On 01/10/2013 07:07 PM, Michael S. Tsirkin wrote:
> On Thu, Jan 10, 2013 at 06:43:20PM +0800, Jason Wang wrote:
>> On 01/10/2013 06:23 PM, Michael S. Tsirkin wrote:
>>> On Thu, Jan 10, 2013 at 08:59:48AM +0100, Stefan Hajnoczi wrote:
>>>> Multiqueue tun devices support detaching a tun_file from its tun_struct
>>>> and re-attaching at a later point in time. This allows users to disable
>>>> a specific queue temporarily.
>>>>
>>>> ioctl(TUNSETIFF) allows the user to specify the network interface to
>>>> attach by name. This means the user can attempt to attach to interface
>>>> "B" after detaching from interface "A".
>>>>
>>>> The driver is not designed to support this so check we are re-attaching
>>>> to the right tun_struct. Failure to do so may lead to oops.
>>>>
>>>> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
>>>> ---
>>>> This fix is for 3.8-rc.
>>>>
>>>> drivers/net/tun.c | 2 ++
>>>> 1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>>>> index fbd106e..cf6da6e 100644
>>>> --- a/drivers/net/tun.c
>>>> +++ b/drivers/net/tun.c
>>>> @@ -491,6 +491,8 @@ static int tun_attach(struct tun_struct *tun, struct
>>>> file *file)
>>>> err = -EINVAL;
>>>> if (rcu_dereference_protected(tfile->tun, lockdep_rtnl_is_held()))
>>>> goto out;
>>>> + if (tfile->detached && tun != tfile->detached)
>>>> + goto out;
>>>>
>>>> err = -EBUSY;
>>>> if (!(tun->flags & TUN_TAP_MQ) && tun->numqueues == 1)
>>>> --
>>>> 1.8.0.2
>>> I agree this is a bug but even with this patch, we still allow:
>>>
>>> SETIFF
>>> SETQUEUE (DISABLED)
>>> SETIFF
>>>
>>> Originally the rule always was that repeated setiff calls fail with
>>> EINVAL. We broke that when we set tun to NULL. It's probably worth
>>> preserving that, even if queue is disabled. Applying something like the
>>> below
>>> instead will address this concern, won't it?
>>>
>>> Note: works with regular userspace but I didn't test
>>> multiqueue userspace. What do you think.
>> Or just fail when tun->detached is not NULL at the beginning of
>> tun_set_iff()?
> Yes that'll also work I think. If you prefer this pls send patch.
Will post a patch, thanks.
>>> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
>>>
>>> ---
>>>
>>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>>> index fbd106e..5ec8b08 100644
>>> --- a/drivers/net/tun.c
>>> +++ b/drivers/net/tun.c
>>> @@ -483,7 +483,7 @@ static void tun_detach_all(struct net_device *dev)
>>> BUG_ON(tun->numdisabled != 0);
>>> }
>>>
>>> -static int tun_attach(struct tun_struct *tun, struct file *file)
>>> +static int tun_attach(struct tun_struct *tun, struct file *file, bool
>>> setiff)
>>> {
>>> struct tun_file *tfile = file->private_data;
>>> int err;
>>> @@ -492,6 +492,9 @@ static int tun_attach(struct tun_struct *tun, struct
>>> file *file)
>>> if (rcu_dereference_protected(tfile->tun, lockdep_rtnl_is_held()))
>>> goto out;
>>>
>>> + if (setiff && tfile->detached)
>>> + goto out;
>>> +
>>> err = -EBUSY;
>>> if (!(tun->flags & TUN_TAP_MQ) && tun->numqueues == 1)
>>> goto out;
>>> @@ -1561,7 +1564,7 @@ static int tun_set_iff(struct net *net, struct file
>>> *file, struct ifreq *ifr)
>>> if (err < 0)
>>> return err;
>>>
>>> - err = tun_attach(tun, file);
>>> + err = tun_attach(tun, file, true);
>>> if (err < 0)
>>> return err;
>>>
>>> @@ -1627,7 +1630,7 @@ static int tun_set_iff(struct net *net, struct file
>>> *file, struct ifreq *ifr)
>>> dev->features = dev->hw_features;
>>>
>>> INIT_LIST_HEAD(&tun->disabled);
>>> - err = tun_attach(tun, file);
>>> + err = tun_attach(tun, file, true);
>>> if (err < 0)
>>> goto err_free_dev;
>>>
>>> @@ -1792,7 +1795,7 @@ static int tun_set_queue(struct file *file, struct
>>> ifreq *ifr)
>>> else if (tun_not_capable(tun))
>>> ret = -EPERM;
>>> else
>>> - ret = tun_attach(tun, file);
>>> + ret = tun_attach(tun, file, false);
>>> } else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
>>> tun = rcu_dereference_protected(tfile->tun,
>>> lockdep_rtnl_is_held());
>>> --
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