Re: [PATCH] iio: adc: ad7124: fix possible OOB array access

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 22 Oct 2025 10:15:05 -0500
David Lechner <dlechner@baylibre.com> wrote:

> Reorder the channel bounds check before using it to index into the
> channels array in ad7124_release_config_slot(). This prevents reading
> past the end of the array.
> 
> The value read from invalid memory was not used, so this was mostly
> harmless, but we still should not be reading out of bounds in the first
> place.
> 
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/linux-iio/aPi6V-hcaKReSNWK@stanley.mountain/
> Fixes: 9065197e0d41 ("iio: adc: ad7124: change setup reg allocation strategy")
> Signed-off-by: David Lechner <dlechner@baylibre.com>
Applied to the togreg branch of iio.git. 
thanks,

J
> ---
>  drivers/iio/adc/ad7124.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
> index 9d58ced7371d0af7004a81153888714e9795d4f4..ed828a82acb71342fb2eae27abfbbd86861cba53 100644
> --- a/drivers/iio/adc/ad7124.c
> +++ b/drivers/iio/adc/ad7124.c
> @@ -586,13 +586,18 @@ static int ad7124_request_config_slot(struct ad7124_state *st, u8 channel)
>  
>  static void ad7124_release_config_slot(struct ad7124_state *st, u8 channel)
>  {
> -	unsigned int slot = st->channels[channel].cfg.cfg_slot;
> +	unsigned int slot;
>  
>  	/*
> -	 * All of these conditions can happen at probe when all channels are
> -	 * disabled. Otherwise, they should not happen normally.
> +	 * All of these early return conditions can happen at probe when all
> +	 * channels are disabled. Otherwise, they should not happen normally.
>  	 */
> -	if (channel >= st->num_channels || slot == AD7124_CFG_SLOT_UNASSIGNED ||
> +	if (channel >= st->num_channels)
> +		return;
> +
> +	slot = st->channels[channel].cfg.cfg_slot;
> +
> +	if (slot == AD7124_CFG_SLOT_UNASSIGNED ||
>  	    st->cfg_slot_use_count[slot] == 0)
>  		return;
>  
> 
> ---
> base-commit: 89cba586b8b4cde09c44b1896624720ea29f0205
> change-id: 20251022-iio-adc-ad7124-fix-possible-oob-array-access-239be24ac692
> 
> Best regards,