On 1/14/20 9:45 AM, Nikolay Aleksandrov wrote:
> On 14/01/2020 18:36, Nikolay Aleksandrov wrote:
>> On 14/01/2020 17:34, David Ahern wrote:
>>> On 1/14/20 6:55 AM, Jakub Kicinski wrote:
>>>> On Mon, 13 Jan 2020 17:52:28 +0200, Nikolay Aleksandrov wrote:
>>>>> +static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
>>>>> +{
>>>>> + int idx = 0, err = 0, s_idx = cb->args[0];
>>>>> + struct net *net = sock_net(skb->sk);
>>>>> + struct br_vlan_msg *bvm;
>>>>> + struct net_device *dev;
>>>>> +
>>>>> + if (cb->nlh->nlmsg_len < nlmsg_msg_size(sizeof(*bvm))) {
>>>>
>>>> I wonder if it'd be useful to make this a strict != check? At least
>>>> when strict validation is on? Perhaps we'll one day want to extend
>>>> the request?
>>>>
>>>
>>> +1. All new code should be using the strict checks.
>>>
>>
>> IIRC, I did it to be able to add filter attributes later, but it should just use nlmsg_parse()
>> instead and all will be taken care of.
>> I'll respin v2 with that change.
>>
>> Thanks,
>> Nik
>>
>
> Actually nlmsg_parse() uses the same "<" check for the size before parsing. :)
> If I change to it and with no attributes to parse would be essentially equal to the
> current situation, but if I make it strict "!=" then we won't be able to add
> filter attributes later as we won't be backwards compatible. I'll continue looking
> into it, but IMO we should leave it as it is in order to be able to add the filtering later.
>
> Thoughts ?
>
>
>
>
If the header is > sizeof(*bvm) I expect this part of
__nla_validate_parse() to kick in:
if (unlikely(rem > 0)) {
pr_warn_ratelimited("netlink: %d bytes leftover after
parsing attributes in process `%s'.\n",
rem, current->comm);
NL_SET_ERR_MSG(extack, "bytes leftover after parsing
attributes");
if (validate & NL_VALIDATE_TRAILING)
return -EINVAL;
}
