net: usb: pegasus: Proper error handing when setting pegasus' MAC address

v2:

If reading the MAC address from eeprom fail don't throw an error, use randomly
generated MAC instead.  Either way the adapter will soldier on and the return
type of set_ethernet_addr() can be reverted to void.

v1:

Fix a bug in set_ethernet_addr() which does not take into account possible
errors (or partial reads) returned by its helpers.  This can potentially lead to
writing random data into device's MAC address registers.

Signed-off-by: Petko Manolov <petko.manolov@konsulko.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: petkomanolov

drivers/net/usb/pegasus.c

@@ -360,28 +360,47 @@ static int write_eprom_word(pegasus_t *pegasus, __u8 index, __u16 data)
 }
 #endif				/* PEGASUS_WRITE_EEPROM */
 
-static inline void get_node_id(pegasus_t *pegasus, __u8 *id)
+static inline int get_node_id(pegasus_t *pegasus, u8 *id)
 {
-	int i;
-	__u16 w16;
+	int i, ret;
+	u16 w16;
 
 	for (i = 0; i < 3; i++) {
-		read_eprom_word(pegasus, i, &w16);
+		ret = read_eprom_word(pegasus, i, &w16);
+		if (ret < 0)
+			return ret;
 		((__le16 *) id)[i] = cpu_to_le16(w16);
 	}
+
+	return 0;
 }
 
 static void set_ethernet_addr(pegasus_t *pegasus)
 {
-	__u8 node_id[6];
+	int ret;
+	u8 node_id[6];
 
 	if (pegasus->features & PEGASUS_II) {
-		get_registers(pegasus, 0x10, sizeof(node_id), node_id);
+		ret = get_registers(pegasus, 0x10, sizeof(node_id), node_id);
+		if (ret < 0)
+			goto err;
 	} else {
-		get_node_id(pegasus, node_id);
-		set_registers(pegasus, EthID, sizeof(node_id), node_id);
+		ret = get_node_id(pegasus, node_id);
+		if (ret < 0)
+			goto err;
+		ret = set_registers(pegasus, EthID, sizeof(node_id), node_id);
+		if (ret < 0)
+			goto err;
 	}
+
 	memcpy(pegasus->net->dev_addr, node_id, sizeof(node_id));
+
+	return;
+err:
+	eth_hw_addr_random(pegasus->net);
+	dev_info(&pegasus->intf->dev, "software assigned MAC address.\n");
+
+	return;
 }
 
 static inline int reset_mac(pegasus_t *pegasus)