Re: [Qemu-devel] [PATCH 2/3] hw/s390x: fix memory leak in s390_init_ipl_dev()

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 29 Mar 2018 11:39:41 +0200
Greg Kurz <groug@kaod.org> wrote:

> On Thu, 29 Mar 2018 11:27:21 +0200
> Igor Mammedov <imammedo@redhat.com> wrote:
> 
> > On Thu, 29 Mar 2018 11:10:06 +0200
> > Greg Kurz <groug@kaod.org> wrote:
> >   
> > > The string returned by object_property_get_str() is dynamically allocated.
> > > 
> > > Fixes: 3c4e9baacf4d9
> > > Signed-off-by: Greg Kurz <groug@kaod.org>
> > > ---
> > >  hw/s390x/s390-virtio-ccw.c |    5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> > > index 864145a7c6f3..435f7c99e77c 100644
> > > --- a/hw/s390x/s390-virtio-ccw.c
> > > +++ b/hw/s390x/s390-virtio-ccw.c
> > > @@ -246,6 +246,7 @@ static void s390_init_ipl_dev(const char *kernel_filename,
> > >  {
> > >      Object *new = object_new(TYPE_S390_IPL);
> > >      DeviceState *dev = DEVICE(new);
> > > +    char *netboot_fw_prop;
> > >  
> > >      if (kernel_filename) {
> > >          qdev_prop_set_string(dev, "kernel", kernel_filename);
> > > @@ -256,9 +257,11 @@ static void s390_init_ipl_dev(const char *kernel_filename,
> > >      qdev_prop_set_string(dev, "cmdline", kernel_cmdline);
> > >      qdev_prop_set_string(dev, "firmware", firmware);
> > >      qdev_prop_set_bit(dev, "enforce_bios", enforce_bios);
> > > -    if (!strlen(object_property_get_str(new, "netboot_fw", &error_abort))) {
> > > +    netboot_fw_prop = object_property_get_str(new, "netboot_fw", &error_abort);
> > > +    if (!strlen(netboot_fw_prop)) {    
> > probably not really issue here but,
> > is strlen really safe in case netboot_fw_prop == NULL?
> >   
> 
> You're right, object_property_get_str() can theoretically return NULL and
> strlen() would crash... Not sure how this would happen though. Anyway, the
> current code doesn't check if object_property_get_str() returns NULL so
> if this needs to be fixed as well, let's do it in a followup patch.

I don't think so - if the attribute exists, we'll always get != NULL if
I read the code correctly.

> 
> > >          qdev_prop_set_string(dev, "netboot_fw", netboot_fw);
> > >      }
> > > +    g_free(netboot_fw_prop);
> > >      object_property_add_child(qdev_get_machine(), TYPE_S390_IPL,
> > >                                new, NULL);
> > >      object_unref(new);
> > > 
> > >     
> >   
>