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

On 02/02/2025 23:56, Sabrina Dubroca wrote:

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)

I can see this happening with two almost-simultaneous netlink PEER_DEL calls.

Thanks, will get rid of the warning.

Regards,

...

• return -ENOENT;
  

• }
• ovpn_peer_remove(peer, reason);
• return 0;

+}