# \[PATCH AUTOSEL 5.10 12/13\] usbnet: sanity check for maxpacket

- From: Sasha Levin \<sashal@kernel.org\>
- Date: 2021-10-25 17:01:46 
- List: linux-usb
- Page: https://ratatoskr.run/linux-usb/2021/10/1552835
- Thread: https://ratatoskr.run/stable/2021/10/1552823/t.md

```text
From: Oliver Neukum <oneukum@suse.com>

[ 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@suse.com>
Reported-by: <redacted>
Reviewed-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20211021122944.21816-1-oneukum@suse.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 6062dc27870e..d0c8aec1b8da 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1755,6 +1755,10 @@ 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

```