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Tue, 20 Apr 2021 23:03:25 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.255]) by smtp.gmail.com with ESMTPSA id nh24sm887161pjb.38.2021.04.20.23.03.22 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Apr 2021 23:03:25 -0700 (PDT) From: Muchun Song To: mike.kravetz@oracle.com, akpm@linux-foundation.org, mhocko@suse.com, osalvador@suse.de Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song Subject: [PATCH] mm: hugetlb: fix a race between memory-failure/soft_offline and gather_surplus_pages Date: Wed, 21 Apr 2021 14:02:59 +0800 Message-Id: <20210421060259.67554-1-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) MIME-Version: 1.0 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: AE28D3C1 X-Stat-Signature: tbfnr6asyqi4qd7tdupm6w7w4jd6syme Received-SPF: none (bytedance.com>: No applicable sender policy available) receiver=imf04; identity=mailfrom; envelope-from=""; helo=mail-pf1-f174.google.com; client-ip=209.85.210.174 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618985004-181130 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The possible bad scenario: CPU0: CPU1: gather_surplus_pages() page = alloc_surplus_huge_page() memory_failure_hugetlb() get_hwpoison_page(page) __get_hwpoison_page(page) get_page_unless_zero(page) zero = put_page_testzero(page) VM_BUG_ON_PAGE(!zero, page) enqueue_huge_page(h, page) put_page(page) The refcount can possibly be increased by memory-failure or soft_offline handlers, we can trigger VM_BUG_ON_PAGE and wrongly add the page to the hugetlb pool list. Signed-off-by: Muchun Song --- mm/hugetlb.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 3476aa06da70..6c96332db34b 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2145,17 +2145,14 @@ static int gather_surplus_pages(struct hstate *h, long delta) /* Free the needed pages to the hugetlb pool */ list_for_each_entry_safe(page, tmp, &surplus_list, lru) { - int zeroed; - if ((--needed) < 0) break; /* - * This page is now managed by the hugetlb allocator and has - * no users -- drop the buddy allocator's reference. + * The refcount can possibly be increased by memory-failure or + * soft_offline handlers. */ - zeroed = put_page_testzero(page); - VM_BUG_ON_PAGE(!zeroed, page); - enqueue_huge_page(h, page); + if (likely(put_page_testzero(page))) + enqueue_huge_page(h, page); } free: spin_unlock_irq(&hugetlb_lock);