From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 12 Jun 2025 04:47:44 +0000 (-0400)
Subject: KVM: x86/mmu: Reject direct bits in gpa passed to KVM_PRE_FAULT_MEMORY
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=8046d29dde17002523f94d3e6e0ebe486ce52166;p=linux-block.git

KVM: x86/mmu: Reject direct bits in gpa passed to KVM_PRE_FAULT_MEMORY

Only let userspace pass the same addresses that were used in KVM_SET_USER_MEMORY_REGION
(or KVM_SET_USER_MEMORY_REGION2); gpas in the the upper half of the address space
are an implementation detail of TDX and KVM.

Extracted from a patch by Sean Christopherson <seanjc@google.com>.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index a4040578b537..4e06e2e89a8f 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4903,6 +4903,9 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
 	if (!vcpu->kvm->arch.pre_fault_allowed)
 		return -EOPNOTSUPP;
 
+	if (kvm_is_gfn_alias(vcpu->kvm, gpa_to_gfn(range->gpa)))
+		return -EINVAL;
+
 	/*
 	 * reload is efficient when called repeatedly, so we can do it on
 	 * every iteration.