From: Casey Schaufler <casey@schaufler-ca.com>
To: John Stultz <john.stultz@linaro.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>,
lkml <linux-kernel@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
Li Zefan <lizefan@huawei.com>, Jonathan Corbet <corbet@lwn.net>,
"open list:CONTROL GROUP \(CGROUP\)" <cgroups@vger.kernel.org>,
Android Kernel Team <kernel-team@android.com>,
Rom Lemarchand <romlem@android.com>,
Colin Cross <ccross@android.com>,
Dmitry Shmidt <dimitrysh@google.com>,
Todd Kjos <tkjos@google.com>,
Christian Poetzsch <christian.potzsch@imgtec.com>,
Amit Pundir <amit.pundir@linaro.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Kees Cook <keescook@chromium.org>,
"Serge E . Hallyn" <serge@hallyn.com>,
Andy Lutomirski <luto@amacapital.net>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH v5] cgroup: Add new capability to allow a process to migrate other tasks between cgroups
Date: Tue, 13 Dec 2016 09:48:40 -0800 [thread overview]
Message-ID: <4c60e1be-c00a-5f26-f5de-7d32b9cb0f62@schaufler-ca.com> (raw)
In-Reply-To: <CALAqxLUgmeNxt5B5k720YRM=pUh=a-b2cg+mCM1n1QG-un2ofQ@mail.gmail.com>
On 12/13/2016 9:24 AM, John Stultz wrote:
> On Tue, Dec 13, 2016 at 9:17 AM, Casey Schaufler <casey@schaufler-ca.com> wrote:
>> On 12/13/2016 8:49 AM, John Stultz wrote:
>>> On Tue, Dec 13, 2016 at 8:39 AM, Casey Schaufler <casey@schaufler-ca.com> wrote:
>>>> On 12/13/2016 1:47 AM, Michael Kerrisk (man-pages) wrote:
>>>>> How about CAP_CGROUP_CONTROL or some such, with the idea that this
>>>>> might be a capability that allows the holder to step outside usual
>>>>> cgroup rules? At the moment, that capability would allow only one such
>>>>> step, but maybe there would be others in the future.
>>>> I agree, but want to put it more strongly. The granularity of
>>>> capabilities can never be fine enough for some people, and this
>>>> is an example of a case where you're going a bit too far. If the
>>>> use case is Android as you say, you don't need this. As my friends
>>>> on the far side of the aisle would say, "just write SELinux policy"
>>>> to correctly control access as required.
>>> So.. The trouble is that while selinux is good for restricting
>>> permissions, the in-kernel permission checks here are already too
>>> restrictive.
>> Why did the original authors of cgroups make it that restrictive?
>> If there isn't a good reason, loosen it up. If there is a good
>> reason, then pay heed to it.
> That's what this patch is proposing. And I agree with Michael that the
> newly proposed cap was a bit to narrowly focused on my immediate use
> case, and broadening it to CGROUP_CONTROL is smart. Then that
> capability could be further restricted w/ selinux policy, as you
> suggest.
Adding a new capability is unnecessary. The current use of CAP_SYS_NICE,
while arguably obscure, provides as much "security" as a new capability
does. While cgroups are a wonderful thing, they don't need a separate
capability.
>
> thanks
> -john
>
next prev parent reply other threads:[~2016-12-13 17:49 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-13 1:39 [PATCH v5] cgroup: Add new capability to allow a process to migrate other tasks between cgroups John Stultz
2016-12-13 1:40 ` John Stultz
2016-12-13 9:47 ` Michael Kerrisk (man-pages)
2016-12-13 16:08 ` John Stultz
2016-12-13 18:40 ` Tejun Heo
2016-12-13 18:47 ` John Stultz
2016-12-13 18:53 ` Tejun Heo
2016-12-13 16:39 ` Casey Schaufler
2016-12-13 16:49 ` John Stultz
2016-12-13 17:17 ` Casey Schaufler
2016-12-13 17:24 ` John Stultz
2016-12-13 17:48 ` Casey Schaufler [this message]
2016-12-13 18:13 ` John Stultz
2016-12-13 18:32 ` Casey Schaufler
2016-12-13 18:47 ` Tejun Heo
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