USB: composite: Fix bug: low byte of w_index is the usb interface number not the whole 2 bytes of w_index

In some usb gadget driver, for example usb audio class device, the high
byte of w_index is the entity id and low byte is the interface number.
If we use the 2 bytes of w_index as the array number, we will get a
wrong pointer or NULL pointer.

This patch fixes this issue.

Signed-off-by: Bryan Wu <cooloney@kernel.org>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 363951eb333c..5d11c291f1ad 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -683,6 +683,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
         struct usb_request              *req = cdev->req;
         int                             value = -EOPNOTSUPP;
         u16                             w_index = le16_to_cpu(ctrl->wIndex);
+        u8                              intf = w_index & 0xFF;
         u16                             w_value = le16_to_cpu(ctrl->wValue);
         u16                             w_length = le16_to_cpu(ctrl->wLength);
         struct usb_function             *f = NULL;
@@ -769,7 +770,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
                         goto unknown;
                 if (!cdev->config || w_index >= MAX_CONFIG_INTERFACES)
                         break;
-                f = cdev->config->interface[w_index];
+                f = cdev->config->interface[intf];
                 if (!f)
                         break;
                 if (w_value && !f->set_alt)
@@ -781,7 +782,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
                         goto unknown;
                 if (!cdev->config || w_index >= MAX_CONFIG_INTERFACES)
                         break;
-                f = cdev->config->interface[w_index];
+                f = cdev->config->interface[intf];
                 if (!f)
                         break;
                 /* lots of interfaces only need altsetting zero... */
@@ -808,7 +809,7 @@ unknown:
                  */
                 if ((ctrl->bRequestType & USB_RECIP_MASK)
                                 == USB_RECIP_INTERFACE) {
-                        f = cdev->config->interface[w_index];
+                        f = cdev->config->interface[intf];
                         if (f && f->setup)
                                 value = f->setup(f, ctrl);
                         else