Re: [PATCH net] vsock: do not reset a socket in connect() once it has connected

[Hyunwoo Kim <imv4bel@gmail.com>]

On Wed, Aug 19, 2026 at 10:54:38AM +0200, Stefano Garzarella wrote:
> On Mon, Aug 17, 2026 at 12:29:11AM +0200, Michal Luczaj wrote:
> > On 8/14/26 03:45, Hyunwoo Kim wrote:
> > > On Thu, Aug 13, 2026 at 11:42:17AM +0200, Michal Luczaj wrote:
> > > > On 8/12/26 22:13, Hyunwoo Kim wrote:
> > > > > commit 002541ef650b ("vsock: Ignore signal/timeout on connect() if
> > > > > already established") stopped connect() from resetting an established
> > > > > socket. The check only looks at whether sk_state is TCP_ESTABLISHED at
> > > > > that moment, and the state can change while connect() sleeps.
> > > > 
> > > > I guess this makes my fix incomplete. "Fixes: 002541ef650b"?
> > > 
> > > It is incomplete, yes. But this has been triggerable since d021c344051a, so
> > > I'd keep Fixes: d021c344051a.
> > 
> > OK, I get it.
> > 
> > > > > A peer RST moves the socket to TCP_CLOSING, and it is not removed from
> > > > > vsock_connected_table on that path. connect() then wakes up, fails the
> > > > > check, and resets a socket that had actually connected to TCP_CLOSE and
> > > > > SS_UNCONNECTED.
> > > > 
> > > > Thanks for the details. Do I get it right: connect() misses the fact that
> > > > socket might have already transitioned TCP_ESTABLISHED -> TCP_CLOSING
> > > > during schedule_timeout()?
> > > 
> > > Yes, that's it.
> > > 
> > > > 
> > > > How about:
> > > > 
> > > > diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> > > > index 622dbd046799..39c42ef016c3 100644
> > > > --- a/net/vmw_vsock/af_vsock.c
> > > > +++ b/net/vmw_vsock/af_vsock.c
> > > > @@ -1807,15 +1807,18 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
> > > >  		timeout = schedule_timeout(timeout);
> > > >  		lock_sock(sk);
> > > > 
> > > > -		/* Connection established. Whatever happens to socket once we
> > > > +		/* Connection (has been) established. Whatever happens to socket once we
> > > >  		 * release it, that's not connect()'s concern. No need to go
> > > >  		 * into signal and timeout handling. Call it a day.
> > > >  		 *
> > > >  		 * Note that allowing to "reset" an already established socket
> > > >  		 * here is racy and insecure.
> > > >  		 */
> > > > -		if (sk->sk_state == TCP_ESTABLISHED)
> > > > -			break;
> > > > +		if (sk->sk_state == TCP_ESTABLISHED ||
> > > > +		    sk->sk_state == TCP_CLOSING) {
> > > > +			err = -sk->sk_err;
> > > > +			goto out_wait;
> > > > +		}
> > > > 
> > > >  		/* If connection was _not_ established and a signal/timeout came
> > > >  		 * to be, we want the socket's state reset. User space may want
> > > > 
> > > > ?
> > > 
> > > Yes, I like it better than mine. I confirmed it fixes the issue.
> > 
> > Great, thanks.
> > 
> > > If you don't mind, would you take the patch from here?
> > 
> > Sure, no problem.
> > 
> > Stefano, does this look good to you?
> 
> Yep, thanks for helping here!
> 
> My only doubt is if it makes sense to leave the `break` there, and add a
> similar check before resetting the socket, I mean something like this:
> 
> 	err = sock_error(sk);
> 	if (err && sk->sk_state != TCP_ESTABLISHED &&
> 		   sk->sk_state != TCP_CLOSING)) {
> 		sk->sk_state = TCP_CLOSE;
> 		sock->state = SS_UNCONNECTED;
> 	}
> 
> Just to be a bit more defensive, but I don't have a strong opinion, your
> version is also fine.
> 
> > And should any sk_err be consumed
> > here, too? (`err = sock_error(sk)` instead of `err = -sk->sk_err`)
> 
> I'd stay with sock_error() to consume the error if it makes sense also for
> you.
> 
> Thanks,
> Stefano
> 

Gentle ping. I'd appreciate an update on where this stands.


Best regards,
Hyunwoo Kim