From mboxrd@z Thu Jan 1 00:00:00 1970 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=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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,USER_AGENT_GIT autolearn=unavailable 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 7AB7BC433DB for ; Mon, 8 Feb 2021 16:12:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37DA464E82 for ; Mon, 8 Feb 2021 16:12:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233743AbhBHQL1 (ORCPT ); Mon, 8 Feb 2021 11:11:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:55494 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233285AbhBHPLQ (ORCPT ); Mon, 8 Feb 2021 10:11:16 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4611164EBF; Mon, 8 Feb 2021 15:08:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612796900; bh=knE+Sry8wET3NPoTsA8H3lstdcgKQmlNIU94BXEZHYA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FQtIUF0mS1kVB1lO9Pg8wQG3xdziTKW5VhcZhqcQ8tM2nq1BnxbvR1ASFTafK9wDu ja80McQswWCFMnffJWTkbGGDTBhOt8ToinyaxDnVwCQNBVAgtyGxzpFyNKueSxF6Cc ZyJRBxCF3gPdx6jWJMVa6vFIA41EDrKDZqH+xAyI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Muchun Song , Mike Kravetz , Oscar Salvador , Michal Hocko , David Hildenbrand , Yang Shi , Andrew Morton , Linus Torvalds Subject: [PATCH 4.19 28/38] mm: hugetlb: fix a race between freeing and dissolving the page Date: Mon, 8 Feb 2021 16:01:15 +0100 Message-Id: <20210208145807.286891562@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210208145806.141056364@linuxfoundation.org> References: <20210208145806.141056364@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Muchun Song commit 7ffddd499ba6122b1a07828f023d1d67629aa017 upstream. 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 window 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. As a result __free_huge_page would corrupt page(s) already in the buddy allocator. Link: https://lkml.kernel.org/r/20210115124942.46403-4-songmuchun@bytedance.com Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage") Signed-off-by: Muchun Song Reviewed-by: Mike Kravetz Reviewed-by: Oscar Salvador Acked-by: Michal Hocko Cc: David Hildenbrand Cc: Yang Shi Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -68,6 +68,21 @@ 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); @@ -858,6 +873,7 @@ 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) @@ -875,6 +891,7 @@ static struct page *dequeue_huge_page_no return NULL; 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; @@ -1305,6 +1322,7 @@ static void prep_new_huge_page(struct hs set_hugetlb_cgroup(page, NULL); h->nr_huge_pages++; h->nr_huge_pages_node[nid]++; + ClearPageHugeFreed(page); spin_unlock(&hugetlb_lock); } @@ -1500,6 +1518,7 @@ int dissolve_free_huge_page(struct page { int rc = -EBUSY; +retry: /* Not to disrupt normal path by vainly holding hugetlb_lock */ if (!PageHuge(page)) return 0; @@ -1516,6 +1535,26 @@ 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))) { + spin_unlock(&hugetlb_lock); + cond_resched(); + + /* + * Theoretically, we should return -EBUSY when we + * encounter this race. In fact, we have a chance + * to successfully dissolve the page if we do a + * retry. Because the race window is quite small. + * If we seize this opportunity, it is an optimization + * for increasing the success rate of dissolving page. + */ + goto retry; + } + /* * Move PageHWPoison flag from head page to the raw error page, * which makes any subpages rather than the error page reusable.