From: Kai Huang <kai.huang@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"Huang, Haitao" <haitao.huang@intel.com>,
"luto@kernel.org" <luto@kernel.org>,
"jarkko@kernel.org" <jarkko@kernel.org>,
"Hansen, Dave" <dave.hansen@intel.com>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"hpa@zytor.com" <hpa@zytor.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"wanpengli@tencent.com" <wanpengli@tencent.com>,
"jmattson@google.com" <jmattson@google.com>
Subject: Re: [RFC PATCH v3 23/27] KVM: VMX: Add SGX ENCLS[ECREATE] handler to enforce CPUID restrictions
Date: Thu, 04 Feb 2021 12:45:34 +1300 [thread overview]
Message-ID: <d5dd889484f6b8c3786ffe75c1505beb944275b3.camel@intel.com> (raw)
In-Reply-To: <YBszcbHsIlo4I8WC@google.com>
On Wed, 2021-02-03 at 15:36 -0800, Sean Christopherson wrote:
> On Thu, Feb 04, 2021, Kai Huang wrote:
> > On Wed, 2021-02-03 at 11:36 -0800, Sean Christopherson wrote:
> > > On Wed, Feb 03, 2021, Edgecombe, Rick P wrote:
> > > > On Tue, 2021-01-26 at 22:31 +1300, Kai Huang wrote:
> > > > > + /* Exit to userspace if copying from a host userspace address
> > > > > fails. */
> > > > > + if (sgx_read_hva(vcpu, m_hva, &miscselect,
> > > > > sizeof(miscselect)) ||
> > > > > + sgx_read_hva(vcpu, a_hva, &attributes,
> > > > > sizeof(attributes)) ||
> > > > > + sgx_read_hva(vcpu, x_hva, &xfrm, sizeof(xfrm)) ||
> > > > > + sgx_read_hva(vcpu, s_hva, &size, sizeof(size)))
> > > > > + return 0;
> > > > > +
> > > > > + /* 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;
> > > > > + }
> > > >
> > > > Don't you need to deep copy the pageinfo.contents struct as well?
> > > > Otherwise the guest could change these after they were checked.
> > > >
> > > > But it seems it is checked by the HW and something is caught that would
> > > > inject a GP anyway? Can you elaborate on the importance of these
> > > > checks?
> > >
> > > Argh, yes. These checks are to allow migration between systems with different
> > > SGX capabilities, and more importantly to prevent userspace from doing an end
> > > around on the restricted access to PROVISIONKEY.
> > >
> > > IIRC, earlier versions did do a deep copy, but then I got clever. Anyways, yeah,
> > > sadly the entire pageinfo.contents page will need to be copied.
> >
> > I don't fully understand the problem. Are you worried about contents being updated by
> > other vcpus during the trap?
> >
> > And I don't see how copy can avoid this problem. Even you do copy, the content can
> > still be modified afterwards, correct? So what's the point of copying?
>
> The goal isn't correctness, it's to prevent a TOCTOU bug. E.g. the guest could
> do ECREATE w/ SECS.SGX_ATTR_PROVISIONKEY=0, and simultaneously set
> SGX_ATTR_PROVISIONKEY to bypass the above check.
Oh ok. Agreed.
However, such attack would require precise timing. Not sure whether it is feasible in
practice.
>
> > Looks a better solution is to kick all vcpus and put them into block state
> > while KVM is doing ENCLS for guest.
>
> No. (a) it won't work, as the memory is writable from host userspace. (b) that
> does not scale, at all.
Good point. Agreed.
