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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 15 Dec 2017 17:10:58 -0800
Message-ID: <CA+55aFz2aY-0hG1E_x7Don1pwgDQkHZfP2J3qW+QbvcvLBWTNQ@mail.gmail.com>
Subject: Re: [PATCH v2 01/17] mm/gup: Fixup p*_access_permitted()
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To: Dan Williams <dan.j.williams@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Dave Hansen <dave.hansen@intel.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>, the arch/x86 maintainers <x86@kernel.org>, Andy Lutomirsky <luto@kernel.org>, Borislav Petkov <bpetkov@suse.de>, Greg KH <gregkh@linuxfoundation.org>, Kees Cook <keescook@google.com>, Hugh Dickins <hughd@google.com>, Brian Gerst <brgerst@gmail.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Denys Vlasenko <dvlasenk@redhat.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Juergen Gross <jgross@suse.com>, David Laight <David.Laight@aculab.com>, Eduardo Valentin <eduval@amazon.com>, "Liguori, Anthony" <aliguori@amazon.com>, Will Deacon <will.deacon@arm.com>, linux-mm <linux-mm@kvack.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

On Fri, Dec 15, 2017 at 4:29 PM, Dan Williams <dan.j.williams@intel.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

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