netdev - Re: [PATCH net v4] virtio-net: fix received length check in big packets

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Message-ID: <CACGkMEtrdXOCsRQiw659Ygze7AXAHw4-uK_Z+zdi3r9V5XDLZQ@mail.gmail.com>
Date: Thu, 23 Oct 2025 10:36:53 +0800
From: Jason Wang <jasowang@...hat.com>
To: Bui Quang Minh <minhquangbui99@...il.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...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>, Paolo Abeni <pabeni@...hat.com>, 
	Gavin Li <gavinl@...dia.com>, Gavi Teitz <gavi@...dia.com>, Parav Pandit <parav@...dia.com>, 
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH net v4] virtio-net: fix received length check in big packets

On Thu, Oct 23, 2025 at 12:08 AM Bui Quang Minh
<minhquangbui99@...il.com> wrote:
>
> Since commit 4959aebba8c0 ("virtio-net: use mtu size as buffer length
> for big packets"), when guest gso is off, the allocated size for big
> packets is not MAX_SKB_FRAGS * PAGE_SIZE anymore but depends on
> negotiated MTU. The number of allocated frags for big packets is stored
> in vi->big_packets_num_skbfrags.
>
> Because the host announced buffer length can be malicious (e.g. the host
> vhost_net driver's get_rx_bufs is modified to announce incorrect
> length), we need a check in virtio_net receive path. Currently, the
> check is not adapted to the new change which can lead to NULL page
> pointer dereference in the below while loop when receiving length that
> is larger than the allocated one.
>
> This commit fixes the received length check corresponding to the new
> change.
>
> Fixes: 4959aebba8c0 ("virtio-net: use mtu size as buffer length for big packets")
> Cc: stable@...r.kernel.org
> Signed-off-by: Bui Quang Minh <minhquangbui99@...il.com>
> ---
> Changes in v4:
> - Remove unrelated changes, add more comments
> Changes in v3:
> - Convert BUG_ON to WARN_ON_ONCE
> Changes in v2:
> - Remove incorrect give_pages call
> ---

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks