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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 E8093C433DB for ; Thu, 28 Jan 2021 00:11:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A804164D99 for ; Thu, 28 Jan 2021 00:11:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231601AbhA1AKf (ORCPT ); Wed, 27 Jan 2021 19:10:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:50842 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229682AbhA1AKF (ORCPT ); Wed, 27 Jan 2021 19:10:05 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 151D764DBD; Thu, 28 Jan 2021 00:09:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1611792562; bh=GUNbpAFQoRcexAEW65OXiQTw8gUoU09C4H2pJGNY8w8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ejDKEIKjTrhulX74BMX2PUUpa2oAmG/+Kyp6rdJZ038ZUiiK3ANEhEVcwC80PP0zn 8uqmlayZ+K0Zn6t6PT6IowaLLDtVfSeKns6UgF8MTSzYlZGzSyPN1f79nu4mslGBLz yhnxAHJvlbTunaa2wBE+H4M9ZQYu/mwqlw1Pb6RI= Date: Wed, 27 Jan 2021 16:09:21 -0800 From: Andrew Morton To: Miaohe Lin Cc: , , , , , , Subject: Re: [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte Message-Id: <20210127160921.989f01c83d6703148f6bc316@linux-foundation.org> In-Reply-To: <20210127093349.39081-1-linmiaohe@huawei.com> References: <20210127093349.39081-1-linmiaohe@huawei.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 27 Jan 2021 04:33:49 -0500 Miaohe Lin wrote: > For PMD-mapped page (usually THP), pvmw->pte is NULL. For PTE-mapped THP, > pvmw->pte is mapped. But for HugeTLB pages, pvmw->pte is not mapped and set > to the relevant page table entry. So in page_vma_mapped_walk_done(), we may > do pte_unmap() for HugeTLB pte which is not mapped. Fix this by checking > pvmw->page against PageHuge before trying to do pte_unmap(). > What are the runtime consequences of this? Is there a workload which is known to trigger it? IOW, how do we justify a -stable backport of this fix? > > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -213,7 +213,8 @@ struct page_vma_mapped_walk { > > static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw) > { > - if (pvmw->pte) > + /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */ > + if (pvmw->pte && !PageHuge(pvmw->page)) > pte_unmap(pvmw->pte); > if (pvmw->ptl) > spin_unlock(pvmw->ptl); > -- > 2.19.1