linux-kernel - Re: [PATCH 1/2] usb: typec: class: Fix NULL pointer access

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Message-ID: <Z93zXHJPO3UHY_YF@google.com>
Date: Fri, 21 Mar 2025 23:16:44 +0000
From: Benson Leung <bleung@...gle.com>
To: Andrei Kuchynski <akuchynski@...omium.org>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Benson Leung <bleung@...omium.org>,
	Jameson Thies <jthies@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] usb: typec: class: Fix NULL pointer access

Hi Andrei,


On Fri, Mar 21, 2025 at 02:37:26PM +0000, Andrei Kuchynski wrote:
> Concurrent calls to typec_partner_unlink_device can lead to a NULL pointer
> dereference. This patch adds a mutex to protect USB device pointers and
> prevent this issue. The same mutex protects both the device pointers and
> the partner device registration.
> 
> Cc: stable@...r.kernel.org
> Fixes: 59de2a56d127 ("usb: typec: Link enumerated USB devices with Type-C partner")       
> Signed-off-by: Andrei Kuchynski <akuchynski@...omium.org>

Reviewed-by: Benson Leung <bleung@...omium.org>

> ---
>  drivers/usb/typec/class.c | 15 +++++++++++++--
>  drivers/usb/typec/class.h |  1 +
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index 9c76c3d0c6cf..eadb150223f8 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -1052,6 +1052,7 @@ struct typec_partner *typec_register_partner(struct typec_port *port,
>  		partner->usb_mode = USB_MODE_USB3;
>  	}
>  
> +	mutex_lock(&port->partner_link_lock);
>  	ret = device_register(&partner->dev);
>  	if (ret) {
>  		dev_err(&port->dev, "failed to register partner (%d)\n", ret);
> @@ -1063,6 +1064,7 @@ struct typec_partner *typec_register_partner(struct typec_port *port,
>  		typec_partner_link_device(partner, port->usb2_dev);
>  	if (port->usb3_dev)
>  		typec_partner_link_device(partner, port->usb3_dev);
> +	mutex_unlock(&port->partner_link_lock);
>  
>  	return partner;
>  }
> @@ -1083,12 +1085,14 @@ void typec_unregister_partner(struct typec_partner *partner)
>  
>  	port = to_typec_port(partner->dev.parent);
>  
> +	mutex_lock(&port->partner_link_lock);
>  	if (port->usb2_dev)
>  		typec_partner_unlink_device(partner, port->usb2_dev);
>  	if (port->usb3_dev)
>  		typec_partner_unlink_device(partner, port->usb3_dev);
>  
>  	device_unregister(&partner->dev);
> +	mutex_unlock(&port->partner_link_lock);
>  }
>  EXPORT_SYMBOL_GPL(typec_unregister_partner);
>  
> @@ -2041,10 +2045,11 @@ static struct typec_partner *typec_get_partner(struct typec_port *port)
>  static void typec_partner_attach(struct typec_connector *con, struct device *dev)
>  {
>  	struct typec_port *port = container_of(con, struct typec_port, con);
> -	struct typec_partner *partner = typec_get_partner(port);
> +	struct typec_partner *partner;
>  	struct usb_device *udev = to_usb_device(dev);
>  	enum usb_mode usb_mode;
>  
> +	mutex_lock(&port->partner_link_lock);
>  	if (udev->speed < USB_SPEED_SUPER) {
>  		usb_mode = USB_MODE_USB2;
>  		port->usb2_dev = dev;
> @@ -2053,18 +2058,22 @@ static void typec_partner_attach(struct typec_connector *con, struct device *dev
>  		port->usb3_dev = dev;
>  	}
>  
> +	partner = typec_get_partner(port);
>  	if (partner) {
>  		typec_partner_set_usb_mode(partner, usb_mode);
>  		typec_partner_link_device(partner, dev);
>  		put_device(&partner->dev);
>  	}
> +	mutex_unlock(&port->partner_link_lock);
>  }
>  
>  static void typec_partner_deattach(struct typec_connector *con, struct device *dev)
>  {
>  	struct typec_port *port = container_of(con, struct typec_port, con);
> -	struct typec_partner *partner = typec_get_partner(port);
> +	struct typec_partner *partner;
>  
> +	mutex_lock(&port->partner_link_lock);
> +	partner = typec_get_partner(port);
>  	if (partner) {
>  		typec_partner_unlink_device(partner, dev);
>  		put_device(&partner->dev);
> @@ -2074,6 +2083,7 @@ static void typec_partner_deattach(struct typec_connector *con, struct device *d
>  		port->usb2_dev = NULL;
>  	else if (port->usb3_dev == dev)
>  		port->usb3_dev = NULL;
> +	mutex_unlock(&port->partner_link_lock);
>  }
>  
>  /**
> @@ -2614,6 +2624,7 @@ struct typec_port *typec_register_port(struct device *parent,
>  
>  	ida_init(&port->mode_ids);
>  	mutex_init(&port->port_type_lock);
> +	mutex_init(&port->partner_link_lock);
>  
>  	port->id = id;
>  	port->ops = cap->ops;
> diff --git a/drivers/usb/typec/class.h b/drivers/usb/typec/class.h
> index b3076a24ad2e..db2fe96c48ff 100644
> --- a/drivers/usb/typec/class.h
> +++ b/drivers/usb/typec/class.h
> @@ -59,6 +59,7 @@ struct typec_port {
>  	enum typec_port_type		port_type;
>  	enum usb_mode			usb_mode;
>  	struct mutex			port_type_lock;
> +	struct mutex			partner_link_lock;
>  
>  	enum typec_orientation		orientation;
>  	struct typec_switch		*sw;
> -- 
> 2.49.0.395.g12beb8f557-goog
> 

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