[PATCH 4.4 082/137] cdc-acm: fix NULL pointer reference

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver Neukum <oneukum@xxxxxxxx>

commit 29c6dd591bbd592472247441de9fa694acdabae8 upstream.

The union descriptor must be checked. Its usage was conditional
before the parser was introduced. This is important, because
many RNDIS device, which also use the common parser, have
bogus extra descriptors.

Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Tested-by: Vasily Galkin <galkin-vv@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/net/usb/cdc_ether.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/net/usb/cdc_ether.c
+++ b/drivers/net/usb/cdc_ether.c
@@ -160,6 +160,12 @@ int usbnet_generic_cdc_bind(struct usbne
 	info->u = header.usb_cdc_union_desc;
 	info->header = header.usb_cdc_header_desc;
 	info->ether = header.usb_cdc_ether_desc;
+	if (!info->u) {
+		if (rndis)
+			goto skip;
+		else /* in that case a quirk is mandatory */
+			goto bad_desc;
+	}
 	/* we need a master/control interface (what we're
 	 * probed with) and a slave/data interface; union
 	 * descriptors sort this all out.
@@ -256,7 +262,7 @@ skip:
 			goto bad_desc;
 		}
 
-	} else if (!info->header || !info->u || (!rndis && !info->ether)) {
+	} else if (!info->header || (!rndis && !info->ether)) {
 		dev_dbg(&intf->dev, "missing cdc %s%s%sdescriptor\n",
 			info->header ? "" : "header ",
 			info->u ? "" : "union ",