[PATCH 3.18 17/45] qmi_wwan: do not steal interfaces from class drivers

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

From: "Bjørn Mork" <bjorn@mork.no>

[ Upstream commit 5697db4a696c41601a1d15c1922150b4dbf5726c ]

The USB_DEVICE_INTERFACE_NUMBER matching macro assumes that
the { vendorid, productid, interfacenumber } set uniquely
identifies one specific function.  This has proven to fail
for some configurable devices. One example is the Quectel
EM06/EP06 where the same interface number can be either
QMI or MBIM, without the device ID changing either.

Fix by requiring the vendor-specific class for interface number
based matching.  Functions of other classes can and should use
class based matching instead.

Fixes: 03304bcb5ec4 ("net: qmi_wwan: use fixed interface number matching")
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/usb/qmi_wwan.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -866,6 +866,7 @@ static int qmi_wwan_probe(struct usb_int
 			  const struct usb_device_id *prod)
 {
 	struct usb_device_id *id = (struct usb_device_id *)prod;
+	struct usb_interface_descriptor *desc = &intf->cur_altsetting->desc;
 
 	/* Workaround to enable dynamic IDs.  This disables usbnet
 	 * blacklisting functionality.  Which, if required, can be
@@ -877,6 +878,18 @@ static int qmi_wwan_probe(struct usb_int
 		id->driver_info = (unsigned long)&qmi_wwan_info;
 	}
 
+	/* There are devices where the same interface number can be
+	 * configured as different functions. We should only bind to
+	 * vendor specific functions when matching on interface number
+	 */
+	if (id->match_flags & USB_DEVICE_ID_MATCH_INT_NUMBER &&
+	    desc->bInterfaceClass != USB_CLASS_VENDOR_SPEC) {
+		dev_dbg(&intf->dev,
+			"Rejecting interface number match for class %02x\n",
+			desc->bInterfaceClass);
+		return -ENODEV;
+	}
+
 	return usbnet_probe(intf, id);
 }