linux-kernel - Re: [PATCH] usb: typec: tcpm: Fix a signedness bug in tcpm_fw_get

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Message-ID: <20190926125310.GA9967@roeck-us.net>
Date:   Thu, 26 Sep 2019 05:53:10 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] usb: typec: tcpm: Fix a signedness bug in
 tcpm_fw_get_caps()

On Wed, Sep 25, 2019 at 02:02:19PM +0300, Dan Carpenter wrote:
> The "port->typec_caps.data" and "port->typec_caps.type" variables are
> enums and in this context GCC will treat them as an unsigned int so they
> can never be less than zero.
> 
> Fixes: ae8a2ca8a221 ("usb: typec: Group all TCPCI/TCPM code together")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 96562744101c..d3b63e000ae2 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -4410,7 +4410,7 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
>  	ret = fwnode_property_read_string(fwnode, "data-role", &cap_str);
>  	if (ret == 0) {
>  		port->typec_caps.data = typec_find_port_data_role(cap_str);
> -		if (port->typec_caps.data < 0)
> +		if ((int)port->typec_caps.data < 0)
>  			return -EINVAL;

Doesn't that also cause a warning about overwriting error return codes ?
I would prefer something like

		ret = typec_find_port_data_role(cap_str);
		if (ret < 0)
			return ret;
		port->typec_caps.data = ret;

Guenter

>  	}
>  
> @@ -4419,7 +4419,7 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
>  		return ret;
>  
>  	port->typec_caps.type = typec_find_port_power_role(cap_str);
> -	if (port->typec_caps.type < 0)
> +	if ((int)port->typec_caps.type < 0)
>  		return -EINVAL;
>  	port->port_type = port->typec_caps.type;
>  
> -- 
> 2.20.1
>