2025-02-27, 02:21:37 +0100, Antonio Quartulli wrote:
> Moreover export tcp_release_cb by means of EXPORT_SYMBOL instead of
> EXPORT_IPV6_MOD, so that other modules can use it, even if IPV6 is
> not compiled in.
Is that really needed? You're saving tcp.sk_cb.prot, so you could just
call peer->tcp.sk_cb.prot->release_cb? (with a bit of care since it's
called after peer_put)
[I don't know what the maintainers' preference is wrt "re-exporting"
symbols that got moved to EXPORT_IPV6_MOD]
[...]
> +static void ovpn_tcp_send_sock(struct ovpn_peer *peer, struct sock *sk)
> +{
> + struct sk_buff *skb = peer->tcp.out_msg.skb;
> +
> + if (!skb)
> + return;
> +
> + if (peer->tcp.tx_in_progress)
> + return;
> +
> + peer->tcp.tx_in_progress = true;
> +
> + do {
> + int ret = skb_send_sock_locked(sk, skb,
> + peer->tcp.out_msg.offset,
> + peer->tcp.out_msg.len);
> + if (unlikely(ret < 0)) {
> + if (ret == -EAGAIN)
> + goto out;
> +
> + net_warn_ratelimited("%s: TCP error to peer %u: %d\n",
> + netdev_name(peer->ovpn->dev),
> + peer->id, ret);
> +
> + /* in case of TCP error we can't recover the VPN
> + * stream therefore we abort the connection
> + */
> + ovpn_peer_del(peer,
> + OVPN_DEL_PEER_REASON_TRANSPORT_ERROR);
I don't think this works:
ovpn_peer_del -> unlock_ovpn -> ovpn_socket_release -> might_sleep
but we can get to ovpn_tcp_send_sock in a few contexts that are not
allowed to sleep:
ovpn_tcp_send_skb -> ovpn_tcp_send_sock_skb -> ovpn_tcp_send_sock
__sk_flush_backlog -> release_cb = ovpn_tcp_release -> ovpn_tcp_send_sock_skb
release_sock -> release_cb = ovpn_tcp_release -> ovpn_tcp_send_sock_skb
(I checked all other paths leading to unlock_ovpn/ovpn_socket_release,
this is the only one I could find that is not allowed to sleep. So it
would likely be easier to push this peer_del (or even just the
handling of release_list) into some other sleepable context than
trying to reshuffle all the other paths)
--
Sabrina
