linux-kernel - Re: [PATCH v2 01/17] mm/gup: Fixup p*_access

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Date:   Fri, 15 Dec 2017 08:51:47 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        tglx@...utronix.de, x86@...nel.org,
        Andy Lutomirsky <luto@...nel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>, keescook@...gle.com,
        hughd@...gle.com, Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>, linux-mm@...ck.org,
        kirill.shutemov@...ux.intel.com, dan.j.williams@...el.com
Subject: Re: [PATCH v2 01/17] mm/gup: Fixup p*_access_permitted()

On Thu, Dec 14, 2017 at 10:09:24PM -0800, Linus Torvalds wrote:
> On Dec 14, 2017 21:04, "Dave Hansen" <dave.hansen@...el.com> wrote:
> Can we please just undo that broken crap instead of trying to "fix" it?
> 
> It was wrong. We absolutely do not want to complicate the gup path.
> 
> Let's fet rid of those broken p??_access_permited() things.

So we actually need the pte_access_permitted() stuff if we want to
ensure we're not stepping on !PAGE_USER things.