Re: [PATCH bpf-next v6 3/4] bpf: support specifying ingress via xdp_md context in BPF_PROG_TEST_RUN

[Zvi Effron <zeffron@riotgames.com>]

On Mon, Jun 21, 2021 at 2:26 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 6/18/21 1:29 AM, Zvi Effron wrote:
> > Support specifying the ingress_ifindex and rx_queue_index of xdp_md
> > contexts for BPF_PROG_TEST_RUN.
> >
> > The intended use case is to allow testing XDP programs that make decisions
> > based on the ingress interface or RX queue.
> >
> > If ingress_ifindex is specified, look up the device by the provided index
> > in the current namespace and use its xdp_rxq for the xdp_buff. If the
> > rx_queue_index is out of range, or is non-zero when the ingress_ifindex is
> > 0, return -EINVAL.
> >
> > Co-developed-by: Cody Haas <chaas@riotgames.com>
> > Signed-off-by: Cody Haas <chaas@riotgames.com>
> > Co-developed-by: Lisa Watanabe <lwatanabe@riotgames.com>
> > Signed-off-by: Lisa Watanabe <lwatanabe@riotgames.com>
> > Signed-off-by: Zvi Effron <zeffron@riotgames.com>
> > ---
> >   net/bpf/test_run.c | 22 +++++++++++++++++++++-
> >   1 file changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> > index 229c5deb813c..1ba15c741517 100644
> > --- a/net/bpf/test_run.c
> > +++ b/net/bpf/test_run.c
> > @@ -690,15 +690,35 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
> >
> >   static int xdp_convert_md_to_buff(struct xdp_md *xdp_md, struct xdp_buff *xdp)
> >   {
> > +     unsigned int ingress_ifindex, rx_queue_index;
> > +     struct netdev_rx_queue *rxqueue;
> > +     struct net_device *device;
> > +
> >       if (!xdp_md)
> >               return 0;
> >
> >       if (xdp_md->egress_ifindex != 0)
> >               return -EINVAL;
> >
> > -     if (xdp_md->ingress_ifindex != 0 || xdp_md->rx_queue_index != 0)
> > +     ingress_ifindex = xdp_md->ingress_ifindex;
> > +     rx_queue_index = xdp_md->rx_queue_index;
> > +
> > +     if (!ingress_ifindex && rx_queue_index)
> >               return -EINVAL;
> >
> > +     if (ingress_ifindex) {
> > +             device = dev_get_by_index(current->nsproxy->net_ns,
> > +                                       ingress_ifindex);
>
> This takes a reference on the device, which seems to be leaked here?

That would be an accurate assessment. Good catch. We'll fix that!

>
> > +             if (!device)
> > +                     return -EINVAL;
> > +
> > +             if (rx_queue_index >= device->real_num_rx_queues)
> > +                     return -EINVAL;
> > +
> > +             rxqueue = __netif_get_rx_queue(device, rx_queue_index);
> > +             xdp->rxq = &rxqueue->xdp_rxq;
> > +     }
> > +
> >       xdp->data = xdp->data_meta + xdp_md->data;
> >
> >       return 0;
> >
>