From patchwork Wed Feb 17 14:24:56 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 12091703 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 47B41C433DB for ; Wed, 17 Feb 2021 14:25:27 +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 DB20164E5B for ; Wed, 17 Feb 2021 14:25:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB20164E5B 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.86283.161866 (Exim 4.92) (envelope-from ) id 1lCNlN-0005KJ-Tq; Wed, 17 Feb 2021 14:25:09 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 86283.161866; Wed, 17 Feb 2021 14:25:09 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlN-0005K6-MU; Wed, 17 Feb 2021 14:25:09 +0000 Received: by outflank-mailman (input) for mailman id 86283; Wed, 17 Feb 2021 14:25:08 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlM-0005JW-KY for xen-devel@lists.xenproject.org; Wed, 17 Feb 2021 14:25:08 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlJ-0004eR-Rh; Wed, 17 Feb 2021 14:25:05 +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 1lCNlJ-00057m-Fa; Wed, 17 Feb 2021 14:25:05 +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=E10KWobPtnAxShnfJroEM2NY8XPPcudrmSVydi6i4NA=; b=kMCv4+ftElp2JtZlu3sfOUMXe W4wdDP4OTTLeHmeSn+X/qNJwqRQlDtAyI4YE6aX64pUTNugb2TNnXjMUuGj6zQy3esu/i8juW89EL CEZ4iWtCGncr3Ie7CLnIDBBlyFyx2iXp6TPKpQNA2kSmawFCCQ7QqPN2s3af4kcQ7qp7Q=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: hongyxia@amazon.co.uk, iwj@xenproject.org, Julien Grall , Jan Beulich , Andrew Cooper , Kevin Tian , Paul Durrant Subject: [for-4.15][PATCH v3 1/3] xen/iommu: x86: Clear the root page-table before freeing the page-tables Date: Wed, 17 Feb 2021 14:24:56 +0000 Message-Id: <20210217142458.3769-2-julien@xen.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210217142458.3769-1-julien@xen.org> References: <20210217142458.3769-1-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. Fixes: 3eef6d07d722 ("x86/iommu: convert VT-d code to use new page table allocator") Signed-off-by: Julien Grall --- 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 | 9 +++++++++ xen/include/xen/iommu.h | 1 + 4 files changed, 32 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..81add0ba26b4 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 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 = 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 d136fe36883b..e1871f6c2bc1 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, @@ -2719,6 +2728,7 @@ 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 cea1032b3d02..f54fc8093f18 100644 --- 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); + 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); From patchwork Wed Feb 17 14:24:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 12091705 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 444BFC433E0 for ; Wed, 17 Feb 2021 14:25:27 +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 DB0DE64E4D for ; Wed, 17 Feb 2021 14:25:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB0DE64E4D 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.86285.161885 (Exim 4.92) (envelope-from ) id 1lCNlO-0005Ln-Kf; Wed, 17 Feb 2021 14:25:10 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 86285.161885; Wed, 17 Feb 2021 14:25:10 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlO-0005LS-At; Wed, 17 Feb 2021 14:25:10 +0000 Received: by outflank-mailman (input) for mailman id 86285; Wed, 17 Feb 2021 14:25:09 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlM-0005Jc-W0 for xen-devel@lists.xenproject.org; Wed, 17 Feb 2021 14:25:08 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlL-0004eT-3C; Wed, 17 Feb 2021 14:25:07 +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 1lCNlK-00057m-QC; Wed, 17 Feb 2021 14:25:07 +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=t6YsWVHT5mEBG6Q0BImhmwLAtI3B16h1jksP0n7ERIQ=; b=3uZES943amRECcWSte8d/Dw7R ooUX+hMcyyiJcd2+SiVkaL03GfOgZudyjNCtUsOlGFIAXRWUKX6zPL084P0mq3UBltQLNE3oIQNtO zRGebw4/RErIbC+mIgjphC42rG3SWLKaKVC/grLUGVeLLo8qTPRk6Fg09klw7eKzFDrbQ=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: hongyxia@amazon.co.uk, iwj@xenproject.org, Julien Grall , Jan Beulich , Andrew Cooper , Kevin Tian , Paul Durrant Subject: [for-4.15][PATCH v3 2/3] xen/x86: iommu: Ignore IOMMU mapping requests when a domain is dying Date: Wed, 17 Feb 2021 14:24:57 +0000 Message-Id: <20210217142458.3769-3-julien@xen.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210217142458.3769-1-julien@xen.org> References: <20210217142458.3769-1-julien@xen.org> From: Julien Grall The new x86 IOMMU page-tables allocator will release the pages when relinquishing the domain resources. However, this is not sufficient when the domain is dying because nothing prevents page-table to be allocated. Currently page-table allocations can only happen from iommu_map(). As the domain is dying, there is no good reason to continue to modify the IOMMU page-tables. In order to observe d->is_dying correctly, we need to rely on per-arch locking, so the check to ignore IOMMU mapping is added on the per-driver map_page() callback. Signed-off-by: Julien Grall --- Changes in v3: - Patch added. This is a replacement of "xen/iommu: iommu_map: Don't crash the domain if it is dying" --- xen/drivers/passthrough/amd/iommu_map.c | 13 +++++++++++++ xen/drivers/passthrough/vtd/iommu.c | 13 +++++++++++++ xen/drivers/passthrough/x86/iommu.c | 3 +++ 3 files changed, 29 insertions(+) diff --git a/xen/drivers/passthrough/amd/iommu_map.c b/xen/drivers/passthrough/amd/iommu_map.c index d3a8b1aec766..ed78a083ba12 100644 --- a/xen/drivers/passthrough/amd/iommu_map.c +++ b/xen/drivers/passthrough/amd/iommu_map.c @@ -285,6 +285,19 @@ int amd_iommu_map_page(struct domain *d, dfn_t dfn, mfn_t mfn, spin_lock(&hd->arch.mapping_lock); + /* + * IOMMU mapping request can be safely ignored when the domain is dying. + * + * hd->arch.mapping_lock guarantees that d->is_dying will be observed + * before any page tables are freed (see iommu_free_pgtables() and + * iommu_clear_root_pgtable()). + */ + if ( d->is_dying ) + { + spin_unlock(&hd->arch.mapping_lock); + return 0; + } + rc = amd_iommu_alloc_root(d); if ( rc ) { diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c index e1871f6c2bc1..239a63f74f64 100644 --- a/xen/drivers/passthrough/vtd/iommu.c +++ b/xen/drivers/passthrough/vtd/iommu.c @@ -1771,6 +1771,19 @@ static int __must_check intel_iommu_map_page(struct domain *d, dfn_t dfn, spin_lock(&hd->arch.mapping_lock); + /* + * IOMMU mapping request can be safely ignored when the domain is dying. + * + * hd->arch.mapping_lock guarantees that d->is_dying will be observed + * before any page tables are freed (see iommu_free_pgtables() and + * iommu_clear_root_pgtable()). + */ + if ( d->is_dying ) + { + spin_unlock(&hd->arch.mapping_lock); + return 0; + } + pg_maddr = addr_to_dma_page_maddr(d, dfn_to_daddr(dfn), 1); if ( !pg_maddr ) { diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c index f54fc8093f18..faa0078db595 100644 --- a/xen/drivers/passthrough/x86/iommu.c +++ b/xen/drivers/passthrough/x86/iommu.c @@ -273,6 +273,9 @@ int iommu_free_pgtables(struct domain *d) /* * 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. + * + * After this call, no more IOMMU mapping can happen. + * */ hd->platform_ops->clear_root_pgtable(d); From patchwork Wed Feb 17 14:24:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 12091707 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 53CF6C433E9 for ; Wed, 17 Feb 2021 14:25:28 +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 0244864E4A for ; Wed, 17 Feb 2021 14:25:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0244864E4A 