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: v4.13.16~28
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f99427bc5d83e5c8546560c006effa91592cfcc4;p=thirdparty%2Fkernel%2Fstable.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 8ab281b478f23..4f88f64cccb49 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.