[PATCH AUTOSEL 4.9 3/4] usbnet: sanity check for maxpacket

[Sasha Levin]

From: Oliver Neukum <oneukum@xxxxxxxx>

[ Upstream commit 397430b50a363d8b7bdda00522123f82df6adc5e ]

maxpacket of 0 makes no sense and oopses as we need to divide
by it. Give up.

V2: fixed typo in log and stylistic issues

Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Reported-by: syzbot+76bb1d34ffa0adc03baa@xxxxxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Johan Hovold <johan@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211021122944.21816-1-oneukum@xxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/usb/usbnet.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 0b5fd1499ac0..965e1a7b179f 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1740,6 +1740,10 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 	if (!dev->rx_urb_size)
 		dev->rx_urb_size = dev->hard_mtu;
 	dev->maxpacket = usb_maxpacket (dev->udev, dev->out, 1);
+	if (dev->maxpacket == 0) {
+		/* that is a broken device */
+		goto out4;
+	}
 
 	/* let userspace know we have a random address */
 	if (ether_addr_equal(net->dev_addr, node_id))
-- 
2.33.0