linux-kernel - Re: [PATCH ghak10 v5 1/2] audit: Add functions to log time adjustments

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Message-ID: <CAFqZXNvADB-E_fjEaQpUymSVvfP-vXQXtk3K+nJ9DqrScHL8bQ@mail.gmail.com>
Date:   Mon, 27 Aug 2018 11:13:17 +0200
From:   Ondrej Mosnacek <omosnace@...hat.com>
To:     Miroslav Lichvar <mlichvar@...hat.com>
Cc:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        Paul Moore <paul@...l-moore.com>,
        Richard Guy Briggs <rgb@...hat.com>,
        Steve Grubb <sgrubb@...hat.com>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH ghak10 v5 1/2] audit: Add functions to log time adjustments

On Mon, Aug 27, 2018 at 9:50 AM Miroslav Lichvar <mlichvar@...hat.com> wrote:
> On Fri, Aug 24, 2018 at 02:00:00PM +0200, Ondrej Mosnacek wrote:
> > This patch adds two auxiliary record types that will be used to annotate
> > the adjtimex SYSCALL records with the NTP/timekeeping values that have
> > been changed.
>
> It seems the "adjust" function intentionally logs also calls/modes
> that don't actually change anything. Can you please explain it a bit
> in the message?
>
> NTP/PTP daemons typically don't read the adjtimex values in a normal
> operation and overwrite them on each update, even if they don't
> change. If the audit function checked that oldval != newval, the
> number of messages would be reduced and it might be easier to follow.

We actually want to log any attempt to change a value, as even an
intention to set/change something could be a hint that the process is
trying to do something bad (see discussion at [1]). There are valid
arguments both for and against this choice, but we have to pick one in
the end... Anyway, I should explain the reasoning in the commit
message better, right now it just states the fact without explanation
(in the second patch), thank you for pointing my attention to it.

[1] https://www.redhat.com/archives/linux-audit/2018-July/msg00061.html

--
Ondrej Mosnacek <omosnace at redhat dot com>
Associate Software Engineer, Security Technologies
Red Hat, Inc.