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Date: Mon, 21 Sep 2026 13:45:58 +0100
From: Simon Horman <horms@kernel.org>
To: Weiming Shi <bestswngs@gmail.com>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Stanislav Fomichev <sdf@fomichev.me>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	co+65e5c76b187f08b2@bugs.sh, Xiang Mei <xmei5@asu.edu>,
	stable@vger.kernel.org
Subject: Re: [PATCH net] veth: manage XDP program pointers during channel
 resize
Message-ID: <20260921124558.GO13925@horms.kernel.org>
References: <20260917153923.904124-3-bestswngs@gmail.com>
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In-Reply-To: <20260917153923.904124-3-bestswngs@gmail.com>

On Thu, Sep 17, 2026 at 11:39:25PM +0800, Weiming Shi wrote:
> veth_set_channels() tears down XDP resources for removed RX queues
> without clearing rq->xdp_prog.  If the program is then detached or
> replaced, those queues keep the old pointer after bpf_prog_put().  A
> later channel increase can re-enable NAPI and run the freed program.
> 
> Clear the program pointer after taking an RX queue offline, and publish
> the current program only after bringing the queue back online succeeds.
> 
>   BUG: unable to handle page fault for address: ffffc90000256048
>   Oops: Oops: 0000 [#1] SMP KASAN NOPTI
>   RIP: veth_xdp_rcv_skb (include/linux/filter.h:779
>                          include/net/xdp.h:696 drivers/net/veth.c:820)
>   Call Trace:
>    veth_xdp_rcv (drivers/net/veth.c:941)
>    veth_poll (drivers/net/veth.c:986)
>    __napi_poll (net/core/dev.c:7787)
>    net_rx_action (net/core/dev.c:7850 net/core/dev.c:8007)
>    handle_softirqs (kernel/softirq.c:645)
>   Kernel panic - not syncing: Fatal exception in interrupt
> 
> Cc: stable@vger.kernel.org
> Fixes: 4752eeb3d891 ("veth: implement support for set_channel ethtool op")
> Reported-by: <co+65e5c76b187f08b2@bugs.sh>
> Assisted-by: LLM
> Signed-off-by: Weiming Shi <bestswngs@gmail.com>

Reviewed-by: Simon Horman <horms@kernel.org>