usbip: stub_rx: fix static checker warning on unnecessary checks

Fix the following static checker warnings:

The patch c6688ef9: "usbip: fix stub_rx: harden CMD_SUBMIT path
to handle malicious input" from Dec 7, 2017, leads to the following
static checker warning:

    drivers/usb/usbip/stub_rx.c:346 get_pipe()
    warn: impossible condition
'(pdu->u.cmd_submit.transfer_buffer_length > ((~0 >> 1))) =>
(s32min-s32max > s32max)'
    drivers/usb/usbip/stub_rx.c:486 stub_recv_cmd_submit()
    warn: always true condition
'(pdu->u.cmd_submit.transfer_buffer_length <= ((~0 >> 1))) =>
(s32min-s32max <= s32max)'
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/usbip/stub_rx.c

@@ -339,14 +339,6 @@ static int get_pipe(struct stub_device *sdev, struct usbip_header *pdu)
 
 	epd = &ep->desc;
 
-	/* validate transfer_buffer_length */
-	if (pdu->u.cmd_submit.transfer_buffer_length > INT_MAX) {
-		dev_err(&sdev->udev->dev,
-			"CMD_SUBMIT: -EMSGSIZE transfer_buffer_length %d\n",
-			pdu->u.cmd_submit.transfer_buffer_length);
-		return -1;
-	}
-
 	if (usb_endpoint_xfer_control(epd)) {
 		if (dir == USBIP_DIR_OUT)
 			return usb_sndctrlpipe(udev, epnum);
@@ -479,8 +471,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	}
 
 	/* allocate urb transfer buffer, if needed */
-	if (pdu->u.cmd_submit.transfer_buffer_length > 0 &&
-	    pdu->u.cmd_submit.transfer_buffer_length <= INT_MAX) {
+	if (pdu->u.cmd_submit.transfer_buffer_length > 0) {
 		priv->urb->transfer_buffer =
 			kzalloc(pdu->u.cmd_submit.transfer_buffer_length,
 				GFP_KERNEL);