Re: ntp audit spew.

From: Richard Guy Briggs <rgb@redhat.com>
To: Paul Moore <paul@paul-moore.com>
Cc: Dave Jones <davej@codemonkey.org.uk>,
	linux-audit@redhat.com,
	Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: ntp audit spew.
Date: Tue, 24 Sep 2019 09:50:46 -0400	[thread overview]
Message-ID: <20190924135046.kkt5hntbjpcampwr@madcap2.tricolour.ca> (raw)
In-Reply-To: <CAHC9VhQPvS7mfmeomRLJ+SyXk=tZprSJQ9Ays3qr=+rqd=L16Q@mail.gmail.com>

On 2019-09-23 23:01, Paul Moore wrote:
> On Mon, Sep 23, 2019 at 5:00 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > On 2019-09-23 12:14, Paul Moore wrote:
> > > On Mon, Sep 23, 2019 at 11:50 AM Dave Jones <davej@codemonkey.org.uk> wrote:
> > > >
> > > > I have some hosts that are constantly spewing audit messages like so:
> > > >
> > > > [46897.591182] audit: type=1333 audit(1569250288.663:220): op=offset old=2543677901372 new=2980866217213
> > > > [46897.591184] audit: type=1333 audit(1569250288.663:221): op=freq old=-2443166611284 new=-2436281764244
> >
> > Odd.  It appears these two above should have the same serial number and
> > should be accompanied by a syscall record.  It appears that it has no
> > context to update to connect the two records.  Is it possible it is not
> > being called in a task context?  If that were the case though, I'd
> > expect audit_dummy_context() to return 1...
> 
> Yeah, I'm a little confused with these messages too.  As you pointed
> out, the different serial numbers imply that the audit_context is NULL
> and if the audit_context is NULL I would have expected it to fail the
> audit_dummy_context() check in audit_ntp_log().  I'm looking at this
> with tired eyes at the moment, so I'm likely missing something, but I
> just don't see it right now ...
> 
> What is even more confusing is that I don't see this issue on my test systems.
> 
> > Checking audit_enabled should not be necessary but might fix the
> > problem, but still not explain why we're getting these records.
> 
> I'd like to understand why this is happening before we start changing the code.

Absolutely.

This looks like a similar issue to the AUDIT_NETFILTER_CFG issue where
we get a lone record unconnected to a syscall when one of the netfilter
table initialization (ipv4 filter) is linked into the kernel rather than
compiled as a module, so it is run in kernel context at boot rather than
in user context as a module load later.  This is why I ask if it is
being run by a kernel thread rather than a user task, perhaps using a
syscall function call internally.

> paul moore

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635