From: Bjørn Mork <bjorn@mork.no>
Date: Mon, 6 Nov 2017 14:37:22 +0000 (+0100)
Subject: net: cdc_ether: fix divide by 0 on bad descriptors
X-Git-Tag: archive/raspbian/4.9.80-2+rpi1~7^2~1232
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=f376621861e3d8a713d6931f4363c4137912330b;p=linux-4.9.git

net: cdc_ether: fix divide by 0 on bad descriptors


[ Upstream commit 2cb80187ba065d7decad7c6614e35e07aec8a974 ]

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

diff --git a/drivers/net/usb/cdc_ether.c b/drivers/net/usb/cdc_ether.c
index b82be816256c..1fca0024f294 100644
--- 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.