linux-kernel - Re: [PATCH v3] usb: fix reference leak in usb_new

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Message-ID: <b564bbbb-f931-45d2-8d74-206c250b77f2@rowland.harvard.edu>
Date: Wed, 18 Dec 2024 10:53:03 -0500
From: Alan Stern <stern@...land.harvard.edu>
To: Ma Ke <make_ruc2021@....com>
Cc: gregkh@...uxfoundation.org, quic_ugoswami@...cinc.com,
	stanley_chang@...ltek.com, christophe.jaillet@...adoo.fr,
	oneukum@...e.com, javier.carrasco@...fvision.net,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v3] usb: fix reference leak in usb_new_device()

On Wed, Dec 18, 2024 at 03:13:46PM +0800, Ma Ke wrote:
> When device_add(&udev->dev) succeeds and a later call fails,
> usb_new_device() does not properly call device_del(). As comment of
> device_add() says, 'if device_add() succeeds, you should call
> device_del() when you want to get rid of it. If device_add() has not
> succeeded, use only put_device() to drop the reference count'.
> 
> Found by code review.
> 
> Cc: stable@...r.kernel.org
> Fixes: 9f8b17e643fe ("USB: make usbdevices export their device nodes instead of using a separate class")
> Signed-off-by: Ma Ke <make_ruc2021@....com>
> ---
> Changes in v3:
> - modified the bug description according to the changes of the patch;
> - removed redundant put_device() in patch v2 as suggestions.
> Changes in v2:
> - modified the bug description to make it more clear;
> - added the missed part of the patch.
> ---

Reviewed-by: Alan Stern <stern@...land.harvard.edu>

>  drivers/usb/core/hub.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 4b93c0bd1d4b..21ac9b464696 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -2663,13 +2663,13 @@ int usb_new_device(struct usb_device *udev)
>  		err = sysfs_create_link(&udev->dev.kobj,
>  				&port_dev->dev.kobj, "port");
>  		if (err)
> -			goto fail;
> +			goto out_del_dev;
>  
>  		err = sysfs_create_link(&port_dev->dev.kobj,
>  				&udev->dev.kobj, "device");
>  		if (err) {
>  			sysfs_remove_link(&udev->dev.kobj, "port");
> -			goto fail;
> +			goto out_del_dev;
>  		}
>  
>  		if (!test_and_set_bit(port1, hub->child_usage_bits))
> @@ -2683,6 +2683,8 @@ int usb_new_device(struct usb_device *udev)
>  	pm_runtime_put_sync_autosuspend(&udev->dev);
>  	return err;
>  
> +out_del_dev:
> +	device_del(&udev->dev);
>  fail:
>  	usb_set_device_state(udev, USB_STATE_NOTATTACHED);
>  	pm_runtime_disable(&udev->dev);
> -- 
> 2.25.1
>