USB: gadget: detect too-big endpoint 0 requests

Sometimes USB hosts can ask for buffers that are too large from endpoint
0, which should not be allowed.  If this happens for OUT requests, stall
the endpoint, but for IN requests, trim the request size to the endpoint
buffer size.

Co-developed-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/composite.c

@@ -1679,6 +1679,18 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 	struct usb_function		*f = NULL;
 	u8				endp;
 
+	if (w_length > USB_COMP_EP0_BUFSIZ) {
+		if (ctrl->bRequestType == USB_DIR_OUT) {
+			goto done;
+		} else {
+			/* 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;
+		}
+	}
+
 	/* partial re-init of the response message; the function or the
 	 * gadget might need to intercept e.g. a control-OUT completion
 	 * when we delegate to it.

drivers/usb/gadget/legacy/dbgp.c

@@ -345,6 +345,19 @@ static int dbgp_setup(struct usb_gadget *gadget,
 	void *data = NULL;
 	u16 len = 0;
 
+	if (length > DBGP_REQ_LEN) {
+		if (ctrl->bRequestType == USB_DIR_OUT) {
+			return err;
+		} else {
+			/* Cast away the const, we are going to overwrite on purpose. */
+			__le16 *temp = (__le16 *)&ctrl->wLength;
+
+			*temp = cpu_to_le16(DBGP_REQ_LEN);
+			length = DBGP_REQ_LEN;
+		}
+	}
+
+
 	if (request == USB_REQ_GET_DESCRIPTOR) {
 		switch (value>>8) {
 		case USB_DT_DEVICE:

drivers/usb/gadget/legacy/inode.c

@@ -110,6 +110,8 @@ enum ep0_state {
 /* enough for the whole queue: most events invalidate others */
 #define	N_EVENT			5
 
+#define RBUF_SIZE		256
+
 struct dev_data {
 	spinlock_t			lock;
 	refcount_t			count;
@@ -144,7 +146,7 @@ struct dev_data {
 	struct dentry			*dentry;
 
 	/* except this scratch i/o buffer for ep0 */
-	u8				rbuf [256];
+	u8				rbuf[RBUF_SIZE];
 };
 
 static inline void get_dev (struct dev_data *data)
@@ -1331,6 +1333,18 @@ gadgetfs_setup (struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 	u16				w_value = le16_to_cpu(ctrl->wValue);
 	u16				w_length = le16_to_cpu(ctrl->wLength);
 
+	if (w_length > RBUF_SIZE) {
+		if (ctrl->bRequestType == USB_DIR_OUT) {
+			return value;
+		} else {
+			/* Cast away the const, we are going to overwrite on purpose. */
+			__le16 *temp = (__le16 *)&ctrl->wLength;
+
+			*temp = cpu_to_le16(RBUF_SIZE);
+			w_length = RBUF_SIZE;
+		}
+	}
+
 	spin_lock (&dev->lock);
 	dev->setup_abort = 0;
 	if (dev->state == STATE_DEV_UNCONNECTED) {