netdev - Re: [PATCH net-next v1 1/4] virtio-net: fix overflow inside virtnet_rq

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Message-ID: <CACGkMEuo7ADSJg-gv_qtiGt=M3VqVjR76Q4baqkDmNLsb7OcAA@mail.gmail.com>
Date: Tue, 5 Nov 2024 17:22:31 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.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>, 
	virtualization@...ts.linux.dev, Si-Wei Liu <si-wei.liu@...cle.com>, 
	Darren Kenny <darren.kenny@...cle.com>
Subject: Re: [PATCH net-next v1 1/4] virtio-net: fix overflow inside virtnet_rq_alloc

On Tue, Oct 29, 2024 at 4:47 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> When the frag just got a page, then may lead to regression on VM.
> Specially if the sysctl net.core.high_order_alloc_disable value is 1,
> then the frag always get a page when do refill.
>
> Which could see reliable crashes or scp failure (scp a file 100M in size
> to VM).
>
> The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning
> of a new frag. When the frag size is larger than PAGE_SIZE,
> everything is fine. However, if the frag is only one page and the
> total size of the buffer and virtnet_rq_dma is larger than one page, an
> overflow may occur.
>
> The commit f9dac92ba908 ("virtio_ring: enable premapped mode whatever
> use_dma_api") introduced this problem. And we reverted some commits to
> fix this in last linux version. Now we try to enable it and fix this
> bug directly.
>
> Here, when the frag size is not enough, we reduce the buffer len to fix
> this problem.
>
> Reported-by: "Si-Wei Liu" <si-wei.liu@...cle.com>
> Tested-by: Darren Kenny <darren.kenny@...cle.com>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>

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

Thanks