netdev - Re: [PATCH net-next v11 18/23] ovpn: implement peer add/get/dump/delete via netlink

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Message-ID: <Zyjk781vOqV4kXhJ@hog>
Date: Mon, 4 Nov 2024 16:14:55 +0100
From: Sabrina Dubroca <sd@...asysnail.net>
To: Antonio Quartulli <antonio@...nvpn.net>
Cc: 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@...n.ch>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v11 18/23] ovpn: implement peer
 add/get/dump/delete via netlink

2024-10-29, 11:47:31 +0100, Antonio Quartulli wrote:
> +static int ovpn_nl_peer_precheck(struct ovpn_struct *ovpn,
> +				 struct genl_info *info,
> +				 struct nlattr **attrs)
> +{
> +	if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_PEER], attrs,
> +			      OVPN_A_PEER_ID))
> +		return -EINVAL;
> +
> +	if (attrs[OVPN_A_PEER_REMOTE_IPV4] && attrs[OVPN_A_PEER_REMOTE_IPV6]) {
> +		NL_SET_ERR_MSG_MOD(info->extack,
> +				   "cannot specify both remote IPv4 or IPv6 address");
> +		return -EINVAL;
> +	}
> +
> +	if (!attrs[OVPN_A_PEER_REMOTE_IPV4] &&
> +	    !attrs[OVPN_A_PEER_REMOTE_IPV6] && attrs[OVPN_A_PEER_REMOTE_PORT]) {
> +		NL_SET_ERR_MSG_MOD(info->extack,
> +				   "cannot specify remote port without IP address");
> +		return -EINVAL;
> +	}
> +
> +	if (!attrs[OVPN_A_PEER_REMOTE_IPV4] &&
> +	    attrs[OVPN_A_PEER_LOCAL_IPV4]) {
> +		NL_SET_ERR_MSG_MOD(info->extack,
> +				   "cannot specify local IPv4 address without remote");
> +		return -EINVAL;
> +	}
> +
> +	if (!attrs[OVPN_A_PEER_REMOTE_IPV6] &&
> +	    attrs[OVPN_A_PEER_LOCAL_IPV6]) {

I think these consistency checks should account for v4mapped
addresses. With remote=v4mapped and local=v6 we'll end up with an
incorrect ipv4 "local" address (taken out of the ipv6 address's first
4B by ovpn_peer_reset_sockaddr). With remote=ipv6 and local=v4mapped,
we'll pass the last 4B of OVPN_A_PEER_LOCAL_IPV6 to
ovpn_peer_reset_sockaddr and try to read 16B (the full ipv6 address)
out of that.

> +		NL_SET_ERR_MSG_MOD(info->extack,
> +				   "cannot specify local IPV6 address without remote");
> +		return -EINVAL;
> +	}


[...]
>  int ovpn_nl_peer_set_doit(struct sk_buff *skb, struct genl_info *info)
>  {
[...]
> +	ret = ovpn_nl_peer_modify(peer, info, attrs);
> +	if (ret < 0) {
> +		ovpn_peer_put(peer);
> +		return ret;
> +	}
> +
> +	/* ret == 1 means that VPN IPv4/6 has been modified and rehashing
> +	 * is required
> +	 */
> +	if (ret > 0) {

&& mode == MP ?

I don't see ovpn_nl_peer_modify checking that before returning 1, and
in P2P mode ovpn->peers will be NULL.

> +		spin_lock_bh(&ovpn->peers->lock);
> +		ovpn_peer_hash_vpn_ip(peer);
> +		spin_unlock_bh(&ovpn->peers->lock);
> +	}
> +
> +	ovpn_peer_put(peer);
> +
> +	return 0;
> +}

>  int ovpn_nl_peer_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
>  {
[...]
> +	} else {
> +		rcu_read_lock();
> +		hash_for_each_rcu(ovpn->peers->by_id, bkt, peer,
> +				  hash_entry_id) {
> +			/* skip already dumped peers that were dumped by
> +			 * previous invocations
> +			 */
> +			if (last_idx > 0) {
> +				last_idx--;
> +				continue;
> +			}

If a peer that was dumped during a previous invocation is removed in
between, we'll miss one that's still present in the overall dump. I
don't know how much it matters (I guses it depends on how the results
of this dump are used by userspace), so I'll let you decide if this
needs to be fixed immediately or if it can be ignored for now.

> +
> +			if (ovpn_nl_send_peer(skb, info, peer,
> +					      NETLINK_CB(cb->skb).portid,
> +					      cb->nlh->nlmsg_seq,
> +					      NLM_F_MULTI) < 0)
> +				break;
> +
> +			/* count peers being dumped during this invocation */
> +			dumped++;
> +		}
> +		rcu_read_unlock();
> +	}
> +
> +out:
> +	netdev_put(ovpn->dev, &ovpn->dev_tracker);
> +
> +	/* sum up peers dumped in this message, so that at the next invocation
> +	 * we can continue from where we left
> +	 */
> +	cb->args[1] += dumped;
> +	return skb->len;
>  }
>  
>  int ovpn_nl_peer_del_doit(struct sk_buff *skb, struct genl_info *info)
>  {
> -	return -EOPNOTSUPP;
> +	struct nlattr *attrs[OVPN_A_PEER_MAX + 1];
> +	struct ovpn_struct *ovpn = info->user_ptr[0];
> +	struct ovpn_peer *peer;
> +	u32 peer_id;
> +	int ret;
> +
> +	if (GENL_REQ_ATTR_CHECK(info, OVPN_A_PEER))
> +		return -EINVAL;
> +
> +	ret = nla_parse_nested(attrs, OVPN_A_PEER_MAX, info->attrs[OVPN_A_PEER],
> +			       ovpn_peer_nl_policy, info->extack);
> +	if (ret)
> +		return ret;
> +
> +	if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_PEER], attrs,
> +			      OVPN_A_PEER_ID))
> +		return -EINVAL;
> +
> +	peer_id = nla_get_u32(attrs[OVPN_A_PEER_ID]);
> +
> +	peer = ovpn_peer_get_by_id(ovpn, peer_id);
> +	if (!peer)

maybe c/p the extack from ovpn_nl_peer_get_doit?

> +		return -ENOENT;
> +
> +	netdev_dbg(ovpn->dev, "%s: peer id=%u\n", __func__, peer->id);
> +	ret = ovpn_peer_del(peer, OVPN_DEL_PEER_REASON_USERSPACE);
> +	ovpn_peer_put(peer);
> +
> +	return ret;
>  }

-- 
Sabrina