netdev - Re: [PATCH bpf] bpf: devmap: fix wrong interface selection in notifier

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Date:   Wed, 24 Oct 2018 20:03:35 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     ast@...nel.org, Netdev <netdev@...r.kernel.org>,
        john.fastabend@...il.com
Subject: Re: [PATCH bpf] bpf: devmap: fix wrong interface selection in notifier_call

Hi Daniel!

On Wed, 24 Oct 2018 at 18:07, Daniel Borkmann <daniel@...earbox.net> wrote:
>
> [ +John ]
>
> On 10/22/2018 05:41 PM, Taehee Yoo wrote:
> > The dev_map_notification() removes interface in devmap if
> > unregistering interface's ifindex is same.
> > But only checking ifindex is not enough because other netns can have
> > same ifindex. so that wrong interface selection could occurred.
> > Hence the net_eq() is needed.
> >
> > Fixes: 2ddf71e23cc2 ("net: add notifier hooks for devmap bpf map")
> > Signed-off-by: Taehee Yoo <ap420073@...il.com>
> > ---
> >  kernel/bpf/devmap.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> > index 141710b82a6c..0d9211e49a4a 100644
> > --- a/kernel/bpf/devmap.c
> > +++ b/kernel/bpf/devmap.c
> > @@ -496,6 +496,7 @@ static int dev_map_notification(struct notifier_block *notifier,
> >                               ulong event, void *ptr)
> >  {
> >       struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
> > +     struct net *net = dev_net(netdev);
> >       struct bpf_dtab *dtab;
> >       int i;
> >
> > @@ -512,7 +513,7 @@ static int dev_map_notification(struct notifier_block *notifier,
> >                               struct bpf_dtab_netdev *dev, *odev;
> >
> >                               dev = READ_ONCE(dtab->netdev_map[i]);
> > -                             if (!dev ||
> > +                             if (!dev || !net_eq(net, dev_net(dev->dev)) ||
> >                                   dev->dev->ifindex != netdev->ifindex)
>
> Can't we just compare netdev pointers directly here?
>

Thank you for review!
I tested what you suggested, It works well and it's more simple.
So that I will send v2 patch that just compares netdev pointer instead of
using ifindex and net_eq().

> >                                       continue;
> >                               odev = cmpxchg(&dtab->netdev_map[i], dev, NULL);
> >
>

Thanks!