usbnet: sanity checking of packet sizes and device mtu

After a reset packet sizes and device mtu can change and need
to be reevaluated to calculate queue sizes.
Malicious devices can set this to zero and we divide by it.
Introduce sanity checking.

Reported-and-tested-by:  syzbot+6102c120be558c885f04@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 58952a79b05fb3122aace9452833759774d14835..e44849499b89e21384b07ef4759ed6b1f5c29d15 100644 (file)
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -339,6 +339,8 @@ void usbnet_update_max_qlen(struct usbnet *dev)
 {
        enum usb_device_speed speed = dev->udev->speed;
 
+       if (!dev->rx_urb_size || !dev->hard_mtu)
+               goto insanity;
        switch (speed) {
        case USB_SPEED_HIGH:
                dev->rx_qlen = MAX_QUEUE_MEMORY / dev->rx_urb_size;
@@ -355,6 +357,7 @@ void usbnet_update_max_qlen(struct usbnet *dev)
                dev->tx_qlen = 5 * MAX_QUEUE_MEMORY / dev->hard_mtu;
                break;
        default:
+insanity:
                dev->rx_qlen = dev->tx_qlen = 4;
        }
 }