Re: [bpf PATCH 1/2] bpf, sockmap: fix sk->prot unhash op reset

Cong Wang
2021-03-25T00:12:26Z

On Wed, Mar 24, 2021 at 1:59 PM John Fastabend <john.fastabend@gmail.com> wrote:
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index 47b7c5334c34..ecb5634b4c4a 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -754,6 +754,12 @@ static void tls_update(struct sock *sk, struct proto *p,
>
> ctx = tls_get_ctx(sk);
> if (likely(ctx)) {
> + /* TLS does not have an unhash proto in SW cases, but we need
> + * to ensure we stop using the sock_map unhash routine because
> + * the associated psock is being removed. So use the original
> + * unhash handler.
> + */
> + WRITE_ONCE(sk->sk_prot->unhash, p->unhash);
> ctx->sk_write_space = write_space;
> ctx->sk_proto = p;

It looks awkward to update sk->sk_proto inside tls_update(),
at least when ctx!=NULL.

What is wrong with updating it in sk_psock_restore_proto()
when inet_csk_has_ulp() is true? It looks better to me.

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 6c09d94be2e9..da5dc3ef0ee3 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -360,8 +360,8 @@ static inline void sk_psock_update_proto(struct sock *sk,
static inline void sk_psock_restore_proto(struct sock *sk,
struct sk_psock *psock)
{
- sk->sk_prot->unhash = psock->saved_unhash;
if (inet_csk_has_ulp(sk)) {
+ sk->sk_prot->unhash = psock->sk_proto->unhash;
tcp_update_ulp(sk, psock->sk_proto, psock->saved_write_space);
} else {
sk->sk_write_space = psock->saved_write_space;

sk_psock_restore_proto() is the only caller of tcp_update_ulp()
so should be equivalent.

Thanks.