[PATCH v3] iio: health: afe4403: Fix oob read in afe4403_read_raw

[PATCH v3] iio: health: afe4403: Fix oob read in afe4403_read_raw

[Wei Yongjun]

From: Wei Yongjun <weiyongjun1@huawei.com>

KASAN report out-of-bounds read as follows:

BUG: KASAN: global-out-of-bounds in afe4403_read_raw+0x42e/0x4c0
Read of size 4 at addr ffffffffc02ac638 by task cat/279

Call Trace:
 afe4403_read_raw
 iio_read_channel_info
 dev_attr_show

The buggy address belongs to the variable:
 afe4403_channel_leds+0x18/0xffffffffffffe9e0

This issue can be reproduced by singe command:

 $ cat /sys/bus/spi/devices/spi0.0/iio\:device0/in_intensity6_raw

The array size of afe4403_channel_leds is less than channels, so access
with chan->address cause OOB read in afe4403_read_raw. Fix it by moving
access before use it.

Fixes: b36e8257641a ("iio: health/afe440x: Use regmap fields")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Andrew Davis <afd@ti.com>
---
v2 -> v3: re-format backtraces
v1 -> v2: also moved 'reg' to right before we use it
          added Acked-by

 drivers/iio/health/afe4403.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/health/afe4403.c b/drivers/iio/health/afe4403.c
index 3bb4028c5d74..df3bc5c3d378 100644
--- a/drivers/iio/health/afe4403.c
+++ b/drivers/iio/health/afe4403.c
@@ -245,14 +245,14 @@ static int afe4403_read_raw(struct iio_dev *indio_dev,
 			    int *val, int *val2, long mask)
 {
 	struct afe4403_data *afe = iio_priv(indio_dev);
-	unsigned int reg = afe4403_channel_values[chan->address];
-	unsigned int field = afe4403_channel_leds[chan->address];
+	unsigned int reg, field;
 	int ret;
 
 	switch (chan->type) {
 	case IIO_INTENSITY:
 		switch (mask) {
 		case IIO_CHAN_INFO_RAW:
+			reg = afe4403_channel_values[chan->address];
 			ret = afe4403_read(afe, reg, val);
 			if (ret)
 				return ret;
@@ -262,6 +262,7 @@ static int afe4403_read_raw(struct iio_dev *indio_dev,
 	case IIO_CURRENT:
 		switch (mask) {
 		case IIO_CHAN_INFO_RAW:
+			field = afe4403_channel_leds[chan->address];
 			ret = regmap_field_read(afe->fields[field], val);
 			if (ret)
 				return ret;
-- 
2.34.1

Re: [PATCH v3] iio: health: afe4403: Fix oob read in afe4403_read_raw

[Jonathan Cameron]

On Mon,  7 Nov 2022 15:19:46 +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 afe4403_read_raw+0x42e/0x4c0
> Read of size 4 at addr ffffffffc02ac638 by task cat/279
> 
> Call Trace:
>  afe4403_read_raw
>  iio_read_channel_info
>  dev_attr_show
> 
> The buggy address belongs to the variable:
>  afe4403_channel_leds+0x18/0xffffffffffffe9e0
> 
> This issue can be reproduced by singe command:
> 
>  $ cat /sys/bus/spi/devices/spi0.0/iio\:device0/in_intensity6_raw
> 
> The array size of afe4403_channel_leds is less than channels, so access
> with chan->address cause OOB read in afe4403_read_raw. Fix it by moving
> access before use it.
> 
> 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/afe4403.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/health/afe4403.c b/drivers/iio/health/afe4403.c
> index 3bb4028c5d74..df3bc5c3d378 100644
> --- a/drivers/iio/health/afe4403.c
> +++ b/drivers/iio/health/afe4403.c
> @@ -245,14 +245,14 @@ static int afe4403_read_raw(struct iio_dev *indio_dev,
>  			    int *val, int *val2, long mask)
>  {
>  	struct afe4403_data *afe = iio_priv(indio_dev);
> -	unsigned int reg = afe4403_channel_values[chan->address];
> -	unsigned int field = afe4403_channel_leds[chan->address];
> +	unsigned int reg, field;
>  	int ret;
>  
>  	switch (chan->type) {
>  	case IIO_INTENSITY:
>  		switch (mask) {
>  		case IIO_CHAN_INFO_RAW:
> +			reg = afe4403_channel_values[chan->address];
>  			ret = afe4403_read(afe, reg, val);
>  			if (ret)
>  				return ret;
> @@ -262,6 +262,7 @@ static int afe4403_read_raw(struct iio_dev *indio_dev,
>  	case IIO_CURRENT:
>  		switch (mask) {
>  		case IIO_CHAN_INFO_RAW:
> +			field = afe4403_channel_leds[chan->address];
>  			ret = regmap_field_read(afe->fields[field], val);
>  			if (ret)
>  				return ret;