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From: Richard Guy Briggs <rgb@redhat.com>
To: Paul Moore <paul@paul-moore.com>
Cc: Steve Grubb <sgrubb@redhat.com>,
	linux-audit@redhat.com, nhorman@tuxdriver.com,
	linux-api@vger.kernel.org, containers@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	dhowells@redhat.com, netfilter-devel@vger.kernel.org,
	ebiederm@xmission.com, simo@redhat.com, netdev@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, Eric Paris <eparis@parisplace.org>,
	mpatel@redhat.com, Serge Hallyn <serge@hallyn.com>
Subject: Re: [PATCH ghak90 V8 07/16] audit: add contid support for signalling the audit daemon
Date: Mon, 30 Mar 2020 11:23:47 -0400
Message-ID: <20200330152347.zjrcd6uuolfnq3fy@madcap2.tricolour.ca> (raw)
In-Reply-To: <CAHC9VhTuYYqAtoNAKLX3qja6DnqEbFuHchi9ESwbcb5WC_Mvtw@mail.gmail.com>

On 2020-03-28 23:17, Paul Moore wrote:
> On Wed, Mar 25, 2020 at 8:29 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > On 2020-03-20 17:56, Paul Moore wrote:
> > > On Thu, Mar 19, 2020 at 5:48 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > On 2020-03-18 17:47, Paul Moore wrote:
> > > > > On Wed, Mar 18, 2020 at 5:42 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > > > On 2020-03-18 17:01, Paul Moore wrote:
> > > > > > > On Fri, Mar 13, 2020 at 3:23 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > > > > > On 2020-03-13 12:42, Paul Moore wrote:
> > > > > > >
> > > > > > > ...
> > > > > > >
> > > > > > > > > The thread has had a lot of starts/stops, so I may be repeating a
> > > > > > > > > previous suggestion, but one idea would be to still emit a "death
> > > > > > > > > record" when the final task in the audit container ID does die, but
> > > > > > > > > block the particular audit container ID from reuse until it the
> > > > > > > > > SIGNAL2 info has been reported.  This gives us the timely ACID death
> > > > > > > > > notification while still preventing confusion and ambiguity caused by
> > > > > > > > > potentially reusing the ACID before the SIGNAL2 record has been sent;
> > > > > > > > > there is a small nit about the ACID being present in the SIGNAL2
> > > > > > > > > *after* its death, but I think that can be easily explained and
> > > > > > > > > understood by admins.
> > > > > > > >
> > > > > > > > Thinking quickly about possible technical solutions to this, maybe it
> > > > > > > > makes sense to have two counters on a contobj so that we know when the
> > > > > > > > last process in that container exits and can issue the death
> > > > > > > > certificate, but we still block reuse of it until all further references
> > > > > > > > to it have been resolved.  This will likely also make it possible to
> > > > > > > > report the full contid chain in SIGNAL2 records.  This will eliminate
> > > > > > > > some of the issues we are discussing with regards to passing a contobj
> > > > > > > > vs a contid to the audit_log_contid function, but won't eliminate them
> > > > > > > > all because there are still some contids that won't have an object
> > > > > > > > associated with them to make it impossible to look them up in the
> > > > > > > > contobj lists.
> > > > > > >
> > > > > > > I'm not sure you need a full second counter, I imagine a simple flag
> > > > > > > would be okay.  I think you just something to indicate that this ACID
> > > > > > > object is marked as "dead" but it still being held for sanity reasons
> > > > > > > and should not be reused.
> > > > > >
> > > > > > Ok, I see your point.  This refcount can be changed to a flag easily
> > > > > > enough without change to the api if we can be sure that more than one
> > > > > > signal can't be delivered to the audit daemon *and* collected by sig2.
> > > > > > I'll have a more careful look at the audit daemon code to see if I can
> > > > > > determine this.
> > > > >
> > > > > Maybe I'm not understanding your concern, but this isn't really
> > > > > different than any of the other things we track for the auditd signal
> > > > > sender, right?  If we are worried about multiple signals being sent
> > > > > then it applies to everything, not just the audit container ID.
> > > >
> > > > Yes, you are right.  In all other cases the information is simply
> > > > overwritten.  In the case of the audit container identifier any
> > > > previous value is put before a new one is referenced, so only the last
> > > > signal is kept.  So, we only need a flag.  Does a flag implemented with
> > > > a rcu-protected refcount sound reasonable to you?
> > >
> > > Well, if I recall correctly you still need to fix the locking in this
> > > patchset so until we see what that looks like it is hard to say for
> > > certain.  Just make sure that the flag is somehow protected from
> > > races; it is probably a lot like the "valid" flags you sometimes see
> > > with RCU protected lists.
> >
> > This is like looking for a needle in a haystack.  Can you point me to
> > some code that does "valid" flags with RCU protected lists.
> 
> Sigh.  Come on Richard, you've been playing in the kernel for some
> time now.  I can't think of one off the top of my head as I write
> this, but there are several resources that deal with RCU protected
> lists in the kernel, Google is your friend and Documentation/RCU is
> your friend.

