ethernet/netronome/nfp: Fix a use after free in nfp_bpf_ctrl_msg_rx

In nfp_bpf_ctrl_msg_rx, if
nfp_ccm_get_type(skb) == NFP_CCM_TYPE_BPF_BPF_EVENT is true, the skb
will be freed. But the skb is still used by nfp_ccm_rx(&bpf->ccm, skb).

My patch adds a return when the skb was freed.

Fixes: bcf0cafa ("nfp: split out common control message handling code")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/bpf/cmsg.c

@@ -454,6 +454,7 @@ void nfp_bpf_ctrl_msg_rx(struct nfp_app *app, struct sk_buff *skb)
 			dev_consume_skb_any(skb);
 		else
 			dev_kfree_skb_any(skb);
+		return;
 	}
 
 	nfp_ccm_rx(&bpf->ccm, skb);