linux-kernel - Re: [PATCH v4 2/2] usb: gadget: clear related members when goto fail

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Date:   Fri, 31 Dec 2021 12:35:03 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Hangyu Hua <hbh25y@...il.com>
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org, axboe@...nel.dk,
        dan.carpenter@...cle.com, jj251510319013@...il.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] usb: gadget: clear related members when goto fail

On Sat, Jan 01, 2022 at 01:21:38AM +0800, Hangyu Hua wrote:
> dev->config and dev->hs_config and dev->dev need to be cleaned if
> dev_config fails to avoid UAF.
> 
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
> ---

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

>  drivers/usb/gadget/legacy/inode.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
> index eaad03c0252f..25c8809e0a38 100644
> --- a/drivers/usb/gadget/legacy/inode.c
> +++ b/drivers/usb/gadget/legacy/inode.c
> @@ -1875,8 +1875,8 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
>  
>  	value = usb_gadget_probe_driver(&gadgetfs_driver);
>  	if (value != 0) {
> -		kfree (dev->buf);
> -		dev->buf = NULL;
> +		spin_lock_irq(&dev->lock);
> +		goto fail;
>  	} else {
>  		/* at this point "good" hardware has for the first time
>  		 * let the USB the host see us.  alternatively, if users
> @@ -1893,6 +1893,9 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
>  	return value;
>  
>  fail:
> +	dev->config = NULL;
> +	dev->hs_config = NULL;
> +	dev->dev = NULL;
>  	spin_unlock_irq (&dev->lock);
>  	pr_debug ("%s: %s fail %zd, %p\n", shortname, __func__, value, dev);
>  	kfree (dev->buf);
> -- 
> 2.25.1
>