> On 21 Jul 2019, at 17:00, Jan Kiszka <jan.kiszka@xxxxxx> wrote: > > On 21.07.19 13:57, Liran Alon wrote: >> >> >>> On 21 Jul 2019, at 14:52, Jan Kiszka <jan.kiszka@xxxxxx> wrote: >>> >>> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >>> >>> Letting this pend may cause nested_get_vmcs12_pages to run against an >>> invalid state, corrupting the effective vmcs of L1. >>> >>> This was triggerable in QEMU after a guest corruption in L2, followed by >>> a L1 reset. >>> >>> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >> >> Good catch. >> Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx> >> >> This would have been more easily diagnosed in case free_nested() would NULL cached_vmcs12 and cached_shadow_vmcs12 >> after kfree() and add to get_vmcs12() & get_shadow_vmcs12() a relevant BUG_ON() call. > > The NULL'ifying makes sense, patch follows. But the helpers are too often called > unconditionally, thus cause false positives when adding the BUG_ON. How would having a BUG_ON(!cached_vmcs12) on get_vmcs12() will cause false positive? I don’t see any legit case it is called and return NULL. -Liran > > Jan > >> >> I would submit such a patch separately. >> >> -Liran >> >>> --- >>> >>> And another gremlin. I'm afraid there is at least one more because >>> vmport access from L2 is still failing in QEMU. This is just another >>> fallout from that. At least the host seems stable now. >>> >>> arch/x86/kvm/vmx/nested.c | 2 ++ >>> 1 file changed, 2 insertions(+) >>> >>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c >>> index 0f1378789bd0..4cdab4b4eff1 100644 >>> --- a/arch/x86/kvm/vmx/nested.c >>> +++ b/arch/x86/kvm/vmx/nested.c >>> @@ -220,6 +220,8 @@ static void free_nested(struct kvm_vcpu *vcpu) >>> if (!vmx->nested.vmxon && !vmx->nested.smm.vmxon) >>> return; >>> >>> + kvm_clear_request(KVM_REQ_GET_VMCS12_PAGES, vcpu); >>> + >>> vmx->nested.vmxon = false; >>> vmx->nested.smm.vmxon = false; >>> free_vpid(vmx->nested.vpid02); >>> -- >>> 2.16.4
