From: Oleg Nesterov <oleg@redhat.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: serge@hallyn.com, ebiederm@xmission.com, agruenba@redhat.com,
linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
paul@paul-moore.com, viro@zeniv.linux.org.uk, avagin@openvz.org,
linux-fsdevel@vger.kernel.org, mtk.manpages@gmail.com,
akpm@linux-foundation.org, luto@amacapital.net,
gorcunov@openvz.org, mingo@kernel.org, keescook@chromium.org
Subject: Re: [PATCH 2/2] pid_ns: Introduce ioctl to set vector of ns_last_pid's on ns hierarhy
Date: Thu, 27 Apr 2017 18:12:57 +0200 [thread overview]
Message-ID: <20170427161255.GA19350@redhat.com> (raw)
In-Reply-To: <785e1986-da03-72aa-06c0-234ed2dbc0fd@virtuozzo.com>
On 04/26, Kirill Tkhai wrote:
>
> On 26.04.2017 18:53, Oleg Nesterov wrote:
> >
> >> +static long set_last_pid_vec(struct pid_namespace *pid_ns,
> >> + struct pidns_ioc_req *req)
> >> +{
> >> + char *str, *p;
> >> + int ret = 0;
> >> + pid_t pid;
> >> +
> >> + read_lock(&tasklist_lock);
> >> + if (!pid_ns->child_reaper)
> >> + ret = -EINVAL;
> >> + read_unlock(&tasklist_lock);
> >> + if (ret)
> >> + return ret;
> >
> > why do you need to check ->child_reaper under tasklist_lock? this looks pointless.
> >
> > In fact I do not understand how it is possible to hit pid_ns->child_reaper == NULL,
> > there must be at least one task in this namespace, otherwise you can't open a file
> > which has f_op == ns_file_operations, no?
>
> Sure, it's impossible to pick a pid_ns, if there is no the pid_ns's tasks. I added
> it under impression of
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=dfda351c729733a401981e8738ce497eaffcaa00
> but here it's completely wrong. It will be removed in v2.
Hmm. But if I read this commit correctly then we really need to check
pid_ns->child_reaper != NULL ?
Currently we can't pick an "empty" pid_ns. But after the commit above a task
can do sys_unshare(CLONE_NEWPID), another (or the same) task can open its
/proc/$pid/ns/pid_for_children and call ns_ioctl() before the 1st alloc_pid() ?
Or I am totally confused?
Oleg.
next prev parent reply other threads:[~2017-04-27 16:13 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-17 17:34 [PATCH 0/2] nsfs: Introduce ioctl to set vector of ns_last_pid's on pid ns hierarhy Kirill Tkhai
2017-04-17 17:36 ` [PATCH 1/2] nsfs: Add namespace-specific ioctl (NS_SPECIFIC_IOC) Kirill Tkhai
2017-04-17 17:36 ` [PATCH 2/2] pid_ns: Introduce ioctl to set vector of ns_last_pid's on ns hierarhy Kirill Tkhai
2017-04-19 20:27 ` Serge E. Hallyn
2017-04-24 19:03 ` Cyrill Gorcunov
2017-04-26 15:53 ` Oleg Nesterov
2017-04-26 16:11 ` Kirill Tkhai
2017-04-26 16:33 ` Kirill Tkhai
2017-04-26 16:32 ` Eric W. Biederman
2017-04-26 16:43 ` Kirill Tkhai
2017-04-26 17:01 ` Eric W. Biederman
2017-04-27 16:12 ` Oleg Nesterov [this message]
2017-04-27 16:17 ` Kirill Tkhai
2017-04-27 16:22 ` Oleg Nesterov
2017-04-28 9:17 ` Kirill Tkhai
2017-05-02 16:33 ` Oleg Nesterov
2017-05-02 17:22 ` Eric W. Biederman
2017-05-02 17:33 ` Kirill Tkhai
2017-05-02 21:13 ` Eric W. Biederman
2017-05-03 10:20 ` Kirill Tkhai
2017-04-27 16:39 ` Eric W. Biederman
2017-04-28 9:22 ` Kirill Tkhai
2017-04-27 16:16 ` Oleg Nesterov
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