mm/rmap: fix potential pte_unmap on an not mapped pte

For PMD-mapped page (usually THP), pvmw->pte is NULL.  For PTE-mapped THP,
pvmw->pte is mapped.  But for HugeTLB pages, pvmw->pte is not mapped and
set to the relevant page table entry.  So in page_vma_mapped_walk_done(),
we may do pte_unmap() for HugeTLB pte which is not mapped.  Fix this by
checking pvmw->page against PageHuge before trying to do pte_unmap().

Link: https://lkml.kernel.org/r/[email protected]
Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()")
Signed-off-by: Hongxiang Lou <[email protected]>
Signed-off-by: Miaohe Lin <[email protected]>
Tested-by: Sedat Dilek <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Wei Yang <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Cc: Brian Geffon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 70085ca1a3fc..def5c62c93b3 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -213,7 +213,8 @@ struct page_vma_mapped_walk {
 
 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
 {
-	if (pvmw->pte)
+	/* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
+	if (pvmw->pte && !PageHuge(pvmw->page))
 		pte_unmap(pvmw->pte);
 	if (pvmw->ptl)
 		spin_unlock(pvmw->ptl);