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[146.148.121.110]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c1f83c686a8sm142753566b.4.2026.07.29.10.06.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Jul 2026 10:06:32 -0700 (PDT) From: Dmytro Maluka To: Sean Christopherson Cc: Paolo Bonzini , Dave Hansen , Chao Gao , Kai Huang , Naveen N Rao , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Vineeth Pillai , Chuanxiao Dong , Aashish Sharma , Grzegorz Jaszczyk , Dmytro Maluka Subject: [PATCH v2 2/2] KVM: VMX: Fix stale PID-pointer table entry left after vCPU free Date: Wed, 29 Jul 2026 17:06:21 +0000 Message-ID: <20260729170621.308809-3-dmaluka@chromium.org> X-Mailer: git-send-email 2.55.0.508.g3f0d502094-goog In-Reply-To: <20260729170621.308809-1-dmaluka@chromium.org> References: <20260729170621.308809-1-dmaluka@chromium.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vCPU creation in kvm_vm_ioctl_create_vcpu() may fail after kvm_arch_vcpu_create() -> vmx_vcpu_create() already succeeded. In such case kvm_vm_ioctl_create_vcpu() destroys the newly created vCPU in the failure path. However, that leaves a side effect: the IPIv pid_table entry remains configured with this vCPU's pi_desc address. As a result, when another vCPU sends an IPI to the APIC ID of this failed-to-create vCPU, it will cause HW to write to this (freed!) pi_desc memory. [*] Fix this by clearing the pid_table entry when destroying the vCPU. Note that the same issue exists for SVM AVIC as well [1], to be fixed. [*] Although, since this memory is freed into the kvm_vcpu_cache kmem cache which is only used for allocating kvm_vcpus, _maybe_ this memory will only be reused for pi_desc of another vCPU, not for anything else. So _maybe_ this will only result in delivering the IPI to a wrong vCPU (possibly of another VM) in the worst case, not in a random corruption of kernel memory. [1] https://lore.kernel.org/kvm/al4rNqpBYy8FGKPw@blrnaveerao1/ Signed-off-by: Dmytro Maluka --- arch/x86/kvm/vmx/vmx.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index cc75feec05da..f98c268b5150 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7665,6 +7665,9 @@ void vmx_vcpu_free(struct kvm_vcpu *vcpu) nested_vmx_free_vcpu(vcpu); free_loaded_vmcs(vmx->loaded_vmcs); free_page((unsigned long)vmx->ve_info); + + if (vmx_can_use_ipiv(vcpu)) + WRITE_ONCE(to_kvm_vmx(vcpu->kvm)->pid_table[vcpu->vcpu_id], 0); } int vmx_vcpu_create(struct kvm_vcpu *vcpu) -- 2.55.0.508.g3f0d502094-goog