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

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Message-ID: <CACKFLik8Ve4=eUV=TJMkwkScLN0H80TtiqPUwtuDqNEji+StSQ@mail.gmail.com>
Date: Tue, 24 Jun 2025 11:00:26 -0700
From: Michael Chan <michael.chan@...adcom.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: Yan Zhai <yan@...udflare.com>, netdev@...r.kernel.org, 
	Pavan Chebbi <pavan.chebbi@...adcom.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Stanislav Fomichev <sdf@...ichev.me>, Andy Gospodarek <andrew.gospodarek@...adcom.com>, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org, kernel-team@...udflare.com
Subject: Re: [PATCH net] bnxt: properly flush XDP redirect lists

On Mon, Jun 23, 2025 at 10:59 PM Jesper Dangaard Brouer <hawk@...nel.org> 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.
Reviewed-by: Michael Chan <michael.chan@...adcom.com>

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