Re: [PATCH 15/16] KVM: x86/mmu: Initialize kvm_page_fault's pfn and hva to error values

From: "Huang, Kai" <kai.huang@intel.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: <kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	Yan Zhao <yan.y.zhao@intel.com>,
	Isaku Yamahata <isaku.yamahata@intel.com>,
	"Michael Roth" <michael.roth@amd.com>,
	Yu Zhang <yu.c.zhang@linux.intel.com>,
	"Chao Peng" <chao.p.peng@linux.intel.com>,
	Fuad Tabba <tabba@google.com>,
	"David Matlack" <dmatlack@google.com>
Subject: Re: [PATCH 15/16] KVM: x86/mmu: Initialize kvm_page_fault's pfn and hva to error values
Date: Thu, 7 Mar 2024 13:46:40 +1300	[thread overview]
Message-ID: <6b6f79df-a099-412d-8a84-06692e77f036@intel.com> (raw)
In-Reply-To: <20240228024147.41573-16-seanjc@google.com>


On 28/02/2024 3:41 pm, Sean Christopherson wrote:
> 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@google.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 74736d517e74..67e32dec9424 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;
>   

Reviewed-by: Kai Huang <kai.huang@intel.com>