net: usb: ax88179_178a: initialize local variables before use

Use memset to initialize local array in drivers/net/usb/ax88179_178a.c, and
also set a local u16 and u32 variable to 0. Fixes a KMSAN found uninit-value bug
reported by syzbot at:
https://syzkaller.appspot.com/bug?id=00371c73c72f72487c1d0bfe0cc9d00de339d5aa

Reported-by: syzbot+4993e4a0e237f1b53747@syzkaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/ax88179_178a.c

@@ -296,12 +296,12 @@ static int ax88179_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
 	int ret;
 
 	if (2 == size) {
-		u16 buf;
+		u16 buf = 0;
 		ret = __ax88179_read_cmd(dev, cmd, value, index, size, &buf, 0);
 		le16_to_cpus(&buf);
 		*((u16 *)data) = buf;
 	} else if (4 == size) {
-		u32 buf;
+		u32 buf = 0;
 		ret = __ax88179_read_cmd(dev, cmd, value, index, size, &buf, 0);
 		le32_to_cpus(&buf);
 		*((u32 *)data) = buf;
@@ -1296,6 +1296,8 @@ static void ax88179_get_mac_addr(struct usbnet *dev)
 {
 	u8 mac[ETH_ALEN];
 
+	memset(mac, 0, sizeof(mac));
+
 	/* Maybe the boot loader passed the MAC address via device tree */
 	if (!eth_platform_get_mac_address(&dev->udev->dev, mac)) {
 		netif_dbg(dev, ifup, dev->net,