From: Oleg Nesterov <oleg@redhat.com>
To: Christian Brauner <christian@brauner.io>
Cc: 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, cyphar@cyphar.com,
joel@joelfernandes.org, dancol@google.com
Subject: Re: [PATCH v2 2/5] clone: add CLONE_PIDFD
Date: Thu, 18 Apr 2019 16:10:20 +0200 [thread overview]
Message-ID: <20190418141019.GD13701@redhat.com> (raw)
In-Reply-To: <20190418132822.untjt7erfvbbiz7a@brauner.io>
On 04/18, Christian Brauner wrote:
>
> On Thu, Apr 18, 2019 at 03:12:07PM +0200, Oleg Nesterov wrote:
> > Should we allow CLONE_THREAD | CLONE_PIDFD ?
>
> I think so, yes. I have thought about this.
OK, I won't insist. But let me explain why did I ask.
> Yes, due to CLONE_FILES |
> CLONE_VM you'd necessarily hand the pidfd to the child but threads are
> no security boundary in the first place.
No, no, I am not not worried about security. CLONE_PARENT | CLONE_PIDFD
looks more problematic to me, but I see nothing dangerous security-wise..
I agree that CLONE_THREAD | CLONE_PIDFD may be usefule, but I am not sure
we should allow this from the very begining, until we have a "real" use-case.
IIUC, we are going to make it pollable soon. OK, but proc_tgid_base_poll()
(which should be turned into pidfd_poll) simply can't work if pid_task() is
not a group leader. poll(pidfd) will hang forever if pidfd was created by
CLONE_THREAD | CLONE_PIDFD.
Sure, we can (should?) improve pidfd_poll() but this will need more nasty
changes in the core kernel code. Do we really need/want this? Right now it
is not clear to me. Instead, we can simply disallow CLONE_THREAD|CLONE_PIDFD
until we decide that yes, we want to poll sub-threads.
But again, I am fine with CLONE_THREAD | CLONE_PIDFD.
Oleg.
next prev parent reply other threads:[~2019-04-18 14:10 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-18 10:18 [PATCH v2 0/5] clone: add CLONE_PIDFD Christian Brauner
2019-04-18 10:18 ` [PATCH v2 1/5] Make anon_inodes unconditional Christian Brauner
2019-04-18 10:18 ` [PATCH v2 2/5] clone: add CLONE_PIDFD Christian Brauner
2019-04-18 13:12 ` Oleg Nesterov
2019-04-18 13:28 ` Christian Brauner
2019-04-18 14:10 ` Oleg Nesterov [this message]
2019-04-18 14:15 ` Christian Brauner
2019-04-19 13:39 ` Aleksa Sarai
2019-04-18 10:18 ` [PATCH v2 3/5] signal: use fdget() since we don't allow O_PATH Christian Brauner
2019-04-18 13:17 ` Oleg Nesterov
2019-04-18 15:37 ` Linus Torvalds
2019-04-18 15:53 ` Christian Brauner
2019-04-18 10:18 ` [PATCH v2 4/5] signal: support CLONE_PIDFD with pidfd_send_signal Christian Brauner
2019-04-18 14:26 ` Oleg Nesterov
2019-04-18 15:01 ` Christian Brauner
2019-04-18 10:18 ` [PATCH v2 5/5] samples: show race-free pidfd metadata access Christian Brauner
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