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

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Message-ID: <CA+55aFz2aY-0hG1E_x7Don1pwgDQkHZfP2J3qW+QbvcvLBWTNQ@mail.gmail.com>
Date:   Fri, 15 Dec 2017 17:10:58 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        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 Fri, Dec 15, 2017 at 4:29 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> So do you want to do a straight revert of these that went in for 4.15:

I think that's the right thing to do, but would want to verify that
there are no *other* issues than just the attempt at PKRU.

The commit message does talk about PAGE_USER, and as mentioned I do
think that's a good thing to check, I just don't think it should be
done this way,

Was there something else going behind these commits? Because if not,
let's revert and then perhaps later introduce a more targeted thing?

Also, aren't the protection keys encoded in the vma?

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.

               Linus