linux-kernel - Re: [PATCH ghak120] audit: trigger accompanying records when no rules present

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Message-ID: <CAHC9VhS9o7wmBEfvF=+=cfUzvfcTs9Hu15KcLJjW+92KxBxQ3g@mail.gmail.com>
Date:   Mon, 9 Mar 2020 19:55:09 -0400
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>, sgrubb@...hat.com,
        omosnace@...hat.com, Eric Paris <eparis@...isplace.org>
Subject: Re: [PATCH ghak120] audit: trigger accompanying records when no rules present

On Mon, Mar 9, 2020 at 4:31 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2020-02-27 20:02, Paul Moore wrote:
> > On Tue, Feb 18, 2020 at 4:01 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> > >
> > > When there are no audit rules registered, mandatory records (config,
> > > etc.) are missing their accompanying records (syscall, proctitle, etc.).
> > >
> > > This is due to audit context dummy set on syscall entry based on absence
> > > of rules that signals that no other records are to be printed.
> > >
> > > Clear the dummy bit in auditsc_set_stamp() when the first record of an
> > > event is generated.
> > >
> > > Please see upstream github issue
> > > https://github.com/linux-audit/audit-kernel/issues/120
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > > ---
> > >  kernel/auditsc.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > index 4effe01ebbe2..31195d122344 100644
> > > --- a/kernel/auditsc.c
> > > +++ b/kernel/auditsc.c
> > > @@ -2176,6 +2176,8 @@ int auditsc_get_stamp(struct audit_context *ctx,
> > >         t->tv_sec  = ctx->ctime.tv_sec;
> > >         t->tv_nsec = ctx->ctime.tv_nsec;
> > >         *serial    = ctx->serial;
> > > +       if (ctx->dummy)
> > > +               ctx->dummy = 0;
> >
> > Two comments:
> >
> > * Why even bother checking to see if ctx->dummy is true?  If it is
> > true you set it to false/0; if it is already false you leave it alone.
> > Either way ctx->dummy is going to be set to false when you are past
> > these two lines, might as well just always set ctx->dummy to false/0.
>
> Ok, no problem.
>
> > * Why are you setting ->dummy to false in auditsc_get_stamp() and not
> > someplace a bit more obvious like audit_log_start()?  Is it because
> > auditsc_get_stamp() only gets called once per event?  I'm willing to
> > take the "hit" of one extra assignment in audit_log_start() to keep
> > this in a more obvious place and not buried in auditsc_get_stamp().
>
> It is because the context is only available when syscall logging is
> enabled (which is on most platforms and hopefully eventually all) and
> makes for cleaner code and lack of need to check existance of the
> context.

At the very least let's create some sort of accessor function for
dummy then, hiding this in auditsc_get_stamp() seems very wrong to me.

-- 
paul moore
www.paul-moore.com