Re: [PATCH v2 1/1] mm: disallow raw PFN mappings of huge/shared zeropage

[Zi Yan]

On 21 Sep 2026, at 1:42, Lance Yang wrote:

> From: Lance Yang <lance.yang@xxxxxxxxx>
>
> Handling the huge/shared zeropage correctly in vmf_insert_pfn_pmd() and
> vmf_insert_pfn_prot() is more involved. We would need to check whether the
> VMA allows it and keep the mapping read-only, similar to the checks in
> vm_mixed_ok().
>
> No in-tree user needs that support, so reject these mappings with
> VM_FAULT_SIGBUS rather than complicate the code for now.
>
> Link: https://lore.kernel.org/all/20260917121010.60966-1-lance.yang@xxxxxxxxx/
> Suggested-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
> Suggested-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> Reviewed-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
> Signed-off-by: Lance Yang <lance.yang@xxxxxxxxx>
> ---
> v1 -> v2:
>  - Reject the shared zeropage in vmf_insert_pfn_prot() (per Kiryl) - thanks!
>  - Explain the VMA validation and read-only requirements (per David) - thanks!
>  - Pick up Kiryl's Reviewed-by tag.
>  - https://lore.kernel.org/all/20260917121010.60966-1-lance.yang@xxxxxxxxx/
>
>  mm/huge_memory.c | 3 +++
>  mm/memory.c      | 3 +++
>  2 files changed, 6 insertions(+)
>
Makes sense to me.

Acked-by: Zi Yan <ziy@xxxxxxxxxx>

Best Regards,
Yan, Zi