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

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Message-ID: <27cc3452-782f-4a9c-a762-b2bdf9ae1acd@redhat.com>
Date: Sat, 11 Jan 2025 10:30:06 +0100
From: Hans de Goede <hdegoede@...hat.com>
To: yangchenyuan <chenyuan0y@...il.com>, ilpo.jarvinen@...ux.intel.com
Cc: platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
 zijie98@...il.com
Subject: Re: [PATCH] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: fix
 race condition

Hi,

On 11-Jan-25 6:35 AM, yangchenyuan wrote:
> From: Chenyuan Yang <chenyuan0y@...il.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@...il.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");