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

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Date:   Thu, 27 Feb 2020 20:02:06 -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>, sgrubb@...hat.com,
        omosnace@...hat.com, Eric Paris <eparis@...isplace.org>
Subject: Re: [PATCH ghak120] audit: trigger accompanying records when no rules present

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.

* 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().

-- 
paul moore
www.paul-moore.com