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Date: Thu, 10 Sep 2020 22:39:04 +0200
From: Jann Horn <jannh@...gle.com>
To: Kees Cook <keescook@...omium.org>, John Wood <john.wood@....com>
Cc: 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: [RESEND][RFC PATCH 0/6] Fork brute force attack mitigation (fbfam)

On Thu, Sep 10, 2020 at 10:21 PM Kees Cook <keescook@...omium.org> wrote:
> [kees: re-sending this series on behalf of John Wood <john.wood@....com>
> also visible at https://github.com/johwood/linux fbfam]
[...]
> The goal of this patch serie is to detect and mitigate a fork brute force
> attack.
>
> Attacks with the purpose to break ASLR or bypass canaries traditionaly use
> some level of brute force with the help of the fork system call. This is
> possible since when creating a new process using fork its memory contents
> are the same as those of the parent process (the process that called the
> fork system call). So, the attacker can test the memory infinite times to
> find the correct memory values or the correct memory addresses without
> worrying about crashing the application.

For the next version of this patchset, you may want to clarify that
this is intended to stop brute force attacks *against vulnerable
userspace processes* that fork off worker processes. I was halfway
through the patch series before I realized that.

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