[PATCH v3] net: usb: rtl8150: set random MAC address when set_ethernet_addr() fails

[Anant Thazhemadam <anant.thazhemadam@gmail.com>]

When get_registers() fails, in set_ethernet_addr(),the uninitialized
value of node_id gets copied as the address. This can be considered as
set_ethernet_addr() itself failing.

The return type of set_ethernet_addr() is modified to indicate if it
failed or not, and return values are appropriately checked by caller.

When set_ethernet_addr() fails, a randomly generated MAC address is set
as the MAC address instead.

On the other hand, for the case when get_registers() does succeed,
set_ethernet_addr() has been updated to use ether_addr_copy() to copy
the address, instead of memcpy().

Reported-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
Tested-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
Acked-by: Petko Manolov <petkan@nucleusys.com>
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
---
Changes in v3:

	* Set a random MAC address to the device rather than making
	  the device not work at all in the even set_ethernet_addr()
	  fails. (Suggested by David Miller <davem@davemloft.net>)

	* Update set_ethernet_addr() to use ether_addr_copy() to copy 
	  the MAC Address (instead of using memcpy() for that same).
	  (Suggested by Joe Perches <joe@perches.com>)


Changes in v2:

	* Modified condition checking get_registers()'s return value to 
		ret == sizeof(node_id)
	  for stricter checking in compliance with the new usb_control_msg_recv()
	  API

	* Added Acked-by: Petko Manolov

 drivers/net/usb/rtl8150.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
index 733f120c852b..bbd49ebdf095 100644
--- a/drivers/net/usb/rtl8150.c
+++ b/drivers/net/usb/rtl8150.c
@@ -274,12 +274,17 @@ static int write_mii_word(rtl8150_t * dev, u8 phy, __u8 indx, u16 reg)
 		return 1;
 }
 
-static inline void set_ethernet_addr(rtl8150_t * dev)
+static bool set_ethernet_addr(rtl8150_t *dev)
 {
-	u8 node_id[6];
+	u8 node_id[ETH_ALEN];
+	int ret;
 
-	get_registers(dev, IDR, sizeof(node_id), node_id);
-	memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
+	ret = get_registers(dev, IDR, sizeof(node_id), node_id);
+	if (ret == sizeof(node_id)) {
+		ether_addr_copy(dev->netdev->dev_addr, node_id);
+		return true;
+	}
+	return false;
 }
 
 static int rtl8150_set_mac_address(struct net_device *netdev, void *p)
@@ -909,7 +914,10 @@ static int rtl8150_probe(struct usb_interface *intf,
 		goto out1;
 	}
 	fill_skb_pool(dev);
-	set_ethernet_addr(dev);
+	if (!set_ethernet_addr(dev)) {
+		dev_err(&intf->dev, "assigining a random MAC address\n");
+		eth_hw_addr_random(dev->netdev);
+	}
 
 	usb_set_intfdata(intf, dev);
 	SET_NETDEV_DEV(netdev, &intf->dev);
-- 
2.25.1