linux-kernel - Re: [PATCH 16/17] KVM: x86/mmu: Initialize kvm_page

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Date: Mon, 13 May 2024 14:29:15 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>, Kai Huang <kai.huang@...el.com>
Subject: Re: [PATCH 16/17] KVM: x86/mmu: Initialize kvm_page_fault's pfn and
 hva to error values

On 5/7/2024 11:58 PM, Paolo Bonzini wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> Explicitly set "pfn" and "hva" to error values in kvm_mmu_do_page_fault()
> to harden KVM against using "uninitialized" values.  In quotes because the
> fields are actually zero-initialized, and zero is a legal value for both
> page frame numbers and virtual addresses.  E.g. failure to set "pfn" prior
> to creating an SPTE could result in KVM pointing at physical address '0',
> which is far less desirable than KVM generating a SPTE with reserved PA
> bits set and thus effectively killing the VM.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Reviewed-by: Kai Huang <kai.huang@...el.com>
> Message-ID: <20240228024147.41573-16-seanjc@...gle.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>

> ---
>   arch/x86/kvm/mmu/mmu_internal.h | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> index dfd9ff383663..ce2fcd19ba6b 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -307,6 +307,9 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>   		.req_level = PG_LEVEL_4K,
>   		.goal_level = PG_LEVEL_4K,
>   		.is_private = err & PFERR_PRIVATE_ACCESS,
> +
> +		.pfn = KVM_PFN_ERR_FAULT,
> +		.hva = KVM_HVA_ERR_BAD,
>   	};
>   	int r;
>