CVE-2022-50542

In the Linux kernel, the following vulnerability has been resolved:

media: si470x: Fix use-after-free in si470x_int_in_callback()

syzbot reported use-after-free in si470x_int_in_callback() [1].  This
indicates that urb->context, which contains struct si470x_device
object, is freed when si470x_int_in_callback() is called.

The cause of this issue is that si470x_int_in_callback() is called for
freed urb.

si470x_usb_driver_probe() calls si470x_start_usb(), which then calls
usb_submit_urb() and si470x_start().  If si470x_start_usb() fails,
si470x_usb_driver_probe() doesn't kill urb, but it just frees struct
si470x_device object, as depicted below:

si470x_usb_driver_probe()
  ...
  si470x_start_usb()
    ...
    usb_submit_urb()
    retval = si470x_start()
    return retval
  if (retval < 0)
    free struct si470x_device object, but don't kill urb

This patch fixes this issue by killing urb when si470x_start_usb()
fails and urb is submitted.  If si470x_start_usb() fails and urb is
not submitted, i.e. submitting usb fails, it just frees struct
si470x_device object.