Re: [PATCH v2 1/1] mm/huge_memory: simplify pgtable deposit detection

[Andrew Morton]

On Thu, 17 Sep 2026 13:40:15 +0800 Lance Yang <lance.yang@xxxxxxxxx> wrote:

> Whether a PMD has a deposited PTE page table only depends on whether the
> architecture requires deposits or the VMA is anonymous.
> 
> Implement this rule directly in vma_has_deposited_pgtable(), avoiding
> mistaking a non-anonymous raw PFN PMD for one with a deposit and attempting
> to withdraw a page table that was never deposited.

A large part of my life is asking $LLM "what are the userspace-visible
runtime effects of this bug".  Because NOBODY EVER TELLS ME!!!

This time it says "Processes using PMD-sized raw PFN mappings can
trigger a kernel NULL-pointer dereference when the mapping is torn
down", which sounds kinda important if true.

Help me out here?

Also, thanks ;)