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.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 73d6d585dd66..880bc36a0d5d 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -8457,6 +8457,7 @@ 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.sync_shadow_vmcs = false; }

static inline void nested_release_vmcs12(struct vcpu_vmx *vmx) @@ -8468,7 +8469,6 @@ static inline void nested_release_vmcs12(struct vcpu_vmx *vmx) /* copy to memory all shadowed fields in case they were modified */ copy_shadow_to_vmcs12(vmx); - vmx->nested.sync_shadow_vmcs = false; vmx_disable_shadow_vmcs(vmx); } vmx->nested.posted_intr_nv = -1; @@ -8668,6 +8668,9 @@ 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); @@ -8706,6 +8709,9 @@ 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++) {

From: Jan Kiszka jan.kiszka@siemens.com

[ Upstream commit cf64527bb33f6cec2ed50f89182fc4688d0056b6 ]

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@siemens.com Reviewed-by: Liran Alon liran.alon@oracle.com Cc: stable@vger.kernel.org Fixes: 7f7f1ba33cf2 ("KVM: x86: do not load vmcs12 pages while still in SMM") Signed-off-by: Paolo Bonzini pbonzini@redhat.com --- arch/x86/kvm/vmx.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 880bc36a0d5d..4cf16378dffe 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -8490,6 +8490,8 @@ static void free_nested(struct vcpu_vmx *vmx) if (!vmx->nested.vmxon && !vmx->nested.smm.vmxon) return;

+ kvm_clear_request(KVM_REQ_GET_VMCS12_PAGES, &vmx->vcpu); + hrtimer_cancel(&vmx->nested.preemption_timer); vmx->nested.vmxon = false; vmx->nested.smm.vmxon = false;