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

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Date: Tue,  7 May 2024 11:58:16 -0400
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>,
	Kai Huang <kai.huang@...el.com>
Subject: [PATCH 16/17] KVM: x86/mmu: Initialize kvm_page_fault's pfn and hva to error values

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>
---
 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;

-- 
2.43.0