next prev parent reply other threads:[~2021-02-03 23:46 UTC|newest]
Thread overview: 156+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 10:10 [RFC PATCH v3 00/27] KVM SGX virtualization support Kai Huang
2021-01-26 9:29 ` Kai Huang
2021-01-26 9:30 ` [RFC PATCH v3 01/27] x86/cpufeatures: Add SGX1 and SGX2 sub-features Kai Huang
2021-01-26 15:34 ` Dave Hansen
2021-01-26 23:18 ` Kai Huang
2021-01-30 13:20 ` Jarkko Sakkinen
2021-02-01 0:01 ` Kai Huang
2021-02-02 17:17 ` Jarkko Sakkinen
2021-02-03 1:09 ` Kai Huang
2021-02-02 17:56 ` Paolo Bonzini
2021-02-02 18:00 ` Dave Hansen
2021-02-02 18:03 ` Paolo Bonzini
2021-02-02 18:42 ` Sean Christopherson
2021-02-03 1:05 ` Kai Huang
2021-01-30 13:11 ` Jarkko Sakkinen
2021-01-26 9:30 ` [RFC PATCH v3 02/27] x86/cpufeatures: Make SGX_LC feature bit depend on SGX bit Kai Huang
2021-01-26 15:35 ` Dave Hansen
2021-01-30 13:22 ` Jarkko Sakkinen
2021-02-01 0:08 ` Kai Huang
2021-01-26 9:30 ` [RFC PATCH v3 03/27] x86/sgx: Remove a warn from sgx_free_epc_page() Kai Huang
2021-01-26 15:39 ` Dave Hansen
2021-01-26 16:30 ` Sean Christopherson
2021-01-27 1:08 ` Kai Huang
2021-01-27 1:12 ` Dave Hansen
2021-01-27 1:26 ` Kai Huang
2021-02-01 0:11 ` Kai Huang
2021-02-03 10:03 ` Jarkko Sakkinen
2021-01-26 9:30 ` [RFC PATCH v3 04/27] x86/sgx: Wipe out EREMOVE " Kai Huang
2021-01-26 16:04 ` Dave Hansen
2021-01-27 1:25 ` Kai Huang
2021-02-02 18:00 ` Paolo Bonzini
2021-02-02 19:25 ` Kai Huang
2021-02-02 19:02 ` Dave Hansen
2021-01-26 9:30 ` [RFC PATCH v3 05/27] x86/sgx: Add SGX_CHILD_PRESENT hardware error code Kai Huang
2021-01-26 15:49 ` Dave Hansen
2021-01-27 0:00 ` Kai Huang
2021-01-27 0:21 ` Dave Hansen
2021-01-27 0:52 ` Kai Huang
2021-01-26 9:30 ` [RFC PATCH v3 06/27] x86/sgx: Introduce virtual EPC for use by KVM guests Kai Huang
2021-01-26 16:19 ` Dave Hansen
2021-01-27 0:16 ` Kai Huang
2021-01-27 0:27 ` Dave Hansen
2021-01-27 0:48 ` Kai Huang
2021-01-30 14:41 ` Jarkko Sakkinen
2021-01-26 9:30 ` [RFC PATCH v3 07/27] x86/cpu/intel: Allow SGX virtualization without Launch Control support Kai Huang
2021-01-26 16:26 ` Dave Hansen
2021-01-26 17:00 ` Sean Christopherson
2021-01-26 23:54 ` Kai Huang
2021-01-26 23:56 ` Kai Huang
2021-01-27 0:18 ` Dave Hansen
2021-01-27 2:02 ` Kai Huang
2021-01-27 17:13 ` Sean Christopherson
2021-01-30 14:42 ` Jarkko Sakkinen
2021-02-01 5:38 ` Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 08/27] x86/sgx: Initialize virtual EPC driver even when SGX driver is disabled Kai Huang
2021-01-26 17:03 ` Dave Hansen
2021-01-26 18:10 ` Andy Lutomirski
2021-01-26 23:25 ` Kai Huang
2021-01-30 14:45 ` Jarkko Sakkinen
2021-02-01 5:40 ` Kai Huang
2021-02-01 15:25 ` Dave Hansen
2021-02-01 17:23 ` Sean Christopherson
2021-02-02 0:12 ` Kai Huang
2021-02-02 23:10 ` Jarkko Sakkinen
2021-02-02 23:07 ` Jarkko Sakkinen
2021-02-02 17:32 ` Jarkko Sakkinen
2021-02-02 18:20 ` Sean Christopherson
2021-02-02 23:16 ` Jarkko Sakkinen
2021-02-03 0:49 ` Kai Huang
2021-02-03 22:02 ` Jarkko Sakkinen
2021-02-03 22:59 ` Sean Christopherson
2021-02-04 1:39 ` Jarkko Sakkinen
2021-02-04 2:59 ` Kai Huang
2021-02-04 3:05 ` Jarkko Sakkinen
2021-02-04 3:09 ` Jarkko Sakkinen
2021-02-04 3:20 ` Kai Huang
2021-02-04 14:51 ` Jarkko Sakkinen
2021-02-04 22:41 ` Dave Hansen
2021-02-04 22:56 ` Kai Huang
2021-02-05 2:08 ` Jarkko Sakkinen
2021-02-05 3:00 ` Huang, Kai
2021-02-02 18:49 ` Kai Huang
2021-02-02 23:17 ` Jarkko Sakkinen
2021-01-26 9:31 ` [RFC PATCH v3 09/27] x86/sgx: Expose SGX architectural definitions to the kernel Kai Huang
2021-01-30 14:46 ` Jarkko Sakkinen
2021-01-26 9:31 ` [RFC PATCH v3 10/27] x86/sgx: Move ENCLS leaf definitions to sgx_arch.h Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 11/27] x86/sgx: Add SGX2 ENCLS leaf definitions (EAUG, EMODPR and EMODT) Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 12/27] x86/sgx: Add encls_faulted() helper Kai Huang
