From: Andy Lutomirski <luto@amacapital.net>
To: Djalal Harouni <tixxdz@gmail.com>
Cc: Linux API <linux-api@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@chromium.org>,
Lafcadio Wluiki <wluikil@gmail.com>
Subject: Re: [PATCH v4 2/2] procfs/tasks: add a simple per-task procfs hidepid= field
Date: Thu, 19 Jan 2017 11:52:54 -0800 [thread overview]
Message-ID: <CALCETrUp9CBWykRUQoJOXeLg9u45H+2VWyQ_BKAhwc9OpBYn+g@mail.gmail.com> (raw)
In-Reply-To: <CAEiveUevjijnmr7oWzQexi52nJm-BjVwAkb3fJinAbet=QvzxQ@mail.gmail.com>
On Thu, Jan 19, 2017 at 5:53 AM, Djalal Harouni <tixxdz@gmail.com> wrote:
> On Thu, Jan 19, 2017 at 12:35 AM, Andy Lutomirski <luto@amacapital.net> wrote:
>> On Wed, Jan 18, 2017 at 2:50 PM, Djalal Harouni <tixxdz@gmail.com> wrote:
>>>> Also, this one-way thing seems wrong to me. I think it should roughly
>>>> follow the no_new_privs rules instead. IOW, if you unshare your
>>>> pidns, it gets cleared. Also, maybe you shouldn't be able to set it
>>>
>>> Andy I don't follow here, no_new_privs is never cleared right ? I
>>> can't see the corresponding clear bit code for it.
>>
>> I believe that unsharing userns clears no_new_privs.
> No, it is not cleared, and I can't see the clear bit for it. Maybe due
> to userns+filesystems limitations it was not noticed.
Hmm, maybe I remembered wrong.
>> I feel like this feature (per-task hidepid) is subtle and complex
>> enough that it should have a very clear purpose and use case before
>> it's merged and that we should make sure that there isn't a better way
>> to accomplish what you're trying to do.
>
> Sure, the hidepid mount option is old enough, and this per-task
> hidepid is clearly defined only for procfs and per task, we can't add
> another switch that's relate to both a filesystem and pid namespaces,
> it will be a bit complicated and not really useful for cases that are
> in *same* pidns where *each* one have to mount its procfs, it will
> propagate. Also as noted by Lafcadio, the gid thing is a bit hard to
> use now.
What I'm trying to say is that I want to understand a complete,
real-world use case. Adding a security-related per-task flag is can
be quite messy and requires a lot of careful thought to get right, and
I'd rather avoid it if at all possible.
I'm imaging something like a new RestrictPidVisisbility= option in
systemd. I agree that this is currently a mess to do. But maybe a
simpler solution would be to add a new mount option local_hidepid to
procfs. If you set that option, then it overrides hidepid for that
instance. Most of these semi-sandboxed daemon processes already have
their own mount namespace, so the overhead should be minimal.
--Andy
next prev parent reply other threads:[~2017-01-19 19:53 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-16 13:23 [PATCH v4 0/2] procfs/tasks: introduce per-task procfs hidepid= field Djalal Harouni
2017-01-16 13:23 ` [PATCH v4 1/2] procfs: use an enum for possible hidepid values Djalal Harouni
2017-02-13 22:16 ` Kees Cook
2017-02-15 0:34 ` Andrew Morton
2017-02-15 8:56 ` Djalal Harouni
2017-01-16 13:23 ` [PATCH v4 2/2] procfs/tasks: add a simple per-task procfs hidepid= field Djalal Harouni
2017-01-16 18:24 ` [kernel-hardening] " Daniel Micay
2017-01-17 9:54 ` Lafcadio Wluiki
[not found] ` <CAEiveUfDvSoW9Hy2Y_uxU2YQ+vR8OvXMqRhxAANTGG7QaQbJeg@mail.gmail.com>
[not found] ` <CALCETrWEGLhEHO_6sTXreVyWFVsEeYmZSrLNNXx-ma5gd+nTQQ@mail.gmail.com>
2017-01-18 22:50 ` Djalal Harouni
2017-01-18 23:35 ` Andy Lutomirski
2017-01-19 13:53 ` Djalal Harouni
2017-01-19 19:52 ` Andy Lutomirski [this message]
2017-01-20 15:56 ` Lafcadio Wluiki
2017-01-20 16:33 ` Djalal Harouni
2017-01-21 0:53 ` Andy Lutomirski
2017-01-23 11:46 ` Djalal Harouni
2017-01-23 20:07 ` Andy Lutomirski
2017-01-26 13:20 ` Djalal Harouni
2017-02-10 14:40 ` Lafcadio Wluiki
2017-02-10 16:18 ` Andy Lutomirski
2017-01-20 15:44 ` Lafcadio Wluiki
2017-02-10 23:44 ` Kees Cook
2017-02-13 19:01 ` Andy Lutomirski
2017-02-13 19:15 ` Kees Cook
2017-02-14 4:11 ` Christian Kujau
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