linux-kernel - Re: [PATCH] sysctl: add config to make randomize_va

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Date:   Fri, 05 May 2023 08:46:41 +0100
From:   Sam James <sam@...too.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Michael McCracken <michael.mccracken@...il.com>,
        linux-kernel@...r.kernel.org, serge@...lyn.com, tycho@...ho.pizza,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] sysctl: add config to make randomize_va_space RO


David Hildenbrand <david@...hat.com> writes:

> On 04.05.23 23:30, Michael McCracken wrote:
>> Add config RO_RANDMAP_SYSCTL to set the mode of the randomize_va_space
>> sysctl to 0444 to disallow all runtime changes. This will prevent
>> accidental changing of this value by a root service.
>> The config is disabled by default to avoid surprises.
>
> Can you elaborate why we care about "accidental changing of this value
> by a root service"?
>
> We cannot really stop root from doing a lot of stupid things (e.g.,
> erase the root fs), so why do we particularly care here?

(I'm really not defending the utility of this, fwiw).

In the past, I've seen fuzzing tools and other debuggers try to set
it, and it might be that an admin doesn't realise that. But they could
easily set other dangerous settings unsuitable for production, so...


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