From d31155b8f29ce380f7816e54dee161db6d752909 Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Tue, 11 Jul 2023 13:50:16 +0800 Subject: [PATCH] mm: memory-failure: fix race window when trying to get hugetlb folio page_folio() is fetched before calling get_hwpoison_hugetlb_folio() without hugetlb_lock being held. So hugetlb page could be demoted before get_hwpoison_hugetlb_folio() holding hugetlb_lock but after page_folio() is fetched. So get_hwpoison_hugetlb_folio() will hold unexpected extra refcnt of hugetlb folio while leaving demoted page un-refcnted. Link: https://lkml.kernel.org/r/20230711055016.2286677-9-linmiaohe@huawei.com Fixes: 25182f05ffed ("mm,hwpoison: fix race with hugetlb page allocation") Signed-off-by: Miaohe Lin Acked-by: Naoya Horiguchi Signed-off-by: Andrew Morton --- mm/memory-failure.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 1337375..70f4418 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1383,8 +1383,15 @@ static int __get_hwpoison_page(struct page *page, unsigned long flags) bool hugetlb = false; ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, false); - if (hugetlb) - return ret; + if (hugetlb) { + /* Make sure hugetlb demotion did not happen from under us. */ + if (folio == page_folio(page)) + return ret; + if (ret > 0) { + folio_put(folio); + folio = page_folio(page); + } + } /* * This check prevents from calling folio_try_get() for any @@ -1473,8 +1480,13 @@ static int __get_unpoison_page(struct page *page) bool hugetlb = false; ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, true); - if (hugetlb) - return ret; + if (hugetlb) { + /* Make sure hugetlb demotion did not happen from under us. */ + if (folio == page_folio(page)) + return ret; + if (ret > 0) + folio_put(folio); + } /* * PageHWPoisonTakenOff pages are not only marked as PG_hwpoison, -- 2.7.4