linux-kernel - Re: [PATCH][V2] usb: typec: unlock dp->lock on error exit path, and also zero ret if successful

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Date:   Fri, 6 Jul 2018 10:10:36 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][V2] usb: typec: unlock dp->lock on error exit path, and
 also zero ret if successful

On Thu, Jul 05, 2018 at 02:36:47PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> One of the error handling paths forgets to unlock dp->lock on the error
> exit path leading to a potential lock-up.  Also the return path for a
> successful call to the function configuration_store can return an
> uninitialized error return code if dp->alt->active is false, so ensure
> ret is zeroed on the successful exit path to avoid garbage being returned.
> 
> Detected by CoverityScan, CID#1471597 ("Unitialized scalar variable")
> 
> Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
> 
> V2: move the ret = 0 assignment to the declaration
> 
> ---
>  drivers/usb/typec/altmodes/displayport.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index ef12b15bd484..3f06e94771a7 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -333,7 +333,7 @@ configuration_store(struct device *dev, struct device_attribute *attr,
>  	u32 conf;
>  	u32 cap;
>  	int con;
> -	int ret;
> +	int ret = 0;
>  
>  	con = sysfs_match_string(configurations, buf);
>  	if (con < 0)
> @@ -349,8 +349,10 @@ configuration_store(struct device *dev, struct device_attribute *attr,
>  	cap = DP_CAP_CAPABILITY(dp->alt->vdo);
>  
>  	if ((con == DP_CONF_DFP_D && !(cap & DP_CAP_DFP_D)) ||
> -	    (con == DP_CONF_UFP_D && !(cap & DP_CAP_UFP_D)))
> -		return -EINVAL;
> +	    (con == DP_CONF_UFP_D && !(cap & DP_CAP_UFP_D))) {
> +		ret = -EINVAL;
> +		goto err_unlock;
> +	}
>  
>  	conf = dp->data.conf & ~DP_CONF_DUAL_D;
>  	conf |= con;

Thanks,

-- 
heikki