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 <wanpeng.li@xxxxxxxxxxxxxxx>
Tested-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
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));
--
1.8.3.1
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