netdev - Re: [PATCH net] virtio-net: drop the multi-buffer XDP packet in zerocopy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <dd087fdf-5d6c-4015-bed3-29760002f859@redhat.com>
Date: Thu, 5 Jun 2025 13:03:01 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Bui Quang Minh <minhquangbui99@...il.com>, netdev@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
 <eperezma@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, virtualization@...ts.linux.dev,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH net] virtio-net: drop the multi-buffer XDP packet in
 zerocopy

On 6/3/25 5:06 PM, Bui Quang Minh wrote:
> In virtio-net, we have not yet supported multi-buffer XDP packet in
> zerocopy mode when there is a binding XDP program. However, in that
> case, when receiving multi-buffer XDP packet, we skip the XDP program
> and return XDP_PASS. As a result, the packet is passed to normal network
> stack which is an incorrect behavior. 

Why? AFAICS the multi-buffer mode depends on features negotiation, which
is not controlled by the VM user.

Let's suppose the user wants to attach an XDP program to do some per
packet stats accounting. That suddenly would cause drop packets
depending on conditions not controlled by the (guest) user. It looks
wrong to me.

XDP_ABORTED looks like a better choice.

/P