linux-kernel - Re: MAP_FIXED for ELF mappings

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Date:   Wed, 4 Oct 2017 10:15:31 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Baoquan He <bhe@...hat.com>, Kees Cook <keescook@...omium.org>,
        Oleg Nesterov <oleg@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
        Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...e.hu>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: MAP_FIXED for ELF mappings

On Wed, Oct 4, 2017 at 10:12 AM, Michal Hocko <mhocko@...nel.org> wrote:
>
> Yes, but we already have a new stack mapped and that was the point of
> the referenced CVE where the binary segments got mapped over the stack
> AFAIU.

Well, if you control the binary to the point where you just make the
ELF section map on top of the stack, what's the problem?

I mean, it's not a security issue. You could just have written the
code to do mmap() instead.

So I think this is a "crazy users can do crazy things, we're not
arbiters of taste" thing.

                       Linus