From patchwork Tue Dec 22 15:43:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 11986993 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=-18.8 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,USER_AGENT_GIT 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 BD3ABC433DB for ; Tue, 22 Dec 2020 15:44:00 +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 8101A23105 for ; Tue, 22 Dec 2020 15:44:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8101A23105 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.57962.101662 (Exim 4.92) (envelope-from ) id 1krjpD-0006es-5j; Tue, 22 Dec 2020 15:43:47 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 57962.101662; Tue, 22 Dec 2020 15:43:47 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1krjpD-0006ed-27; Tue, 22 Dec 2020 15:43:47 +0000 Received: by outflank-mailman (input) for mailman id 57962; Tue, 22 Dec 2020 15:43:45 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1krjpB-0006cH-8H for xen-devel@lists.xenproject.org; Tue, 22 Dec 2020 15:43:45 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1krjpA-0001pv-Q2; Tue, 22 Dec 2020 15:43:44 +0000 Received: from 54-240-197-235.amazon.com ([54.240.197.235] helo=ufe34d9ed68d054.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1krjpA-0002Vd-Gp; Tue, 22 Dec 2020 15:43:44 +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=References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From; bh=kSPSsNxqjRsah0K2F/khe3S48PU9Vn+ea2ql+1qJVow=; b=u7zwD9TpUghLdk5/4t796dN7R OOEKsJTI9epORlTXPMuVoXxnmmbIjmRfUdkldFMZAy9GA+ZhknOA4hcvMVw4n4cUV2qqawv7dMhOd Of74k7GR4v8G7Rb07S7LfRq8ISeZ5tbsc5hBO8WlTOoK7umNxl8HSn0bLLoh193yGWF7c=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: hongyxia@amazon.co.uk, Julien Grall , Jan Beulich , Paul Durrant Subject: [PATCH for-4.15 3/4] [RFC] xen/iommu: x86: Clear the root page-table before freeing the page-tables Date: Tue, 22 Dec 2020 15:43:37 +0000 Message-Id: <20201222154338.9459-4-julien@xen.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20201222154338.9459-1-julien@xen.org> References: <20201222154338.9459-1-julien@xen.org> From: Julien Grall The new per-domain IOMMU page-table allocator will now free the page-tables when domain's resources are relinquished. However, the root page-table (i.e. hd->arch.pg_maddr) will not be cleared. Xen may access the IOMMU page-tables afterwards at least in the case of PV domain: (XEN) Xen call trace: (XEN) [] R iommu.c#addr_to_dma_page_maddr+0x12e/0x1d8 (XEN) [] F iommu.c#intel_iommu_unmap_page+0x5d/0xf8 (XEN) [] F iommu_unmap+0x9c/0x129 (XEN) [] F iommu_legacy_unmap+0x26/0x63 (XEN) [] F mm.c#cleanup_page_mappings+0x139/0x144 (XEN) [] F put_page+0x4b/0xb3 (XEN) [] F put_page_from_l1e+0x136/0x13b (XEN) [] F devalidate_page+0x256/0x8dc (XEN) [] F mm.c#_put_page_type+0x236/0x47e (XEN) [] F mm.c#put_pt_page+0x6f/0x80 (XEN) [] F mm.c#put_page_from_l2e+0x8a/0xcf (XEN) [] F devalidate_page+0x3a3/0x8dc (XEN) [] F mm.c#_put_page_type+0x236/0x47e (XEN) [] F mm.c#put_pt_page+0x6f/0x80 (XEN) [] F mm.c#put_page_from_l3e+0x8a/0xcf (XEN) [] F devalidate_page+0x56c/0x8dc (XEN) [] F mm.c#_put_page_type+0x236/0x47e (XEN) [] F mm.c#put_pt_page+0x6f/0x80 (XEN) [] F mm.c#put_page_from_l4e+0x69/0x6d (XEN) [] F devalidate_page+0x6a0/0x8dc (XEN) [] F mm.c#_put_page_type+0x236/0x47e (XEN) [] F put_page_type_preemptible+0x13/0x15 (XEN) [] F domain.c#relinquish_memory+0x1ff/0x4e9 (XEN) [] F domain_relinquish_resources+0x2b6/0x36a (XEN) [] F domain_kill+0xb8/0x141 (XEN) [] F do_domctl+0xb6f/0x18e5 (XEN) [] F pv_hypercall+0x2f0/0x55f (XEN) [] F lstar_enter+0x112/0x120 This will result to a use after-free and possibly an host crash or memory corruption. Freeing the page-tables further down in domain_relinquish_resources() would not work because pages may not be released until later if another domain hold a reference on them. Once all the PCI devices have been de-assigned, it is actually pointless to access modify the IOMMU page-tables. So we can simply clear the root page-table address. Fixes: 3eef6d07d722 ("x86/iommu: convert VT-d code to use new page table allocator") Signed-off-by: Julien Grall --- This is an RFC because it would break AMD IOMMU driver. One option would be to move the call to the teardown callback earlier on. Any opinions? --- xen/drivers/passthrough/x86/iommu.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c index 779dbb5b98ba..99a23177b3d2 100644 --- a/xen/drivers/passthrough/x86/iommu.c +++ b/xen/drivers/passthrough/x86/iommu.c @@ -267,6 +267,16 @@ int iommu_free_pgtables(struct domain *d) struct page_info *pg; unsigned int done = 0; + /* + * Pages will be moved to the free list in a bit. So we want to + * clear the root page-table to avoid any potential use after-free. + * + * XXX: This only code works for Intel vT-D. + */ + spin_lock(&hd->arch.mapping_lock); + hd->arch.vtd.pgd_maddr = 0; + spin_unlock(&hd->arch.mapping_lock); + spin_lock(&hd->arch.pgtables.lock); while ( (pg = page_list_remove_head(&hd->arch.pgtables.list)) ) {