Re: [PATCH v2 1/2] mm: kmsan: fix iounmap metadata teardown

[Andrew Morton]

On Fri,  2 Oct 2026 23:05:07 +0300 Dima Koziuk <dmytrokoziuk68@xxxxxxxxx> wrote:

> kmsan_vmalloc_to_page_or_null() rejects addresses outside the regular
> vmalloc and module ranges, including the shadow and origin addresses
> passed by its callers. As a result, iounmap does not free the metadata
> backing pages. Also, the first iteration of the teardown loop
> unmaps the entire metadata range, preventing subsequent iterations from
> finding their pages even if the address lookup is fixed.
> 
> Factor the page-table walk out of vmalloc_to_page() into
> __vmalloc_to_page(), keeping the address check in the public wrapper.
> Use the unchecked helper in kmsan_vmalloc_to_page_or_null() and check
> for NULL before converting the returned page to a PFN. Mark
> __vmalloc_to_page() as __always_inline to avoid an additional function
> call in vmalloc_to_page().
> 
> Move metadata teardown into kmsan_iounmap_pages(). Free the backing
> blocks while their mappings are still available, then unmap each
> metadata range once and flush its TLB entries.

Thanks, I'll queue these for test and further review.

Could people please offer opinions on whether we should backport
one/both into -stable kernels?