net: cdc_ncm: only the control intf can be probed

The probed interface must be the master/control interface of the
function.  Make this explicit and simplify redundant tests.

Cc: Alexey Orishko <alexey.orishko@gmail.com>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 435fcc75d706..5aa3e60851d0 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -394,6 +394,9 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
         /* store ctx pointer in device data field */
         dev->data[0] = (unsigned long)ctx;
 
+        /* only the control interface can be successfully probed */
+        ctx->control = intf;
+
         /* get some pointers */
         driver = driver_of(intf);
         buf = intf->cur_altsetting->extra;
@@ -411,9 +414,10 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
                                 break;
 
                         union_desc = (const struct usb_cdc_union_desc *)buf;
-
-                        ctx->control = usb_ifnum_to_if(dev->udev,
-                                                       union_desc->bMasterInterface0);
+                        /* the master must be the interface we are probing */
+                        if (intf->cur_altsetting->desc.bInterfaceNumber !=
+                            union_desc->bMasterInterface0)
+                                goto error;
                         ctx->data = usb_ifnum_to_if(dev->udev,
                                                     union_desc->bSlaveInterface0);
                         break;
@@ -459,14 +463,12 @@ advance:
 
         /* some buggy devices have an IAD but no CDC Union */
         if (!union_desc && intf->intf_assoc && intf->intf_assoc->bInterfaceCount == 2) {
-                ctx->control = intf;
                 ctx->data = usb_ifnum_to_if(dev->udev, intf->cur_altsetting->desc.bInterfaceNumber + 1);
                 dev_dbg(&intf->dev, "CDC Union missing - got slave from IAD\n");
         }
 
         /* check if we got everything */
-        if ((ctx->control == NULL) || (ctx->data == NULL) ||
-            ((!ctx->mbim_desc) && ((ctx->ether_desc == NULL) || (ctx->control != intf))))
+        if (!ctx->data || (!ctx->mbim_desc && !ctx->ether_desc))
                 goto error;
 
         /* claim data interface, if different from control */