2021-01-30 14:48 ` Jarkko Sakkinen
2021-01-26 9:31 ` [RFC PATCH v3 13/27] x86/sgx: Add helper to update SGX_LEPUBKEYHASHn MSRs Kai Huang
2021-01-30 14:49 ` Jarkko Sakkinen
2021-02-01 1:17 ` Kai Huang
2021-02-01 21:22 ` Dave Hansen
2021-01-26 9:31 ` [RFC PATCH v3 14/27] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM Kai Huang
2021-01-30 14:51 ` Jarkko Sakkinen
2021-02-01 0:17 ` Kai Huang
2021-02-02 17:20 ` Jarkko Sakkinen
2021-02-02 20:35 ` Kai Huang
2021-02-04 3:53 ` Kai Huang
2021-02-05 0:32 ` Sean Christopherson
2021-02-05 1:39 ` Huang, Kai
2021-01-26 9:31 ` [RFC PATCH v3 15/27] x86/sgx: Move provisioning device creation out of SGX driver Kai Huang
2021-01-30 14:52 ` Jarkko Sakkinen
2021-01-26 9:31 ` [RFC PATCH v3 16/27] KVM: VMX: Convert vcpu_vmx.exit_reason to a union Kai Huang
2021-01-30 15:00 ` Jarkko Sakkinen
2021-02-01 0:32 ` Kai Huang
2021-02-02 17:24 ` Jarkko Sakkinen
2021-02-02 19:23 ` Kai Huang
2021-02-02 22:41 ` Jarkko Sakkinen
2021-02-03 0:42 ` Kai Huang
2021-02-01 17:12 ` Sean Christopherson
2021-02-02 22:38 ` Jarkko Sakkinen
2021-01-26 9:31 ` [RFC PATCH v3 17/27] KVM: x86: Export kvm_mmu_gva_to_gpa_{read,write}() for SGX (VMX) Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 18/27] KVM: x86: Define new #PF SGX error code bit Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 19/27] KVM: x86: Add support for reverse CPUID lookup of scattered features Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 20/27] KVM: x86: Add reverse-CPUID lookup support for scattered SGX features Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 21/27] KVM: VMX: Add basic handling of VM-Exit from SGX enclave Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 22/27] KVM: VMX: Frame in ENCLS handler for SGX virtualization Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 23/27] KVM: VMX: Add SGX ENCLS[ECREATE] handler to enforce CPUID restrictions Kai Huang
2021-02-03 0:52 ` Edgecombe, Rick P
2021-02-03 1:36 ` Sean Christopherson
2021-02-03 9:11 ` Kai Huang
2021-02-03 17:07 ` Sean Christopherson
2021-02-03 23:11 ` Kai Huang
2021-02-03 18:47 ` Edgecombe, Rick P
2021-02-03 19:36 ` Sean Christopherson
2021-02-03 23:29 ` Kai Huang
2021-02-03 23:36 ` Sean Christopherson
2021-02-03 23:45 ` Kai Huang [this message]
2021-02-03 23:59 ` Sean Christopherson
2021-02-04 0:11 ` Kai Huang
2021-02-04 2:01 ` Sean Christopherson
2021-01-26 9:31 ` [RFC PATCH v3 24/27] KVM: VMX: Add emulation of SGX Launch Control LE hash MSRs Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 25/27] KVM: VMX: Add ENCLS[EINIT] handler to support SGX Launch Control (LC) Kai Huang
2021-01-26 9:31 ` [RFC PATCH v3 26/27] KVM: VMX: Enable SGX virtualization for SGX1, SGX2 and LC Kai Huang
2021-01-26 9:32 ` [RFC PATCH v3 27/27] KVM: x86: Add capability to grant VM access to privileged SGX attribute Kai Huang
2021-02-02 22:21 ` [RFC PATCH v3 00/27] KVM SGX virtualization support Edgecombe, Rick P
2021-02-02 22:33 ` Sean Christopherson
2021-02-02 23:21 ` Dave Hansen
2021-02-02 23:56 ` Sean Christopherson
2021-02-03 0:43 ` Dave Hansen
2021-02-03 15:10 ` Dave Hansen
2021-02-03 17:36 ` Sean Christopherson
2021-02-03 17:43 ` Paolo Bonzini
2021-02-03 17:46 ` Dave Hansen
2021-02-03 23:09 ` Kai Huang
2021-02-03 23:32 ` Sean Christopherson
2021-02-03 23:37 ` Dave Hansen
2021-02-04 0:04 ` Kai Huang
2021-02-04 0:28 ` Sean Christopherson
2021-02-04 3:18 ` Kai Huang
2021-02-04 16:28 ` Sean Christopherson
2021-02-04 16:48 ` Dave Hansen
2021-02-05 12:32 ` Kai Huang
2021-02-05 16:51 ` Sean Christopherson
2021-02-02 22:36 ` Dave Hansen
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