net: cdc_ncm: do not bind to NCM compatible MBIM devices

The MBIM specification allows a MBIM device to disguise
itself as NCM for backwards compatibility, using additional
altsettings with different subclass (control) or protocol
(data):

C:* #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=0d Prot=00 Driver=cdc_mbim
E:  Ad=81(I) Atr=03(Int.) MxPS=  64 Ivl=7ms
I:* If#= 0 Alt= 1 #EPs= 1 Cls=02(comm.) Sub=0e Prot=00 Driver=cdc_mbim
E:  Ad=81(I) Atr=03(Int.) MxPS=  64 Ivl=7ms
I:  If#= 1 Alt= 0 #EPs= 0 Cls=0a(data ) Sub=00 Prot=01 Driver=cdc_mbim
I:  If#= 1 Alt= 1 #EPs= 2 Cls=0a(data ) Sub=00 Prot=01 Driver=cdc_mbim
E:  Ad=81(I) Atr=02(Bulk) MxPS=  64 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=  64 Ivl=0ms
I:* If#= 1 Alt= 2 #EPs= 2 Cls=0a(data ) Sub=00 Prot=02 Driver=cdc_mbim
E:  Ad=81(I) Atr=02(Bulk) MxPS=  64 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=  64 Ivl=0ms

If the MBIM driver is enabled then that should have priority
for devices providing such a NCM 1.0 backward compatibility
mode.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Suarez <gsuarez@smithmicro.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 17b4ba03cb55c83c9eb3c4baf857e966df3bdb6f..0ed03b1ba39a0b5b1dfa0371350e340dbb223aa3 100644 (file)
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -563,6 +563,33 @@ static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
 {
        int ret;
 
+       /* The MBIM spec defines a NCM compatible default altsetting,
+        * which we may have matched:
+        *
+        *  "Functions that implement both NCM 1.0 and MBIM (an
+        *   “NCM/MBIM function”) according to this recommendation
+        *   shall provide two alternate settings for the
+        *   Communication Interface.  Alternate setting 0, and the
+        *   associated class and endpoint descriptors, shall be
+        *   constructed according to the rules given for the
+        *   Communication Interface in section 5 of [USBNCM10].
+        *   Alternate setting 1, and the associated class and
+        *   endpoint descriptors, shall be constructed according to
+        *   the rules given in section 6 (USB Device Model) of this
+        *   specification."
+        *
+        * Do not bind to such interfaces, allowing cdc_mbim to handle
+        * them
+        */
+#if IS_ENABLED(CONFIG_USB_NET_CDC_MBIM)
+       if ((intf->num_altsetting == 2) &&
+           !usb_set_interface(dev->udev,
+                              intf->cur_altsetting->desc.bInterfaceNumber,
+                              CDC_NCM_COMM_ALTSETTING_MBIM) &&
+           cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
+               return -ENODEV;
+#endif
+
        /* NCM data altsetting is always 1 */
        ret = cdc_ncm_bind_common(dev, intf, 1);