Re: [PATCH] net: rtnl: avoid uninitialized data in IFLA_VF_VLAN_LIST handling

[Tariq Toukan]

Hi Arnd,


On 30/09/2016 7:38 PM, Arnd Bergmann wrote:
> On Friday 30 September 2016, Eric Dumazet wrote:
> > > @@ -1753,6 +1753,9 @@ static int do_setvfinfo(struct net_device *dev, struct nlattr **tb)
> > >
> > >                          len++;
> > >                  }
> > > +               if (len == 0)
> > > +                       return -EINVAL;
> > > +
> > >                  err = ops->ndo_set_vf_vlan(dev, ivvl[0]->vf, ivvl[0]->vlan,
> > >                                             ivvl[0]->qos, ivvl[0]->vlan_proto);
> > >                  if (err < 0)
> > > --
> > > 2.9.0
Reviewed-by: Moshe Shemesh <moshe@xxxxxxxxxxxx>

Thanks for the fix, I will add the flag to my makefile.
> > So, if I read this code, we build an array, but call ndo_set_vf_vlan()
> > only using first element ?
> >
> > Looks like the bug should be fixed in a different way.
> I was wondering about this too, but didn't understand enough about it to say
> if it was intentional or not.
It is intentional.
The change we need here is the option to set the VF vlan protocol, so 
our hw will insert either S-TAG or C-TAG per VF. The previous version of 
this patch didn't use any array.
Then we got a comment, which makes sense, that the new UAPI interface 
should be able to support a future driver that might want to set both 
S-TAG and C-TAG per VF.
We could have used a single struct on kernel side instead of a list of 
size 1, but this would cause bad/not scalable code in the parsing stage.
As the UAPI is a list, in the parsing stage we thought it is more 
correct to use the constant MAX_VLAN_LIST_LEN and iterate as of a 
general case, even though currently the list size is one.

>   I just realized that I forgot to add Moshe and Tariq
> on Cc (I relied on scripts/get_maintainer.pl, but didn't double-check).
> I've added them to Cc now, hope they can clarify this.
>
> 	Arnd

Regards,
Moshe and Tariq