Re: [PATCH net] bnxt: properly flush XDP redirect lists

[Andy Gospodarek]

On Tue, Jun 24, 2025 at 2:00 PM Michael Chan <michael.chan@xxxxxxxxxxxx> wrote:
>
> On Mon, Jun 23, 2025 at 10:59 PM Jesper Dangaard Brouer <hawk@xxxxxxxxxx> wrote:
> >
> > On 23/06/2025 18.06, Yan Zhai wrote:
> > > We encountered following crash when testing a XDP_REDIRECT feature
> > > in production:
> > >
> > [...]
> > >
> > (To Andy + Michael:)
> > The initial bug was introduced in [1] commit a7559bc8c17c ("bnxt:
> > support transmit and free of aggregation buffers") in bnxt_rx_xdp()
> > where case XDP_TX zeros the *event, that also carries the XDP-redirect
> > indication.
> > I'm wondering if the driver should not reset the *event value?
> > (all other drive code paths doesn't)
>
> Resetting *event was only correct before XDP_REDIRECT support was added.
>
> >
> >
> > > We can stably reproduce this crash by returning XDP_TX
> > > and XDP_REDIRECT randomly for incoming packets in a naive XDP program.
> > > Properly propagate the XDP_REDIRECT events back fixes the crash.
>
> Thanks for the patch.  The fix is similar to edc0140cc3b7 ("bnxt_en:
> Flush XDP for bnxt_poll_nitroa0()'s NAPI")
>
> Somehow the fix was only applied to one chip's poll function and not
> the other chips' poll functions.

Odd that we missed this back then.  Thanks for the fix for all other devices.

> Reviewed-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
Reviewed-by: Andy Gospodarek <gospo@xxxxxxxxxxxx>