linux-kernel - Re: [PATCH v6 3/3] fanotify,audit: Allow audit to use the full permission event response

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Message-ID: <CAHC9VhQY3zfwh_=6swUN7BWGSQdsLDxw-dbyTh6rayZq7q-x5w@mail.gmail.com>
Date:   Fri, 27 Jan 2023 15:02:13 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     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>, Jan Kara <jack@...e.cz>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH v6 3/3] fanotify,audit: Allow audit to use the full
 permission event response

On Wed, Jan 25, 2023 at 5:11 PM Richard Guy Briggs <rgb@...hat.com> wrote:
>
> On 2023-01-20 13:58, Paul Moore wrote:
> > On Tue, Jan 17, 2023 at 4:14 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> > >
> > > This patch passes the full response so that the audit function can use all
> > > of it. The audit function was updated to log the additional information in
> > > the AUDIT_FANOTIFY record.
> > >
> > > Currently the only type of fanotify info that is defined is an audit
> > > rule number, but convert it to hex encoding to future-proof the field.
> > > Hex encoding suggested by Paul Moore <paul@...l-moore.com>.
> > >
> > > The {subj,obj}_trust values are {0,1,2}, corresponding to no, yes, unknown.
> > >
> > > Sample records:
> > >   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=3F subj_trust=2 obj_trust=2
> > >
> > > Suggested-by: Steve Grubb <sgrubb@...hat.com>
> > > Link: https://lore.kernel.org/r/3075502.aeNJFYEL58@x2
> > > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > > ---
> > >  fs/notify/fanotify/fanotify.c |  3 ++-
> > >  include/linux/audit.h         |  9 +++++----
> > >  kernel/auditsc.c              | 16 +++++++++++++---
> > >  3 files changed, 20 insertions(+), 8 deletions(-)
> >
> > ...
> >
> > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > index d1fb821de104..3133c4175c15 100644
> > > --- a/kernel/auditsc.c
> > > +++ b/kernel/auditsc.c
> > > @@ -2877,10 +2878,19 @@ void __audit_log_kern_module(char *name)
> > >         context->type = AUDIT_KERN_MODULE;
> > >  }
> > >
> > > -void __audit_fanotify(u32 response)
> > > +void __audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar)
> > >  {
> > > -       audit_log(audit_context(), GFP_KERNEL,
> > > -               AUDIT_FANOTIFY, "resp=%u", response);
> > > +       /* {subj,obj}_trust values are {0,1,2}: no,yes,unknown */
> > > +       if (friar->hdr.type == FAN_RESPONSE_INFO_NONE) {
> > > +               audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
> > > +                         "resp=%u fan_type=%u fan_info=3F subj_trust=2 obj_trust=2",
> > > +                         response, FAN_RESPONSE_INFO_NONE);
> > > +               return;
> > > +       }
> > > +       audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
> > > +                 "resp=%u fan_type=%u fan_info=%X subj_trust=%u obj_trust=%u",
> > > +                 response, friar->hdr.type, friar->rule_number,
> > > +                 friar->subj_trust, friar->obj_trust);
> > >  }
> >
> > The only thing that comes to mind might be to convert the if-return
> > into a switch statement to make it a bit cleaner and easier to patch
> > in the future, but that is soooo far removed from any real concern
> > that I debated even mentioning it.  I only bring it up in case the
> > "3F" discussion results in a respin, and even then I'm not going to
> > hold my ACK over something as silly as a if-return vs switch.
> >
> > For clarity, this is what I was thinking:
> >
> > void __audit_fanontify(...)
> > {
> >   switch (type) {
> >   case FAN_RESPONSE_INFO_NONE:
> >     audit_log(...);
> >     break;
> >   default:
> >     audit_log(...);
> >   }
> > }
>
> I agree that would be cleaner ...

As I said, the "3F" concern of Steve is really the only thing I would
bother respinning for, my other comments were just passing
observations.

-- 
paul-moore.com