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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 3F169C43219 for ; Fri, 26 Apr 2019 13:38:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B8642084F for ; Fri, 26 Apr 2019 13:38:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726295AbfDZNiy (ORCPT ); Fri, 26 Apr 2019 09:38:54 -0400 Received: from 8bytes.org ([81.169.241.247]:37616 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726169AbfDZNit (ORCPT ); Fri, 26 Apr 2019 09:38:49 -0400 Received: by theia.8bytes.org (Postfix, from userid 1000) id AC762447; Fri, 26 Apr 2019 15:38:48 +0200 (CEST) Date: Fri, 26 Apr 2019 15:38:46 +0200 From: Joerg Roedel To: Pan Bian Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jacob Pan , David Woodhouse Subject: Re: iommu/vt-d: drop mm use count if address is not canonical Message-ID: <20190426133846.GC24576@8bytes.org> References: <1555492377-79859-1-git-send-email-bianpan2016@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1555492377-79859-1-git-send-email-bianpan2016@163.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Adding more people. ] On Wed, Apr 17, 2019 at 05:12:57PM +0800, Pan Bian wrote: > The use count of svm->mm is incremented by mmget_not_zero. However, it > is not dropped when the address is not canonical. This patch fixes the > bug. > > Fixes: 9d8c3af31607("iommu/vt-d: IOMMU Page Request needs to check if > address is canonical.") > > Signed-off-by: Pan Bian > --- > drivers/iommu/intel-svm.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c > index 3a4b09a..2630d2e 100644 > --- a/drivers/iommu/intel-svm.c > +++ b/drivers/iommu/intel-svm.c > @@ -574,8 +574,10 @@ static irqreturn_t prq_event_thread(int irq, void *d) > goto bad_req; > > /* If address is not canonical, return invalid response */ > - if (!is_canonical_address(address)) > + if (!is_canonical_address(address)) { > + mmput(svm->mm); > goto bad_req; > + } > > down_read(&svm->mm->mmap_sem); > vma = find_extend_vma(svm->mm, address); I think it is better to move the canonical address check before mmget_not_zero() like in the diff below. But I let David and Jacob comment on this. Regards, Joerg diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c index 8f87304f915c..5e9e1eee8336 100644 --- a/drivers/iommu/intel-svm.c +++ b/drivers/iommu/intel-svm.c @@ -586,14 +586,15 @@ static irqreturn_t prq_event_thread(int irq, void *d) * any faults on kernel addresses. */ if (!svm->mm) goto bad_req; - /* If the mm is already defunct, don't handle faults. */ - if (!mmget_not_zero(svm->mm)) - goto bad_req; /* If address is not canonical, return invalid response */ if (!is_canonical_address(address)) goto bad_req; + /* If the mm is already defunct, don't handle faults. */ + if (!mmget_not_zero(svm->mm)) + goto bad_req; + down_read(&svm->mm->mmap_sem); vma = find_extend_vma(svm->mm, address); if (!vma || address < vma->vm_start)