| Message ID | 1563554534-46556-3-git-send-email-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: nVMX: do not use dangling shadow VMCS after guest reset | expand |
> On 19 Jul 2019, at 19:42, Paolo Bonzini <pbonzini@redhat.com> wrote: > > 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> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> First, nested_release_vmcs12() also sets need_vmcs12_to_shadow_sync to false explicitly. This can now be removed. Second, I suggest putting a WARN_ON_ONCE() on copy_vmcs12_to_shadow() in case shadow_vmcs==NULL. To assist catching these kind of errors more easily in the future. Besides that, the fix seems correct to me. Reviewed-by: Liran Alon <liran.alon@oracle.com> -Liran > --- > arch/x86/kvm/vmx/nested.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index 6e88f459b323..6119b30347c6 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -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) > -- > 1.8.3.1 >
On 19/07/19 23:01, Liran Alon wrote: > > >> On 19 Jul 2019, at 19:42, Paolo Bonzini <pbonzini@redhat.com> wrote: >> >> 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> >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > > First, nested_release_vmcs12() also sets need_vmcs12_to_shadow_sync > to false explicitly. This can now be removed. > > Second, I suggest putting a WARN_ON_ONCE() on copy_vmcs12_to_shadow() > in case shadow_vmcs==NULL. Both good ideas. Thanks for the quick review! Paolo > To assist catching these kind of errors more easily in the future. > > Besides that, the fix seems correct to me. > Reviewed-by: Liran Alon <liran.alon@oracle.com> > > -Liran > >> --- >> arch/x86/kvm/vmx/nested.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c >> index 6e88f459b323..6119b30347c6 100644 >> --- a/arch/x86/kvm/vmx/nested.c >> +++ b/arch/x86/kvm/vmx/nested.c >> @@ -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) >> -- >> 1.8.3.1 >> >
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 6e88f459b323..6119b30347c6 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -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)
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> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/vmx/nested.c | 1 + 1 file changed, 1 insertion(+)