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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 07E04C43331 for ; Mon, 1 Mar 2021 17:31:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2E916528D for ; Mon, 1 Mar 2021 17:31:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238149AbhCARa5 (ORCPT ); Mon, 1 Mar 2021 12:30:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47356 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238076AbhCARWo (ORCPT ); Mon, 1 Mar 2021 12:22:44 -0500 Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF566C061A27 for ; Mon, 1 Mar 2021 09:20:23 -0800 (PST) Received: by mail-pl1-x62f.google.com with SMTP id d11so10315937plo.8 for ; Mon, 01 Mar 2021 09:20:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=CkOp2ds10H7JHrs2ACjlS7kM4oIeGR3JMxdGORMrv/w=; b=ul130P/TIyb4+FqEAleYjjEP35j0ynkGb8FGZvO7ybk9+E8Ttp1/wVE0s9d8mLssHi YPotvWzJs4KD0i5lw4jRhewDIfn5fFK3O4Us5qzO73lUeuZK8TlhHxc965MNW95rlYfb KBESgBdJfO2UluZ9d6LR93XaSd7HBDocksZOa0hU1jC59/q8k2aYFQNidOAglwfqssr1 M/Z9emdUmE6f+XeNXx40BidwWBM8Cg/44on2D+j7e8LO/tdJj5Iul0KquNDq4l+O4aI8 ex/8vRGweOSl5QwFb88cFY/LsvwC77ubMmvZjkDZ+G2Eou3uymY9mKho74/mtVOM6Mpo +9Wg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=CkOp2ds10H7JHrs2ACjlS7kM4oIeGR3JMxdGORMrv/w=; b=dh1cy383gzC41A6vsox5YPs3GIHk4yEgbsrBNCPOzmUrCyF7ZPm/BoX48nPSShfWni skXuBqe7JNxfILfXF0UMuGWJZm4d3KR6uN+IqxO0G+AZHgowuRww5M9bMvzjF05/Xwlh UB1kPS8lJsJIRT+eSUQJZb3jz/vept2sykhuJMDsynWx3Dqjn4C3xWbW4WS57971z5C/ SPx3STb+oeVQhc7R50KWlcm0bs/n9gyZUvMQRS9w897GiI02m9/nmLM1y2URVnBZRC7o NWjJ2ckn+mNn+8liFS+SLtViN6OMhtbB5mLfh360gJsiKYcwVoqsoAXNhVC/mNN9hGH7 muWQ== X-Gm-Message-State: AOAM533+IjY7s8Cna/FdruuNFMmemMik7xWe0d/pB7Bq+Rc7hOnpQw1E dbEreLWWP96iqiKRwB5h9b4KRw== X-Google-Smtp-Source: ABdhPJw+36HCmWr/OqL/LXYgXeqn2jhJQa4myfL54PrCkCfEQWuGiprII1E/lXZIaQSsCIM5DAp7Zg== X-Received: by 2002:a17:902:aa49:b029:e4:3825:dcd2 with SMTP id c9-20020a170902aa49b02900e43825dcd2mr16353250plr.39.1614619223032; Mon, 01 Mar 2021 09:20:23 -0800 (PST) Received: from google.com ([2620:15c:f:10:5d06:6d3c:7b9:20c9]) by smtp.gmail.com with ESMTPSA id o3sm16706871pgm.60.2021.03.01.09.20.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Mar 2021 09:20:22 -0800 (PST) Date: Mon, 1 Mar 2021 09:20:15 -0800 From: Sean Christopherson To: Kai Huang Cc: kvm@vger.kernel.org, x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, jarkko@kernel.org, luto@kernel.org, dave.hansen@intel.com, rick.p.edgecombe@intel.com, haitao.huang@intel.com, pbonzini@redhat.com, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, jmattson@google.com, joro@8bytes.org, vkuznets@redhat.com, wanpengli@tencent.com Subject: Re: [PATCH 21/25] KVM: VMX: Add SGX ENCLS[ECREATE] handler to enforce CPUID restrictions Message-ID: References: <58db33aae58582de8f644b686fc99b27f39d4d8f.1614590788.git.kai.huang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <58db33aae58582de8f644b686fc99b27f39d4d8f.1614590788.git.kai.huang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Mon, Mar 