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.86284.161875 (Exim 4.92) (envelope-from ) id 1lCNlO-0005L2-6e; Wed, 17 Feb 2021 14:25:10 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 86284.161875; Wed, 17 Feb 2021 14:25:10 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlO-0005Kq-0d; Wed, 17 Feb 2021 14:25:10 +0000 Received: by outflank-mailman (input) for mailman id 86284; Wed, 17 Feb 2021 14:25:09 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlM-0005Jb-Vv for xen-devel@lists.xenproject.org; Wed, 17 Feb 2021 14:25:08 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lCNlM-0004eb-6H; Wed, 17 Feb 2021 14:25:08 +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 1lCNlL-00057m-TP; Wed, 17 Feb 2021 14:25:08 +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=eHbALjFmdHYfqoCsH6vCHJNGB5r0g1/oYxtKAGV8sK0=; b=JYG72ERHoej3PUjHk2Ezhu6HI 6R/Jd6aWbu6IG7m/idXbr+zjnMm4YDUpSLitQsM0p3sdFlVMYxW+Y4SehyOKFh6vWnDyufcfjxkcE giAPs4bmXmGSCWr/sm29fqlQmzIR+ogVnElCABJ24D83UU9bgwQGoOm1acNo3zL1PLYMs=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: hongyxia@amazon.co.uk, iwj@xenproject.org, Julien Grall , Jan Beulich , Paul Durrant Subject: [for-4.15][PATCH v3 3/3] xen/iommu: x86: Harden the IOMMU page-table allocator Date: Wed, 17 Feb 2021 14:24:58 +0000 Message-Id: <20210217142458.3769-4-julien@xen.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210217142458.3769-1-julien@xen.org> References: <20210217142458.3769-1-julien@xen.org> From: Julien Grall At the moment, we are assuming that only iommu_map() can allocate IOMMU page-table. Given the complexity of the IOMMU framework, it would be sensible to have a check closer to the IOMMU allocator. This would avoid to leak IOMMU page-tables again in the future. iommu_alloc_pgtable() is now checking if the domain is dying before adding the page in the list. We are relying on &hd->arch.pgtables.lock to synchronize d->is_dying. Take the opportunity to add an ASSERT() in arch_iommu_domain_destroy() to check if we freed all the IOMMU page tables. Signed-off-by: Julien Grall --- Changes in v3: - Rename the patch. This was originally "xen/iommu: x86: Don't leak the IOMMU page-tables" - Rework the commit message - Move the patch towards the end of the series Changes in v2: - Rework the approach - Move the patch earlier in the series --- xen/drivers/passthrough/x86/iommu.c | 33 ++++++++++++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c index faa0078db595..a67075f0045d 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, @@ -279,6 +286,9 @@ int iommu_free_pgtables(struct domain *d) */ hd->platform_ops->clear_root_pgtable(d); + /* After this barrier no new page allocations can occur. */ + spin_barrier(&hd->arch.pgtables.lock); + while ( (pg = page_list_remove_head(&hd->arch.pgtables.list)) ) { free_domheap_page(pg); @@ -296,6 +306,7 @@ struct page_info *iommu_alloc_pgtable(struct domain *d) unsigned int memflags = 0; struct page_info *pg; void *p; + bool alive = false; #ifdef CONFIG_NUMA if ( hd->node != NUMA_NO_NODE ) @@ -315,9 +326,29 @@ struct page_info *iommu_alloc_pgtable(struct domain *d) unmap_domain_page(p); spin_lock(&hd->arch.pgtables.lock); - page_list_add(pg, &hd->arch.pgtables.list); + /* + * The IOMMU page-tables are freed when relinquishing the domain, but + * nothing prevent allocation to happen afterwards. There is no valid + * reasons to continue to update the IOMMU page-tables while the + * domain is dying. + * + * So prevent page-table allocation when the domain is dying. + * + * We relying on &hd->arch.pgtables.lock to synchronize d->is_dying. + */ + if ( likely(!d->is_dying) ) + { + alive = true; + page_list_add(pg, &hd->arch.pgtables.list); + } spin_unlock(&hd->arch.pgtables.lock); + if ( unlikely(!alive) ) + { + free_domheap_page(pg); + pg = NULL; + } + return pg; }