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=-12.3 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,USER_AGENT_SANE_1 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 AADD1C433DB for ; Wed, 17 Feb 2021 15:00:57 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6AABF64E2F for ; Wed, 17 Feb 2021 15:00:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6AABF64E2F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.86307.161943 (Exim 4.92) (envelope-from ) id 1lCOJo-0001C7-A6; Wed, 17 Feb 2021 15:00:44 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 86307.161943; Wed, 17 Feb 2021 15:00:44 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCOJo-0001C0-6n; Wed, 17 Feb 2021 15:00:44 +0000 Received: by outflank-mailman (input) for mailman id 86307; Wed, 17 Feb 2021 15:00:42 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCOJm-0001Bv-IG for xen-devel@lists.xenproject.org; Wed, 17 Feb 2021 15:00:42 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCOJj-0005Gs-K8; Wed, 17 Feb 2021 15:00:39 +0000 Received: from [54.239.6.188] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1lCOJj-0007yi-BB; Wed, 17 Feb 2021 15:00:39 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=cOHzgwAC2Z9qphFZQv3GbMtfyp4vQstE7EdLfDTxIpA=; b=Cq0Vm+Vfm1JJuwsgpavP6jOo4n ssIpJoDLdEr6iP3PdOzmHhxzHdtACSvStnL6Zjdp72VPxwKu6QzEotZlggCpQ2VkQZDWEmjL2cbAY ZRyf/hCU4m45OA3g2t41BtBUwndsfB/Eh8mWDwrWUgkai2O8U4bN9zV6/SVcVROechaI=; Subject: Re: [for-4.15][PATCH v3 1/3] xen/iommu: x86: Clear the root page-table before freeing the page-tables To: Jan Beulich Cc: hongyxia@amazon.co.uk, iwj@xenproject.org, Julien Grall , Andrew Cooper , Kevin Tian , Paul Durrant , xen-devel@lists.xenproject.org References: <20210217142458.3769-1-julien@xen.org> <20210217142458.3769-2-julien@xen.org> From: Julien Grall Message-ID: <87548d76-36fa-f587-0137-6806280617ad@xen.org> Date: Wed, 17 Feb 2021 15:00:37 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Jan, On 17/02/2021 14:54, Jan Beulich wrote: > On 17.02.2021 15:24, Julien Grall wrote: >> --- a/xen/drivers/passthrough/x86/iommu.c >> +++ b/xen/drivers/passthrough/x86/iommu.c >> @@ -267,6 +267,15 @@ int iommu_free_pgtables(struct domain *d) >> struct page_info *pg; >> unsigned int done = 0; >> >> + if ( !is_iommu_enabled(d) ) >> + return 0; >> + >> + /* >> + * Pages will be moved to the free list below. So we want to >> + * clear the root page-table to avoid any potential use after-free. >> + */ >> + hd->platform_ops->clear_root_pgtable(d); > > Taking amd_iommu_alloc_root() as example, is this really correct > prior to what is now patch 2? Yes, there are no more use-after-free... > What guarantees a new root table > won't get allocated subsequently? It doesn't prevent root table allocation. I view the two as distincts issues, hence the two patches. Cheers, -- Julien Grall