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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Tue, 26 Feb 2019 15:39:08 +0100
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Subject: Re: [PATCH v10 07/12] fs, arm64: untag user pointers in fs/userfaultfd.c
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
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On Sat, Feb 23, 2019 at 12:06 AM Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 2/22/19 4:53 AM, Andrey Konovalov wrote:
> > userfaultfd_register() and userfaultfd_unregister() use provided user
> > pointers for vma lookups, which can only by done with untagged pointers.
>
> So, we have to patch all these sites before the tagged values get to the
> point of hitting the vma lookup functions.  Dumb question: Why don't we
> just patch the vma lookup functions themselves instead of all of these
> callers?

That might be a working approach as well. We'll still need to fix up
places where the vma fields are accessed directly. Catalin, what do
you think?