Subject: Re: [PATCH net-next v18 05/25] ovpn: introduce the ovpn_peer object

From: Sabrina Dubroca <[email-masked]>
Date: Sun, 2 Feb 2025 23:56:58 +0100

2025-01-13, 10:31:24 +0100, Antonio Quartulli wrote:
> +static int ovpn_peer_del_p2p(struct ovpn_peer *peer,
> +			     enum ovpn_del_peer_reason reason)
> +{
> +	struct ovpn_peer *tmp;
> +
> +	lockdep_assert_held(&peer->ovpn->lock);
> +
> +	tmp = rcu_dereference_protected(peer->ovpn->peer,
> +					lockdep_is_held(&peer->ovpn->lock));
> +	if (tmp != peer) {
> +		DEBUG_NET_WARN_ON_ONCE(1);

I think this WARN should be removed. If 2 almost-simultanenous
DEL_PEER manage to fetch the peer, the first will delete it and NULL
peer->ovpn->peer, then when it releases ovpn->lock, the 2nd will find
NULL != peer and hit this WARN.

(probably not happening in practical cases, but syzbot will manage to
hit it)

> +		return -ENOENT;
> +	}
> +
> +	ovpn_peer_remove(peer, reason);
> +
> +	return 0;
> +}

-- 
Sabrina