Re: [PATCH v2 6/6] mm/mprotect: use huge_ptep_get() for hugetlb

[Muchun Song]

> On Jul 2, 2026, at 13:13, Dev Jain <dev.jain@xxxxxxx> wrote:
> 
> prot_none_hugetlb_entry() is the hugetlb callback for the early
> mprotect(PROT_NONE) PFN permission walk on x86.
> 
> The callback passes the decoded PFN to pfn_modify_allowed(). For a
> hugetlb callback, the pte pointer refers to a hugetlb entry. On
> architectures where hugetlb entries need huge_ptep_get(), reading that
> entry with ptep_get() can make the permission check use the wrong PFN.
> 
> Use huge_ptep_get() before decoding the hugetlb PFN.
> 
> Currently there is no path which can trigger a bug: huge_ptep_get() is a
> simple ptep_get() for x86, and the prot_none walk occurs only for x86.
> 
> So no need to backport - use the correct helper anyways.
> 
> Fixes: 42e4089c7890 ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings")
> Signed-off-by: Dev Jain <dev.jain@xxxxxxx>

Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>

Thanks.