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Date:   Fri, 15 Dec 2017 17:25:20 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...gle.com>,
        Hugh Dickins <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>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        Will Deacon <will.deacon@....com>,
        linux-mm <linux-mm@...ck.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v2 01/17] mm/gup: Fixup p*_access_permitted()

On 12/15/2017 05:10 PM, Linus Torvalds wrote:
> Because *if* we want to check protection keys, I think we should do
> that at the vma layer, partly exactly because the exact implementation
> of protection keys is so architecture-specific, and partly because I
> don't think it makes sense to check them for every page anyway.

So, there are VMA checks against protection keys.  The problem _here_ is
that we are checking against the VMA (and correctly skipping the PKRU
checks) and then _mistakenly_ applying the PTE checks against PKRU.

I think the reason we needed VMA and PTE checks was the
get_user_pages_fast() path not having a VMA.

I need to go re-read the commits, though.

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