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.
> > 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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