ANDROID: usb: f_accessory: Check buffer size when initialised via com…

…posite

When communicating with accessory devices via USBFS, the initialisation
call-stack looks like:

  ConfigFS > Gadget ConfigFS > UDC > Gadget ConfigFS > Composite

Eventually ending up in composite_dev_prepare() where memory for the
data buffer is allocated and initialised.  The default size used for the
allocation is USB_COMP_EP0_BUFSIZ (4k).  When handling bulk transfers,
acc_ctrlrequest() needs to be able to handle buffers up to
BULK_BUFFER_SIZE (16k).  Instead of adding new generic attributes to
'struct usb_request' to track the size of the allocated buffer, we can
simply split off the affected thread of execution to travel via a
knowledgeable abstracted function acc_ctrlrequest_composite() where we
can complete the necessary specific checks.

Bug: 264029575
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ia1280f85499621d3fa57f7262b4a2c80f4be7773
Signed-off-by: Lee Jones <joneslee@google.com>

drivers/usb/gadget/configfs.c

@@ -16,7 +16,7 @@
 #include <linux/usb/ch9.h>
 
 #ifdef CONFIG_USB_CONFIGFS_F_ACC
-extern int acc_ctrlrequest(struct usb_composite_dev *cdev,
+extern int acc_ctrlrequest_composite(struct usb_composite_dev *cdev,
 				const struct usb_ctrlrequest *ctrl);
 void acc_disconnect(void);
 #endif
@@ -1562,7 +1562,7 @@ static int android_setup(struct usb_gadget *gadget,
 
 #ifdef CONFIG_USB_CONFIGFS_F_ACC
 	if (value < 0)
-		value = acc_ctrlrequest(cdev, c);
+		value = acc_ctrlrequest_composite(cdev, c);
 #endif
 
 	if (value < 0)

drivers/usb/gadget/function/f_accessory.c

@@ -1076,6 +1076,26 @@ int acc_ctrlrequest(struct usb_composite_dev *cdev,
 }
 EXPORT_SYMBOL_GPL(acc_ctrlrequest);
 
+int acc_ctrlrequest_composite(struct usb_composite_dev *cdev,
+			      const struct usb_ctrlrequest *ctrl)
+{
+	u16 w_length = le16_to_cpu(ctrl->wLength);
+
+	if (w_length > USB_COMP_EP0_BUFSIZ) {
+		if (ctrl->bRequestType & USB_DIR_IN) {
+			/* Cast away the const, we are going to overwrite on purpose. */
+			__le16 *temp = (__le16 *)&ctrl->wLength;
+
+			*temp = cpu_to_le16(USB_COMP_EP0_BUFSIZ);
+			w_length = USB_COMP_EP0_BUFSIZ;
+		} else {
+			return -EINVAL;
+		}
+	}
+	return acc_ctrlrequest(cdev, ctrl);
+}
+EXPORT_SYMBOL_GPL(acc_ctrlrequest_composite);
+
 static int
 __acc_function_bind(struct usb_configuration *c,
 			struct usb_function *f, bool configfs)