From patchwork Tue Jan 12 04:57:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 361799 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 785CAC433DB for ; Tue, 12 Jan 2021 04:57:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 48D5A22510 for ; Tue, 12 Jan 2021 04:57:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387505AbhALE54 (ORCPT ); Mon, 11 Jan 2021 23:57:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:40534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733273AbhALE54 (ORCPT ); Mon, 11 Jan 2021 23:57:56 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0CA33225AB; Tue, 12 Jan 2021 04:57:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1610427435; bh=I2uFxUg/rcbbAgX3Wx1MNoUXKNn13iuJJ5aTgIPBk4Y=; h=Date:From:To:Subject:From; b=Cmxg2Ar76rETllG8udSxN+2wlxX6Ew0TR0DyaD+QxgKZPwJFcKr+UEzkdKokpE0CQ DVeFqcVc7DhbXmpPx8UhcStHIZyl7cId8eEYf3DkERoOtY6eF7zi9aEEOrWim6PWGw zBDg2j3smspvGXtSJ3yZXjuZMoU+sGF+zfQMMnG8= Date: Mon, 11 Jan 2021 20:57:14 -0800 From: akpm@linux-foundation.org To: ak@linux.intel.com, mhocko@suse.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, n-horiguchi@ah.jp.nec.com, songmuchun@bytedance.com, stable@vger.kernel.org Subject: + mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page.patch added to -mm tree Message-ID: <20210112045714.R3O20039Y%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm: hugetlb: fix a race between freeing and dissolving the page has been added to the -mm tree. Its filename is mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Muchun Song Subject: mm: hugetlb: fix a race between freeing and dissolving the page There is a race condition between __free_huge_page() and dissolve_free_huge_page(). CPU0: CPU1: // page_count(page) == 1 put_page(page) __free_huge_page(page) dissolve_free_huge_page(page) spin_lock(&hugetlb_lock) // PageHuge(page) && !page_count(page) update_and_free_page(page) // page is freed to the buddy spin_unlock(&hugetlb_lock) spin_lock(&hugetlb_lock) clear_page_huge_active(page) enqueue_huge_page(page) // It is wrong, the page is already freed spin_unlock(&hugetlb_lock) The race windows is between put_page() and dissolve_free_huge_page(). We should make sure that the page is already on the free list when it is dissolved. Link: https://lkml.kernel.org/r/20210110124017.86750-4-songmuchun@bytedance.com Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage") Signed-off-by: Muchun Song Cc: Andi Kleen Cc: Michal Hocko Cc: Mike Kravetz Cc: Naoya Horiguchi Cc: Signed-off-by: Andrew Morton --- mm/hugetlb.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) --- a/mm/hugetlb.c~mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page +++ a/mm/hugetlb.c @@ -79,6 +79,21 @@ DEFINE_SPINLOCK(hugetlb_lock); static int num_fault_mutexes; struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp; +static inline bool PageHugeFreed(struct page *head) +{ + return page_private(head + 4) == -1UL; +} + +static inline void SetPageHugeFreed(struct page *head) +{ + set_page_private(head + 4, -1UL); +} + +static inline void ClearPageHugeFreed(struct page *head) +{ + set_page_private(head + 4, 0); +} + /* Forward declaration */ static int hugetlb_acct_memory(struct hstate *h, long delta); @@ -1028,6 +1043,7 @@ static void enqueue_huge_page(struct hst list_move(&page->lru, &h->hugepage_freelists[nid]); h->free_huge_pages++; h->free_huge_pages_node[nid]++; + SetPageHugeFreed(page); } static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid) @@ -1044,6 +1060,7 @@ static struct page *dequeue_huge_page_no list_move(&page->lru, &h->hugepage_activelist); set_page_refcounted(page); + ClearPageHugeFreed(page); h->free_huge_pages--; h->free_huge_pages_node[nid]--; return page; @@ -1505,6 +1522,7 @@ static void prep_new_huge_page(struct hs spin_lock(&hugetlb_lock); h->nr_huge_pages++; h->nr_huge_pages_node[nid]++; + ClearPageHugeFreed(page); spin_unlock(&hugetlb_lock); } @@ -1771,6 +1789,14 @@ int dissolve_free_huge_page(struct page int nid = page_to_nid(head); if (h->free_huge_pages - h->resv_huge_pages == 0) goto out; + + /* + * We should make sure that the page is already on the free list + * when it is dissolved. + */ + if (unlikely(!PageHugeFreed(head))) + goto out; + /* * Move PageHWPoison flag from head page to the raw error page, * which makes any subpages rather than the error page reusable.