Re: [PATCH 2/2] usb: cdns3: fix memory double free when handle zero package

[Roger Quadros]

Hello Frank,

On 02/02/2024 07:18, Frank Li wrote:
> 829  if (request->complete) {
> 830          spin_unlock(&priv_dev->lock);
> 831          usb_gadget_giveback_request(&priv_ep->endpoint,
> 832                                    request);
> 833          spin_lock(&priv_dev->lock);
> 834  }
> 835
> 836  if (request->buf == priv_dev->zlp_buf)
> 837      cdns3_gadget_ep_free_request(&priv_ep->endpoint, request);
> 
> Driver append an additional zero package request when queue a package,
> which length mod max package size is 0. When transfer complete, run to
> line 831, usb_gadget_giveback_request() will free this requestion. 836
> condition is true, so cdns3_gadget_ep_free_request() free this request
> again.

Please replace "package" with "packet" in subject and description.

> 
> Log:
> 
> [ 1920.140696][  T150] BUG: KFENCE: use-after-free read in cdns3_gadget_giveback+0x134/0x2c0 [cdns3]
> [ 1920.140696][  T150]
> [ 1920.151837][  T150] Use-after-free read at 0x000000003d1cd10b (in kfence-#36):
> [ 1920.159082][  T150]  cdns3_gadget_giveback+0x134/0x2c0 [cdns3]
> [ 1920.164988][  T150]  cdns3_transfer_completed+0x438/0x5f8 [cdns3]
> 
> Add check at line 829, skip call usb_gadget_giveback_request() if it is
> additional zero length package request. Needn't call
> usb_gadget_giveback_request() because it is allocated in this driver.
> 
> Cc: <stable@xxxxxxxxxxxxxxx>
> Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
> Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> ---
>  drivers/usb/cdns3/cdns3-gadget.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
> index d6723d31fc6e2..fd1beb10bba72 100644
> --- a/drivers/usb/cdns3/cdns3-gadget.c
> +++ b/drivers/usb/cdns3/cdns3-gadget.c
> @@ -828,7 +828,11 @@ void cdns3_gadget_giveback(struct cdns3_endpoint *priv_ep,
>  			return;
>  	}
>  
> -	if (request->complete) {
> +	/*
> +	 * zlp request is appended by driver, needn't call usb_gadget_giveback_request() to notify
> +	 * gadget composite driver.
> +	 */
> +	if (request->complete && request->buf != priv_dev->zlp_buf) {
>  		spin_unlock(&priv_dev->lock);
>  		usb_gadget_giveback_request(&priv_ep->endpoint,
>  					    request);

-- 
cheers,
-roger