diff mbox series

[stable-5.2,1/3] KVM: nVMX: do not use dangling shadow VMCS after guest reset

Message ID 20190725120436.5432-2-vkuznets@redhat.com (mailing list archive)
State New, archived
Headers show
Series KVM: x86: FPU and nested VMX guest reset fixes | expand

Commit Message

Vitaly Kuznetsov July 25, 2019, 12:04 p.m. UTC 
From: Paolo Bonzini <pbonzini@redhat.com>

[ Upstream commit 88dddc11a8d6b09201b4db9d255b3394d9bc9e57 ]

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 | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 46af3a5e9209..b72d6aec4e90 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -184,6 +184,7 @@  static void vmx_disable_shadow_vmcs(struct vcpu_vmx *vmx)
 {
 	vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL, SECONDARY_EXEC_SHADOW_VMCS);
 	vmcs_write64(VMCS_LINK_POINTER, -1ull);
+	vmx->nested.need_vmcs12_sync = false;
 }
 
 static inline void nested_release_evmcs(struct kvm_vcpu *vcpu)
@@ -1321,6 +1322,9 @@  static void copy_shadow_to_vmcs12(struct vcpu_vmx *vmx)
 	u64 field_value;
 	struct vmcs *shadow_vmcs = vmx->vmcs01.shadow_vmcs;
 
+	if (WARN_ON(!shadow_vmcs))
+		return;
+
 	preempt_disable();
 
 	vmcs_load(shadow_vmcs);
@@ -1359,6 +1363,9 @@  static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx)
 	u64 field_value = 0;
 	struct vmcs *shadow_vmcs = vmx->vmcs01.shadow_vmcs;
 
+	if (WARN_ON(!shadow_vmcs))
+		return;
+
 	vmcs_load(shadow_vmcs);
 
 	for (q = 0; q < ARRAY_SIZE(fields); q++) {
@@ -4304,7 +4311,6 @@  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_sync = false;
 		vmx_disable_shadow_vmcs(vmx);
 	}
 	vmx->nested.posted_intr_nv = -1;