[PATCH v2] vsock/virtio: fix accept queue count leak on transport mismatch

[Dudu Lu <phx0fer@gmail.com>]

virtio_transport_recv_listen() calls sk_acceptq_added() before
vsock_assign_transport(). If vsock_assign_transport() fails or
selects a different transport, the error path returns without
calling sk_acceptq_removed(), permanently incrementing
sk_ack_backlog.

After approximately backlog+1 such failures, sk_acceptq_is_full()
returns true, causing the listener to reject all new connections.

Fix by moving sk_acceptq_added() to after the transport validation,
matching the pattern used by vmci_transport and hyperv_transport.

Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Signed-off-by: Dudu Lu <phx0fer@gmail.com>
---
 net/vmw_vsock/virtio_transport_common.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 8a9fb23c6e85..e01d983488e5 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1560,8 +1560,6 @@ virtio_transport_recv_listen(struct sock *sk, struct sk_buff *skb,
 		return -ENOMEM;
 	}
 
-	sk_acceptq_added(sk);
-
 	lock_sock_nested(child, SINGLE_DEPTH_NESTING);
 
 	child->sk_state = TCP_ESTABLISHED;
@@ -1583,6 +1581,7 @@ virtio_transport_recv_listen(struct sock *sk, struct sk_buff *skb,
 		return ret;
 	}
 
+	sk_acceptq_added(sk);
 	if (virtio_transport_space_update(child, skb))
 		child->sk_write_space(child);
 
-- 
2.39.3 (Apple Git-145)