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

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Message-ID: <c79317ca-27ba-48bc-8245-ff6d1eb0cba9@roeck-us.net>
Date: Thu, 24 Apr 2025 15:35:35 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Eugene Shalygin <eugene.shalygin@...il.com>,
 Alexei Safin <a.safin@...a.ru>
Cc: Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
 linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] hwmon: (asus-ec-sensors) check sensor index in
 read_string()

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@...a.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@...a.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)
>>
>