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From: Richard Guy Briggs <rgb@redhat.com>
To: Paul Moore <paul@paul-moore.com>
Cc: nhorman@tuxdriver.com, linux-api@vger.kernel.org,
	containers@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	dhowells@redhat.com,
	Linux-Audit Mailing List <linux-audit@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: Thu, 23 Jan 2020 15:04:12 -0500
Message-ID: <20200123200412.j2aucdp3cvk57prw@madcap2.tricolour.ca> (raw)
In-Reply-To: <CAHC9VhTusiQoudB8G5jjDFyM9WxBUAjZ6_X35ywJ063Jb75dQA@mail.gmail.com>

On 2020-01-23 12:09, Paul Moore wrote:
> On Thu, Jan 23, 2020 at 11:29 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > On 2020-01-22 16:28, Paul Moore wrote:
> > > On Tue, Dec 31, 2019 at 2:50 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > >
> > > > Add audit container identifier support to the action of signalling the
> > > > audit daemon.
> > > >
> > > > Since this would need to add an element to the audit_sig_info struct,
> > > > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > > > audit_sig_info2 struct.  Corresponding support is required in the
> > > > userspace code to reflect the new record request and reply type.
> > > > An older userspace won't break since it won't know to request this
> > > > record type.
> > > >
> > > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > > > ---
> > > >  include/linux/audit.h       |  7 +++++++
> > > >  include/uapi/linux/audit.h  |  1 +
> > > >  kernel/audit.c              | 35 +++++++++++++++++++++++++++++++++++
> > > >  kernel/audit.h              |  1 +
> > > >  security/selinux/nlmsgtab.c |  1 +
> > > >  5 files changed, 45 insertions(+)
> > >
> > > ...
> > >
> > > > diff --git a/kernel/audit.c b/kernel/audit.c
> > > > index 0871c3e5d6df..51159c94041c 100644
> > > > --- a/kernel/audit.c
> > > > +++ b/kernel/audit.c
> > > > @@ -126,6 +126,14 @@ struct auditd_connection {
> > > >  kuid_t         audit_sig_uid = INVALID_UID;
> > > >  pid_t          audit_sig_pid = -1;
> > > >  u32            audit_sig_sid = 0;
> > > > +/* Since the signal information is stored in the record buffer at the
> > > > + * time of the signal, but not retrieved until later, there is a chance
> > > > + * that the last process in the container could terminate before the
> > > > + * signal record is delivered.  In this circumstance, there is a chance
> > > > + * the orchestrator could reuse the audit container identifier, causing
> > > > + * an overlap of audit records that refer to the same audit container
> > > > + * identifier, but a different container instance.  */
> > > > +u64            audit_sig_cid = AUDIT_CID_UNSET;
> > >
> > > I believe we could prevent the case mentioned above by taking an
> > > additional reference to the audit container ID object when the signal
> > > information is collected, dropping it only after the signal
> > > information is collected by userspace or another process signals the
> > > audit daemon.  Yes, it would block that audit container ID from being
> > > reused immediately, but since we are talking about one number out of
> > > 2^64 that seems like a reasonable tradeoff.
> >
> > I had thought that through and should have been more explicit about that
> > situation when I documented it.  We could do that, but then the syscall
> > records would be connected with the call from auditd on shutdown to
> > request that signal information, rather than the exit of that last
> > process that was using that container.  This strikes me as misleading.
> > Is that really what we want?
> 
>  ???
> 
> I think one of us is not understanding the other; maybe it's me, maybe
> it's you, maybe it's both of us.
> 
> Anyway, here is what I was trying to convey with my original comment
> ... When we record the audit container ID in audit_signal_info() we
> take an extra reference to the audit container ID object so that it
> will not disappear (and get reused) until after we respond with an
> AUDIT_SIGNAL_INFO2.  In audit_receive_msg() when we do the
> AUDIT_SIGNAL_INFO2 processing we drop the extra reference we took in
> audit_signal_info().  Unless I'm missing some other change you made,
> this *shouldn't* affect the syscall records, all it does is preserve
> the audit container ID object in the kernel's ACID store so it doesn't
> get reused.

This is exactly what I had understood.  I hadn't considered the extra
details below in detail due to my original syscall concern, but they
make sense.

The syscall I refer to is the one connected with the drop of the
audit container identifier by the last process that was in that
container in patch 5/16.  The production of this record is contingent on
the last ref in a contobj being dropped.  So if it is due to that ref
being maintained by audit_signal_info() until the AUDIT_SIGNAL_INFO2
record it fetched, then it will appear that the fetch action closed the
container rather than the last process in the container to exit.

Does this make sense?

> (We do need to do some extra housekeeping in audit_signal_info() to
> deal with the case where nobody asks for AUDIT_SIGNAL_INFO2 -
> basically if audit_sig_cid is not NULL we should drop a reference
> before assigning it a new object pointer, and of course we would need
> to set audit_sig_cid to NULL in audit_receive_msg() after sending it
> up to userspace and dropping the extra ref.)
> 
> 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: 95+ 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 [this message]
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
2020-03-12 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
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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