linux-kernel - Re: [PATCH v7 0/3] fanotify: Allow user space to pass back additional audit info

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Date:   Wed, 8 Feb 2023 10:03:24 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Richard Guy Briggs <rgb@...hat.com>,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
        Eric Paris <eparis@...isplace.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH v7 0/3] fanotify: Allow user space to pass back additional
 audit info

On Wed, Feb 8, 2023 at 7:08 AM Jan Kara <jack@...e.cz> wrote:
> On Tue 07-02-23 09:54:11, Paul Moore wrote:
> > On Tue, Feb 7, 2023 at 7:09 AM Jan Kara <jack@...e.cz> wrote:
> > > On Fri 03-02-23 16:35:13, Richard Guy Briggs wrote:
> > > > The Fanotify API can be used for access control by requesting permission
> > > > event notification. The user space tooling that uses it may have a
> > > > complicated policy that inherently contains additional context for the
> > > > decision. If this information were available in the audit trail, policy
> > > > writers can close the loop on debugging policy. Also, if this additional
> > > > information were available, it would enable the creation of tools that
> > > > can suggest changes to the policy similar to how audit2allow can help
> > > > refine labeled security.
> > > >
> > > > This patchset defines a new flag (FAN_INFO) and new extensions that
> > > > define additional information which are appended after the response
> > > > structure returned from user space on a permission event.  The appended
> > > > information is organized with headers containing a type and size that
> > > > can be delegated to interested subsystems.  One new information type is
> > > > defined to audit the triggering rule number.
> > > >
> > > > A newer kernel will work with an older userspace and an older kernel
> > > > will behave as expected and reject a newer userspace, leaving it up to
> > > > the newer userspace to test appropriately and adapt as necessary.  This
> > > > is done by providing a a fully-formed FAN_INFO extension but setting the
> > > > fd to FAN_NOFD.  On a capable kernel, it will succeed but issue no audit
> > > > record, whereas on an older kernel it will fail.
> > > >
> > > > The audit function was updated to log the additional information in the
> > > > AUDIT_FANOTIFY record. The following are examples of the new record
> > > > format:
> > > >   type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5
> > > >   type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2
> > >
> > > Thanks! I've applied this series to my tree.
> >
> > While I think this version of the patchset is fine, for future
> > reference it would have been nice if you had waited for my ACK on
> > patch 3/3; while Steve maintains his userspace tools, I'm the one
> > responsible for maintaining the Linux Kernel's audit subsystem.
>
> Aha, I'm sorry for that. I had the impression that on the last version of
> the series you've said you don't see anything for which the series should
> be respun so once Steve's objections where addressed and you were silent
> for a few days, I thought you consider the thing settled... My bad.

That's understandable, especially given inconsistencies across
subsystems.  If it helps, if I'm going to ACK something I make it
explicit with a proper 'Acked-by: ...' line in my reply; if I say
something looks good but there is no explicit ACK, there is usually
something outstanding that needs to be resolved, e.g. questions,
additional testing, etc.

In this particular case I posed some questions in that thread and
never saw a reply with any answers, hence the lack of an ACK.  While I
think the patches were reasonable, I withheld my ACK until the
questions were answered ... which they never were from what I can
tell, we just saw a new patchset with changes.

/me shrugs

-- 
paul-moore.com