Re: [PATCH] hw/net: prevent potential NULL dereference

[Peter Maydell <peter.maydell@linaro.org>]

On Thu, 30 May 2024 at 01:52, David Gibson <david@gibson.dropbear.id.au> wrote:
>
> On Wed, May 29, 2024 at 02:07:18PM +0300, Oleg Sviridov wrote:
> > Pointer, returned from function 'spapr_vio_find_by_reg', may be NULL and is dereferenced immediately after.
> >
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> >
> > Signed-off-by: Oleg Sviridov <oleg.sviridov@red-soft.ru>
> > ---
> >  hw/net/spapr_llan.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/hw/net/spapr_llan.c b/hw/net/spapr_llan.c
> > index ecb30b7c76..f40b733229 100644
> > --- a/hw/net/spapr_llan.c
> > +++ b/hw/net/spapr_llan.c
> > @@ -770,6 +770,10 @@ static target_ulong h_change_logical_lan_mac(PowerPCCPU *cpu,
> >      SpaprVioVlan *dev = VIO_SPAPR_VLAN_DEVICE(sdev);
>
> Hmm... I thought VIO_SPAPR_VLAN_DEVICE() was supposed to abort if sdev
> was NULL or not of the right type.  Or have the rules for qom helpers
> changed since I wrote this.

QOM casts abort if the type is wrong, but a NULL pointer is
passed through as a NULL pointer.

thanks
-- PMM