KVM: Initialize kvm before registering the mmu notifier

It doesn't make sense to ever see a half-initialized kvm structure on
mmu notifier callbacks.  Previously, 85722cda changed the ordering to
ensure that the mmu_lock was initialized before mmu notifier
registration, but there is still a race where the mmu notifier could
come in and try accessing other portions of struct kvm before they are
intialized.

Solve this by moving the mmu notifier registration to occur after the
structure is completely initialized.

Google-Bug-Id: 452199
Signed-off-by: Mike Waychison <mikew@google.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 383f492a66038fa5fa4f121f1365a9fbb2759e74..96ebc0679415baeff88d7764b1c0e956820adad2 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -467,12 +467,8 @@ static struct kvm *kvm_create_vm(void)
                if (!kvm->buses[i])
                        goto out_err;
        }
-       spin_lock_init(&kvm->mmu_lock);
-
-       r = kvm_init_mmu_notifier(kvm);
-       if (r)
-               goto out_err;
 
+       spin_lock_init(&kvm->mmu_lock);
        kvm->mm = current->mm;
        atomic_inc(&kvm->mm->mm_count);
        kvm_eventfd_init(kvm);
@@ -480,6 +476,11 @@ static struct kvm *kvm_create_vm(void)
        mutex_init(&kvm->irq_lock);
        mutex_init(&kvm->slots_lock);
        atomic_set(&kvm->users_count, 1);
+
+       r = kvm_init_mmu_notifier(kvm);
+       if (r)
+               goto out_err;
+
        raw_spin_lock(&kvm_lock);
        list_add(&kvm->vm_list, &vm_list);
        raw_spin_unlock(&kvm_lock);