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&gt; wrote: > On Mon, 28 Jan 2019 11:26:51 -0500 > Paul Moore <paul(a)paul-moore.com&gt; wrote: > > > On Mon, Jan 28, 2019 at 10:38 AM Sverdlin, Alexander (Nokia - > > DE/Ulm) <alexander.sverdlin(a)nokia.com&gt; 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&gt; > > > >>>> 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