On Fri, Sep 22, 2017 at 1:48 PM, Petar Penkov <peterpenko...@gmail.com> wrote:
> On Fri, Sep 22, 2017 at 9:51 AM, Mahesh Bandewar (महेश बंडेवार)
> <mahe...@google.com> wrote:
>> On Fri, Sep 22, 2017 at 7:06 AM, Willem de Bruijn
>> <willemdebruijn.ker...@gmail.com> wrote:
>>>> @@ -2061,6 +2174,9 @@ static int tun_set_iff(struct net *net, struct file
>>>> *file, struct ifreq *ifr)
>>>> if (tfile->detached)
>>>> return -EINVAL;
>>>>
>>>> + if ((ifr->ifr_flags & IFF_NAPI_FRAGS) && !capable(CAP_NET_ADMIN))
>>>> + return -EPERM;
>>>> +
>>>
>>> This should perhaps be moved into the !dev branch, directly below the
>>> ns_capable check.
>>>
>> Hmm, does that mean fail only on creation but allow to attach if
>> exists? That would be wrong, isn't it? Correct me if I'm wrong but we
>> want to prevent both these scenarios if user does not have sufficient
>> privileges (i.e. NET_ADMIN in init-ns).
Ok.
>>
> My understanding is we want to protect both scenarios.
>>>> dev = __dev_get_by_name(net, ifr->ifr_name);
>>>> if (dev) {
>>>> if (ifr->ifr_flags & IFF_TUN_EXCL)
>>>> @@ -2185,6 +2301,9 @@ static int tun_set_iff(struct net *net, struct file
>>>> *file, struct ifreq *ifr)
>>>> tun->flags = (tun->flags & ~TUN_FEATURES) |
>>>> (ifr->ifr_flags & TUN_FEATURES);
>>>>
>>>> + if (!(tun->flags & IFF_NAPI) || (tun->flags & TUN_TYPE_MASK) !=
>>>> IFF_TAP)
>>>> + tun->flags = tun->flags & ~IFF_NAPI_FRAGS;
>>>> +
>>>
>>> Similarly, this check only need to be performed in that branch.
>>> Instead of reverting to non-frags mode, a tun_set_iff with the wrong
>>> set of flags should probably fail hard.
>> Yes, agree, wrong set of flags should fail hard and probably be done
>> before attach or open, no?
> Agreed, in v3 I will push this check before the conditional so both
> branches can be rejected with EINVAL.
Sounds great.
