linux-kernel - Re: [patch] mm: mlock: document scary-looking stack expansion mlock chain

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Message-ID: <CANN689Hwp-fm-SUzAXAqLKGkGHxjw2X+pkQRr01=Fjq=BaSoDQ@mail.gmail.com>
Date:	Wed, 20 Feb 2013 22:24:02 +0800
From:	Michel Lespinasse <walken@...gle.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] mm: mlock: document scary-looking stack expansion mlock chain

On Fri, Feb 1, 2013 at 2:10 PM, Johannes Weiner <hannes@...xchg.org> wrote:
> The fact that mlock calls get_user_pages, and get_user_pages might
> call mlock when expanding a stack looks like a potential recursion.
>
> However, mlock makes sure the requested range is already contained
> within a vma, so no stack expansion will actually happen from mlock.
>
> Should this ever change: the stack expansion mlocks only the newly
> expanded range and so will not result in recursive expansion.
>
> Reported-by: Al Viro <viro@...IV.linux.org.uk>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Michel Lespinasse <walken@...gle.com>

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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