netdev - Re: [PATCH bpf] bpf: net: Set sk_bpf_storage back to NULL for cloned sk

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Date:   Tue, 9 Jul 2019 09:33:21 -0700
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     Martin KaFai Lau <kafai@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>, kernel-team@...com
Subject: Re: [PATCH bpf] bpf: net: Set sk_bpf_storage back to NULL for cloned
 sk

On 06/11, Martin KaFai Lau wrote:
> The cloned sk should not carry its parent-listener's sk_bpf_storage.
> This patch fixes it by setting it back to NULL.
Have you thought about some kind of inheritance for listener sockets'
storage? Suppose I have a situation where I write something
to listener's sk storage (directly or via recently added sockopts hooks)
and I want to inherit that state for a freshly established connection.

I was looking into adding possibility to call bpf_get_listener_sock form
BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB callback to manually
copy some data form the listener socket, but I don't think
at this point there is any association between newly established
socket and the listener.

Thoughts/ideas?

(Btw, sorry for digging up this old mail, but it feels relevant).

> Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage")
> Signed-off-by: Martin KaFai Lau <kafai@...com>
> ---
>  net/core/sock.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 2b3701958486..d90fd04622e5 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1850,6 +1850,9 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
>  			goto out;
>  		}
>  		RCU_INIT_POINTER(newsk->sk_reuseport_cb, NULL);
> +#ifdef CONFIG_BPF_SYSCALL
> +		RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL);
> +#endif
>  
>  		newsk->sk_err	   = 0;
>  		newsk->sk_err_soft = 0;
> -- 
> 2.17.1
>