linux-kernel - Re: [2/3] mm: fix up some user-visible effects of the stack guard page

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Message-ID: <CA+55aFyDM2vV-_zax3-8mhDzsThXs6RAKp_ipHbNHaL0CcsiSw@mail.gmail.com>
Date:	Mon, 5 Jan 2015 13:11:20 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jay Foad <jay.foad@...il.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [2/3] mm: fix up some user-visible effects of the stack guard page

On Mon, Jan 5, 2015 at 1:03 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Yup, your analysis sounds correct.  My completely untested gut feel is
> that the problem is that we don't actually return the error from the
> expand_stack() call, so then do_anonymous_page() will allow the extra
> guard-page access.
>
> IOW, *maybe* a patch like this. TOTALLY UNTESTED! I may have missed
> something, and this may be complete crap.

.. and ti's still untested, but I'm pretty sure it's right - except we
should probably also allow an extra page for the stack rlimit (so that
the guard page doesn't count towards the limit).

                          Linus
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