linux-kernel - Re: [RFC PATCH 6/6] security/fbfam: Mitigate a fork brute force attack

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Message-ID: <20200919080143.GA2998@ubuntu>
Date:   Sat, 19 Sep 2020 10:01:43 +0200
From:   John Wood <john.wood@....com>
To:     Kees Cook <keescook@...omium.org>
Cc:     John Wood <john.wood@....com>, kernel-hardening@...ts.openwall.com,
        Jann Horn <jannh@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [RFC PATCH 6/6] security/fbfam: Mitigate a fork brute force
 attack

On Fri, Sep 18, 2020 at 02:35:12PM -0700, Kees Cook wrote:
> On Fri, Sep 18, 2020 at 06:02:16PM +0200, John Wood wrote:
> > On Thu, Sep 10, 2020 at 04:56:19PM -0700, Kees Cook wrote:
> > > On Thu, Sep 10, 2020 at 01:21:07PM -0700, Kees Cook wrote:
> > > > +		pr_warn("fbfam: Offending process with PID %d killed\n",
> > > > +			p->pid);
> > >
> > > I'd make this ratelimited (along with Jann's suggestions).
> >
> > Sorry, but I don't understand what you mean with "make this ratelimited".
> > A clarification would be greatly appreciated.
>
> Ah! Yes, sorry for not being more clear. There are ratelimit helpers for
> the pr_*() family of functions, e.g.:
>
> 	pr_warn_ratelimited("brute: Offending process with PID...

Thanks for the clarification.

> --
> Kees Cook

Regards,
John Wood