linux-kernel - Re: [PATCH] usb: gadget : fix use-after-free in composite_dev

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Message-ID: <2025071946-dilation-elongated-b68f@gregkh>
Date: Sat, 19 Jul 2025 08:56:49 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Tao Xue <xuetao09@...wei.com>
Cc: Thinh.Nguyen@...opsys.com, prashanth.k@....qualcomm.com,
	m.grzeschik@...gutronix.de, Chris.Wulff@...mp.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	caiyadong@...wei.com, suzhuangluan@...ilicon.com,
	weiwenwen3@...wei.com
Subject: Re: [PATCH] usb: gadget : fix use-after-free in
 composite_dev_cleanup()

On Sat, Jul 19, 2025 at 12:56:12PM +0800, Tao Xue wrote:
> The pointer cdev->os_desc_req need to be set null when kmalloc failed in
> composite_os_desc_req_prepare(),otherwise the use-after-free issue will
> be encountered in composite_dev_cleanup()
> 
> BUG: KASAN: use-after-free in composite_dev_cleanup+0xf4/0x2c0
> Read of size 8 at addr 0000004827837a00 by task init/1
> 
> CPU: 10 PID: 1 Comm: init Tainted: G           O      5.10.97-oh #1
>  kasan_report+0x188/0x1cc
>  __asan_load8+0xb4/0xbc
>  composite_dev_cleanup+0xf4/0x2c0
>  configfs_composite_bind+0x210/0x7ac
>  udc_bind_to_driver+0xb4/0x1ec
>  usb_gadget_probe_driver+0xec/0x21c
>  gadget_dev_desc_UDC_store+0x264/0x27c
> 
> Fixes: 37a3a533429e ("usb: gadget: OS Feature Descriptors support")
> Signed-off-by: Tao Xue <xuetao09@...wei.com>
> Signed-off-by: weiwenwen <weiwenwen3@...wei.com>

The order of signed-off-by is odd here.  And I need a "full" name for
the last one please.

> ---
>  drivers/usb/gadget/composite.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index 8dbc132a505e..385398a039ea 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -2489,6 +2489,7 @@ int composite_os_desc_req_prepare(struct usb_composite_dev *cdev,
>  	if (!cdev->os_desc_req->buf) {
>  		ret = -ENOMEM;
>  		usb_ep_free_request(ep0, cdev->os_desc_req);
> +		cdev->os_desc_req = NULL;

Can you add a comment here as to why you need to set this to NULL, as it
is not obvious at all.

thanks,

greg k-h