From: Jakub Kicinski <kuba@kernel.org>
To: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: netdev@vger.kernel.org, Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
Willem de Bruijn <willemb@google.com>,
Petr Machata <petrm@nvidia.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] netdevsim: fix panic when NETIF_F_LOOPBACK is set on a VF port
Date: Mon, 31 Aug 2026 20:16:38 -0700 [thread overview]
Message-ID: <20260831201638.3bcaefcd@kernel.org> (raw)
In-Reply-To: <20260831042221.137137-1-jiayuan.chen@linux.dev>
On Mon, 31 Aug 2026 12:22:20 +0800 Jiayuan Chen wrote:
> A netdevsim VF port cannot process incoming data. It never runs
> nsim_queue_init(), so ns->rq is NULL, and nsim_vf_netdev_ops has no
> ->ndo_open, so its NAPI is never set up either.
>
> Since commit 358008f41d9b ("netdevsim: add loopback support") an outgoing
> netdevsim can also be the incoming device. nsim_setup() is shared by PF
> and VF ports and offers NETIF_F_LOOPBACK to both, so the feature can be
> turned on for a VF; nsim_start_xmit() then takes ns as peer_ns and
> dereferences peer_ns->rq[], which panics.
None of the offloads are there either, hm.. VF already has its own
net_device_ops struct. Let's replace:
.ndo_start_xmit = nsim_start_xmit,
with some dedicated nsim_start_xmit_vf() which unconditionally
drops the traffic? Even if we clear the LOOPBACK it will be easy
to re-introduce the bug by adding some PF-only code in the PF xmit.
--
pw-bot: cr
prev parent reply other threads:[~2026-09-01 3:16 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-31 4:22 [PATCH net] netdevsim: fix panic when NETIF_F_LOOPBACK is set on a VF port Jiayuan Chen
2026-09-01 3:16 ` Jakub Kicinski [this message]
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