From: Jakub Kicinski <kuba@kernel.org>
To: Til Kaiser <mail@tk154.de>
Cc: netdev@vger.kernel.org, marcin.s.wojtas@gmail.com,
linux@armlinux.org.uk, andrew+netdev@lunn.ch,
davem@davemloft.net, edumazet@google.com, pabeni@redhat.com,
ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org,
john.fastabend@gmail.com, sdf@fomichev.me, mcroce@microsoft.com,
sven.auhagen@voleatech.de, bpf@vger.kernel.org
Subject: Re: [PATCH] net: mvpp2: fix skb not reflecting XDP modifications on XDP_PASS
Date: Wed, 27 May 2026 19:02:49 -0700 [thread overview]
Message-ID: <20260527190249.0eefda22@kernel.org> (raw)
In-Reply-To: <20260524122334.1730451-1-mail@tk154.de>
On Sun, 24 May 2026 14:23:34 +0200 Til Kaiser wrote:
> When an XDP program uses bpf_xdp_adjust_head() or bpf_xdp_adjust_tail()
> and then returns XDP_PASS, the driver ignores the updated xdp_buff
> pointers and builds the skb from hardcoded offsets derived from the
> original RX descriptor. This means any packet modifications made by the
> XDP program are silently discarded before the skb reaches the network
> stack.
>
> Fix this by saving the post-XDP data pointer offset and length back into
> rx_offset and rx_bytes when XDP_PASS is returned, so the subsequent
> skb_reserve()/skb_put() calls use the actual packet geometry as seen by
> the XDP program. When no XDP program is loaded the variables retain
> their original descriptor-derived values and the non-XDP fast path is
> unaffected.
>
> Fixes: 07dd0a7aae7f ("mvpp2: add basic XDP support")
> Signed-off-by: Til Kaiser <mail@tk154.de>
Other than the checksum complaint Sashiko review looks legit.
Please respin and try to fix more of this issues in one series.
Could you try to run:
tools/testing/selftests/drivers/net/xdp.py
it may surface other common driver bugs.
See: tools/testing/selftests/drivers/net/README.rst for instructions
--
pw-bot: cr
prev parent reply other threads:[~2026-05-28 2:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-24 12:23 [PATCH] net: mvpp2: fix skb not reflecting XDP modifications on XDP_PASS Til Kaiser
2026-05-24 13:14 ` sashiko-bot
2026-05-28 2:02 ` Jakub Kicinski [this message]
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