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Date:   Mon,  5 Oct 2020 18:59:58 +0530
From:   Anant Thazhemadam <anant.thazhemadam@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org, joe@...ches.com,
        Anant Thazhemadam <anant.thazhemadam@...il.com>,
        syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.com,
        Petko Manolov <petkan@...leusys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4] net: usb: rtl8150: set random MAC address when set_ethernet_addr() fails

When get_registers() fails in set_ethernet_addr(),the uninitialized
value of node_id gets copied over as the address.
So, check the return value of get_registers().

If get_registers() executed successfully (i.e., it returns
sizeof(node_id)), copy over the MAC address using ether_addr_copy()
(instead of using memcpy()).

Else, if get_registers() failed instead, a randomly generated MAC
address is set as the MAC address instead.

Reported-by: syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.com
Tested-by: syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.com
Acked-by: Petko Manolov <petkan@...leusys.com>
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
---
Changes in v4:
	* Use netdev_notice() instead of dev_warn() and update the 
	  logged message to show the new random MAC as well 
	  (Suggested by Joe Perches <joe@...ches.com>)
	* Convert set_ethernet_addr()'s return type back to void.
	  Since we're not treating get_registers() (and thus 
	  set_ethernet_addr()) failing as an erroneous condition,
	  we can perform the error handling (setting a random
	  ethernet address) that was being done in v3 within 
	  set_ethernet_addr() itself.
	  (Suggested by Petko Manolov <petkan@...leusys.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@...emloft.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@...ches.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 
	  (Suggested by Petko Manolov <petkan@...leusys.com>)
	* Added Acked-by: Petko Manolov

 drivers/net/usb/rtl8150.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
index 733f120c852b..9d079dc2a535 100644
--- a/drivers/net/usb/rtl8150.c
+++ b/drivers/net/usb/rtl8150.c
@@ -274,12 +274,20 @@ 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 void set_ethernet_addr(rtl8150_t *dev)
 {
-	u8 node_id[6];
+	u8 node_id[ETH_ALEN];
+	int ret;
+
+	ret = get_registers(dev, IDR, sizeof(node_id), node_id);
 
-	get_registers(dev, IDR, sizeof(node_id), node_id);
-	memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
+	if (ret == sizeof(node_id)) {
+		ether_addr_copy(dev->netdev->dev_addr, node_id);
+	} else {
+		eth_hw_addr_random(dev->netdev);
+		netdev_notice(dev->netdev, "Assigned a random MAC address: %pM\n",
+			      dev->netdev->dev_addr);
+	}
 }
 
 static int rtl8150_set_mac_address(struct net_device *netdev, void *p)
-- 
2.25.1

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