From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Babu Moger <babu.moger@amd.com>,
Joao Martins <joao.m.martins@oracle.com>,
David Woodhouse <dwmw@amazon.co.uk>
Subject: Re: [PATCH v2 2/9] KVM: x86: Check CR3 GPA for validity regardless of vCPU mode
Date: Thu, 22 Apr 2021 08:51:54 +0200 [thread overview]
Message-ID: <8716951d-cddb-d5f9-e7e2-b651120a51e7@redhat.com> (raw)
In-Reply-To: <20210422022128.3464144-3-seanjc@google.com>
On 22/04/21 04:21, Sean Christopherson wrote:
> Check CR3 for an invalid GPA even if the vCPU isn't in long mode. For
> bigger emulation flows, notably RSM, the vCPU mode may not be accurate
> if CR0/CR4 are loaded after CR3. For MOV CR3 and similar flows, the
> caller is responsible for truncating the value.
>
> Note, SMRAM.CR3 is read-only, so this is mostly a theoretical bug since
> KVM will not have stored an illegal CR3 into SMRAM during SMI emulation.
Well, the guest could have changed it...
Paolo
> Fixes: 660a5d517aaa ("KVM: x86: save/load state on SMM switch")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/x86.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c9ba6f2d9bcd..63af93211871 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1078,10 +1078,15 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> return 0;
> }
>
> - if (is_long_mode(vcpu) && kvm_vcpu_is_illegal_gpa(vcpu, cr3))
> + /*
> + * Do not condition the GPA check on long mode, this helper is used to
> + * stuff CR3, e.g. for RSM emulation, and there is no guarantee that
> + * the current vCPU mode is accurate.
> + */
> + if (kvm_vcpu_is_illegal_gpa(vcpu, cr3))
> return 1;
> - else if (is_pae_paging(vcpu) &&
> - !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
> +
> + if (is_pae_paging(vcpu) && !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
> return 1;
>
> kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);
>
next prev parent reply other threads:[~2021-04-22 6:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 2:21 [PATCH v2 0/9] KVM: x86: Fixes for (benign?) truncation bugs Sean Christopherson
2021-04-22 2:21 ` [PATCH v2 1/9] KVM: x86: Remove emulator's broken checks on CR0/CR3/CR4 loads Sean Christopherson
2021-04-22 6:50 ` Paolo Bonzini
2021-04-22 2:21 ` [PATCH v2 2/9] KVM: x86: Check CR3 GPA for validity regardless of vCPU mode Sean Christopherson
2021-04-22 6:51 ` Paolo Bonzini [this message]
2021-04-22 16:55 ` Sean Christopherson
2021-04-22 2:21 ` [PATCH v2 3/9] KVM: SVM: Truncate GPR value for DR and CR accesses in !64-bit mode Sean Christopherson
2021-04-22 2:21 ` [PATCH v2 4/9] KVM: VMX: Truncate GPR value for DR and CR reads " Sean Christopherson
2021-04-22 2:21 ` [PATCH v2 5/9] KVM: nVMX: Truncate bits 63:32 of VMCS field on nested check in !64-bit Sean Christopherson
2021-04-22 2:21 ` [PATCH v2 6/9] KVM: nVMX: Truncate base/index GPR value on address calc " Sean Christopherson
2021-04-22 2:21 ` [PATCH v2 7/9] KVM: x86/xen: Drop RAX[63:32] when processing hypercall Sean Christopherson
2021-04-22 9:51 ` Vitaly Kuznetsov
2021-04-22 10:35 ` Paolo Bonzini
2021-04-22 10:49 ` Vitaly Kuznetsov
2021-04-22 2:21 ` [PATCH v2 8/9] KVM: SVM: Use default rAX size for INVLPGA emulation Sean Christopherson
2021-04-22 2:21 ` [PATCH v2 9/9] KVM: x86: Rename GPR accessors to make mode-aware variants the defaults Sean Christopherson
2021-04-22 6:55 ` [PATCH v2 0/9] KVM: x86: Fixes for (benign?) truncation bugs Paolo Bonzini
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