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

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Message-ID: <20200310005858.m4s23fl3huwevyp5@madcap2.tricolour.ca>
Date:   Mon, 9 Mar 2020 20:58:58 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Paul Moore <paul@...l-moore.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 2020-03-09 19:55, Paul Moore wrote:
> 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.

Ok.  Anything else?

I also found useless context and dummy checks in audit_log_proctitle
and removed them since it can't be called if the context doesn't exist.

> paul moore

- RGB

--
Richard Guy Briggs <rgb@...hat.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