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=-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=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 6A9DCC433DB for ; Wed, 13 Jan 2021 09:32:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21797233A1 for ; Wed, 13 Jan 2021 09:32:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727111AbhAMJcX (ORCPT ); Wed, 13 Jan 2021 04:32:23 -0500 Received: from mx2.suse.de ([195.135.220.15]:51220 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725781AbhAMJcX (ORCPT ); Wed, 13 Jan 2021 04:32:23 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1610530296; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=0TE8MKnmDo3Q30xN4tt6yxvQ6N8u1DSzcLaJ0wteucg=; b=C/YeCjaaeIBE95MvMP4f4ySuRAHJt8gowjXdlmD3OggLBLDDC/Dj8qjKtuvAzYQgNHynjX ptGwSuKrTH0NIZX7mODXgrPoX+rR3GBCptU9G+cNUkq1DcPWfDEJUnjXvNyygh/Iba/yTn 5HMQQPhcEo+mj1OKKUQ5Qi32vso+2Ns= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 390CAAA6F; Wed, 13 Jan 2021 09:31:36 +0000 (UTC) Date: Wed, 13 Jan 2021 10:31:34 +0100 From: Michal Hocko To: Muchun Song Cc: mike.kravetz@oracle.com, akpm@linux-foundation.org, n-horiguchi@ah.jp.nec.com, ak@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v4 3/6] mm: hugetlb: fix a race between freeing and dissolving the page Message-ID: <20210113093134.GU22493@dhcp22.suse.cz> References: <20210113052209.75531-1-songmuchun@bytedance.com> <20210113052209.75531-4-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210113052209.75531-4-songmuchun@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 13-01-21 13:22:06, Muchun Song wrote: > 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. Please describe the effect of the bug. " As a result __free_huge_page would corrupt page(s) already in the buddy allocator. " > > Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage") > Signed-off-by: Muchun Song > Reviewed-by: Mike Kravetz > Cc: stable@vger.kernel.org [...] > @@ -1770,6 +1788,14 @@ int dissolve_free_huge_page(struct page *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; I believe we have agreed to retry for this temporary state. > + > /* > * Move PageHWPoison flag from head page to the raw error page, > * which makes any subpages rather than the error page reusable. > -- > 2.11.0 -- Michal Hocko SUSE Labs