[PATCH v2] iio: health: afe4404: Fix oob read in afe4404_[read|write]_raw

[PATCH v2] iio: health: afe4404: Fix oob read in afe4404_[read|write]_raw

[Wei Yongjun]

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 [afe4404]
Read of size 4 at addr ffffffffc00e4658 by task cat/278

CPU: 1 PID: 278 Comm: cat Tainted: G
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Call Trace:
 <TASK>
 afe4404_read_raw+0x2ce/0x380 [afe4404]
 iio_read_channel_info+0x249/0x2e0 [industrialio]
 dev_attr_show+0x4b/0xa0 drivers/base/core.c:2195
 sysfs_kf_seq_show+0x1ec/0x390 fs/sysfs/file.c:59
 seq_read_iter+0x48d/0x10b0 fs/seq_file.c:230
 kernfs_fop_read_iter+0x4e6/0x710 fs/kernfs/file.c:275
 call_read_iter include/linux/fs.h:2153 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x5f2/0x890 fs/read_write.c:470
 ksys_read+0x106/0x220 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7fe9c5ef6992
 </TASK>

The buggy address belongs to the variable:
 afe4404_channel_leds+0x18/0xffffffffffffe9c0 [afe4404]

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>
---
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;
-- 
2.34.1

Re: [PATCH v2] iio: health: afe4404: Fix oob read in afe4404_[read|write]_raw

[Andy Shevchenko]

On Mon, Nov 07, 2022 at 02:04:25AM +0000, Wei Yongjun 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 [afe4404]
> Read of size 4 at addr ffffffffc00e4658 by task cat/278
> 
> CPU: 1 PID: 278 Comm: cat Tainted: G
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> Call Trace:
>  <TASK>
>  afe4404_read_raw+0x2ce/0x380 [afe4404]
>  iio_read_channel_info+0x249/0x2e0 [industrialio]
>  dev_attr_show+0x4b/0xa0 drivers/base/core.c:2195
>  sysfs_kf_seq_show+0x1ec/0x390 fs/sysfs/file.c:59
>  seq_read_iter+0x48d/0x10b0 fs/seq_file.c:230
>  kernfs_fop_read_iter+0x4e6/0x710 fs/kernfs/file.c:275
>  call_read_iter include/linux/fs.h:2153 [inline]
>  new_sync_read fs/read_write.c:389 [inline]
>  vfs_read+0x5f2/0x890 fs/read_write.c:470
>  ksys_read+0x106/0x220 fs/read_write.c:613
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x38/0xa0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x72/0xdc
> RIP: 0033:0x7fe9c5ef6992
>  </TASK>

Read this
https://www.kernel.org/doc/html/latest/process/submitting-patches.html#backtraces-in-commit-messages
and update your commit message accordingly.

> The buggy address belongs to the variable:
>  afe4404_channel_leds+0x18/0xffffffffffffe9c0 [afe4404]
> 
> 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.

-- 
With Best Regards,
Andy Shevchenko