On Thu, Mar 19, 2020 at 5:48 PM Richard Guy Briggs [off-list ref] wrote:

On 2020-03-18 17:47, Paul Moore wrote:

quoted

On Wed, Mar 18, 2020 at 5:42 PM Richard Guy Briggs [off-list ref] wrote:

quoted

On 2020-03-18 17:01, Paul Moore wrote:

quoted

On Fri, Mar 13, 2020 at 3:23 PM Richard Guy Briggs [off-list ref] wrote:

quoted

On 2020-03-13 12:42, Paul Moore wrote:

...

quoted

quoted

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.

quoted

quoted

Another question occurs to me is that what if the audit daemon is sent a
signal and it cannot or will not collect the sig2 information from the
kernel (SIGKILL?)?  Does that audit container identifier remain dead
until reboot, or do we institute some other form of reaping, possibly
time-based?

In order to preserve the integrity of the audit log that ACID value
would need to remain unavailable until the ACID which contains the
associated auditd is "dead" (no one can request the signal sender's
info if that container is dead).

I don't understand why it would be associated with the contid of the
audit daemon process rather than with the audit daemon process itself.
How does the signal collection somehow get transferred or delegated to
another member of that audit daemon's container?

Presumably once we support multiple audit daemons we will need a
struct to contain the associated connection state, with at most one
struct (and one auditd) allowed for a given ACID.  I would expect that
the signal sender info would be part of that state included in that
struct.  If a task sent a signal to it's associated auditd, and no one
ever queried the signal information stored in the per-ACID state
struct, I would expect that the refcount/flag/whatever would remain
held for the signal sender's ACID until the auditd state's ACID died
(the struct would be reaped as part of the ACID death).  In cases
where the container orchestrator blocks sending signals across ACID
boundaries this really isn't an issue as it will all be the same ACID,
but since we don't want to impose any restrictions on what a container
*could* be it is important to make sure we handle the case where the
signal sender's ACID may be different from the associated auditd's
ACID.

Thinking aloud here, the audit daemon's exit when it calls audit_free()
needs to ..._put_sig and cancel that audit_sig_cid (which in the future
will be allocated per auditd rather than the global it is now since
there is only one audit daemon).

quoted

paul moore

- RGB

--
Richard Guy Briggs [off-list ref]
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

-- 
paul moore
www.paul-moore.com