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).
>
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.
