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Subject: Re: [PATCH v2 01/17] mm/gup: Fixup p*_access_permitted()
To: Linus Torvalds <torvalds@linux-foundation.org>,
        Dan Williams <dan.j.williams@intel.com>
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From: Dave Hansen <dave.hansen@intel.com>
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Date: Fri, 15 Dec 2017 17:25:20 -0800
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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.