vsock/bpf: Warn on socket without transport

In the spirit of commit 91751e248256 ("vsock: prevent null-ptr-deref in
vsock_*[has_data|has_space]"), armorize the "impossible" cases with a
warning.

Fixes: 634f1a7110b4 ("vsock: support sockmap")
Signed-off-by: Michal Luczaj <[e-mail]>
Reviewed-by: Stefano Garzarella <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

net/vmw_vsock/af_vsock.c

···
 {
 	struct vsock_sock *vsk = vsock_sk(sk);
 
+	if (WARN_ON_ONCE(!vsk->transport))
+		return -ENODEV;
+
 	return vsk->transport->read_skb(vsk, read_actor);
 }
 

net/vmw_vsock/vsock_bpf.c

···
 	lock_sock(sk);
 	vsk = vsock_sk(sk);
 
-	if (!vsk->transport) {
+	if (WARN_ON_ONCE(!vsk->transport)) {
 		copied = -ENODEV;
 		goto out;
 	}