[PATCH] USB: usbcore: Don't assume a USB configuration includes any interfaces

In a couple of places, usbcore assumes that a USB device configuration
will have a nonzero number of interfaces.  Having no interfaces may or
may not be allowed by the USB spec; in any event we shouldn't die if we
encounter such a thing.  This patch (as662) removes the assumptions.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 10 insertions, 6 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 7dd28f8e1cea..8e65f7a237e4 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1179,8 +1179,11 @@ static int choose_configuration(struct usb_device *udev)
         c = udev->config;
         num_configs = udev->descriptor.bNumConfigurations;
         for (i = 0; i < num_configs; (i++, c++)) {
-                struct usb_interface_descriptor *desc =
-                                &c->intf_cache[0]->altsetting->desc;
+                struct usb_interface_descriptor *desc = NULL;
+
+                /* It's possible that a config has no interfaces! */
+                if (c->desc.bNumInterfaces > 0)
+                        desc = &c->intf_cache[0]->altsetting->desc;
 
                 /*
                  * HP's USB bus-powered keyboard has only one configuration
@@ -1215,7 +1218,8 @@ static int choose_configuration(struct usb_device *udev)
                 /* If the first config's first interface is COMM/2/0xff
                  * (MSFT RNDIS), rule it out unless Linux has host-side
                  * RNDIS support. */
-                if (i == 0 && desc->bInterfaceClass == USB_CLASS_COMM
+                if (i == 0 && desc
+                                && desc->bInterfaceClass == USB_CLASS_COMM
                                 && desc->bInterfaceSubClass == 2
                                 && desc->bInterfaceProtocol == 0xff) {
 #ifndef CONFIG_USB_NET_RNDIS
@@ -1231,8 +1235,8 @@ static int choose_configuration(struct usb_device *udev)
                  * than a vendor-specific driver. */
                 else if (udev->descriptor.bDeviceClass !=
                                                 USB_CLASS_VENDOR_SPEC &&
-                                desc->bInterfaceClass !=
-                                                USB_CLASS_VENDOR_SPEC) {
+                                (!desc || desc->bInterfaceClass !=
+                                                USB_CLASS_VENDOR_SPEC)) {
                         best = c;
                         break;
                 }
@@ -3024,7 +3028,7 @@ int usb_reset_device(struct usb_device *udev)
         parent_hub = hdev_to_hub(parent_hdev);
 
         /* If we're resetting an active hub, take some special actions */
-        if (udev->actconfig &&
+        if (udev->actconfig && udev->actconfig->desc.bNumInterfaces > 0 &&
                         udev->actconfig->interface[0]->dev.driver ==
                                 &hub_driver.driver &&
                         (hub = hdev_to_hub(udev)) != NULL) {