linux-kernel - Re: [PATCH v3 1/3] fs/exec: don't force writing memory access

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Message-ID: <20161103182439.GC11212@redhat.com>
Date:   Thu, 3 Nov 2016 19:24:39 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Jann Horn <jann@...jh.net>
Cc:     security@...nel.org, Alexander Viro <viro@...iv.linux.org.uk>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E. Hallyn" <serge@...lyn.com>, mchong@...gle.com,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Nick Kralevich <nnk@...gle.com>,
        Janis Danisevskis <jdanis@...gle.com>,
        linux-security-module@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] fs/exec: don't force writing memory access

On 11/03, Jann Horn wrote:
>
> This shouldn't change behavior in any way - at this point, there should be
> no non-writable mappings, only the initial stack mapping -,

So this FOLL_FORCE just adds the unnecessary confusion,

> but this change
> makes it easier to reason about the correctness of the following commits
> that place restrictions on forced memory writes.

and to me it looks like a good cleanup regardless. Exactly because it
is not clear why do we need FOLL_FORCE.

> Signed-off-by: Jann Horn <jann@...jh.net>
> Reviewed-by: Janis Danisevskis <jdanis@...roid.com>

Acked-by: Oleg Nesterov <oleg@...hat.com>