cdrom: fix improper type cast, which can leat to information leak.

There is another cast from unsigned long to int which causes
a bounds check to fail with specially crafted input. The value is
then used as an index in the slot array in cdrom_slot_status().

This issue is similar to CVE-2018-16658 and CVE-2018-10940.

Signed-off-by: Young_X <YangX92@hotmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
int cdrom_media_changed(struct cdrom_device_info *cdi)
{
	/* This talks to the VFS, which doesn't like errors - just 1 or 0.  
	 * Returning "0" is always safe (media hasn't been changed). Do that 
	 * if the low-level cdrom driver dosn't support media changed. */ 
	if (cdi == NULL || cdi->ops->media_changed == NULL)
		return 0;
	if (!CDROM_CAN(CDC_MEDIA_CHANGED))
		return 0;
	return media_changed(cdi, 0);
}

int cdrom_media_changed(struct cdrom_device_info *cdi)
{
	/* This talks to the VFS, which doesn't like errors - just 1 or 0.  
	 * Returning "0" is always safe (media hasn't been changed). Do that 
	 * if the low-level cdrom driver dosn't support media changed. */ 
	if (cdi == NULL || cdi->ops->media_changed == NULL)
		return 0;
	if (!CDROM_CAN(CDC_MEDIA_CHANGED))
		return 0;
	return media_changed(cdi, 0);
}
