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

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

[Miaohe Lin]

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@huawei.com>
Cc: <stable@vger.kernel.org>
---
 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

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

[Muchun Song]

> On Jul 8, 2024, at 10:51, Miaohe Lin <linmiaohe@huawei.com> wrote:
> 
> 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@huawei.com>

Acked-by: Muchun Song <muchun.song@linux.dev>

Thanks.

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

[Oscar Salvador]

On Mon, Jul 08, 2024 at 10:51:27AM +0800, Miaohe Lin wrote:
> 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@huawei.com>
> Cc: <stable@vger.kernel.org>

Reviewed-by: Oscar Salvador <osalvador@suse.de>


-- 
Oscar Salvador
SUSE Labs