mm/hugetlb: fix potential race in __update_and_free_hugetlb_folio()

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 the 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.

Link: https://lkml.kernel.org/r/20240708025127.107713-1-linmiaohe@huawei.com
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>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2afb70171b769bb3c8e3ef9bd8c85a008aff1ea4..fe44324d6383f2346309fa784053d23755f9cc65 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1725,13 +1725,6 @@ 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.
@@ -1742,6 +1735,13 @@ 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);
 
        /*