski <luto@kernel.org> wrote:
>> > 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.
>>
>> Maybe: he didn't provide a reason. What's your point?
>
> My point is that an API that involves a file like /proc/PID/kill is
> very tricky to get right.  Here are some considerations:

Moot. write(2) for this interface is off the table anyway. The right
approach here is a system call that accepts a /proc/pid directory file
descriptor, a signal number, and a signal information field (as in
sigqueue(2)).

> Now if we had an ioctlat() API, maybe it would make sense.  But we
> don't, and I think it would be a bit crazy to add one.

A process is not a driver. Why won't this idea of using an ioctl for
the kill-process-by-dfd thing just won't die? An ioctl has *zero*
advantage in this context.

  reply	other threads:[~2018-11-18 17:17 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
2018-11-18 16:29         ` Daniel Colascione
2018-11-18 17:13           ` Andy Lutomirski
2018-11-18 17:17             ` Daniel Colascione [this message]
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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