Re: [Qemu-devel] [qemu-s390x] [PATCH] s390: avoid potential null dereference in s390_pcihost_unplug()

[Halil Pasic <pasic@linux.ibm.com>]

On Thu, 3 Jan 2019 15:54:38 +0100
Cornelia Huck <cohuck@redhat.com> wrote:

> On Thu,  3 Jan 2019 06:02:46 -0800
> Li Qiang <liq3ea@163.com> wrote:
> 
> > When getting the 'pbdev', the if...else has no default branch.
> > From Coverity, the 'pbdev' maybe null when the 'dev' is not
> > the TYPE_PCI_BRIDGE/TYPE_PCI_DEVICE/TYPE_S390_PCI_DEVICE.
> > 
> > Spotted by Coverity: CID 1398593
> > 
> > Signed-off-by: Li Qiang <liq3ea@163.com>
> > ---
> >  hw/s390x/s390-pci-bus.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> > index 15759b6514..b3122268a3 100644
> > --- a/hw/s390x/s390-pci-bus.c
> > +++ b/hw/s390x/s390-pci-bus.c
> > @@ -956,6 +956,10 @@ static void s390_pcihost_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_S390_PCI_DEVICE)) {
> >          pbdev = S390_PCI_DEVICE(dev);
> >          pci_dev = pbdev->pdev;
> > +    } else {
> > +        error_setg(errp, "s390: device unplug for not supported device"
> > +                   " type: %s", object_get_typename(OBJECT(dev)));
> > +        return;
> 
> I think that is something that really Should Not Happen. However,
> looking at s390_pcihost_plug, we just do nothing if the plugged device
> does not match any of the expected three values. Maybe we should also
> set an error in that case there?
> 

Really Should Not Happen is in this case a programming error AFAIU.
Wouldn't something more assert like reflect that better?

> >      }
> >  
> >      switch (pbdev->state) {
> 
>