[PATCH net-next 1/3] bpf: use skb_to_full_sk helper in bpf_skb_under_cgroup

[Daniel Borkmann]

We need to use skb_to_full_sk() helper introduced in commit bd5eb35f16a9
("xfrm: take care of request sockets") as otherwise we miss tcp synack
messages, since ownership is on request socket and therefore it would
miss the sk_fullsock() check. Use skb_to_full_sk() as also done similarly
in the bpf_get_cgroup_classid() helper via 2309236c13fe ("cls_cgroup:
get sk_classid only from full sockets") fix to not let this fall through.

Fixes: 4a482f34afcc ("cgroup: bpf: Add bpf_skb_in_cgroup_proto")
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
Acked-by: Alexei Starovoitov <a...@kernel.org>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 0920c2a..e5d9977 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2408,7 +2408,7 @@ BPF_CALL_3(bpf_skb_under_cgroup, struct sk_buff *, skb, 
struct bpf_map *, map,
        struct cgroup *cgrp;
        struct sock *sk;
 
-       sk = skb->sk;
+       sk = skb_to_full_sk(skb);
        if (!sk || !sk_fullsock(sk))
                return -ENOENT;
        if (unlikely(idx >= array->map.max_entries))
-- 
1.9.3