On 17.04.25 12:06, Alexey wrote:

On 17.04.2025 11:51, Juergen Gross wrote:

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On 17.04.25 10:45, Alexey wrote:

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On 17.04.2025 10:12, Jürgen Groß wrote:

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On 17.04.25 09:00, Alexey wrote:

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On 17.04.2025 03:58, Jakub Kicinski wrote:

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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()

Agreed. But what if xennet_xdp_xmit() returns an error < 0?

In this case xdp_return_frame_rx_napi() won't be called.

Juergen

Agreed. There is no explicit freed pdata in the calling function xennet_get_responses(). Without this, the page referenced by pdata could be leaked.

I suggest:

case XDP_TX:

• get_page(pdata);
  

  xdpf = xdp_convert_buff_to_frame(xdp);

• if (unlikely(!xdpf)) {
  

• 	trace_xdp_exception(queue->info->netdev, prog, act);
  

• 	break;
  

• }
  

• get_page(pdata);
  

  err = xennet_xdp_xmit(queue->info->netdev, 1, &xdpf, 0); if (unlikely(!err)) xdp_return_frame_rx_napi(xdpf);

• else if (unlikely(err < 0))
  

• else if (unlikely(err < 0)) {
  trace_xdp_exception(queue->info->netdev, prog, act);
  

• 	xdp_return_frame_rx_napi(xdpf);
  

• }
  

Could you please merge the two if () blocks, as they share the call of xdp_return_frame_rx_napi() now? Something like:

if (unlikely(err <= 0)) { if (err < 0) trace_xdp_exception(queue->info->netdev, prog, act); xdp_return_frame_rx_napi(xdpf); }

break;

case XDP_REDIRECT: get_page(pdata); err = xdp_do_redirect(queue->info->netdev, xdp, prog); *need_xdp_flush = true;

• if (unlikely(err))
  

• if (unlikely(err)) {
  trace_xdp_exception(queue->info->netdev, prog, act);
  

• 	__xdp_return(page_address(pdata), &xdp->mem, true, xdp);
  

• }
  

  break;

Juergen

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