net: cdc_ether: fix divide by 0 on bad descriptors

bmork · davem330 · commit 2cb80187ba06 · 2017-11-08T13:42:01.000+09:00
Setting dev-&gt;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 &lt;bjorn@mork.no&gt;
Acked-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/drivers/net/usb/cdc_ether.c b/drivers/net/usb/cdc_ether.c
@@ -230,7 +230,7 @@ int usbnet_generic_cdc_bind(struct usbnet *dev, struct usb_interface *intf)
 			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.

Original file line number	Diff line number	Diff line change
`@@ -230,7 +230,7 @@ int usbnet_generic_cdc_bind(struct usbnet dev, struct usb_interface intf)`
`230`	`230`	`goto bad_desc;`
`231`	`231`	`}`
`232`	`232`
`233`		`- if (header.usb_cdc_ether_desc) {`
	`233`	`+ if (header.usb_cdc_ether_desc && info->ether->wMaxSegmentSize) {`
`234`	`234`	`dev->hard_mtu = le16_to_cpu(info->ether->wMaxSegmentSize);`
`235`	`235`	`/* because of Zaurus, we may be ignoring the host`
`236`	`236`	`* side link address we were given.`