netdev - Re: [PATCH bpf-next] bpf: emit audit messages upon successful prog load and unload

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Message-ID: <20181005184434.uphwrbqkfx2isbx4@ast-mbp.dhcp.thefacebook.com>
Date:   Fri, 5 Oct 2018 11:44:35 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>, ast@...nel.org,
        netdev@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        acme@...nel.org
Subject: Re: [PATCH bpf-next] bpf: emit audit messages upon successful prog
 load and unload

On Fri, Oct 05, 2018 at 08:14:09AM +0200, Jiri Olsa wrote:
> On Thu, Oct 04, 2018 at 03:10:15PM -0700, Alexei Starovoitov wrote:
> > On Thu, Oct 04, 2018 at 10:22:31PM +0200, Jesper Dangaard Brouer wrote:
> > > On Thu, 4 Oct 2018 21:41:17 +0200 Daniel Borkmann <daniel@...earbox.net> wrote:
> > > 
> > > > On 10/04/2018 08:39 PM, Jesper Dangaard Brouer wrote:
> > > > > On Thu, 4 Oct 2018 10:11:43 -0700 Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:  
> > > > >> On Thu, Oct 04, 2018 at 03:50:38PM +0200, Daniel Borkmann wrote:  
> > > [...]
> > > > >>
> > > > >> If the purpose of the patch is to give user space visibility into
> > > > >> bpf prog load/unload as a notification, then I completely agree that
> > > > >> some notification mechanism is necessary.  
> > > > 
> > > > Yeah, I did only regard it as only that, nothing more. Some means
> > > > of timeline and notification that can be kept in a record in user
> > > > space and later retrieved e.g. for introspection on what has been
> > > > loaded.
> > > > 
> > > > >> I've started working on such mechanism via perf ring buffer which is
> > > > >> the fastest mechanism we have in the kernel so far.
> > > > >> See long discussion here: https://patchwork.ozlabs.org/patch/971970/  
> 
> cool, could you please CC me if there's another version
> of that patchset?

will do.

> > > > 
> > > > That one is definitely needed in any case to resolve the kallsyms
> > > > limitations, and it does have overlap in that in either case we
> > > > want to look at past BPF programs that have been unloaded in the
> > > > meantime, so I don't have a strong preference either way, and the
> > > > former is needed in any case. Though thought was that audit might
> > > > be an option for those not running profiling daemons 24/7, but
> > > > presumably bpftool could be extended to record these events as
> > > > well if we don't want to reuse audit infra.
> > > 
> > > Yes, exactly, I don't want to run a profiling daemon 24/7 to record
> > > these events.  I do acknowledge that this perf event is relevant,
> > > especially for catching the kernel symbols (I need that myself), but it
> > > does not cover my use-case.
> > > 
> > > My use-case is to 24/7 collect and keep records in userspace, and have a
> > > timeline of these notifications, for later retrieval.  The idea is that
> > > our support engineers can look at these records when troubleshooting
> > > the system.  And the plan is also to collect these records as part of
> > > our sosreport tool, which is part of the support case.
> > 
> > I don't think you're implying that prog load/unload should be spamming dmesg
> > and auditd not even running...
> 
> I think the problem Jesper implied is that in order to collect
> those logs you'll need perf tool running all the time.. which
> it's not equipped for yet

I'm not proposing to run 'perf' binary all the time.
Setting up perf ring buffer just for these new bpf prog load/unload events
and epolling it is simple enough to do from any application including auditd.
selftests/bpf/ do it for bpf output events.