[PATCH] mm/hugetlb: fix potential race in __update_and_free_hugetlb_folio()

From: Miaohe Lin
Date: Sun Jul 07 2024 - 22:56:00 EST


There is a potential race between __update_and_free_hugetlb_folio() and
try_memory_failure_hugetlb():

CPU1 CPU2
__update_and_free_hugetlb_folio try_memory_failure_hugetlb
folio_test_hugetlb
-- It's still hugetlb folio.
folio_clear_hugetlb_hwpoison
spin_lock_irq(&hugetlb_lock);
__get_huge_page_for_hwpoison
folio_set_hugetlb_hwpoison
spin_unlock_irq(&hugetlb_lock);
spin_lock_irq(&hugetlb_lock);
__folio_clear_hugetlb(folio);
-- Hugetlb flag is cleared but too late.
spin_unlock_irq(&hugetlb_lock);

When above race occurs, raw error page info will be leaked. Even worse,
raw error pages won't have hwpoisoned flag set and hit pcplists/buddy.
Fix this issue by deferring folio_clear_hugetlb_hwpoison() until
__folio_clear_hugetlb() is done. So all raw error pages will have
hwpoisoned flag set.

Fixes: 32c877191e02 ("hugetlb: do not clear hugetlb dtor until allocating vmemmap")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 61847f799b6a..63a2f1132a81 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1729,13 +1729,6 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
return;
}

- /*
- * Move PageHWPoison flag from head page to the raw error pages,
- * which makes any healthy subpages reusable.
- */
- if (unlikely(folio_test_hwpoison(folio)))
- folio_clear_hugetlb_hwpoison(folio);
-
/*
* If vmemmap pages were allocated above, then we need to clear the
* hugetlb flag under the hugetlb lock.
@@ -1746,6 +1739,13 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
spin_unlock_irq(&hugetlb_lock);
}

+ /*
+ * Move PageHWPoison flag from head page to the raw error pages,
+ * which makes any healthy subpages reusable.
+ */
+ if (unlikely(folio_test_hwpoison(folio)))
+ folio_clear_hugetlb_hwpoison(folio);
+
folio_ref_unfreeze(folio, 1);

/*
--
2.33.0