netdev - Re: [bpf PATCH v2 6/6] bpf: sockmap/tls, close can race with map free

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Date:   Tue, 09 Jul 2019 20:33:58 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        John Fastabend <john.fastabend@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        edumazet@...gle.com, bpf@...r.kernel.org
Subject: Re: [bpf PATCH v2 6/6] bpf: sockmap/tls, close can race with map free

Jakub Kicinski wrote:
> On Mon, 08 Jul 2019 19:15:18 +0000, John Fastabend wrote:
> > @@ -352,15 +354,18 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
> >  	if (ctx->tx_conf == TLS_BASE && ctx->rx_conf == TLS_BASE)
> >  		goto skip_tx_cleanup;
> >  
> > -	sk->sk_prot = ctx->sk_proto;
> >  	tls_sk_proto_cleanup(sk, ctx, timeo);
> >  
> >  skip_tx_cleanup:
> > +	write_lock_bh(&sk->sk_callback_lock);
> > +	icsk->icsk_ulp_data = NULL;
> 
> Is ulp_data pointer now supposed to be updated under the
> sk_callback_lock?

Yes otherwise it can race with tls_update(). I didn't remove the
ulp pointer null set from tcp_ulp.c though. Could be done in this
patch or as a follow up.
> 
> > +	if (sk->sk_prot->close == tls_sk_proto_close)
> > +		sk->sk_prot = ctx->sk_proto;
> > +	write_unlock_bh(&sk->sk_callback_lock);
> >  	release_sock(sk);
> >  	if (ctx->rx_conf == TLS_SW)
> >  		tls_sw_release_strp_rx(ctx);
> > -	sk_proto_close(sk, timeout);
> > -
> > +	ctx->sk_proto_close(sk, timeout);
> >  	if (ctx->tx_conf != TLS_HW && ctx->rx_conf != TLS_HW &&
> >  	    ctx->tx_conf != TLS_HW_RECORD && ctx->rx_conf != TLS_HW_RECORD)
> >  		tls_ctx_free(ctx);