linux-kernel - Re: [RFC PATCH 1/6] security/fbfam: Add a Kconfig to enable the fbfam feature

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Message-ID: <20200917173209.GA3637@ubuntu>
Date:   Thu, 17 Sep 2020 19:32:09 +0200
From:   John Wood <john.wood@....com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>, John Wood <john.wood@....com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.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,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [RFC PATCH 1/6] security/fbfam: Add a Kconfig to enable the
 fbfam feature

On Thu, Sep 10, 2020 at 11:21:58PM +0200, Jann Horn wrote:
> On Thu, Sep 10, 2020 at 10:21 PM Kees Cook <keescook@...omium.org> wrote:
> > From: John Wood <john.wood@....com>
> >
> > Add a menu entry under "Security options" to enable the "Fork brute
> > force attack mitigation" feature.
> [...]
> > +config FBFAM
>
> Please give this a more descriptive name than FBFAM. Some name where,
> if a random kernel developer sees an "#ifdef" with that name in some
> random piece of kernel code, they immediately have a rough idea for
> what kind of feature this is.
>
> Perhaps something like THROTTLE_FORK_CRASHES. Or something else that
> is equally descriptive.

Ok, understood. This will be fixed for the next version. Thanks.

> > +       bool "Fork brute force attack mitigation"
> > +       default n
>
> "default n" is superfluous and should AFAIK be omitted.

Ok. I will remove it. Thanks.

> > +       help
> > +         This is a user defense that detects any fork brute force attack
> > +         based on the application's crashing rate. When this measure is
> > +         triggered the fork system call is blocked.
>
> This help text claims that the mitigation will block fork(), but patch
> 6/6 actually kills the process hierarchy.

Sorry, it's a mistake. It was the first idea but finally the implementation
changed and this description not was modified. Apologies. It will be fixed
for the next version.

Thanks,
John Wood