From patchwork Tue Feb 23 12:34:33 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 12100291 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 6EA94C43381 for ; Tue, 23 Feb 2021 12:34:52 +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 2E57264E4B for ; Tue, 23 Feb 2021 12:34:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E57264E4B 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.88758.167056 (Exim 4.92) (envelope-from ) id 1lEWtj-0008UY-HQ; Tue, 23 Feb 2021 12:34:39 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 88758.167056; Tue, 23 Feb 2021 12:34:39 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lEWtj-0008UP-Dl; Tue, 23 Feb 2021 12:34:39 +0000 Received: by outflank-mailman (input) for mailman id 88758; Tue, 23 Feb 2021 12:34:38 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lEWti-0008Sw-4l for xen-devel@lists.xenproject.org; Tue, 23 Feb 2021 12:34:38 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lEWth-0002e2-NV; Tue, 23 Feb 2021 12:34:37 +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 1lEWth-0000cJ-F6; Tue, 23 Feb 2021 12:34:37 +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=rHfC/wahEJYSijbiVGgEzgUQtxG8SVxu1zXJPzObAQE=; b=SphyqBbfEuOUuRq48A581W8Xk RZ2tIxprE1m2FJrKTMYslahhcwruXd8/SBSyo5UpyPQt7vd4kXoD0Vs+FQYeyt1OwPvWMTqruce2q Zfwl5TAhnWL20YNkvgFipjNY6zawL+xjAApo98egh85rpBJW0WlmNxZYmBT1l+nsjg7l4=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: hongyxia@amazon.co.uk, iwj@xenproject.org, Julien Grall Subject: [for-4.15][PATCH v4 2/2] xen/iommu: x86: Clear the root page-table before freeing the page-tables Date: Tue, 23 Feb 2021 12:34:33 +0000 Message-Id: <20210223123433.19645-3-julien@xen.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210223123433.19645-1-julien@xen.org> References: <20210223123433.19645-1-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 per-domain IOMMU structure will still contain a dangling pointer to the root page-table. 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. It would not be possible to free the page-tables further down in domain_relinquish_resources() because cleanup_page_mappings() will only be called when the last reference on the page dropped. This may happen much later if another domain still hold a reference. After all the PCI devices have been de-assigned, nobody should use the IOMMU page-tables and it is therefore pointless to try to modify them. So we can simply clear any reference to the root page-table in the per-domain IOMMU structure. This requires to introduce a new callback of the method will depend on the IOMMU driver used. Take the opportunity to add an ASSERT() in arch_iommu_domain_destroy() to check if we freed all the IOMMU page tables. Fixes: 3eef6d07d722 ("x86/iommu: convert VT-d code to use new page table allocator") Signed-off-by: Julien Grall --- Changes in v4: - Move the patch later in the series as we need to prevent iommu_map() to allocate memory first. - Add an ASSERT() in arch_iommu_domain_destroy(). Changes in v3: - Move the patch earlier in the series - Reword the commit message Changes in v2: - Introduce clear_root_pgtable() - Move the patch later in the series --- xen/drivers/passthrough/amd/pci_amd_iommu.c | 12 +++++++++++- xen/drivers/passthrough/vtd/iommu.c | 12 +++++++++++- xen/drivers/passthrough/x86/iommu.c | 13 +++++++++++++ xen/include/xen/iommu.h | 1 + 4 files changed, 36 insertions(+), 2 deletions(-) diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c b/xen/drivers/passthrough/amd/pci_amd_iommu.c index 42b5a5a9bec4..085fe2f5771e 100644 --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c @@ -381,9 +381,18 @@ static int amd_iommu_assign_device(struct domain *d, u8 devfn, return reassign_device(pdev->domain, d, devfn, pdev); } +static void amd_iommu_clear_root_pgtable(struct domain *d) +{ + struct domain_iommu *hd = dom_iommu(d); + + spin_lock(&hd->arch.mapping_lock); + hd->arch.amd.root_table = NULL; + spin_unlock(&hd->arch.mapping_lock); +} + static void amd_iommu_domain_destroy(struct domain *d) { - dom_iommu(d)->arch.amd.root_table = NULL; + ASSERT(!dom_iommu(d)->arch.amd.root_table); } static int amd_iommu_add_device(u8 devfn, struct pci_dev *pdev) @@ -565,6 +574,7 @@ static const struct iommu_ops __initconstrel _iommu_ops = { .remove_device = amd_iommu_remove_device, .assign_device = amd_iommu_assign_device, .teardown = amd_iommu_domain_destroy, + .clear_root_pgtable = amd_iommu_clear_root_pgtable, .map_page = amd_iommu_map_page, .unmap_page = amd_iommu_unmap_page, .iotlb_flush = amd_iommu_flush_iotlb_pages, diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c index b549a71530d5..475efb3be3bd 100644 --- a/xen/drivers/passthrough/vtd/iommu.c +++ b/xen/drivers/passthrough/vtd/iommu.c @@ -1726,6 +1726,15 @@ out: return ret; } +static void iommu_clear_root_pgtable(struct domain *d) +{ + struct domain_iommu *hd = dom_iommu(d); + + spin_lock(&hd->arch.mapping_lock); + hd->arch.vtd.pgd_maddr = 0; + spin_unlock(&hd->arch.mapping_lock); +} + static void iommu_domain_teardown(struct domain *d) { struct domain_iommu *hd = dom_iommu(d); @@ -1740,7 +1749,7 @@ static void iommu_domain_teardown(struct domain *d) xfree(mrmrr); } - hd->arch.vtd.pgd_maddr = 0; + ASSERT(!hd->arch.vtd.pgd_maddr); } static int __must_check intel_iommu_map_page(struct domain *d, dfn_t dfn, @@ -2731,6 +2740,7 @@ static struct iommu_ops __initdata vtd_ops = { .remove_device = intel_iommu_remove_device, .assign_device = intel_iommu_assign_device, .teardown = iommu_domain_teardown, + .clear_root_pgtable = iommu_clear_root_pgtable, .map_page = intel_iommu_map_page, .unmap_page = intel_iommu_unmap_page, .lookup_page = intel_iommu_lookup_page, diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c index c6b03624fe28..faeb549591d8 100644 --- a/xen/drivers/passthrough/x86/iommu.c +++ b/xen/drivers/passthrough/x86/iommu.c @@ -149,6 +149,13 @@ int arch_iommu_domain_init(struct domain *d) void arch_iommu_domain_destroy(struct domain *d) { + /* + * There should be not page-tables left allocated by the time the + * domain is destroyed. Note that arch_iommu_domain_destroy() is + * called unconditionally, so pgtables may be unitialized. + */ + ASSERT(dom_iommu(d)->platform_ops == NULL || + page_list_empty(&dom_iommu(d)->arch.pgtables.list)); } static bool __hwdom_init hwdom_iommu_map(const struct domain *d, @@ -273,6 +280,12 @@ int iommu_free_pgtables(struct domain *d) /* After this barrier, no more IOMMU mapping can happen */ spin_barrier(&hd->arch.mapping_lock); + /* + * 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); + while ( (pg = page_list_remove_head(&hd->arch.pgtables.list)) ) { free_domheap_page(pg); diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h index 863a68fe1622..d59ed7cbad43 100644 --- a/xen/include/xen/iommu.h +++ b/xen/include/xen/iommu.h @@ -272,6 +272,7 @@ struct iommu_ops { int (*adjust_irq_affinities)(void); void (*sync_cache)(const void *addr, unsigned int size); + void (*clear_root_pgtable)(struct domain *d); #endif /* CONFIG_X86 */ int __must_check (*suspend)(void);