Re: [PATCH] Don't audit SECCOMP_KILL/RET_ERRNO when syscall auditing is disabled

[Paul Moore]

On Sun, Apr 10, 2016 at 6:31 PM, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:
> On Sun, Apr 10, 2016 at 06:17:53PM -0400, Paul Moore wrote:
>> On Sat, Apr 9, 2016 at 10:41 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>> >> What kernel version are you using?  I believe we fixed that in Linux
>> >> 4.5 with the following:
>> >
>> > This is 4.6-rc2.
>> >>
>> >>   commit 96368701e1c89057bbf39222e965161c68a85b4b
>> >>   From: Paul Moore <pmoore@xxxxxxxxxx>
>> >>   Date: Wed, 13 Jan 2016 10:18:55 -0400 (09:18 -0500)
>> >>
>> >>   audit: force seccomp event logging to honor the audit_enabled flag
>> >
>> > No you didn't fix it because audit_enabled is always enabled by systemd
>> > for user space auditing, see the original description of my patch.
>>
>> [NOTE: adding the audit list to the CC line]
>
> This mailing list is marked subscriber only in MAINTAINERS so I
> intentionally didn't add it. It's unlikely that my emails
> will make it through.

Steve Grubb checks it on a regular basis and approves anything
remotely audit related.  Please make use of it in the future; it's
listed in MAINTAINERS for a reason.

>> Sorry, I read your email too quickly; you are correct, that commit
>> fixed a different problem.
>>
>> Let me think on this a bit more.  Technically I don't see this as a
>> bug with the kernel, userspace is enabling audit and you are getting
>> audit messages as a result; from my opinion this is the expected
>
> It's a bug in the kernel because seccomp is different from everything else.

This behavior has existed since seccomp auditing was first introduced.
I disagree with your opinion that it is a bug, but I don't think it is
worth arguing over the distinction since we are talking about changing
it regardless.

>> ... However, we've talked in the past about providing better
>> control over seccomp's auditing/logging and that work would allow you
>> to quiet all seccomp messages if you desired.
>>
>> If you are interested, I started tracking this issue at the link below:
>>
>>  * https://github.com/linux-audit/audit-kernel/issues/13
>
> Making it a sysctl is fine for me as long as it is disabled by default
> so that user space doesn't need to be modified to make seccomp
> stop spamming.
>
> Audit should always be opt-in, not opt-out.

>From my perspective, you, or rather systemd in your case, is opting in
by enabling audit.

> However I think making it conditional on syscall auditing like
> in my patch is equivalent and much simpler.
>
> If you really insist on the sysctl I can send patch.

As I said earlier, I haven't given this a lot of thought as of yet,
but so far I like the sysctl approach much more than the patch you
sent earlier.

-- 
paul moore
www.paul-moore.com