Re: [PATCH v3] iio: health: afe4404: Fix oob read in afe4404_[read|write]_raw

[Jonathan Cameron <jic23@kernel.org>]

On Mon,  7 Nov 2022 15:20:10 +0000
Wei Yongjun <weiyongjun@huaweicloud.com> wrote:

> From: Wei Yongjun <weiyongjun1@huawei.com>
> 
> KASAN report out-of-bounds read as follows:
> 
> BUG: KASAN: global-out-of-bounds in afe4404_read_raw+0x2ce/0x380
> Read of size 4 at addr ffffffffc00e4658 by task cat/278
> 
> Call Trace:
>  afe4404_read_raw
>  iio_read_channel_info
>  dev_attr_show
> 
> The buggy address belongs to the variable:
>  afe4404_channel_leds+0x18/0xffffffffffffe9c0
> 
> This issue can be reproduce by singe command:
> 
>  $ cat /sys/bus/i2c/devices/0-0058/iio\:device0/in_intensity6_raw
> 
> The array size of afe4404_channel_leds and afe4404_channel_offdacs
> are less than channels, so access with chan->address cause OOB read
> in afe4404_[read|write]_raw. Fix it by moving access before use them.
> 
> Fixes: b36e8257641a ("iio: health/afe440x: Use regmap fields")
> Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
> Acked-by: Andrew Davis <afd@ti.com>

Applied to the fixes-togreg branch of iio.git.

Thanks,

Jonathan
> ---
> v2 -> v3: re-format backtraces
> v1 -> v2: also moved 'reg' to right before we use it
>           added Acked-by
> 
>  drivers/iio/health/afe4404.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/health/afe4404.c b/drivers/iio/health/afe4404.c
> index 8fca787b2524..836da31b7e30 100644
> --- a/drivers/iio/health/afe4404.c
> +++ b/drivers/iio/health/afe4404.c
> @@ -250,20 +250,20 @@ static int afe4404_read_raw(struct iio_dev *indio_dev,
>  			    int *val, int *val2, long mask)
>  {
>  	struct afe4404_data *afe = iio_priv(indio_dev);
> -	unsigned int value_reg = afe4404_channel_values[chan->address];
> -	unsigned int led_field = afe4404_channel_leds[chan->address];
> -	unsigned int offdac_field = afe4404_channel_offdacs[chan->address];
> +	unsigned int value_reg, led_field, offdac_field;
>  	int ret;
>  
>  	switch (chan->type) {
>  	case IIO_INTENSITY:
>  		switch (mask) {
>  		case IIO_CHAN_INFO_RAW:
> +			value_reg = afe4404_channel_values[chan->address];
>  			ret = regmap_read(afe->regmap, value_reg, val);
>  			if (ret)
>  				return ret;
>  			return IIO_VAL_INT;
>  		case IIO_CHAN_INFO_OFFSET:
> +			offdac_field = afe4404_channel_offdacs[chan->address];
>  			ret = regmap_field_read(afe->fields[offdac_field], val);
>  			if (ret)
>  				return ret;
> @@ -273,6 +273,7 @@ static int afe4404_read_raw(struct iio_dev *indio_dev,
>  	case IIO_CURRENT:
>  		switch (mask) {
>  		case IIO_CHAN_INFO_RAW:
> +			led_field = afe4404_channel_leds[chan->address];
>  			ret = regmap_field_read(afe->fields[led_field], val);
>  			if (ret)
>  				return ret;
> @@ -295,19 +296,20 @@ static int afe4404_write_raw(struct iio_dev *indio_dev,
>  			     int val, int val2, long mask)
>  {
>  	struct afe4404_data *afe = iio_priv(indio_dev);
> -	unsigned int led_field = afe4404_channel_leds[chan->address];
> -	unsigned int offdac_field = afe4404_channel_offdacs[chan->address];
> +	unsigned int led_field, offdac_field;
>  
>  	switch (chan->type) {
>  	case IIO_INTENSITY:
>  		switch (mask) {
>  		case IIO_CHAN_INFO_OFFSET:
> +			offdac_field = afe4404_channel_offdacs[chan->address];
>  			return regmap_field_write(afe->fields[offdac_field], val);
>  		}
>  		break;
>  	case IIO_CURRENT:
>  		switch (mask) {
>  		case IIO_CHAN_INFO_RAW:
> +			led_field = afe4404_channel_leds[chan->address];
>  			return regmap_field_write(afe->fields[led_field], val);
>  		}
>  		break;