From 4fa7734c62cdd8c07edd54fa5a5e91482273071a Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 17 Jul 2014 12:25:16 +0200 Subject: [PATCH] KVM: nVMX: fix lifetime issues for vmcs02 free_nested needs the loaded_vmcs to be valid if it is a vmcs02, in order to detach it from the shadow vmcs. However, this is not available anymore after commit 26a865f4aa8e (KVM: VMX: fix use after free of vmx->loaded_vmcs, 2014-01-03). Revert that patch, and fix its problem by forcing a vmcs01 as the active VMCS before freeing all the nested VMX state. Reported-by: Wanpeng Li Tested-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx.c | 49 +++++++++++++++++++++++++++++++--------------- 1 file changed, 33 insertions(+), 16 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 7534a9f67cc8..462334eaa3c0 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -5772,22 +5772,27 @@ static void nested_free_vmcs02(struct vcpu_vmx *vmx, gpa_t vmptr) /* * Free all VMCSs saved for this vcpu, except the one pointed by - * vmx->loaded_vmcs. These include the VMCSs in vmcs02_pool (except the one - * currently used, if running L2), and vmcs01 when running L2. + * vmx->loaded_vmcs. We must be running L1, so vmx->loaded_vmcs + * must be &vmx->vmcs01. */ static void nested_free_all_saved_vmcss(struct vcpu_vmx *vmx) { struct vmcs02_list *item, *n; + + WARN_ON(vmx->loaded_vmcs != &vmx->vmcs01); list_for_each_entry_safe(item, n, &vmx->nested.vmcs02_pool, list) { - if (vmx->loaded_vmcs != &item->vmcs02) - free_loaded_vmcs(&item->vmcs02); + /* + * Something will leak if the above WARN triggers. Better than + * a use-after-free. + */ + if (vmx->loaded_vmcs == &item->vmcs02) + continue; + + free_loaded_vmcs(&item->vmcs02); list_del(&item->list); kfree(item); + vmx->nested.vmcs02_num--; } - vmx->nested.vmcs02_num = 0; - - if (vmx->loaded_vmcs != &vmx->vmcs01) - free_loaded_vmcs(&vmx->vmcs01); } /* @@ -7557,13 +7562,31 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) vmx_complete_interrupts(vmx); } +static void vmx_load_vmcs01(struct kvm_vcpu *vcpu) +{ + struct vcpu_vmx *vmx = to_vmx(vcpu); + int cpu; + + if (vmx->loaded_vmcs == &vmx->vmcs01) + return; + + cpu = get_cpu(); + vmx->loaded_vmcs = &vmx->vmcs01; + vmx_vcpu_put(vcpu); + vmx_vcpu_load(vcpu, cpu); + vcpu->cpu = cpu; + put_cpu(); +} + static void vmx_free_vcpu(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); free_vpid(vmx); - free_loaded_vmcs(vmx->loaded_vmcs); + leave_guest_mode(vcpu); + vmx_load_vmcs01(vcpu); free_nested(vmx); + free_loaded_vmcs(vmx->loaded_vmcs); kfree(vmx->guest_msrs); kvm_vcpu_uninit(vcpu); kmem_cache_free(kvm_vcpu_cache, vmx); @@ -8721,7 +8744,6 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason, unsigned long exit_qualification) { struct vcpu_vmx *vmx = to_vmx(vcpu); - int cpu; struct vmcs12 *vmcs12 = get_vmcs12(vcpu); /* trying to cancel vmlaunch/vmresume is a bug */ @@ -8746,12 +8768,7 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason, vmcs12->vm_exit_intr_error_code, KVM_ISA_VMX); - cpu = get_cpu(); - vmx->loaded_vmcs = &vmx->vmcs01; - vmx_vcpu_put(vcpu); - vmx_vcpu_load(vcpu, cpu); - vcpu->cpu = cpu; - put_cpu(); + vmx_load_vmcs01(vcpu); vm_entry_controls_init(vmx, vmcs_read32(VM_ENTRY_CONTROLS)); vm_exit_controls_init(vmx, vmcs_read32(VM_EXIT_CONTROLS)); -- 2.20.1