linux-kernel - Re: [PATCH] net: rtnl: avoid uninitialized data in IFLA_VF_VLAN

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Date:   Sun, 2 Oct 2016 12:03:37 +0300
From:   Tariq Toukan <tariqt@...lanox.com>
To:     Arnd Bergmann <arnd@...db.de>, Eric Dumazet <edumazet@...gle.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        "Hannes Frederic Sowa" <hannes@...essinduktion.org>,
        Nogah Frankel <nogahf@...lanox.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Moshe Shemesh" <moshe@...lanox.com>
Subject: Re: [PATCH] net: rtnl: avoid uninitialized data in IFLA_VF_VLAN_LIST
 handling

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@...lanox.com>

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