Prevent a potential invalid memory access when the requested sensor
is not found.

find_ec_sensor_index() may return a negative value (e.g. -ENOENT),
but its result was used without checking, which could lead to
undefined behavior when passed to get_sensor_info().

Add a proper check to return -EINVAL if sensor_index is negative.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: d0ddfd241e57 ("hwmon: (asus-ec-sensors) add driver for ASUS EC")
Signed-off-by: Alexei Safin <a.safin@rosa.ru>
---
 drivers/hwmon/asus-ec-sensors.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hwmon/asus-ec-sensors.c b/drivers/hwmon/asus-ec-sensors.c
index d893cfd1cb82..769725ea18db 100644
--- a/drivers/hwmon/asus-ec-sensors.c
+++ b/drivers/hwmon/asus-ec-sensors.c
@@ -839,6 +839,10 @@ static int asus_ec_hwmon_read_string(struct device *dev,
 {
 	struct ec_sensors_data *state = dev_get_drvdata(dev);
 	int sensor_index = find_ec_sensor_index(state, type, channel);
+
+	if (sensor_index < 0)
+		return -EINVAL;
+
 	*str = get_sensor_info(state, sensor_index)->label;
 
 	return 0;
-- 
2.39.5 (Apple Git-154)

On Thu, Apr 24, 2025 at 11:26:54PM +0300, Alexei Safin wrote:
> Prevent a potential invalid memory access when the requested sensor
> is not found.
> 
> find_ec_sensor_index() may return a negative value (e.g. -ENOENT),
> but its result was used without checking, which could lead to
> undefined behavior when passed to get_sensor_info().
> 
> Add a proper check to return -EINVAL if sensor_index is negative.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: d0ddfd241e57 ("hwmon: (asus-ec-sensors) add driver for ASUS EC")
> Signed-off-by: Alexei Safin <a.safin@rosa.ru>

Since we can't agree on warn or not or how, I decided to apply this
version after changing the error return value as suggested.

Guenter

On Fri, 2 May 2025 at 05:07, Guenter Roeck <linux@roeck-us.net> wrote:
> Since we can't agree on warn or not or how, I decided to apply this
> version after changing the error return value as suggested.

OK, thanks!

Eugene

Hi,

maybe return the value of sensor_index, which already contains the
error code, rather than EINVAL?

Eugene

On Thu, 24 Apr 2025 at 22:27, Alexei Safin <a.safin@rosa.ru> wrote:
>
> Prevent a potential invalid memory access when the requested sensor
> is not found.
>
> find_ec_sensor_index() may return a negative value (e.g. -ENOENT),
> but its result was used without checking, which could lead to
> undefined behavior when passed to get_sensor_info().
>
> Add a proper check to return -EINVAL if sensor_index is negative.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: d0ddfd241e57 ("hwmon: (asus-ec-sensors) add driver for ASUS EC")
> Signed-off-by: Alexei Safin <a.safin@rosa.ru>
> ---
>  drivers/hwmon/asus-ec-sensors.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/hwmon/asus-ec-sensors.c b/drivers/hwmon/asus-ec-sensors.c
> index d893cfd1cb82..769725ea18db 100644
> --- a/drivers/hwmon/asus-ec-sensors.c
> +++ b/drivers/hwmon/asus-ec-sensors.c
> @@ -839,6 +839,10 @@ static int asus_ec_hwmon_read_string(struct device *dev,
>  {
>         struct ec_sensors_data *state = dev_get_drvdata(dev);
>         int sensor_index = find_ec_sensor_index(state, type, channel);
> +
> +       if (sensor_index < 0)
> +               return -EINVAL;
> +
>         *str = get_sensor_info(state, sensor_index)->label;
>
>         return 0;
> --
> 2.39.5 (Apple Git-154)
>

On 4/24/25 13:39, Eugene Shalygin wrote:
> Hi,
> 
> maybe return the value of sensor_index, which already contains the
> error code, rather than EINVAL?
> 

Yes. The error is theoretic since attributed which are not supported
will be filtered out in asus_ec_hwmon_is_visible(), but the error return
from find_ec_sensor_index() should not be replaced. Also, returning
-EINVAL is just plain wrong.

FWIW, this should really be WARN_ONCE() instead of just an error
return because it indicates a programming error. This also applies
to the same check in asus_ec_hwmon_read().

Guenter

> Eugene
> 
> On Thu, 24 Apr 2025 at 22:27, Alexei Safin <a.safin@rosa.ru> wrote:
>>
>> Prevent a potential invalid memory access when the requested sensor
>> is not found.
>>
>> find_ec_sensor_index() may return a negative value (e.g. -ENOENT),
>> but its result was used without checking, which could lead to
>> undefined behavior when passed to get_sensor_info().
>>
>> Add a proper check to return -EINVAL if sensor_index is negative.
>>
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Fixes: d0ddfd241e57 ("hwmon: (asus-ec-sensors) add driver for ASUS EC")
>> Signed-off-by: Alexei Safin <a.safin@rosa.ru>
>> ---
>>   drivers/hwmon/asus-ec-sensors.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/hwmon/asus-ec-sensors.c b/drivers/hwmon/asus-ec-sensors.c
>> index d893cfd1cb82..769725ea18db 100644
>> --- a/drivers/hwmon/asus-ec-sensors.c
>> +++ b/drivers/hwmon/asus-ec-sensors.c
>> @@ -839,6 +839,10 @@ static int asus_ec_hwmon_read_string(struct device *dev,
>>   {
>>          struct ec_sensors_data *state = dev_get_drvdata(dev);
>>          int sensor_index = find_ec_sensor_index(state, type, channel);
>> +
>> +       if (sensor_index < 0)
>> +               return -EINVAL;
>> +
>>          *str = get_sensor_info(state, sensor_index)->label;
>>
>>          return 0;
>> --
>> 2.39.5 (Apple Git-154)
>>
>