net: hsr: fix mac_len checks

Commit 2e9f60932a2c ("net: hsr: check skb can contain struct hsr_ethhdr
in fill_frame_info") added the following which resulted in -EINVAL
always being returned:
if (skb->mac_len < sizeof(struct hsr_ethhdr))
return -EINVAL;

mac_len was not being set correctly so this check completely broke
HSR/PRP since it was always 14, not 20.

Set mac_len correctly and modify the mac_len checks to test in the
correct places since sometimes it is legitimately 14.

Fixes: 2e9f60932a2c ("net: hsr: check skb can contain struct hsr_ethhdr in fill_frame_info")
Signed-off-by: George McCollister <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/hsr/hsr_device.c

···
 	if (master) {
 		skb->dev = master->dev;
 		skb_reset_mac_header(skb);
+		skb_reset_mac_len(skb);
 		hsr_forward_skb(skb, master);
 	} else {
 		atomic_long_inc(&dev->tx_dropped);
···
 		goto out;
 
 	skb_reset_mac_header(skb);
+	skb_reset_mac_len(skb);
 	skb_reset_network_header(skb);
 	skb_reset_transport_header(skb);
 

net/hsr/hsr_forward.c

···
 	}
 }
 
-void hsr_fill_frame_info(__be16 proto, struct sk_buff *skb,
-			 struct hsr_frame_info *frame)
+int hsr_fill_frame_info(__be16 proto, struct sk_buff *skb,
+			struct hsr_frame_info *frame)
 {
 	struct hsr_port *port = frame->port_rcv;
 	struct hsr_priv *hsr = port->hsr;
···
 	/* HSRv0 supervisory frames double as a tag so treat them as tagged. */
 	if ((!hsr->prot_version && proto == htons(ETH_P_PRP)) ||
 	    proto == htons(ETH_P_HSR)) {
+		/* Check if skb contains hsr_ethhdr */
+		if (skb->mac_len < sizeof(struct hsr_ethhdr))
+			return -EINVAL;
+
 		/* HSR tagged frame :- Data or Supervision */
 		frame->skb_std = NULL;
 		frame->skb_prp = NULL;
 		frame->skb_hsr = skb;
 		frame->sequence_nr = hsr_get_skb_sequence_nr(skb);
-		return;
+		return 0;
 	}
 
 	/* Standard frame or PRP from master port */
 	handle_std_frame(skb, frame);
+
+	return 0;
 }
 
-void prp_fill_frame_info(__be16 proto, struct sk_buff *skb,
-			 struct hsr_frame_info *frame)
+int prp_fill_frame_info(__be16 proto, struct sk_buff *skb,
+			struct hsr_frame_info *frame)
 {
 	/* Supervision frame */
 	struct prp_rct *rct = skb_get_PRP_rct(skb);
···
 		frame->skb_std = NULL;
 		frame->skb_prp = skb;
 		frame->sequence_nr = prp_get_skb_sequence_nr(rct);
-		return;
+		return 0;
 	}
 	handle_std_frame(skb, frame);
+
+	return 0;
 }
 
 static int fill_frame_info(struct hsr_frame_info *frame,
···
 	struct hsr_vlan_ethhdr *vlan_hdr;
 	struct ethhdr *ethhdr;
 	__be16 proto;
+	int ret;
 
-	/* Check if skb contains hsr_ethhdr */
-	if (skb->mac_len < sizeof(struct hsr_ethhdr))
+	/* Check if skb contains ethhdr */
+	if (skb->mac_len < sizeof(struct ethhdr))
 		return -EINVAL;
 
 	memset(frame, 0, sizeof(*frame));
···
 
 	frame->is_from_san = false;
 	frame->port_rcv = port;
-	hsr->proto_ops->fill_frame_info(proto, skb, frame);
+	ret = hsr->proto_ops->fill_frame_info(proto, skb, frame);
+	if (ret)
+		return ret;
+
 	check_local_dest(port->hsr, skb, frame);
 
 	return 0;

net/hsr/hsr_forward.h

···
 				       struct hsr_port *port);
 bool prp_drop_frame(struct hsr_frame_info *frame, struct hsr_port *port);
 bool hsr_drop_frame(struct hsr_frame_info *frame, struct hsr_port *port);
-void prp_fill_frame_info(__be16 proto, struct sk_buff *skb,
-			 struct hsr_frame_info *frame);
-void hsr_fill_frame_info(__be16 proto, struct sk_buff *skb,
-			 struct hsr_frame_info *frame);
+int prp_fill_frame_info(__be16 proto, struct sk_buff *skb,
+			struct hsr_frame_info *frame);
+int hsr_fill_frame_info(__be16 proto, struct sk_buff *skb,
+			struct hsr_frame_info *frame);
 #endif /* __HSR_FORWARD_H */

net/hsr/hsr_main.h

···
 					       struct hsr_port *port);
 	struct sk_buff * (*create_tagged_frame)(struct hsr_frame_info *frame,
 						struct hsr_port *port);
-	void (*fill_frame_info)(__be16 proto, struct sk_buff *skb,
-				struct hsr_frame_info *frame);
+	int (*fill_frame_info)(__be16 proto, struct sk_buff *skb,
+			       struct hsr_frame_info *frame);
 	bool (*invalid_dan_ingress_frame)(__be16 protocol);
 	void (*update_san_info)(struct hsr_node *node, bool is_sup);
 };

net/hsr/hsr_slave.c

···
 		goto finish_pass;
 
 	skb_push(skb, ETH_HLEN);
-
-	if (skb_mac_header(skb) != skb->data) {
-		WARN_ONCE(1, "%s:%d: Malformed frame at source port %s)\n",
-			  __func__, __LINE__, port->dev->name);
-		goto finish_consume;
-	}
+	skb_reset_mac_header(skb);
+	if ((!hsr->prot_version && protocol == htons(ETH_P_PRP)) ||
+	    protocol == htons(ETH_P_HSR))
+		skb_set_network_header(skb, ETH_HLEN + HSR_HLEN);
+	skb_reset_mac_len(skb);
 
 	hsr_forward_skb(skb, port);