Date:   Fri, 10 Feb 2023 17:00:36 -0500
From:   Richard Guy Briggs <rgb@redhat.com>
To:     Paul Moore <paul@paul-moore.com>
Cc:     Jens Axboe <axboe@kernel.dk>, Steve Grubb <sgrubb@redhat.com>,
        Linux-Audit Mailing List <linux-audit@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, io-uring@vger.kernel.org,
        Eric Paris <eparis@parisplace.org>,
        Christian Brauner <brauner@kernel.org>,
        Stefan Roesch <shr@fb.com>
Subject: Re: [PATCH v2] io_uring,audit: don't log IORING_OP_MADVISE
Message-ID: <Y+a+hBtDwAXBgjsg@madcap2.tricolour.ca>
References: <b5dfdcd541115c86dbc774aa9dd502c964849c5f.1675282642.git.rgb@redhat.com>
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On 2023-02-10 11:52, Paul Moore wrote:
> On Fri, Feb 10, 2023 at 11:00 AM Jens Axboe <axboe@kernel.dk> wrote:
> > On 2/10/23 8:39?AM, Paul Moore wrote:
> > > On Thu, Feb 9, 2023 at 7:15 PM Jens Axboe <axboe@kernel.dk> wrote:
> > >> On 2/9/23 3:54?PM, Steve Grubb wrote:
> > >>> On Thursday, February 9, 2023 5:37:22 PM EST Paul Moore wrote:
> > >>>> On Thu, Feb 9, 2023 at 4:53 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > >>>>> On 2023-02-01 16:18, Paul Moore wrote:
> > >>>>>> On Wed, Feb 1, 2023 at 3:34 PM Richard Guy Briggs <rgb@redhat.com>
> > >>> wrote:
> > >>>>>>> fadvise and madvise both provide hints for caching or access pattern
> > >>>>>>> for file and memory respectively.  Skip them.
> > >>>>>>
> > >>>>>> You forgot to update the first sentence in the commit description :/
> > >>>>>
> > >>>>> I didn't forget.  I updated that sentence to reflect the fact that the
> > >>>>> two should be treated similarly rather than differently.
> > >>>>
> > >>>> Ooookay.  Can we at least agree that the commit description should be
> > >>>> rephrased to make it clear that the patch only adjusts madvise?  Right
> > >>>> now I read the commit description and it sounds like you are adjusting
> > >>>> the behavior for both fadvise and madvise in this patch, which is not
> > >>>> true.
> > >>>>
> > >>>>>> I'm still looking for some type of statement that you've done some
> > >>>>>> homework on the IORING_OP_MADVISE case to ensure that it doesn't end
> > >>>>>> up calling into the LSM, see my previous emails on this.  I need more
> > >>>>>> than "Steve told me to do this".
> > >>>>>>
> > >>>>>> I basically just want to see that some care and thought has gone into
> > >>>>>> this patch to verify it is correct and good.
> > >>>>>
> > >>>>> Steve suggested I look into a number of iouring ops.  I looked at the
> > >>>>> description code and agreed that it wasn't necessary to audit madvise.
> > >>>>> The rationale for fadvise was detemined to have been conflated with
> > >>>>> fallocate and subsequently dropped.  Steve also suggested a number of
> > >>>>> others and after investigation I decided that their current state was
> > >>>>> correct.  *getxattr you've advised against, so it was dropped.  It
> > >>>>> appears fewer modifications were necessary than originally suspected.
> > >>>>
> > >>>> My concern is that three of the four changes you initially proposed
> > >>>> were rejected, which gives me pause about the fourth.  You mention
> > >>>> that based on your reading of madvise's description you feel auditing
> > >>>> isn't necessary - and you may be right - but based on our experience
> > >>>> so far with this patchset I would like to hear that you have properly
> > >>>> investigated all of the madvise code paths, and I would like that in
> > >>>> the commit description.
> > >>>
> > >>> I think you're being unnecessarily hard on this. Yes, the commit message
> > >>> might be touched up. But madvise is advisory in nature. It is not security
> > >>> relevant. And a grep through the security directory doesn't turn up any
> > >>> hooks.
> > >>
> > >> Agree, it's getting a bit anal... FWIW, patch looks fine to me.
> > >
> > > Call it whatever you want, but the details are often important at this
> > > level of code, and when I see a patch author pushing back on verifying
> > > that their patch is correct it makes me very skeptical.
> >
> > Maybe it isn't intended, but the replies have generally had a pretty
> > condescending tone to them. That's not the best way to engage folks, and
> > may very well be why people just kind of give up on it. Nobody likes
> > debating one-liners forever, particularly not if it isn't inviting.
> 
> I appreciate that you are coming from a different space, but I stand
> by my comments.  Of course you are welcome to your own opinion, but I
> would encourage you to spend some time reading the audit mail archives
> going back a few years before you make comments like the above ... or
> not, that's your call; I recognize it is usually easier to criticize.
> 
> On a quasi related note to the list/archives: unfortunately there was
> continued resistance to opening up the linux-audit list so I've setup
> audit@vger for upstream audit kernel work moving forward.  The list
> address in MAINTAINERS will get updated during the next merge window
> so hopefully some of the problems you had in the beginning of this
> discussion will be better in the future.
> 
> > > I really would have preferred that you held off from merging this
> > > until this was resolved and ACK'd ... oh well.
> >
> > It's still top of tree. If you want to ack it, let me know and I'll add
> > it. If you want to nak it, give me something concrete to work off of.
> 
> I can't in good conscience ACK it without some comment from Richard
> that he has traced the code paths; this shouldn't be surprising at
> this point.  I'm not going to NACK it or post a revert, I would have
> done that already if I felt that was appropriate.  Right now this
> patch is in a gray area for me in that I suspect it is good, but I
> can't ACK it without some comment that it has been properly
> researched.

I feel a bit silly replying in this thread.  My dad claims that I need
to have the last word in any argument, so that way he gets it instead...

I appear to have accidentally omitted the connector word "and" between
"description" and "code" above, which may have led you to doubt I had
gone back and re-looked at the code.

> paul-moore.com

- 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