Re: [PATCH RFC net-next] vsock: Reschedule connect_work for O_NONBLOCK connect() requests

On Fri, Aug 05, 2022 at 02:42:39PM +0200, Stefano Garzarella wrote:

On Thu, Aug 04, 2022 at 04:44:47PM -0700, Peilin Ye wrote:

quoted

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.

Right, I forgot about sk_error_report().  Let us use the simpler version
then.

quoted

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.

Sure, I will send them this week.  Thanks!

Peilin Ye