usb: misc: usbtest: Fix overflow in usbtest_do_ioctl()

There used to be a test against "if (param->sglen > MAX_SGLEN)" but it
was removed during a refactor.  It leads to an integer overflow and a
stack overflow in test_queue() if we try to create a too large urbs[]
array on the stack.

There is a second integer overflow in test_queue() as well if
"param->iterations" is too high.  I don't immediately see that it's
harmful but I've added a check to prevent it and silence the static
checker warning.

Fixes: 18fc4ebdc705 ("usb: misc: usbtest: Remove timeval usage")
Acked-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/misc/usbtest.c

@@ -1964,6 +1964,9 @@ test_queue(struct usbtest_dev *dev, struct usbtest_param_32 *param,
 	int			status = 0;
 	struct urb		*urbs[param->sglen];
 
+	if (!param->sglen || param->iterations > UINT_MAX / param->sglen)
+		return -EINVAL;
+
 	memset(&context, 0, sizeof(context));
 	context.count = param->iterations * param->sglen;
 	context.dev = dev;
@@ -2087,6 +2090,8 @@ usbtest_do_ioctl(struct usb_interface *intf, struct usbtest_param_32 *param)
 
 	if (param->iterations <= 0)
 		return -EINVAL;
+	if (param->sglen > MAX_SGLEN)
+		return -EINVAL;
 	/*
 	 * Just a bunch of test cases that every HCD is expected to handle.
 	 *