linux-kernel - Re: [PATCH] usb: roles: fix a potential use after free

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Message-ID: <20191126154913.GB6428@kuha.fi.intel.com>
Date:   Tue, 26 Nov 2019 17:49:13 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Wen Yang <wenyang@...ux.alibaba.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: roles: fix a potential use after free

On Sun, Nov 24, 2019 at 10:22:36PM +0800, Wen Yang wrote:
> Free the sw structure only after we are done using it.
> This patch just moves the put_device() down a bit to avoid the
> use after free.
> 
> Fixes: 5c54fcac9a9d ("usb: roles: Take care of driver module reference counting")
> Signed-off-by: Wen Yang <wenyang@...ux.alibaba.com>
> Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Cc: Hans de Goede <hdegoede@...hat.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Chunfeng Yun <chunfeng.yun@...iatek.com>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: linux-usb@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/usb/roles/class.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index 8273126..63a00ff 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -169,8 +169,8 @@ struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
>  void usb_role_switch_put(struct usb_role_switch *sw)
>  {
>  	if (!IS_ERR_OR_NULL(sw)) {
> -		put_device(&sw->dev);
>  		module_put(sw->dev.parent->driver->owner);
> +		put_device(&sw->dev);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(usb_role_switch_put);
> -- 
> 1.8.3.1

-- 
heikki