On Mon, Sep 24, 2018 at 1:52 PM Willem de Bruijn
<willemdebruijn.ker...@gmail.com> wrote:
>
> From: Willem de Bruijn <will...@google.com>
>
> BPF flow dissectors are configured per network namespace.
> __skb_flow_dissect looks up the netns through dev_net(skb->dev).
>
> In some dissector paths skb->dev is NULL, such as for Unix sockets.
> In these cases fall back to looking up the netns by socket.
>
> Analyzing the codepaths leading to __skb_flow_dissect I did not find
> a case where both skb->dev and skb->sk are NULL. Warn and fall back to
> standard flow dissector if one is found.
>
> Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook")
> Reported-by: Eric Dumazet <eduma...@google.com>
> Signed-off-by: Willem de Bruijn <will...@google.com>
Acked-by: Song Liu <songliubrav...@fb.com>
> ---
> net/core/flow_dissector.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 5c5dd74b5b3b..738c7562e1e0 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -714,7 +714,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
> struct flow_dissector_key_vlan *key_vlan;
> enum flow_dissect_ret fdret;
> enum flow_dissector_key_id dissector_vlan = FLOW_DISSECTOR_KEY_MAX;
> - struct bpf_prog *attached;
> + struct bpf_prog *attached = NULL;
> int num_hdrs = 0;
> u8 ip_proto = 0;
> bool ret;
> @@ -755,8 +755,14 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
> target_container);
>
> rcu_read_lock();
> - attached = skb ?
> rcu_dereference(dev_net(skb->dev)->flow_dissector_prog)
> - : NULL;
> + if (skb) {
> + if (skb->dev)
> + attached =
> rcu_dereference(dev_net(skb->dev)->flow_dissector_prog);
> + else if (skb->sk)
> + attached =
> rcu_dereference(sock_net(skb->sk)->flow_dissector_prog);
> + else
> + WARN_ON_ONCE(1);
> + }
> if (attached) {
> /* Note that even though the const qualifier is discarded
> * throughout the execution of the BPF program, all
> changes(the
> --
> 2.19.0.444.g18242da7ef-goog
>
