[PATCH 4/5] mm/page_vma_mapped: use huge_ptep_get() for hugetlb

[Dev Jain]

check_pte() is the final validation step in page_vma_mapped_walk().
It reads pvmw->pte with ptep_get() to decide whether the entry maps
the PFN range being walked. For hugetlb VMAs, that pointer refers
to a hugetlb entry.

On arches which provide their own huge_ptep_get() to dereference a huge
pte pointer, accessing via ptep_get() would cause pte_pfn(),
pte_present() etc to misbehave.

It is not clear whether this has a trivially visible effect to userspace.

Use huge_ptep_get() to dereference a huge pte pointer.

Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
 mm/page_vma_mapped.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 2ccbabfb2cc17..18e1d341f463c 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -107,7 +107,13 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
 static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
 {
 	unsigned long pfn;
-	pte_t ptent = ptep_get(pvmw->pte);
+	pte_t ptent;
+
+	if (is_vm_hugetlb_page(pvmw->vma))
+		ptent = huge_ptep_get(pvmw->vma->vm_mm, pvmw->address,
+				      pvmw->pte);
+	else
+		ptent = ptep_get(pvmw->pte);
 
 	if (pvmw->flags & PVMW_MIGRATION) {
 		const softleaf_t entry = softleaf_from_pte(ptent);
-- 
2.43.0