KVM: nVMX: do not use dangling shadow VMCS after guest reset (88dddc11) · Commits · 戴 / test

If a KVM guest is reset while running a nested guest, free_nested will disable the shadow VMCS execution control in the vmcs01. However, on the next KVM_RUN vmx_vcpu_run would nevertheless try to sync the VMCS12 to the shadow VMCS which has since been freed. This causes a vmptrld of a NULL pointer on my machime, but Jan reports the host to hang altogether. Let's see how much this trivial patch fixes. Reported-by:

Jan Kiszka <jan.kiszka@siemens.com> Cc: Liran Alon <liran.alon@oracle.com> Cc: stable@vger.kernel.org Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -194,6 +194,7 @@ static void vmx_disable_shadow_vmcs(struct vcpu_vmx *vmx)
		{
		secondary_exec_controls_clearbit(vmx, SECONDARY_EXEC_SHADOW_VMCS);
		vmcs_write64(VMCS_LINK_POINTER, -1ull);
		vmx->nested.need_vmcs12_to_shadow_sync = false;
		}

		static inline void nested_release_evmcs(struct kvm_vcpu *vcpu)
		@@ -1341,6 +1342,9 @@ static void copy_shadow_to_vmcs12(struct vcpu_vmx *vmx)
		unsigned long val;
		int i;

		if (WARN_ON(!shadow_vmcs))
		return;

		preempt_disable();

		vmcs_load(shadow_vmcs);
		@@ -1373,6 +1377,9 @@ static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx)
		unsigned long val;
		int i, q;

		if (WARN_ON(!shadow_vmcs))
		return;

		vmcs_load(shadow_vmcs);

		for (q = 0; q < ARRAY_SIZE(fields); q++) {
		@@ -4436,7 +4443,6 @@ static inline void nested_release_vmcs12(struct kvm_vcpu *vcpu)
		/* copy to memory all shadowed fields in case
		they were modified */
		copy_shadow_to_vmcs12(vmx);
		vmx->nested.need_vmcs12_to_shadow_sync = false;
		vmx_disable_shadow_vmcs(vmx);
		}
		vmx->nested.posted_intr_nv = -1;

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