netdev - Re: [bpf PATCH v4 1/4] bpf: tls, implement unhash to avoid transition out of ESTABLISHED

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Date:   Fri, 10 May 2019 10:00:54 -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,
        bpf@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [bpf PATCH v4 1/4] bpf: tls, implement unhash to avoid
 transition out of ESTABLISHED

On Thu, 09 May 2019 21:57:49 -0700, John Fastabend wrote:
> @@ -2042,12 +2060,14 @@ void tls_sw_free_resources_tx(struct sock *sk)
>  	if (atomic_read(&ctx->encrypt_pending))
>  		crypto_wait_req(-EINPROGRESS, &ctx->async_wait);
>  
> -	release_sock(sk);
> +	if (locked)
> +		release_sock(sk);
>  	cancel_delayed_work_sync(&ctx->tx_work.work);

So in the splat I got (on a slightly hacked up kernel) it seemed like
unhash may be called in atomic context:

[  783.232150]  tls_sk_proto_unhash+0x72/0x110 [tls]
[  783.237497]  tcp_set_state+0x484/0x640
[  783.241776]  ? __sk_mem_reduce_allocated+0x72/0x4a0
[  783.247317]  ? tcp_recv_timestamp+0x5c0/0x5c0
[  783.252265]  ? tcp_write_queue_purge+0xa6a/0x1180
[  783.257614]  tcp_done+0xac/0x260
[  783.261309]  tcp_reset+0xbe/0x350
[  783.265101]  tcp_validate_incoming+0xd9d/0x1530

I may have been unclear off-list, I only tested the patch no longer
crashes the offload :(

> -	lock_sock(sk);
> +	if (locked)
> +		lock_sock(sk);
>  
>  	/* Tx whatever records we can transmit and abandon the rest */
> -	tls_tx_records(sk, -1);
> +	tls_tx_records(sk, tls_ctx, -1);
>  
>  	/* Free up un-sent records in tx_list. First, free
>  	 * the partially sent record if any at head of tx_list.