[Patch net] bpf: check NULL for sk_to_full_sk() return value

[Cong Wang]

When req->rsk_listener is NULL, sk_to_full_sk() returns
NULL too, so we have to check its return value against
NULL here.

Fixes: 40304b2a1567 ("bpf: BPF support for sock_ops")
Reported-by: David Ahern <dsah...@gmail.com>
Tested-by: David Ahern <dsah...@gmail.com>
Cc: Lawrence Brakmo <bra...@fb.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 include/linux/bpf-cgroup.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 360c082e885c..d41d40ac3efd 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -85,7 +85,7 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
        int __ret = 0;                                                         \
        if (cgroup_bpf_enabled && (sock_ops)->sk) {            \
                typeof(sk) __sk = sk_to_full_sk((sock_ops)->sk);               \
-               if (sk_fullsock(__sk))                                         \
+               if (__sk && sk_fullsock(__sk))                                 \
                        __ret = __cgroup_bpf_run_filter_sock_ops(__sk,         \
                                                                 sock_ops,     \
                                                         BPF_CGROUP_SOCK_OPS); \
-- 
2.13.0