Re: [PATCH] xen-netfront: handle NULL returned by xdp_convert_buff_to_frame()

Alexey
2025-04-17T08:45:38Z

On 17.04.2025 10:12, Jürgen Groß wrote:
> On 17.04.25 09:00, Alexey wrote:
>>
>> On 17.04.2025 03:58, Jakub Kicinski wrote:
>>> On Mon, 14 Apr 2025 18:34:01 +0000 Alexey Nepomnyashih wrote:
>>>>           get_page(pdata);
>>> Please notice this get_page() here.
>>>
>>>>           xdpf = xdp_convert_buff_to_frame(xdp);
>>>> +        if (unlikely(!xdpf)) {
>>>> +            trace_xdp_exception(queue->info->netdev, prog, act);
>>>> +            break;
>>>> +        }
>> Do you mean that it would be better to move the get_page(pdata) call
>> lower,
>> after checking for NULL in xdpf, so that the reference count is only
>> increased
>> after a successful conversion?
>
> I think the error handling here is generally broken (or at least very
> questionable).
>
> I suspect that in case of at least some errors the get_page() is leaking
> even without this new patch.
>
> In case I'm wrong a comment reasoning why there is no leak should be
> added.
>
>
> Juergen

I think pdata is freed in xdp_return_frame_rx_napi() -> __xdp_return()