Re: [Patch bpf-next v8 10/16] sock: introduce sk->sk_prot->psock_update_sk_prot()

[Eric Dumazet]

On 3/31/21 4:32 AM, Cong Wang wrote:
> From: Cong Wang <cong.w...@bytedance.com>
> 
> Currently sockmap calls into each protocol to update the struct
> proto and replace it. This certainly won't work when the protocol
> is implemented as a module, for example, AF_UNIX.
> 
> Introduce a new ops sk->sk_prot->psock_update_sk_prot(), so each
> protocol can implement its own way to replace the struct proto.
> This also helps get rid of symbol dependencies on CONFIG_INET.

[...]


>  
> -struct proto *tcp_bpf_get_proto(struct sock *sk, struct sk_psock *psock)
> +int tcp_bpf_update_proto(struct sock *sk, bool restore)
>  {
> +     struct sk_psock *psock = sk_psock(sk);

I do not think RCU is held here ?

sk_psock() is using rcu_dereference_sk_user_data()

>       int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
>       int config = psock->progs.msg_parser   ? TCP_BPF_TX   : TCP_BPF_BASE;
>  

Same issue in udp_bpf_update_proto() of course.