usbnet: sanity checking of packet sizes and device mtu

[ Upstream commit 280ceaed79f18db930c0cc8bb21f6493490bf29c ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 07c00e378a5cdfbd9b62bec5f085b65f32ff3626..ef1d667b0108bb949df0f33e0a3ea5f06ad03c95 100644 (file)
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -344,6 +344,8 @@ 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;
@@ -360,6 +362,7 @@ 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;
        }
 }