Re: [Qemu-devel] [PULL 7/7] hw/misc/mmio_interface: Return after error_setg() to avoid crash

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 14 Aug 2017 12:45:16 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:

> On 14 August 2017 at 12:07, Michael Tokarev <mjt@tls.msk.ru> wrote:
> > From: Thomas Huth <thuth@redhat.com>
> >
> > QEMU currently abort()s if the user tries to specify the mmio_interface
> > device without parameters:
> >
> > x86_64-softmmu/qemu-system-x86_64 -nographic -device mmio_interface
> > qemu-system-x86_64: /home/thuth/devel/qemu/util/error.c:57: error_setv:
> >  Assertion `*errp == ((void *)0)' failed.
> > Aborted (core dumped)
> >
> > This happens because the realize function is trying to set the errp
> > twice in this case. After setting an error, the realize function
> > should immediately return instead.  
> 
> It seems like it should be an error to permit this to be
> created from the command line at all -- the device is intended
> only as an internal implementation detail of the memory system,
> and it has a PROP_PTR property which can't be sensibly set
> from the command line.
> 
> This patch is a correct fix for an immediate problem, but we should disable
> using this via -device somehow.

Setting DeviceClass::user_creatable to false should prevent creating device
with device_add interface. See: qdev_get_device_class()

> 
> thanks
> -- PMM
>