Hi Markus,
On Tue, Jul 23, 2024 at 12:21:17PM +0200, Markus Armbruster wrote:
> Date: Tue, 23 Jul 2024 12:21:17 +0200
> From: Markus Armbruster <arm...@redhat.com>
> Subject: Re: [PATCH] hw/nubus/nubus-virtio-mmio: Fix missing ERRP_GUARD()
> in nubus_virtio_mmio_realize()
>
> Zhao Liu <zhao1....@intel.com> writes:
>
> > As the comment in qapi/error, dereferencing @errp requires
>
> Suggest "According to the comment in qapi/error.h".
Thanks! Good words.
> > ERRP_GUARD():
> >
> > * = Why, when and how to use ERRP_GUARD() =
> > *
> > * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> > * - It must not be dereferenced, because it may be null.
> > ...
> > * 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.
> > *
> > * Using it when it's not needed is safe, but please avoid cluttering
> > * the source with useless code.
> >
> > But in nubus_virtio_mmio_realize(), @errp is dereferenced without
> > ERRP_GUARD().
>
> Suggest to scratch "But".
No problem, will do.
> > Although nubus_virtio_mmio_realize() - as a DeviceClass.realize()
> > method - doesn't get the NULL @errp parameter, it hasn't triggered the
> > bug that dereferencing the NULL @errp. It's still necessary to follow
> > the requirement of @errp, so add missing ERRP_GUARD() in
> > nubus_virtio_mmio_realize().
>
> Suggest
>
> Although nubus_virtio_mmio_realize() - as a DeviceClass.realize()
> method - is never passed a null @errp argument, it should follow the
> rules on @errp usage. Add the ERRP_GUARD() there.
Thanks for the text! It sounds much more authentic!
> > Cc: Laurent Vivier <laur...@vivier.eu>
> > Cc: Philippe Mathieu-Daudé <phi...@linaro.org>
> > Signed-off-by: Zhao Liu <zhao1....@intel.com>
> > ---
> > hw/nubus/nubus-virtio-mmio.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/hw/nubus/nubus-virtio-mmio.c b/hw/nubus/nubus-virtio-mmio.c
> > index 58a63c84d0be..a5558d3ec28b 100644
> > --- a/hw/nubus/nubus-virtio-mmio.c
> > +++ b/hw/nubus/nubus-virtio-mmio.c
> > @@ -23,6 +23,7 @@ static void nubus_virtio_mmio_set_input_irq(void *opaque,
> > int n, int level)
> >
> > static void nubus_virtio_mmio_realize(DeviceState *dev, Error **errp)
> > {
> > + ERRP_GUARD();
> > NubusVirtioMMIODeviceClass *nvmdc = NUBUS_VIRTIO_MMIO_GET_CLASS(dev);
> > NubusVirtioMMIO *s = NUBUS_VIRTIO_MMIO(dev);
> > NubusDevice *nd = NUBUS_DEVICE(dev);
> SysBusDevice *sbd;
> int i, offset;
>
> nvmdc->parent_realize(dev, errp);
>
> Here's the dereference:
>
> if (*errp) {
> return;
> }
>
> Reviewed-by: Markus Armbruster <arm...@redhat.com>
>
Thanks! Will refresh a v2 soon.
Regards,
Zhao
