linux-kernel - Re: [PATCH v3 3/3] selinux: add permission names to trace event

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Date:   Fri, 21 Aug 2020 15:39:11 +0200
From:   peter enderborg <peter.enderborg@...y.com>
To:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>
CC:     Steven Rostedt <rostedt@...dmis.org>,
        Thiébaud Weksteen <tweek@...gle.com>,
        Nick Kralevich <nnk@...gle.com>,
        Eric Paris <eparis@...isplace.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        SElinux list <selinux@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] selinux: add permission names to trace event

On 8/21/20 3:19 PM, Paul Moore wrote:
> On Fri, Aug 21, 2020 at 8:29 AM Stephen Smalley
> <stephen.smalley.work@...il.com> wrote:
>> On Thu, Aug 20, 2020 at 10:31 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>>> On Wed, 19 Aug 2020 09:11:08 -0400
>>> Stephen Smalley <stephen.smalley.work@...il.com> wrote:
>>>
>>>> So we'll need to update this plugin whenever we modify
>>>> security/selinux/include/classmap.h to keep them in sync.  Is that a
>>>> concern?  I don't suppose the plugin could directly include classmap.h?
>>>> I guess we'd have to export it as a public header. It isn't considered
>>>> to be part of the kernel API/ABI and can change anytime (but in practice
>>>> changes are not that frequent, and usually just additive in nature).
>>> Yes, it would require some stability between userspace and the plugin.
>>> If the value indexes don't change then that would work fine. If you add
>>> new ones, that too should be OK, just have a way to state "unknown" in
>>> the plugin.
>> Since we introduced the dynamic class/perm mapping support, it has
>> been possible for the values of existing classes/permissions to
>> change, and that has happened at time, e.g. when we added watch
>> permissions to the common file perms, that shifted the values of the
>> class file perms like entrypoint, when we added the process2 class
>> right after the process class, it shifted the values of all the
>> subsequent classes in the classmap.h.  So you can't rely on those
>> values remaining stable across kernel versions.
> I think it is becoming increasingly clear that generating the
> permission set string in userspace isn't really workable without
> breaking the dynamic class/permission mapping to some degree.
> Unfortunately I don't see these perf changes as a big enough "win" to
> offset the loss of the dynamic mapping loss.
>
> I'm okay with merging patches 1/3 and 2/3 wth the changes Stephen
> suggested, but I think we will need to leave patch 3/3 out of this for
> now.
>
Ok.