net: cdc_ether: fix divide by 0 on bad descriptors

commit 2cb80187ba065d7decad7c6614e35e07aec8a974 upstream.

Setting dev->hard_mtu to 0 will cause a divide error in
usbnet_probe. Protect against devices with bogus CDC Ethernet
functional descriptors by ignoring a zero wMaxSegmentSize.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/usb/cdc_ether.c b/drivers/net/usb/cdc_ether.c
index 8c408aa..f9343be 100644 (file)
--- a/drivers/net/usb/cdc_ether.c
+++ b/drivers/net/usb/cdc_ether.c
@@ -221,7 +221,7 @@ skip:
                        goto bad_desc;
        }
 
-       if (header.usb_cdc_ether_desc) {
+       if (header.usb_cdc_ether_desc && info->ether->wMaxSegmentSize) {
                dev->hard_mtu = le16_to_cpu(info->ether->wMaxSegmentSize);
                /* because of Zaurus, we may be ignoring the host
                 * side link address we were given.