linux-kernel - Re: [PATCH v2 2/2] arm64/mm: fix incorrect file_map

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Date:   Tue, 22 Nov 2022 09:24:57 +0800
From:   Liu Shixin <liushixin2@...wei.com>
To:     Will Deacon <will@...nel.org>
CC:     Catalin Marinas <catalin.marinas@....com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        "Anshuman Khandual" <anshuman.khandual@....com>,
        David Hildenbrand <dhildenb@...hat.com>,
        Rafael Aquini <raquini@...hat.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] arm64/mm: fix incorrect file_map_count for invalid
 pmd/pud



On 2022/11/22 2:16, Will Deacon wrote:
> On Mon, Nov 21, 2022 at 11:15:49AM +0800, Liu Shixin wrote:
>> On 2022/11/18 22:34, Will Deacon wrote:
>>> On Thu, Nov 17, 2022 at 03:56:02PM +0800, Liu Shixin wrote:
>>>>  static inline bool pud_user_accessible_page(pud_t pud)
>>>>  {
>>>> -	return pud_leaf(pud) && pud_user(pud);
>>>> +	return pud_valid(pud) && pud_leaf(pud) && pud_user(pud);
>>> Not caused by this patch, but why don't we have something like a
>>> pud_user_exec() check here like we do for the pte and pmd levels?
>> As far as I know, there is no user use the user executable pud on arm64, so didn't define pud_user_exec().
> I can believe they don't get exposed to userspace at all, but exposing only
> as non-executable doesn't sound right. So I would have thought that either
> pud_user_accessible_page() would always return false or it would need to
> check for the executable case too.
Thanks for your advice, I will add the check for the executable case too.

>
> Will
> .
>