Re: [PATCH v1] fs/proc/task_mmu: fix PAGE_IS_PFNZERO detection for the huge zero folio

[Andrew Morton]

On Tue, 17 Jun 2025 16:35:32 +0200 David Hildenbrand <david@xxxxxxxxxx> wrote:

> is_zero_pfn() does not work for the huge zero folio. Fix it by using
> is_huge_zero_pmd().
> 
> Found by code inspection.
> 
> Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
> 
> Probably we should Cc stable, thoughts?

Depends on the userspace effects.  I'm thinking these are "This can
cause the PAGEMAP_SCAN ioctl against /proc/pid/pagemap to omit pages"
so yup, cc:stable.