linux-kernel - Re: [PATCH] usb: core: Unregister device on component

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Date:   Wed, 9 Feb 2022 16:00:09 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+60df062e1c41940cae0f@...kaller.appspotmail.com
Subject: Re: [PATCH] usb: core: Unregister device on component_add() failure

On Tue, Feb 08, 2022 at 06:00:48PM +0100, Fabio M. De Francesco wrote:
> Commit 8c67d06f3fd9 ("usb: Link the ports to the connectors they are
> attached to") creates a link to the USB Type-C connector for every new
> port that is added when possible. If component_add() fails,
> usb_hub_create_port_device() prints a warning but does not unregister
> the device and does not return errors to the callers.
> 
> Syzbot reported a "WARNING in component_del()".
> 
> Fix this issue in usb_hub_create_port_device by calling device_unregister()
> and returning the errors from component_add().
> 
> Reported-by: syzbot+60df062e1c41940cae0f@...kaller.appspotmail.com
> Fixes: 8c67d06f3fd9 ("usb: Link the ports to the connectors they are attached to")
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---
>  drivers/usb/core/port.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index c2bbf97a79be..8455b235976a 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -605,8 +605,11 @@ int usb_hub_create_port_device(struct usb_hub *hub, int port1)
>  	find_and_link_peer(hub, port1);
>  
>  	retval = component_add(&port_dev->dev, &connector_ops);
> -	if (retval)
> +	if (retval) {
>  		dev_warn(&port_dev->dev, "failed to add component\n");
> +		device_unregister(&port_dev->dev);
> +		return retval;

You didn't remove the peer links. Either remove them here separately,
or alternatively you can also just shuffle the code so that you only
create those links after the component_add() call:

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index c2bbf97a79bec..d5bc36ca5b1f7 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -602,11 +602,14 @@ int usb_hub_create_port_device(struct usb_hub *hub, int port1)
                return retval;
        }
 
-       find_and_link_peer(hub, port1);
-
        retval = component_add(&port_dev->dev, &connector_ops);
-       if (retval)
+       if (retval) {
                dev_warn(&port_dev->dev, "failed to add component\n");
+               device_unregister(&port_dev->dev);
+               return retval;
+       }
+
+       find_and_link_peer(hub, port1);
 
        /*
         * Enable runtime pm and hold a refernce that hub_configure()

thanks,

-- 
heikki