Re: [PATCH 1/3] hwmon: lenovo-ec-sensors: Fix EC signature check logic in probe

[Guenter Roeck]

On 5/13/26 18:14, Kean wrote:
> The probe function reads a 4-byte signature ("MCHP") from the EC to
> verify it is a Microchip EC before binding the driver. The condition
> uses && (AND) to check if each byte differs from the expected value:
>
>    if ((byte0 != 'M') && (byte1 != 'C') && (byte2 != 'H') && (byte3 != 'P'))
>
> This rejects the device only if ALL four bytes are wrong simultaneously.
> A partially matching signature (e.g. "MXXX") would pass the check and
> cause the driver to bind to a non-Microchip EC, as long as at least one
> byte matches the expected value.
>
> Change && to || so the driver is rejected when ANY byte does not match
> the expected "MCHP" signature.
>
> Signed-off-by: Kean <rh_king@xxxxxxx>
>
> Reviewed-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx>

As with the other patches: How do I know that this review really happened ?

Guenter

> ---
>   drivers/hwmon/lenovo-ec-sensors.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hwmon/lenovo-ec-sensors.c b/drivers/hwmon/lenovo-ec-sensors.c
> index 8681bbf6665b..a32b1f2c6a3a 100644
> --- a/drivers/hwmon/lenovo-ec-sensors.c
> +++ b/drivers/hwmon/lenovo-ec-sensors.c
> @@ -537,9 +537,9 @@ static int lenovo_ec_probe(struct platform_device *pdev)
>   	outw_p(MCHP_SING_IDX, MCHP_EMI0_EC_ADDRESS);
>   	mutex_unlock(&ec_data->mec_mutex);
>   
> -	if ((inb_p(MCHP_EMI0_EC_DATA_BYTE0) != 'M') &&
> -	    (inb_p(MCHP_EMI0_EC_DATA_BYTE1) != 'C') &&
> -	    (inb_p(MCHP_EMI0_EC_DATA_BYTE2) != 'H') &&
> +	if ((inb_p(MCHP_EMI0_EC_DATA_BYTE0) != 'M') ||
> +	    (inb_p(MCHP_EMI0_EC_DATA_BYTE1) != 'C') ||
> +	    (inb_p(MCHP_EMI0_EC_DATA_BYTE2) != 'H') ||
>   	    (inb_p(MCHP_EMI0_EC_DATA_BYTE3) != 'P')) {
>   		release_region(IO_REGION_START, IO_REGION_LENGTH);
>   		return -ENODEV;