Ok, I thought you were talking about a specific piece of code...

> Spending time to learn how RCU works and how to use it properly is not
> time wasted.  It's a tricky thing to get right (I have to refresh my
> memory on some of the more subtle details each time I write/review RCU
> code), but it's very cool when done correctly.

I review Documentation/RCU almost every time I work on RCU...

> 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


  reply index

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-31 19:48 [PATCH ghak90 V8 00/16] audit: implement container identifier Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 01/16] audit: collect audit task parameters Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 02/16] audit: add container id Richard Guy Briggs
2020-01-22 21:28   ` Paul Moore
2020-01-30 17:53     ` Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 03/16] audit: read container ID of a process Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 04/16] audit: convert to contid list to check for orch/engine ownership Richard Guy Briggs
2020-01-22 21:28   ` Paul Moore
2020-02-04 22:51     ` Richard Guy Briggs
2020-02-05 22:40       ` Paul Moore
2019-12-31 19:48 ` [PATCH ghak90 V8 05/16] audit: log drop of contid on exit of last task Richard Guy Briggs
2020-01-22 21:28   ` Paul Moore
2020-02-04 23:02     ` Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 06/16] audit: log container info of syscalls Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 07/16] audit: add contid support for signalling the audit daemon Richard Guy Briggs
2020-01-22 21:28   ` Paul Moore
2020-01-23 16:29     ` Richard Guy Briggs
2020-01-23 17:09       ` Paul Moore
2020-01-23 20:04         ` Richard Guy Briggs
2020-01-23 21:35           ` Paul Moore
2020-02-04 23:14             ` Richard Guy Briggs
2020-02-05 22:50               ` Paul Moore
2020-02-12 22:38                 ` Steve Grubb
2020-02-13  0:09                   ` Paul Moore
2020-02-13 21:44                     ` Paul Moore
2020-03-12 19:30                       ` Richard Guy Briggs
2020-03-13 16:29                         ` Paul Moore
2020-03-13 18:59                           ` Richard Guy Briggs
2020-03-18 20:56                             ` Paul Moore
2020-03-18 21:26                               ` Richard Guy Briggs
2020-03-18 21:42                                 ` Paul Moore
2020-03-18 21:55                                   ` Richard Guy Briggs
2020-03-18 22:06                                     ` Paul Moore
2020-03-19 22:02                                       ` Richard Guy Briggs
2020-03-24  0:16                                         ` Paul Moore
2020-03-24 21:01                                           ` Richard Guy Briggs
2020-03-29  3:11                                             ` Paul Moore
2020-03-30 13:47                                               ` Richard Guy Briggs
2020-03-30 14:26                                                 ` Paul Moore
2020-03-30 16:21                                                   ` Richard Guy Briggs
2020-03-30 17:34                                                     ` Paul Moore
2020-03-30 17:49                                                       ` Richard Guy Briggs
2020-03-30 19:55                                                         ` Paul Moore
2020-04-16 20:33                                                           ` Eric W. Biederman
