sound/usb/mixer_scarlett2.c:4972 scarlett2_ioctl_select_flash_segment() warn: potential spectre issue 'private->flash_segment_nums' [r] (local cap)

[Dan Carpenter]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   de2f378f2b771b39594c04695feee86476743a69
commit: 6a7508e64ee3e8320c886020bcdcd70f7fcbff2c ALSA: scarlett2: Add ioctl commands to erase flash segments
date:   11 months ago
config: x86_64-randconfig-161-20241110 (https://download.01.org/0day-ci/archive/20241110/202411101058.RkdgFPCg-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
| Closes: https://lore.kernel.org/r/202411101058.RkdgFPCg-lkp@xxxxxxxxx/

smatch warnings:
sound/usb/mixer_scarlett2.c:4972 scarlett2_ioctl_select_flash_segment() warn: potential spectre issue 'private->flash_segment_nums' [r] (local cap)
sound/usb/mixer_scarlett2.c:4973 scarlett2_ioctl_select_flash_segment() warn: possible spectre second half.  'segment_num'

vim +4972 sound/usb/mixer_scarlett2.c

6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4957  /* Select a flash segment for erasing (and possibly writing to) */
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4958  static int scarlett2_ioctl_select_flash_segment(
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4959  	struct usb_mixer_interface *mixer,
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4960  	unsigned long arg)
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4961  {
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4962  	struct scarlett2_data *private = mixer->private_data;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4963  	int segment_id, segment_num;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4964  
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4965  	if (get_user(segment_id, (int __user *)arg))
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4966  		return -EFAULT;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4967  
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4968  	/* Check the segment ID and segment number */
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4969  	if (segment_id < 0 || segment_id >= SCARLETT2_SEGMENT_ID_COUNT)
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4970  		return -EINVAL;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4971  
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20 @4972  	segment_num = private->flash_segment_nums[segment_id];

I suspect this does need an array_index_nospec().

6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20 @4973  	if (segment_num < SCARLETT2_SEGMENT_NUM_MIN ||
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4974  	    segment_num > SCARLETT2_SEGMENT_NUM_MAX) {
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4975  		usb_audio_err(mixer->chip,
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4976  			      "%s: invalid segment number %d\n",
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4977  			      __func__, segment_id);
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4978  		return -EFAULT;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4979  	}
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4980  
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4981  	/* If erasing, wait for it to complete */
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4982  	if (private->flash_write_state == SCARLETT2_FLASH_WRITE_STATE_ERASING) {
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4983  		int err = scarlett2_wait_for_erase(mixer);
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4984  
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4985  		if (err < 0)
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4986  			return err;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4987  	}
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4988  
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4989  	/* Save the selected segment ID and set the state to SELECTED */
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4990  	private->selected_flash_segment_id = segment_id;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4991  	private->flash_write_state = SCARLETT2_FLASH_WRITE_STATE_SELECTED;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4992  
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4993  	return 0;
6a7508e64ee3e8 Geoffrey D. Bennett 2023-12-20  4994  }

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