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

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Date:   Wed, 10 Jul 2019 12:35:43 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     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

On Tue, 09 Jul 2019 20:33:58 -0700, John Fastabend wrote:
> 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.

Do we need to hold the lock in unhash, too, or is unhash called with
sk_callback_lock held?

> > > +	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);