linux-kernel - [Linux-kernel-mentees][PATCH] net: usb: rtl8150: prevent set_ethernet

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Date:   Tue, 29 Sep 2020 13:50:28 +0530
From:   Anant Thazhemadam <anant.thazhemadam@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        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: [Linux-kernel-mentees][PATCH] net: usb: rtl8150: prevent set_ethernet_addr from setting uninit address

When get_registers() fails (which happens when usb_control_msg() fails)
in set_ethernet_addr(), the uninitialized value of node_id gets copied
as the address.

Checking for the return values appropriately, and handling the case
wherein set_ethernet_addr() fails like this, helps in avoiding the
mac address being incorrectly set in this manner.

Reported-by: syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.com
Tested-by: syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.com
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
---
 drivers/net/usb/rtl8150.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
index 733f120c852b..e542a9ab2ff8 100644
--- a/drivers/net/usb/rtl8150.c
+++ b/drivers/net/usb/rtl8150.c
@@ -150,7 +150,7 @@ static const char driver_name [] = "rtl8150";
 **	device related part of the code
 **
 */
-static int get_registers(rtl8150_t * dev, u16 indx, u16 size, void *data)
+static int get_registers(rtl8150_t *dev, u16 indx, u16 size, void *data)
 {
 	void *buf;
 	int ret;
@@ -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];
+	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 > 0 && ret <= sizeof(node_id)) {
+		memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
+		return true;
+	}
+	return false;
 }
 
 static int rtl8150_set_mac_address(struct net_device *netdev, void *p)
@@ -909,21 +914,24 @@ 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, "couldn't set the ethernet address for the device\n");
+		goto out2;
+	}
 	usb_set_intfdata(intf, dev);
 	SET_NETDEV_DEV(netdev, &intf->dev);
 	if (register_netdev(netdev) != 0) {
 		dev_err(&intf->dev, "couldn't register the device\n");
-		goto out2;
+		goto out3;
 	}
 
 	dev_info(&intf->dev, "%s: rtl8150 is detected\n", netdev->name);
 
 	return 0;
 
-out2:
+out3:
 	usb_set_intfdata(intf, NULL);
+out2:
 	free_skb_pool(dev);
 out1:
 	free_all_urbs(dev);
-- 
2.25.1