linux-kernel - Re: [PATCH net-next v18 07/25] ovpn: implement basic TX path (UDP)

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Message-ID: <4c97399a-8975-40ca-aa6a-0c18a366d596@openvpn.net>
Date: Wed, 5 Feb 2025 10:12:45 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: Sabrina Dubroca <sd@...asysnail.net>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Donald Hunter <donald.hunter@...il.com>, Shuah Khan <shuah@...nel.org>,
 ryazanov.s.a@...il.com, Andrew Lunn <andrew+netdev@...n.ch>,
 Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Xiao Liang <shaw.leon@...il.com>
Subject: Re: [PATCH net-next v18 07/25] ovpn: implement basic TX path (UDP)

On 04/02/2025 17:18, Sabrina Dubroca wrote:
> 2025-02-03, 10:52:41 +0100, Sabrina Dubroca wrote:
>> 2025-01-13, 10:31:26 +0100, Antonio Quartulli wrote:
>>> +static void ovpn_encrypt_post(struct sk_buff *skb, int ret)
>>> +{
>>> +	struct ovpn_peer *peer = ovpn_skb_cb(skb)->peer;
>>> +
>>> +	if (unlikely(ret < 0))
>>> +		goto err;
>>> +
>>> +	skb_mark_not_on_list(skb);
>>> +
>>> +	switch (peer->sock->sock->sk->sk_protocol) {
>>
>> We have a ref on the peer, but not on the ovpn_sock. DEL_PEER could
>> have detached the sock by the time the crypto completes.
>>
>> (unfortunately I don't have any idea to fix this yet)
> 
> Maybe an idea:
> 
> Since ovpn_sock itself lives under RCU (because of sk_user_data),
> peer->sock should be an RCU pointer and also follow RCU rules. For
> most parts (io.c, netlink.c) the conversion is not too
> problematic. TCP is more difficult.
> 
> I still need to think about whether this works, and whether this is
> worth the complexity, or if we could solve this in another way.

It may actually be a reasonable solution.
And maybe it is not that complex to get done.

I'll see what I come up with.

Regards,


-- 
Antonio Quartulli
OpenVPN Inc.