linux-kernel - Re: [PATCH ghak25 v2 4/9] audit: record nfcfg params

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Date:   Tue, 18 Feb 2020 17:47:20 -0500
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>,
        netfilter-devel@...r.kernel.org, sgrubb@...hat.com,
        omosnace@...hat.com, fw@...len.de, twoerner@...hat.com,
        Eric Paris <eparis@...isplace.org>, ebiederm@...ssion.com,
        tgraf@...radead.org
Subject: Re: [PATCH ghak25 v2 4/9] audit: record nfcfg params

On 2020-01-30 22:18, Paul Moore wrote:
> On Mon, Jan 6, 2020 at 1:55 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> > Record the auditable parameters of any non-empty netfilter table
> > configuration change.
> >
> > See: https://github.com/linux-audit/audit-kernel/issues/25
> > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > ---
> >  include/linux/audit.h | 11 +++++++++++
> >  kernel/auditsc.c      | 16 ++++++++++++++++
> >  2 files changed, 27 insertions(+)
> 
> I can not see a good reason why this patch is separate from patches 5
> and 6, please squash them down into one patch.  As it currently stands
> the logging function introduced here has no caller so it is pointless
> by itself.  Strive to make an individual patch have some significance
> on its own whenever possible.
> 
> This will also help you write a better commit description, right now
> the commit description tells me nothing, but if you bring in the other
> patches you can talk about consolidating similar code into a common
> function.

Fair enough.  I could see squashing some of these, but there are a
number of issues being addressed and would like to see some granularity,
but as you point out, each patch should stand on its own...

> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index f9ceae57ca8d..96cabb095eed 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -379,6 +379,7 @@ extern int __audit_log_bprm_fcaps(struct linux_binprm *bprm,
> >  extern void __audit_fanotify(unsigned int response);
> >  extern void __audit_tk_injoffset(struct timespec64 offset);
> >  extern void __audit_ntp_log(const struct audit_ntp_data *ad);
> > +extern void __audit_nf_cfg(const char *name, u8 af, int nentries);
> >
> >  static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp)
> >  {
> > @@ -514,6 +515,12 @@ static inline void audit_ntp_log(const struct audit_ntp_data *ad)
> >                 __audit_ntp_log(ad);
> >  }
> >
> > +static inline void audit_nf_cfg(const char *name, u8 af, int nentries)
> > +{
> > +       if (!audit_dummy_context())
> > +               __audit_nf_cfg(name, af, nentries);
> 
> See my comments below about audit_enabled.

I've cleaned up audit_enabled and removed dummy due to ghak120.

> > +}
> > +
> >  extern int audit_n_rules;
> >  extern int audit_signals;
> >  #else /* CONFIG_AUDITSYSCALL */
> > @@ -646,6 +653,10 @@ static inline void audit_ntp_log(const struct audit_ntp_data *ad)
> >
> >  static inline void audit_ptrace(struct task_struct *t)
> >  { }
> > +
> > +static inline void audit_nf_cfg(const char *name, u8 af, int nentries)
> > +{ }
> > +
> >  #define audit_n_rules 0
> >  #define audit_signals 0
> >  #endif /* CONFIG_AUDITSYSCALL */
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index 4effe01ebbe2..4e1df4233cd3 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -2545,6 +2545,22 @@ void __audit_ntp_log(const struct audit_ntp_data *ad)
> >         audit_log_ntp_val(ad, "adjust", AUDIT_NTP_ADJUST);
> >  }
> >
> > +void __audit_nf_cfg(const char *name, u8 af, int nentries)
> 
> Should nentries be an unsigned int?

Yes, it should, thank you.

> > +{
> > +       struct audit_buffer *ab;
> > +       struct audit_context *context = audit_context();
> 
> This is a good example of why the context of a caller matters; taken
> alone I would say that we need a check for audit_enabled here, but if
> we look at the latter patches we can see that the caller already has
> the audit_enabled check.
> 
> Considering that the caller is already doing an audit_enabled check,
> we might want to consider moving the audit_enabled check into
> audit_nf_cfg() where we do the dummy context check.  It's a static
> inline so there shouldn't be a performance impact and it makes the
> caller's code cleaner.
> 
> > +       if (!nentries)
> > +               return;
> > +       ab = audit_log_start(context, GFP_KERNEL, AUDIT_NETFILTER_CFG);
> 
> Why do we need the context variable, why not just call audit_context()
> here directly?

Context has been cleaned up.

> > +       if (!ab)
> > +               return; /* audit_panic or being filtered */
> 
> We generally don't add comments when audit_log_start() fails
> elsewhere, please don't do it here.

Ok.

> > +       audit_log_format(ab, "table=%s family=%u entries=%u",
> > +                        name, af, nentries);
> > +       audit_log_end(ab);
> > +}
> > +EXPORT_SYMBOL_GPL(__audit_nf_cfg);
> > +
> >  static void audit_log_task(struct audit_buffer *ab)
> >  {
> >         kuid_t auid, uid;
> > --
> > 1.8.3.1
> 
> --
> paul moore
> www.paul-moore.com
> 

- 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