Re: [PATCH v5 18/39] mm: Handle faultless write upgrades for shstk

David Hildenbrand
2023-02-01T18:04:47Z

On 01.02.23 18:32, Edgecombe, Rick P wrote:
> On Wed, 2023-02-01 at 10:03 +0100, David Hildenbrand wrote:
>>>
>>> The other problem is that one of NULL passers is not for kernel
>>> memory.
>>> huge_pte_mkwrite() calls pte_mkwrite(). Shadow stack memory can't
>>> be
>>> created with MAP_HUGETLB, so it is not needed. Using
>>> pte_mkwrite_kernel() would look weird in this case, but making
>>> huge_pte_mkwrite() take a VMA would be for no reason. Maybe making
>>> huge_pte_mkwrite() take a VMA is the better of those two options.
>>> Or
>>> keep the NULL semantics... Any thoughts?
>>
>> Well, the reason would be consistency. From a core-mm point of view
>> it
>> makes sense to handle this all consistency, even if the single user
>> (x86) wouldn't strictly require it right now.
>>
>> I'd just pass in the VMA and call it a day :)
>
> Ok, I'll give it a spin.

It would be good to get more opinions on that, but I'm afraid we won't
get more deep down in this thread :)

--
Thanks,

David / dhildenb