2020-04-16 21:53                                                             ` Paul Moore
2020-04-17 22:23                                                               ` Eric W. Biederman
2020-04-22 17:24                                                                 ` Paul Moore
2020-03-12 20:27                     ` Richard Guy Briggs
2020-03-13 16:42                       ` Paul Moore
2020-03-13 16:45                         ` Steve Grubb
2020-03-13 16:49                           ` Paul Moore
2020-03-13 19:23                         ` Richard Guy Briggs
2020-03-18 21:01                           ` Paul Moore
2020-03-18 21:41                             ` Richard Guy Briggs
2020-03-18 21:47                               ` Paul Moore
2020-03-19 21:47                                 ` Richard Guy Briggs
2020-03-20 21:56                                   ` Paul Moore
2020-03-25 12:29                                     ` Richard Guy Briggs
2020-03-29  3:17                                       ` Paul Moore
2020-03-30 15:23                                         ` Richard Guy Briggs [this message]
2019-12-31 19:48 ` [PATCH ghak90 V8 08/16] audit: add support for non-syscall auxiliary records Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 09/16] audit: add containerid support for user records Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 10/16] audit: add containerid filtering Richard Guy Briggs
2019-12-31 19:48 ` [PATCH ghak90 V8 11/16] audit: add support for containerid to network namespaces Richard Guy Briggs
2020-01-22 21:28   ` Paul Moore
2020-02-04 23:42     ` Richard Guy Briggs
2020-02-05 22:51       ` Paul Moore
2019-12-31 19:48 ` [PATCH ghak90 V8 12/16] audit: contid check descendancy and nesting Richard Guy Briggs
2020-01-22 21:29   ` Paul Moore
2020-01-23 21:02     ` Richard Guy Briggs
2020-01-23 21:47       ` Paul Moore
2019-12-31 19:48 ` [PATCH ghak90 V8 13/16] audit: track container nesting Richard Guy Briggs
2020-01-22 21:29   ` Paul Moore
2020-01-30 19:27     ` Richard Guy Briggs
2020-02-05 23:05       ` Paul Moore
2020-02-05 23:50         ` Richard Guy Briggs
2020-02-13 21:49           ` Paul Moore
2020-03-12 20:51             ` Richard Guy Briggs
2020-03-13 16:47               ` Paul Moore
2020-03-14 22:42                 ` Richard Guy Briggs
2020-03-17 18:28                   ` Richard Guy Briggs
2020-03-18 21:08                   ` Paul Moore
2020-01-31 14:50     ` Steve Grubb
2020-02-04 13:19       ` Richard Guy Briggs
2020-02-04 15:47         ` Steve Grubb
2020-02-04 15:52           ` Paul Moore
2020-02-04 18:12             ` Steve Grubb
2020-02-05 22:57               ` Paul Moore
2019-12-31 19:48 ` [PATCH ghak90 V8 14/16] audit: check contid depth and add limit config param Richard Guy Briggs
2020-01-22 21:29   ` Paul Moore
2019-12-31 19:48 ` [PATCH ghak90 V8 15/16] audit: check contid count per netns and add config param limit Richard Guy Briggs
2020-01-22 21:29   ` Paul Moore
2019-12-31 19:48 ` [PATCH ghak90 V8 16/16] audit: add capcontid to set contid outside init_user_ns Richard Guy Briggs
2020-01-22 21:29   ` Paul Moore
2020-02-05  0:39     ` Richard Guy Briggs
2020-02-05 22:56       ` Paul Moore
2020-02-06 12:51         ` Richard Guy Briggs
2020-02-13 21:58           ` Paul Moore
2020-03-12 21:58             ` Richard Guy Briggs

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