Re: [PATCH v2 25/29] hw/virtio/vhost-vsock: Fix missing ERRP_GUARD() for error_prepend()

[Thomas Huth <thuth@redhat.com>]

On 11/03/2024 04.38, Zhao Liu wrote:
> From: Zhao Liu <zhao1.liu@intel.com>
> 
> As the comment in qapi/error, passing @errp to error_prepend() requires
> ERRP_GUARD():
> 
> * = Why, when and how to use ERRP_GUARD() =
> *
> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> ...
> * - It should not be passed to error_prepend(), error_vprepend() or
> *   error_append_hint(), because that doesn't work with &error_fatal.
> * ERRP_GUARD() lifts these restrictions.
> *
> * To use ERRP_GUARD(), add it right at the beginning of the function.
> * @errp can then be used without worrying about the argument being
> * NULL or &error_fatal.
> 
> ERRP_GUARD() could avoid the case when @errp is &error_fatal, the user
> can't see this additional information, because exit() happens in
> error_setg earlier than information is added [1].
> 
> The vhost_vsock_device_realize() passes @errp to error_prepend(), and as
> a VirtioDeviceClass.realize method, its @errp is from
> DeviceClass.realize so that there is no guarantee that the @errp won't
> point to @error_fatal.
> 
> To avoid the issue like [1] said, add missing ERRP_GUARD() at the
> beginning of this function.
> 
> [1]: Issue description in the commit message of commit ae7c80a7bd73
>       ("error: New macro ERRP_GUARD()").
> 
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
>   hw/virtio/vhost-vsock.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
> index d5ca0b5a1055..3d4a5a97f484 100644
> --- a/hw/virtio/vhost-vsock.c
> +++ b/hw/virtio/vhost-vsock.c
> @@ -121,6 +121,7 @@ static const VMStateDescription vmstate_virtio_vhost_vsock = {
>   
>   static void vhost_vsock_device_realize(DeviceState *dev, Error **errp)
>   {
> +    ERRP_GUARD();
>       VHostVSockCommon *vvc = VHOST_VSOCK_COMMON(dev);
>       VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>       VHostVSock *vsock = VHOST_VSOCK(dev);

Reviewed-by: Thomas Huth <thuth@redhat.com>