linux-kernel - Re: [PATCH v2] usb: typec: tcpm: IS_ERR_OR

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Date:   Fri, 4 Aug 2023 11:24:16 +0200
From:   Ladislav Michl <oss-lists@...ops.cz>
To:     Jimmy Hu <hhhuuu@...gle.com>
Cc:     linux@...ck-us.net, heikki.krogerus@...ux.intel.com,
        gregkh@...uxfoundation.org, kyletso@...gle.com, badhri@...gle.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] usb: typec: tcpm: IS_ERR_OR_NULL check for
 port->partner

Hi Jimmy,

On Fri, Aug 04, 2023 at 08:49:28AM +0000, Jimmy Hu wrote:
> port->partner may be an error or NULL, so we must check it with
> IS_ERR_OR_NULL() before dereferencing it.
> 
> Move the check to the beginning of the tcpm_handle_vdm_request function.
> 
> Fixes: 5e1d4c49fbc8 ("usb: typec: tcpm: Determine common SVDM Version")
> Signed-off-by: Jimmy Hu <hhhuuu@...gle.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 829d75ebab42..2c6a0af155ab 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -1683,10 +1683,6 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
>  			      (VDO_SVDM_VERS(typec_get_negotiated_svdm_version(typec)));
>  		break;
>  	case CMDT_RSP_ACK:
> -		/* silently drop message if we are not connected */
> -		if (IS_ERR_OR_NULL(port->partner))
> -			break;
> -
>  		tcpm_ams_finish(port);
>  
>  		switch (cmd) {
> @@ -1792,6 +1788,12 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
>  	u32 response[8] = { };
>  	int i, rlen = 0;
>  
> +	/* silently drop message if we are not connected */

...comment moved.

> +	if (IS_ERR_OR_NULL(port->partner)) {
> +		dev_warn(port->dev, "port partner is an error or NULL\n");

But code is actually not silent. Also, does the verbsity make sense? And
if it does, is knowing what error port->partner is containing usefull?

> +		return;
> +	}
> +
>  	for (i = 0; i < cnt; i++)
>  		p[i] = le32_to_cpu(payload[i]);
>  
> -- 
> 2.41.0.585.gd2178a4bd4-goog