On Thu, Aug 04, 2022 at 04:44:47PM -0700, Peilin Ye wrote:
Hi Stefano,
On Thu, Aug 04, 2022 at 08:59:23AM +0200, Stefano Garzarella wrote:
The last thing I was trying to figure out before sending the patch was
whether to set sock->state = SS_UNCONNECTED in vsock_connect_timeout().
I think we should do that, otherwise a subsequent to connect() with
O_NONBLOCK set would keep returning -EALREADY, even though the timeout has
expired.
What do you think?
Thanks for bringing this up, after thinking about sock->state, I have 3
thoughts:
1. I think the root cause of this memleak is, we keep @connect_work
pending, even after the 2nd, blocking request times out (or gets
interrupted) and sets sock->state back to SS_UNCONNECTED.
@connect_work is effectively no-op when sk->sk_state is
TCP_CLOS{E,ING} anyway, so why not we just cancel @connect_work when
blocking requests time out or get interrupted? Something like:
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index f04abf662ec6..62628af84164 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1402,6 +1402,9 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
lock_sock(sk);
if (signal_pending(current)) {
+ if (cancel_delayed_work(&vsk->connect_work))
+ sock_put(sk);
+
err = sock_intr_errno(timeout);
sk->sk_state = sk->sk_state == TCP_ESTABLISHED ? TCP_CLOSING : TCP_CLOSE;
sock->state = SS_UNCONNECTED;
@@ -1409,6 +1412,9 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
vsock_remove_connected(vsk);
goto out_wait;
} else if (timeout == 0) {
+ if (cancel_delayed_work(&vsk->connect_work))
+ sock_put(sk);
+
err = -ETIMEDOUT;
sk->sk_state = TCP_CLOSE;
sock->state = SS_UNCONNECTED;
Then no need to worry about rescheduling @connect_work, and the state
machine becomes more accurate. What do you think? I will ask syzbot
to test this.
It could work, but should we set `sk->sk_err` and call sk_error_report()
to wake up thread waiting on poll()?
Maybe the previous version is simpler.
2. About your suggestion of setting sock->state = SS_UNCONNECTED in
vsock_connect_timeout(), I think it makes sense. Are you going to
send a net-next patch for this?
If you have time, feel free to send it.
Since it is a fix, I believe you can use the "net" tree. (Also for this
patch).
Remember to put the "Fixes" tag that should be the same.
3. After a TCP_SYN_SENT sock receives VIRTIO_VSOCK_OP_RESPONSE in
virtio_transport_recv_connecting(), why don't we cancel
@connect_work?
Am I missing something?
Because when the timeout will fire, vsock_connect_timeout() will just
call sock_put() since sk->sk_state is changed.
Of course, we can cancel it if we want, but I think it's not worth it.
In the end, this rescheduling patch should solve all the problems.
Thanks,
Stefano
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