linux-kernel - Re: [PATCH] mm: optionally disable brk()

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Message-ID: <4f0b1f0e-ab26-cd4e-607c-2c5b9933f10a@gmail.com>
Date:   Mon, 5 Oct 2020 12:03:27 +0300
From:   Topi Miettinen <toiwoton@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: optionally disable brk()

On 5.10.2020 11.22, Michal Hocko wrote:
> On Mon 05-10-20 11:11:35, Topi Miettinen wrote:
> [...]
>> I think hardened, security oriented systems should disable brk() completely
>> because it will increase the randomization of the process address space
>> (ASLR). This wouldn't be a good option to enable for systems where maximum
>> compatibility with legacy software is more important than any hardening.
> 
> I believe we already do have means to filter syscalls from userspace for
> security hardened environements. Or is there any reason to duplicate
> that and control during the configuration time?

This is true, but seccomp can't be used for cases where NoNewPrivileges 
can't be enabled (setuid/setgid binaries present which sadly is still 
often the case even in otherwise hardened system), so it's typically not 
possible to install a filter for the whole system.

-Topi