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Subject[PATCH] mm/madvise: fix potential pte_unmap_unlock pte error
Date
We can't assume pte_offset_map_lock will return same orig_pte value. So
it's necessary to reacquire the orig_pte or pte_unmap_unlock will unmap
the stale pte.

Fixes: 9c276cc65a58 ("mm: introduce MADV_COLD")
Fixes: 854e9ed09ded ("mm: support madvise(MADV_FREE)")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/madvise.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index ec03a76244b7..4d6592488b51 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -437,12 +437,12 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
if (split_huge_page(page)) {
unlock_page(page);
put_page(page);
- pte_offset_map_lock(mm, pmd, addr, &ptl);
+ orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
break;
}
unlock_page(page);
put_page(page);
- pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+ orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
pte--;
addr -= PAGE_SIZE;
continue;
@@ -653,12 +653,12 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
if (split_huge_page(page)) {
unlock_page(page);
put_page(page);
- pte_offset_map_lock(mm, pmd, addr, &ptl);
+ orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
goto out;
}
unlock_page(page);
put_page(page);
- pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+ orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
pte--;
addr -= PAGE_SIZE;
continue;
--
2.23.0
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