[PATCH] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: fix race condition

[PATCH] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: fix race condition

[yangchenyuan]

From: Chenyuan Yang <chenyuan0y@gmail.com>

The yt2_1380_fc_serdev_probe() function calls devm_serdev_device_open()
before it calls serdev_device_set_client_ops(). This can trigger a NULL
pointer dereference.
This is similar to 5e700b384ec13f5bcac9855cb28fcc674f1d3593.

Fixes: b2ed33e8d486 ("platform/x86: Add lenovo-yoga-tab2-pro-1380-fastcharger driver")
Signed-off-by: Chenyuan Yang <chenyuan0y@gmail.com>

---
 .../platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c  | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c b/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c
index d2699ca24f34..1a4e66464a7e 100644
--- a/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c
+++ b/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c
@@ -199,15 +199,15 @@ static int yt2_1380_fc_serdev_probe(struct serdev_device *serdev)
 	if (ret)
 		return ret;
 
-	ret = devm_serdev_device_open(dev, serdev);
-	if (ret)
-		return dev_err_probe(dev, ret, "opening UART device\n");
-
 	serdev_device_set_baudrate(serdev, 600);
 	serdev_device_set_flow_control(serdev, false);
 	serdev_device_set_drvdata(serdev, fc);
 	serdev_device_set_client_ops(serdev, &yt2_1380_fc_serdev_ops);
 
+	ret = devm_serdev_device_open(dev, serdev);
+	if (ret)
+		return dev_err_probe(dev, ret, "opening UART device\n");
+
 	ret = devm_extcon_register_notifier_all(dev, fc->extcon, &fc->nb);
 	if (ret)
 		return dev_err_probe(dev, ret, "registering extcon notifier\n");
-- 
2.34.1

Re: [PATCH] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: fix race condition

[Hans de Goede]

Hi,

On 11-Jan-25 6:35 AM, yangchenyuan wrote:
> From: Chenyuan Yang <chenyuan0y@gmail.com>
> 
> The yt2_1380_fc_serdev_probe() function calls devm_serdev_device_open()
> before it calls serdev_device_set_client_ops(). This can trigger a NULL
> pointer dereference.
> This is similar to 5e700b384ec13f5bcac9855cb28fcc674f1d3593.
> 
> Fixes: b2ed33e8d486 ("platform/x86: Add lenovo-yoga-tab2-pro-1380-fastcharger driver")
> Signed-off-by: Chenyuan Yang <chenyuan0y@gmail.com>

Thank you for your patch.

> ---
>  .../platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c  | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c b/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c
> index d2699ca24f34..1a4e66464a7e 100644
> --- a/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c
> +++ b/drivers/platform/x86/lenovo-yoga-tab2-pro-1380-fastcharger.c
> @@ -199,15 +199,15 @@ static int yt2_1380_fc_serdev_probe(struct serdev_device *serdev)
>  	if (ret)
>  		return ret;
>  
> -	ret = devm_serdev_device_open(dev, serdev);
> -	if (ret)
> -		return dev_err_probe(dev, ret, "opening UART device\n");
> -
>  	serdev_device_set_baudrate(serdev, 600);
>  	serdev_device_set_flow_control(serdev, false);
>  	serdev_device_set_drvdata(serdev, fc);
>  	serdev_device_set_client_ops(serdev, &yt2_1380_fc_serdev_ops);
>  
> +	ret = devm_serdev_device_open(dev, serdev);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "opening UART device\n");
> +

serdev_device_open() resets the termios settings such as flow-control,
so you need to move the serdev_device_set_baudrate() and
serdev_device_set_flow_control() calls to after the new location of
the devm_serdev_device_open() call, just like commit 5e700b384ec1
("platform/chrome: cros_ec_uart: properly fix race condition") does.

Regards,

Hans




>  	ret = devm_extcon_register_notifier_all(dev, fc->extcon, &fc->nb);
>  	if (ret)
>  		return dev_err_probe(dev, ret, "registering extcon notifier\n");