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

From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	ast@kernel.org, netdev@vger.kernel.org,
	Jiri Olsa <jolsa@kernel.org>,
	acme@kernel.org
Subject: Re: [PATCH bpf-next] bpf: emit audit messages upon successful prog load and unload
Date: Thu, 4 Oct 2018 15:10:15 -0700	[thread overview]
Message-ID: <20181004221013.o3c5junwfyaasuxo@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20181004222231.2edd5add@redhat.com>

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@iogearbox.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@gmail.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/  
> > 
> > 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...
Also auditd has to be changed to support retrieving prog related info (like license)
via sys_bpf system call when it sees prog_id.
Since it has to change it can just as easily use perf ring buffer
to receive notifications.
So we solve notification problem once and all user space tools can use it.