01, 2021, Kai Huang wrote: > +static int handle_encls_ecreate(struct kvm_vcpu *vcpu) > +{ > + struct kvm_cpuid_entry2 *sgx_12_0, *sgx_12_1; > + gva_t pageinfo_gva, secs_gva; > + gva_t metadata_gva, contents_gva; > + gpa_t metadata_gpa, contents_gpa, secs_gpa; > + unsigned long metadata_hva, contents_hva, secs_hva; > + struct sgx_pageinfo pageinfo; > + struct sgx_secs *contents; > + u64 attributes, xfrm, size; > + u32 miscselect; > + struct x86_exception ex; > + u8 max_size_log2; > + int trapnr, r; > + (see below) --- cut here --- >8 > + sgx_12_0 = kvm_find_cpuid_entry(vcpu, 0x12, 0); > + sgx_12_1 = kvm_find_cpuid_entry(vcpu, 0x12, 1); > + if (!sgx_12_0 || !sgx_12_1) { > + kvm_inject_gp(vcpu, 0); This should probably be an emulation failure. This code is reached iff SGX1 is enabled in the guest, userspace done messed up if they enabled SGX1 without defining CPUID.0x12.1. That also makes it more obvious that burying this in a helper after a bunch of other checks isn't wrong, i.e. KVM has already verified that SGX1 is enabled in the guest. > + return 1; > + } --- > + > + if (sgx_get_encls_gva(vcpu, kvm_rbx_read(vcpu), 32, 32, &pageinfo_gva) || > + sgx_get_encls_gva(vcpu, kvm_rcx_read(vcpu), 4096, 4096, &secs_gva)) > + return 1; > + > + /* > + * Copy the PAGEINFO to local memory, its pointers need to be > + * translated, i.e. we need to do a deep copy/translate. > + */ > + r = kvm_read_guest_virt(vcpu, pageinfo_gva, &pageinfo, > + sizeof(pageinfo), &ex); > + if (r == X86EMUL_PROPAGATE_FAULT) { > + kvm_inject_emulated_page_fault(vcpu, &ex); > + return 1; > + } else if (r != X86EMUL_CONTINUE) { > + sgx_handle_emulation_failure(vcpu, pageinfo_gva, size); > + return 0; > + } > + > + if (sgx_get_encls_gva(vcpu, pageinfo.metadata, 64, 64, &metadata_gva) || > + sgx_get_encls_gva(vcpu, pageinfo.contents, 4096, 4096, > + &contents_gva)) > + return 1; > + > + /* > + * Translate the SECINFO, SOURCE and SECS pointers from GVA to GPA. > + * Resume the guest on failure to inject a #PF. > + */ > + if (sgx_gva_to_gpa(vcpu, metadata_gva, false, &metadata_gpa) || > + sgx_gva_to_gpa(vcpu, contents_gva, false, &contents_gpa) || > + sgx_gva_to_gpa(vcpu, secs_gva, true, &secs_gpa)) > + return 1; > + > + /* > + * ...and then to HVA. The order of accesses isn't architectural, i.e. > + * KVM doesn't have to fully process one address at a time. Exit to > + * userspace if a GPA is invalid. > + */ > + if (sgx_gpa_to_hva(vcpu, metadata_gpa, &metadata_hva) || > + sgx_gpa_to_hva(vcpu, contents_gpa, &contents_hva) || > + sgx_gpa_to_hva(vcpu, secs_gpa, &secs_hva)) > + return 0; > + /* > + * Copy contents into kernel memory to prevent TOCTOU attack. E.g. the > + * guest could do ECREATE w/ SECS.SGX_ATTR_PROVISIONKEY=0, and > + * simultaneously set SGX_ATTR_PROVISIONKEY to bypass the