[PATCH net v3 3/8] vsock: do not preserve transport assignment

[Michal Luczaj]

Introduce vsock_unconnected_reset() and adapt vsock_connect().

Change transport assignment life cycle. On connect(), socket gets a
transport assigned. If connection fails (init went wrong, peer
misbehaviour, time out, signal), transport is de-assigned and socket state
is re-initialized. Once the connection is established, transport remains
assigned until close().

Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
---
 net/vmw_vsock/af_vsock.c | 74 ++++++++++++++++++++++++++++++------------------
 1 file changed, 47 insertions(+), 27 deletions(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 5c8e7e7d35b4..20181ddde114 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1679,6 +1679,42 @@ static int vsock_transport_cancel_pkt(struct vsock_sock *vsk)
 	return transport->cancel_pkt(vsk);
 }
 
+static void vsock_unconnected_reset(struct sock *sk)
+{
+	struct vsock_sock *vsk = vsock_sk(sk);
+
+	sock_owned_by_me(sk);
+
+	/*
+	 * Only connected socks may have peer_shutdown or SOCK_DONE set.
+	 *
+	 * Once established (TCP_ESTABLISHED, TCP_CLOSING), a socket can be
+	 * de-assigned only on close(). But we can narrow the check down to
+	 * states we actually expect (TCP_SYN_SENT, TCP_CLOSE).
+	 */
+	if (WARN_ON_ONCE(vsk->peer_shutdown) ||
+	    WARN_ON_ONCE(sock_flag(sk, SOCK_DONE)) ||
+	    WARN_ON_ONCE(sk->sk_state != TCP_SYN_SENT &&
+			 sk->sk_state != TCP_CLOSE))
+		return;
+
+	/*
+	 * Try to cancel a VIRTIO_VSOCK_OP_REQUEST skb that may have been sent
+	 * out by transport->connect().
+	 */
+	vsock_transport_cancel_pkt(vsk);
+
+	/*
+	 * No need to invoke transport->release() for unconnected connectible
+	 * sockets. Go straight for transport deassign.
+	 */
+	vsock_deassign_transport(vsk);
+
+	/* Revert socket to initial state. Keep sk_err. */
+	WRITE_ONCE(sk->sk_state, TCP_CLOSE);
+	sk->sk_socket->state = SS_UNCONNECTED;
+}
+
 static void vsock_connect_timeout(struct work_struct *work)
 {
 	struct sock *sk;
@@ -1690,11 +1726,9 @@ static void vsock_connect_timeout(struct work_struct *work)
 	lock_sock(sk);
 	if (sk->sk_state == TCP_SYN_SENT &&
 	    (sk->sk_shutdown != SHUTDOWN_MASK)) {
-		sk->sk_state = TCP_CLOSE;
-		sk->sk_socket->state = SS_UNCONNECTED;
 		sk->sk_err = ETIMEDOUT;
 		sk_error_report(sk);
-		vsock_transport_cancel_pkt(vsk);
+		vsock_unconnected_reset(sk);
 	}
 	release_sock(sk);
 
@@ -1760,7 +1794,7 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
 		if (!transport->stream_allow(vsk, remote_addr->svm_cid,
 					     remote_addr->svm_port)) {
 			err = -ENETUNREACH;
-			goto out;
+			goto out_reset;
 		}
 
 		if (vsock_msgzerocopy_allow(transport)) {
@@ -1771,18 +1805,18 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
 			 * feature is supported here.
 			 */
 			err = -EOPNOTSUPP;
-			goto out;
+			goto out_reset;
 		}
 
 		err = vsock_auto_bind(vsk);
 		if (err)
-			goto out;
+			goto out_reset;
 
 		sk->sk_state = TCP_SYN_SENT;
 
 		err = transport->connect(vsk);
 		if (err < 0)
-			goto out;
+			goto out_reset;
 
 		/* sk_err might have been set as a result of an earlier
 		 * (failed) connect attempt.
@@ -1825,8 +1859,9 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
 					     timeout))
 				sock_put(sk);
 
+			finish_wait(sk_sleep(sk), &wait);
 			/* Skip ahead to preserve error code set above. */
-			goto out_wait;
+			goto out;
 		}
 
 		release_sock(sk);
@@ -1844,12 +1879,7 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
 			break;
 
 		/* If connection was _not_ established and a signal/timeout came
-		 * to be, we want the socket's state reset. User space may want
-		 * to retry.
-		 *
-		 * sk_state != TCP_ESTABLISHED implies that socket is not on
-		 * vsock_connected_table. We keep the binding and the transport
-		 * assigned.
+		 * to be, we want the socket's state reset. We keep the binding.
 		 */
 		if (signal_pending(current) || timeout == 0) {
 			err = timeout == 0 ? -ETIMEDOUT : sock_intr_errno(timeout);
@@ -1859,14 +1889,6 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
 			 * sk_state == TCP_SYN_SENT, which hereby we break.
 			 * In such case VIRTIO_VSOCK_OP_RST will follow.
 			 */
-			sk->sk_state = TCP_CLOSE;
-			sock->state = SS_UNCONNECTED;
-
-			/* Try to cancel VIRTIO_VSOCK_OP_REQUEST skb sent out by
-			 * transport->connect().
-			 */
-			vsock_transport_cancel_pkt(vsk);
-
 			goto out_wait;
 		}
 
@@ -1874,13 +1896,11 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
 	}
 
 	err = sock_error(sk);
-	if (err) {
-		sk->sk_state = TCP_CLOSE;
-		sock->state = SS_UNCONNECTED;
-	}
-
 out_wait:
 	finish_wait(sk_sleep(sk), &wait);
+out_reset:
+	if (err)
+		vsock_unconnected_reset(sk);
 out:
 	release_sock(sk);
 	return err;

-- 
2.55.0