Re: [PATCH] audit: always enable syscall auditing when supported and audit is enabled
On Mon, Jan 28, 2019 at 3:03 PM Steve Grubb <sgrubb(a)redhat.com> wrote:
On Mon, 28 Jan 2019 11:26:51 -0500
Paul Moore <paul(a)paul-moore.com> wrote:
> On Mon, Jan 28, 2019 at 10:38 AM Sverdlin, Alexander (Nokia - DE/Ulm)
> <alexander.sverdlin(a)nokia.com> wrote:
> > Hello Paul,
> >
> > On 28/01/2019 15:52, Paul Moore wrote:
> > >>>>> time also enables syscall auditing; this patch simplifies
the
> > >>>>> Kconfig menus by removing the option to disable syscall
> > >>>>> auditing when audit is selected and the target arch
supports
> > >>>>> it.
> > >>>>>
> > >>>>> Signed-off-by: Paul Moore <pmoore(a)redhat.com>
> > >>>> this patch is responsible for massive performance degradation
> > >>>> for those who used only CONFIG_SECURITY_APPARMOR.
> > >>>>
> > >>>> And the numbers are, take the following test for instance:
> > >>>>
> > >>>> dd if=/dev/zero of=/dev/null count=2M
> > >>>>
> > >>>> ARM64: 500MB/s -> 350MB/s
> > >>>> ARM: 400MB/s -> 300MB/s
> > >>> Hi there.
> > >>>
> > >>> Out of curiosity, what kernel/distribution are you running, or
> > >>> is this a custom kernel compile? Can you also share the output
> > >>> of 'auditctl
> > >> This test was carried out with Linux 4.9. Custom built.
> > > I suspected that was the case, thanks.
> > >
> > >>> -l' from your system? The general approach taken by everyone
to
> > >>> turn-off the per-syscall audit overhead is to add the "-a
> > >>> never,task" rule to their audit configuration:
> > >>>
> > >>> # auditctl -a never,task
> > >>>
> > >>> If you are using Fedora/CentOS/RHEL, or a similarly configured
> > >>> system,
> > >> This is an embedded distribution. We are not using auditctl or
> > >> any other audit-related user-space packages.
> > >>
> > >>> you can find this configuration in the /etc/audit/audit.rules
> > >>> file (be warned, that file is automatically generated based on
> > >>> /etc/audit/rules.d).
> > >> I suppose in this case rule list must be empty. Is there a way
> > >> to check this without extra user-space packages?
> > > Yes, unless you are loading rules through some other method I
> > > would expect that your audit rule list is empty.
> > >
> > > I'm not aware of any other tools besides auditctl to load audit
> > > rules into the kernel, although I haven't ever had a need for
> > > another tool so I haven't looked very hard. If you didn't want
> > > to bring auditctl into your distribution, I expect it would be a
> > > rather trivial task to create a small tool to load a single "-a
> > > never,task" into the kernel.
> >
> > I've done a quick test on my x86_64 PC and got the following
> > results:
>
> ...
>
> > Which brings me to an idea, that the subject patch should have been
> > accompanied by a default "never,task" rule inside the kernel,
> > otherwise you require an extra user-space package (audit) just to
> > bring Linux 4.5+ to 4.4 performance levels.
>
> [NOTE: I dropped pmoore(a)redhat.com from the To/CC line, I left Red Hat
> for greener pastures several months ago.]
>
> Well, it generally hasn't been an issue as 1) most people that enable
> audit also enable syscall auditing and 2) most people that enable
> audit have some sort of audit userspace tools to work with the audit
> logs (and configure audit if necessary). I don't want to diminish
> your report, but this change was made several years ago and we really
> haven't heard of many issues surrounding the change. If we can ever
> get all of the different arches to support syscall auditing, I'd love
> to get rid of the syscall auditing Kconfig knob entirely.
>
> If you wanted to put together a patch that added a single "-a
> never,task" rule on boot I could get behind that, just make it default
> to off.
That will make processes unauditable for everyone. That's how it gets a
speedup is not entering into the audit machinery.
That is pretty much what is being asked for in this thread. It's
really no different from what Fedora/CentOS/RHEL (and who knows how
many others) ship with their default audit config. It's important to
note that you could always delete this rule at runtime; all that is
being proposed is to have the kernel populate the the audit ruleset
with the "-a never,task" rule *IF* the proposed kernel Kconfig option
is enabled (and it would default to being off, you would have to turn
it on during build).
I suppose its possible that people may want MAC hardwired events but
no syscall
events. I don't know if there are other kconfig audit options. but
maybe getting it down to audit enabled and syscall auditing as the only
choices is probably the most performant.
-Steve
--
paul moore
www.paul-moore.com