linux-kernel - Re: [syzbot] [kvm?] [net?] [virt?] WARNING in virtio_transport_send_pkt

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Message-ID: <aJ8HVCbE-fIoS1U4@willie-the-truck>
Date: Fri, 15 Aug 2025 11:09:24 +0100
From: Will Deacon <will@...nel.org>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: syzbot <syzbot+b4d960daf7a3c7c2b7b1@...kaller.appspotmail.com>,
	davem@...emloft.net, edumazet@...gle.com, eperezma@...hat.com,
	horms@...nel.org, jasowang@...hat.com, kuba@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, pabeni@...hat.com, sgarzare@...hat.com,
	stefanha@...hat.com, syzkaller-bugs@...glegroups.com,
	virtualization@...ts.linux.dev, xuanzhuo@...ux.alibaba.com
Subject: Re: [syzbot] [kvm?] [net?] [virt?] WARNING in
 virtio_transport_send_pkt_info

On Tue, Aug 12, 2025 at 06:15:46AM -0400, Michael S. Tsirkin wrote:
> On Tue, Aug 12, 2025 at 03:03:02AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> > WARNING in virtio_transport_send_pkt_info
> 
> OK so the issue triggers on
> commit 6693731487a8145a9b039bc983d77edc47693855
> Author: Will Deacon <will@...nel.org>
> Date:   Thu Jul 17 10:01:16 2025 +0100
> 
>     vsock/virtio: Allocate nonlinear SKBs for handling large transmit buffers
>     
> 
> but does not trigger on:
> 
> commit 8ca76151d2c8219edea82f1925a2a25907ff6a9d
> Author: Will Deacon <will@...nel.org>
> Date:   Thu Jul 17 10:01:15 2025 +0100
> 
>     vsock/virtio: Rename virtio_vsock_skb_rx_put()
>     
> 
> 
> Will, I suspect your patch merely uncovers a latent bug
> in zero copy handling elsewhere.
> Want to take a look?

Sorry for the delay, I was debugging something else!

I see Hillf already tried some stuff in the other thread, but I can take
a look as well.

Will