Re: [PATCH v2 net-next 2/3] net: dsa: lan9303: define LAN9303_NUM_PORTS 3

[Egil Hjelmeland]

On 01. aug. 2017 15:27, Andrew Lunn wrote:
> On Tue, Aug 01, 2017 at 02:31:44PM +0200, Egil Hjelmeland wrote:
> > On 01. aug. 2017 13:49, Juergen Borleis wrote:
> > > Hi Egil,
> > >
> > > On Tuesday 01 August 2017 13:14:38 Egil Hjelmeland wrote:
> > > > Will be used instead of '3' in upcomming patches.
> > > >
> > > >
> > > > +#define LAN9303_NUM_PORTS 3
> > > > +
> > >
> > > Maybe we should put this macro into a shared location because
> > > in "net/dsa/tag_lan9303.c" there is already a "#define LAN9303_MAX_PORTS
> > > 3".
> > >
> > > jb
> >
> > Is there any suitable shared location for such driver specific
> > definitions?
> > I could change the name to LAN9303_MAX_PORTS so it the same.
> > Rhymes better with DSA_MAX_PORTS too.
>
> Hi Egil, Juergen
>
> The other tag drivers do:
>
>          if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
>                  return NULL;
>
> or just
>
>          if (!ds->ports[port].netdev)
>                  return NULL;
>
> The first version is the safest, since a malicious switch could return
> port 42, and you are accessing way off the end of ds->ports[]. It does
> however require you call dsa_switch_alloc() with the correct number of
> ports.
>
>       Andrew

Related question: If the driver does dsa_switch_alloc(3), can it then
trust that all "port" params passed in DSA methods will be between
0 and 2?

Egil