Re: [PATCH RFC] perf_event: Add support for LSM and SELinux checks

From: Casey Schaufler <casey@schaufler-ca.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: James Morris <jmorris@namei.org>,
	linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	rostedt@goodmis.org, primiano@google.com, rsavitski@google.com,
	jeffv@google.com, kernel-team@android.com,
	Alexei Starovoitov <ast@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	bpf@vger.kernel.org, Daniel Borkmann <daniel@iogearbox.net>,
	Ingo Molnar <mingo@redhat.com>, Jiri Olsa <jolsa@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	linux-security-module@vger.kernel.org,
	Matthew Garrett <matthewgarrett@google.com>,
	Namhyung Kim <namhyung@kernel.org>,
	selinux@vger.kernel.org, Song Liu <songliubraving@fb.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, Yonghong Song <yhs@fb.com>,
	casey@schaufler-ca.com
Subject: Re: [PATCH RFC] perf_event: Add support for LSM and SELinux checks
Date: Wed, 9 Oct 2019 17:53:41 -0700	[thread overview]
Message-ID: <ea32212d-bd45-c363-841a-f4397aafd323@schaufler-ca.com> (raw)
In-Reply-To: <20191010004023.GC96813@google.com>

On 10/9/2019 5:40 PM, Joel Fernandes wrote:
> On Wed, Oct 09, 2019 at 03:41:56PM -0700, Casey Schaufler wrote:
>> On 10/9/2019 3:14 PM, James Morris wrote:
>>> On Wed, 9 Oct 2019, Casey Schaufler wrote:
>>>
>>>> Please consider making the perf_alloc security blob maintained
>>>> by the infrastructure rather than the individual modules. This
>>>> will save it having to be changed later.
>>> Is anyone planning on using this with full stacking?
>>>
>>> If not, we don't need the extra code & complexity. Stacking should only 
>>> cover what's concretely required by in-tree users.
>> I don't believe it's any simpler for SELinux to do the allocation
>> than for the infrastructure to do it. I don't see anyone's head
>> exploding over the existing infrastructure allocation of blobs.
>> We're likely to want it at some point, so why not avoid the hassle
>> and delay by doing it the "new" way up front?
>>
> I don't see how it can be maintained by the users (assuming you meant
> infrastructure as perf_event subsystem).

No, I meant allocated in security.c. Look at how file blobs are allocated.

>  The blob contains a SID which as far
> as I know, is specific to SELinux. Do you have an in-tree example of this?
>
> Further, this is also exactly it is done for BPF objects which I used as a
> reference.

There's no real harm in doing it that way, just that it is a change that
I'll have to make at some point in the future* and it would be really nice
if I didn't have to.

> thanks,
>
>  - Joel

-----
* When? After I get the current AppArmor/SELinux stacking enabling in
  and can get to the Smack backlong, which includes BPF and perf_events.