[v7,2/8] mm: pagewalk: Take the pagetable lock in walk_pte_range()

Commit Message

Thomas Hellström (Intel) Nov. 7, 2019, 8:41 a.m. UTC

From: Thomas Hellstrom <[e-mail]>

Without the lock, anybody modifying a pte from within this function might
have it concurrently modified by someone else.

Cc: Matthew Wilcox <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Rik van Riel <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Huang Ying <[e-mail]>
Cc: Jérôme Glisse <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Suggested-by: Linus Torvalds <[e-mail]>
Signed-off-by: Thomas Hellstrom <[e-mail]>
Acked-by: Kirill A. Shutemov <[e-mail]>
---
 mm/pagewalk.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Patch

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index d48c2a986ea3..c5fa42cab14f 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -10,8 +10,9 @@  static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 	pte_t *pte;
 	int err = 0;
 	const struct mm_walk_ops *ops = walk->ops;
+	spinlock_t *ptl;
 
-	pte = pte_offset_map(pmd, addr);
+	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
 	for (;;) {
 		err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
 		if (err)
@@ -22,7 +23,7 @@  static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 		pte++;
 	}
 
-	pte_unmap(pte);
+	pte_unmap_unlock(pte, ptl);
 	return err;
 }