Re: [PATCH 3/4] net/virtio: avoid passing NULL to qdev_set_parent_bus

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 14, 2019 at 03:16:12PM +0100, Jens Freimann wrote:
> Make sure no arguments for qdev_set_parent_bus are NULL.
> This fixes CID 1407224.
> 
> Fixes: 9711cd0dfc3f ("net/virtio: add failover support")
> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
> ---
>  hw/net/virtio-net.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index ac4d19109e..81650d4dc0 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -2809,8 +2809,16 @@ static bool failover_replug_primary(VirtIONet *n, Error **errp)
>      if (n->primary_device_opts) {
>          if (n->primary_dev) {
>              n->primary_bus = n->primary_dev->parent_bus;
> +            if (n->primary_bus) {
> +                qdev_set_parent_bus(n->primary_dev, n->primary_bus);
> +            } else  {
> +                error_setg(errp, "virtio_net: couldn't set bus for primary");
> +                goto out;
> +            }
> +        } else {
> +            error_setg(errp, "virtio_net: couldn't find primary device");
> +            goto out;
>          }


A bit less messy:

if (!n->primary_dev) {
            error_setg(errp, "virtio_net: couldn't find primary device");
            goto err;
}

n->primary_bus = n->primary_dev->parent_bus;
if (!n->primary_bus) {
      error_setg(errp, "virtio_net: couldn't find primary device");
          goto err;
}

qdev_set_parent_bus(n->primary_dev, n->primary_bus);

err:
	return false;

also is it valid for primary_device_opts to not be present at all?
Maybe we should check that too.



> -        qdev_set_parent_bus(n->primary_dev, n->primary_bus);
>          n->primary_should_be_hidden = false;
>          qemu_opt_set_bool(n->primary_device_opts,
>                  "partially_hotplugged", true, errp);
> @@ -2819,10 +2827,8 @@ static bool failover_replug_primary(VirtIONet *n, Error **errp)
>              hotplug_handler_pre_plug(hotplug_ctrl, n->primary_dev, errp);
>              hotplug_handler_plug(hotplug_ctrl, n->primary_dev, errp);
>          }
> -        if (!n->primary_dev) {
> -            error_setg(errp, "virtio_net: couldn't find primary device");
> -        }
>      }
> +out:
>      return *errp != NULL;
>  }

I'd handle errors separately from good path.
BTW I don't understand something here:
*errp != NULL is true on error, no?
Why are we returning success?
Confused.
Just return true would be cleaner imho.

>  
> -- 
> 2.21.0