check to > + * enforce restriction of access to the PROVISIONKEY. > + */ > + contents = (struct sgx_secs *)__get_free_page(GFP_KERNEL); > + if (!contents) > + return -ENOMEM; --- cut here --- >8 > + > + /* Exit to userspace if copying from a host userspace address fails. */ > + if (sgx_read_hva(vcpu, contents_hva, (void *)contents, PAGE_SIZE)) This, and every failure path below, will leak 'contents'. The easiest thing is probably to wrap everything in "cut here" in a separate helper. The CPUID lookups can be , e.g. contents = (struct sgx_secs *)__get_free_page(GFP_KERNEL); if (!contents) return -ENOMEM; r = __handle_encls_ecreate(vcpu, &pageinfo, secs); free_page((unsigned long)contents); return r; And then the helper can be everything below, plus the CPUID lookup: sgx_12_0 = kvm_find_cpuid_entry(vcpu, 0x12, 0); sgx_12_1 = kvm_find_cpuid_entry(vcpu, 0x12, 1); if (!sgx_12_0 || !sgx_12_1) { vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; vcpu->run->internal.ndata = 0; return 0; } > + return 0; > + > + miscselect = contents->miscselect; > + attributes = contents->attributes; > + xfrm = contents->xfrm; > + size = contents->size; > + > + /* Enforce restriction of access to the PROVISIONKEY. */ > + if (!vcpu->kvm->arch.sgx_provisioning_allowed && > + (attributes & SGX_ATTR_PROVISIONKEY)) { > + if (sgx_12_1->eax & SGX_ATTR_PROVISIONKEY) > + pr_warn_once("KVM: SGX PROVISIONKEY advertised but not allowed\n"); > + kvm_inject_gp(vcpu, 0); > + return 1; > + } > + > + /* Enforce CPUID restrictions on MISCSELECT, ATTRIBUTES and XFRM. */ > + if ((u32)miscselect & ~sgx_12_0->ebx || > + (u32)attributes & ~sgx_12_1->eax || > + (u32)(attributes >> 32) & ~sgx_12_1->ebx || > + (u32)xfrm & ~sgx_12_1->ecx || > + (u32)(xfrm >> 32) & ~sgx_12_1->edx) { > + kvm_inject_gp(vcpu, 0); > + return 1; > + } > + > + /* Enforce CPUID restriction on max enclave size. */ > + max_size_log2 = (attributes & SGX_ATTR_MODE64BIT) ? sgx_12_0->edx >> 8 : > + sgx_12_0->edx; > + if (size >= BIT_ULL(max_size_log2)) > + kvm_inject_gp(vcpu, 0); > + > + pageinfo.metadata = metadata_hva; > + pageinfo.contents = (u64)contents; > + > + r = sgx_virt_ecreate(&pageinfo, (void __user *)secs_hva, &trapnr); > + > + free_page((unsigned long)contents); > + > + if (r) > + return sgx_inject_fault(vcpu, secs_gva, trapnr); > + > + return kvm_skip_emulated_instruction(vcpu); --- > +} > + > static inline bool encls_leaf_enabled_in_guest(struct kvm_vcpu *vcpu, u32 leaf) > { > if (!enable_sgx || !guest_cpuid_has(vcpu, X86_FEATURE_SGX)) > @@ -41,6 +286,8 @@ int handle_encls(struct kvm_vcpu *vcpu) > } else if (!sgx_enabled_in_guest_bios(vcpu)) { > kvm_inject_gp(vcpu, 0); > } else { > + if (leaf == ECREATE) > + return handle_encls_ecreate(vcpu); > WARN(1, "KVM: unexpected exit on ENCLS[%u]", leaf); > vcpu->run->exit_reason = KVM_EXIT_UNKNOWN; > vcpu->run->hw.hardware_exit_reason = EXIT_REASON_ENCLS; > -- > 2.29.2 >