netdev - Re: [bpf PATCH 1/3] bpf: tls, implement unhash to avoid transition out of ESTABLISHED

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Date:   Wed, 24 Apr 2019 20:34:43 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [bpf PATCH 1/3] bpf: tls, implement unhash to avoid transition
 out of ESTABLISHED

On 4/24/19 8:07 PM, Jakub Kicinski wrote:
> On Wed, 24 Apr 2019 12:21:03 -0700, John Fastabend wrote:
>> It is possible (via shutdown()) for TCP socks to go through TCP_CLOSE
>> state via tcp_disconnect() without calling into close callback. This
>> would allow a kTLS enabled socket to exist outside of ESTABLISHED
>> state which is not supported.
>>
>> Solve this the same way we solved the sock{map|hash} case by adding
>> an unhash hook to remove tear down the TLS state.
>>
>> In the process we also make the close hook more robust. We add a put
>> call into the close path, also in the unhash path, to remove the
>> reference to ulp data after free. Its no longer valid and may confuse
>> things later if the socket (re)enters kTLS code paths. Second we add
>> an 'if(ctx)' check to ensure the ctx is still valid and not released
>> from a previous unhash/close path.
>>
>> Fixes: d91c3e17f75f2 ("net/tls: Only attach to sockets in ESTABLISHED state")
>> Reported-by: Eric Dumazet <edumazet@...gle.com>
>> Signed-off-by: John Fastabend <john.fastabend@...il.com>
> 
> Ah, EDOESNTBUILD, now I get to nitpick too? :)
> 

Oops messed up a merge conflict. nitpicks seems like a fair enough
punishment.

# CONFIG_TLS_DEVICE is not set


[...]

>>  static inline struct tls_sw_context_rx *tls_sw_ctx_rx(
>>  		const struct tls_context *tls_ctx)
>> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
>> index 7e546b8ec000..2973048957bd 100644
>> --- a/net/tls/tls_main.c
>> +++ b/net/tls/tls_main.c
>> @@ -261,23 +261,16 @@ static void tls_ctx_free(struct tls_context *ctx)
>>  	kfree(ctx);
>>  }
>>  
>> -static void tls_sk_proto_close(struct sock *sk, long timeout)
>> +static bool tls_sk_proto_destroy(struct sock *sk,
>> +				 struct tls_context *ctx, bool destroy)
> 
> perhaps this destroy should rather be called locked?  It doesn't really
> control destroying AFACT..
> 

Sure we can call it locked.

>>  {
>> -	struct tls_context *ctx = tls_get_ctx(sk);
>>  	long timeo = sock_sndtimeo(sk, 0);
>> -	void (*sk_proto_close)(struct sock *sk, long timeout);
>> -	bool free_ctx = false;
>> -
>> -	lock_sock(sk);
>> -	sk_proto_close = ctx->sk_proto_close;
>>  
>>  	if (ctx->tx_conf == TLS_HW_RECORD && ctx->rx_conf == TLS_HW_RECORD)
>> -		goto skip_tx_cleanup;
>> +		return false;
>>  
>> -	if (ctx->tx_conf == TLS_BASE && ctx->rx_conf == TLS_BASE) {
>> -		free_ctx = true;
>> -		goto skip_tx_cleanup;
>> -	}
>> +	if (ctx->tx_conf == TLS_BASE && ctx->rx_conf == TLS_BASE)
>> +		return true;
>>  
>>  	if (!tls_complete_pending_work(sk, ctx, 0, &timeo))
>>  		tls_handle_open_record(sk, 0);
>> @@ -286,10 +279,10 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
>>  	if (ctx->tx_conf == TLS_SW) {
>>  		kfree(ctx->tx.rec_seq);
>>  		kfree(ctx->tx.iv);
>> -		tls_sw_free_resources_tx(sk);
>> +		tls_sw_free_resources_tx(sk, destroy);
>>  #ifdef CONFIG_TLS_DEVICE
>>  	} else if (ctx->tx_conf == TLS_HW) {
>> -		tls_device_free_resources_tx(sk);
>> +		tls_device_free_resources_tx(sk, destroy);
> 
> this part breaks the build tls_device_free_resources_tx() doesn't need
> changes.  tls_device_offload_cleanup_rx() will though, cause it sleeps.

OK will touch that path as well.

> 
>>  #endif
>>  	}
>>  
>> @@ -310,8 +303,39 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
>>  		tls_ctx_free(ctx);
>>  		ctx = NULL;
>>  	}
>> +	return false;
>> +}
>> +
>> +static void tls_sk_proto_unhash(struct sock *sk)
>> +{
>> +	struct tls_context *ctx = tls_get_ctx(sk);
>> +	void (*sk_proto_unhash)(struct sock *sk);
>> +	bool free_ctx;
>> +
>> +	if (!ctx)
>> +		return sk->sk_prot->unhash(sk);
>> +	sk_proto_unhash = ctx->sk_proto_unhash;
>> +	free_ctx = tls_sk_proto_destroy(sk, ctx, false);
>> +	tls_put_ctx(sk);
>> +	if (sk_proto_unhash)
>> +		sk_proto_unhash(sk);
>> +	if (free_ctx)
>> +		tls_ctx_free(ctx);
>> +}
>>  
>> -skip_tx_cleanup:
>> +static void tls_sk_proto_close(struct sock *sk, long timeout)
>> +{
>> +	struct tls_context *ctx = tls_get_ctx(sk);
>> +	void (*sk_proto_close)(struct sock *sk, long timeout);
> 
> reverse xmas tree
> 

+1

>> +	bool free_ctx;
>> +
>> +	if (!ctx)
>> +		return sk->sk_prot->destroy(sk);
>> +
>> +	lock_sock(sk);
>> +	sk_proto_close = ctx->sk_proto_close;
>> +	free_ctx = tls_sk_proto_destroy(sk, ctx, true);
>> +	tls_put_ctx(sk);
>>  	release_sock(sk);
>>  	sk_proto_close(sk, timeout);
>>  	/* free ctx for TLS_HW_RECORD, used by tcp_set_state


Thanks for reviewing.