vsock/bpf: Warn on socket without transport

In the spirit of commit 91751e2 ("vsock: prevent null-ptr-deref in
vsock_*[has_data|has_space]"), armorize the "impossible" cases with a
warning.

Fixes: 634f1a7 ("vsock: support sockmap")
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: mmhal

net/vmw_vsock/af_vsock.c

@@ -1189,6 +1189,9 @@ static int vsock_read_skb(struct sock *sk, skb_read_actor_t read_actor)
 {
 	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

@@ -87,7 +87,7 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
 	lock_sock(sk);
 	vsk = vsock_sk(sk);
 
-	if (!vsk->transport) {
+	if (WARN_ON_ONCE(!vsk->transport)) {
 		copied = -ENODEV;
 		goto out;
 	}