[PATCH 5.10 078/105] KVM: Dont null dereference ops->destroy

[Greg Kroah-Hartman]

From: Alexey Kardashevskiy <aik@xxxxxxxxx>

commit e8bc2427018826e02add7b0ed0fc625a60390ae5 upstream.

A KVM device cleanup happens in either of two callbacks:
1) destroy() which is called when the VM is being destroyed;
2) release() which is called when a device fd is closed.

Most KVM devices use 1) but Book3s's interrupt controller KVM devices
(XICS, XIVE, XIVE-native) use 2) as they need to close and reopen during
the machine execution. The error handling in kvm_ioctl_create_device()
assumes destroy() is always defined which leads to NULL dereference as
discovered by Syzkaller.

This adds a checks for destroy!=NULL and adds a missing release().

This is not changing kvm_destroy_devices() as devices with defined
release() should have been removed from the KVM devices list by then.

Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 virt/kvm/kvm_main.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3644,8 +3644,11 @@ static int kvm_ioctl_create_device(struc
 		kvm_put_kvm_no_destroy(kvm);
 		mutex_lock(&kvm->lock);
 		list_del(&dev->vm_node);
+		if (ops->release)
+			ops->release(dev);
 		mutex_unlock(&kvm->lock);
-		ops->destroy(dev);
+		if (ops->destroy)
+			ops->destroy(dev);
 		return ret;
 	}