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

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

[Colin King]

From: Colin Ian King <colin.king@canonical.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@canonical.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;
-- 
2.17.1

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

[Heikki Krogerus]

On Thu, Jul 05, 2018 at 02:36:47PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.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@canonical.com>

Acked-by: Heikki Krogerus <heikki.krogerus@linux.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