cdc_ether: Ignore bogus union descriptor for RNDIS devices

Some RNDIS devices include a bogus CDC Union descriptor pointing
to non-existing interfaces.  The RNDIS code is already prepared
to handle devices without a CDC Union descriptor by hardwiring
the driver to use interfaces 0 and 1, which is correct for the
devices with the bogus descriptor as well. So we can reuse the
existing workaround.

Cc: Markus Kolb <linux-201011@tower-net.de>
Cc: Iker Salmón San Millán <shaola@esdebian.org>
Cc: Jonathan Nieder <jrnieder@gmail.com>
Cc: Oliver Neukum <oliver@neukum.org>
Cc: 655387@bugs.debian.org
Cc: stable@vger.kernel.org
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 2 deletions

diff --git a/drivers/net/usb/cdc_ether.c b/drivers/net/usb/cdc_ether.c
index 90a30026a931..00880edba048 100644
--- a/drivers/net/usb/cdc_ether.c
+++ b/drivers/net/usb/cdc_ether.c
@@ -83,6 +83,7 @@ int usbnet_generic_cdc_bind(struct usbnet *dev, struct usb_interface *intf)
         struct cdc_state                *info = (void *) &dev->data;
         int                             status;
         int                             rndis;
+        bool                            android_rndis_quirk = false;
         struct usb_driver               *driver = driver_of(intf);
         struct usb_cdc_mdlm_desc        *desc = NULL;
         struct usb_cdc_mdlm_detail_desc *detail = NULL;
@@ -195,6 +196,11 @@ int usbnet_generic_cdc_bind(struct usbnet *dev, struct usb_interface *intf)
                                         info->control,
                                         info->u->bSlaveInterface0,
                                         info->data);
+                                /* fall back to hard-wiring for RNDIS */
+                                if (rndis) {
+                                        android_rndis_quirk = true;
+                                        goto next_desc;
+                                }
                                 goto bad_desc;
                         }
                         if (info->control != intf) {
@@ -271,11 +277,15 @@ next_desc:
         /* Microsoft ActiveSync based and some regular RNDIS devices lack the
          * CDC descriptors, so we'll hard-wire the interfaces and not check
          * for descriptors.
+         *
+         * Some Android RNDIS devices have a CDC Union descriptor pointing
+         * to non-existing interfaces.  Ignore that and attempt the same
+         * hard-wired 0 and 1 interfaces.
          */
-        if (rndis && !info->u) {
+        if (rndis && (!info->u || android_rndis_quirk)) {
                 info->control = usb_ifnum_to_if(dev->udev, 0);
                 info->data = usb_ifnum_to_if(dev->udev, 1);
-                if (!info->control || !info->data) {
+                if (!info->control || !info->data || info->control != intf) {
                         dev_dbg(&intf->dev,
                                 "rndis: master #0/%p slave #1/%p\n",
                                 info->control,