Re: [PATCH] platform/chrome: cros_ec_uart: fix negative type promoted to high

[Tzung-Bi Shih <tzungbi@kernel.org>]

On Mon, Jan 09, 2023 at 04:15:54PM +0800, Tzung-Bi Shih wrote:
> serdev_device_write_buf() returns negative numbers on errors.  When
> the return value compares to unsigned integer `len`, it promotes to
> quite large positive number.
> 
> Fix it.
> 
> Fixes: 04a8bdd135cc ("platform/chrome: cros_ec_uart: Add transport layer")
> Reported-by: Dan Carpenter <error27@gmail.com>
> Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
> ---
> Reported in https://lore.kernel.org/chrome-platform/Y7fhw4S7Tb0GcHMF@kili/T/#u.
> 
>  drivers/platform/chrome/cros_ec_uart.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec_uart.c b/drivers/platform/chrome/cros_ec_uart.c
> index 6916069f1599..788246559bbb 100644
> --- a/drivers/platform/chrome/cros_ec_uart.c
> +++ b/drivers/platform/chrome/cros_ec_uart.c
> @@ -149,9 +149,10 @@ static int cros_ec_uart_pkt_xfer(struct cros_ec_device *ec_dev,
>  	resp->status = 0;
>  
>  	ret = serdev_device_write_buf(serdev, ec_dev->dout, len);
> -	if (ret < len) {
> +	if (ret < 0 || ret < len) {
>  		dev_err(ec_dev->dev, "Unable to write data\n");
> -		ret = -EIO;
> +		if (ret >= 0)
> +			ret = -EIO;
>  		goto exit;
>  	}

Does this patch make sense to someone in the mailing list?