Re: [PATCH] hwmon: (asus-ec-sensors) check sensor index in read_string()

[Guenter Roeck]

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@xxxxxxx> 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@xxxxxxx>
> > ---
> >   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)