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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 14 Dec 2017 14:14:00 -0800
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Subject: Re: [PATCH v2 11/17] selftests/x86/ldt_gdt: Prepare for access bit forced
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>,
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On Thu, Dec 14, 2017 at 2:02 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> _Should_ being the operative word, because I cannot currently see it
> DTRT. But maybe I'm missing the obvious -- I tend to do that at times.

At least the old get_user_pages_fast() code used to check the USER bit:

        unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;

        if (write)
                need_pte_bits |= _PAGE_RW;

but that may have been lost when we converted over to the generic code.

It shouldn't actually _matter_, since we'd need to change access_ok()
anyway (and gup had better check that!)

             Linus