Re: [Qemu-devel] [PATCH] qdev: Fix use after free in qdev_init_nofail error path

[Fam Zheng <famz@redhat.com>]

On Tue, 08/02 10:14, Igor Mammedov wrote:
> On Tue, 2 Aug 2016 00:00:27 -0400
> John Snow <jsnow@redhat.com> wrote:
> 
> > On 08/01/2016 11:41 PM, Fam Zheng wrote:
> > > Since 69382d8b (qdev: Fix object reference leak in case device.realize()
> > > fails), object_property_set_bool could release the object. The error
> > > path wants the type name, so hold an reference before realizing it.
> > >
> > > Cc: Igor Mammedov <imammedo@redhat.com>
> > > Signed-off-by: Fam Zheng <famz@redhat.com>
> > > ---
> > >  hw/core/qdev.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> > > index ee4a083..5783442 100644
> > > --- a/hw/core/qdev.c
> > > +++ b/hw/core/qdev.c
> > > @@ -354,12 +354,14 @@ void qdev_init_nofail(DeviceState *dev)
> > >
> > >      assert(!dev->realized);
> > >
> > > +    object_ref(OBJECT(dev));
> > >      object_property_set_bool(OBJECT(dev), true, "realized", &err);
> > >      if (err) {
> > >          error_reportf_err(err, "Initialization of device %s failed: ",
> > >                            object_get_typename(OBJECT(dev)));
> > >          exit(1);
> > >      }
> > > +    object_unref(OBJECT(dev));
> > >  }
> > >
> > >  void qdev_machine_creation_done(void)
> > >  
> > 
> > Thanks :)
> > 
> > (For the list: this fixes qcow2 iotest 051. This is for-2.7.)
> I don't see any error at 'make check' time,
> could you provide reproducer CLI?

It crashes for me with something as simple as:

 $ qemu-system-x86_64 -drive if=ide

Fam