[PATCH 06/11] mm: page_vma_mapped_walk(): crossing page table boundary

Hugh Dickins
2021-06-10T06:44:16Z

page_vma_mapped_walk() cleanup: adjust the test for crossing page table
boundary - I believe pvmw->address is always page-aligned, but nothing
else here assumed that; and remember to reset pvmw->pte to NULL after
unmapping the page table, though I never saw any bug from that.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
---
mm/page_vma_mapped.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index b96fae568bc2..0fe6e558d336 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -247,16 +247,16 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
if (pvmw->address >= end)
return not_found(pvmw);
/* Did we cross page table boundary? */
- if (pvmw->address % PMD_SIZE == 0) {
- pte_unmap(pvmw->pte);
+ if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
if (pvmw->ptl) {
spin_unlock(pvmw->ptl);
pvmw->ptl = NULL;
}
+ pte_unmap(pvmw->pte);
+ pvmw->pte = NULL;
goto restart;
- } else {
- pvmw->pte++;
}
+ pvmw->pte++;
} while (pte_none(*pvmw->pte));

if (!pvmw->ptl) {
--
2.26.2