[PATCH 4.19 15/34] mm: page_vma_mapped_walk(): crossing page table boundary

Greg Kroah-Hartman
2021-07-09T13:21:39Z

From: Hugh Dickins <hughd@google.com>

[ Upstream commit 448282487483d6fa5b2eeeafaa0acc681e544a9c ]

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.

Link: https://lkml.kernel.org/r/799b3f9c-2a9e-dfef-5d89-26e9f76fd97@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Wang Yugui <wangyugui@e16-tech.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@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 e32ed7912923..1fccadd0eb6d 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -240,16 +240,16 @@ 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) {
--
2.30.2