netdev - Re: [PATCH net] virtio_net: bugfix overflow inside xdp_linearize

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Message-ID: <CACGkMEsE8TosCxyf4GwmsBzo1Ot9FiLtsWt16oz0f0J99DGYCg@mail.gmail.com>
Date:   Fri, 14 Apr 2023 13:40:32 +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>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        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-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH net] virtio_net: bugfix overflow inside xdp_linearize_page()

On Thu, Apr 13, 2023 at 8:19 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> Here we copy the data from the original buf to the new page. But we
> not check that it may be overflow.
>
> As long as the size received(including vnethdr) is greater than 3840
> (PAGE_SIZE -VIRTIO_XDP_HEADROOM). Then the memcpy will overflow.
>
> And this is completely possible, as long as the MTU is large, such
> as 4096. In our test environment, this will cause crash. Since crash is
> caused by the written memory, it is meaningless, so I do not include it.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>

Missing fixes tag?

Other than this,

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

Thanks

> ---
>  drivers/net/virtio_net.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 2396c28c0122..ea1bd4bb326d 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -814,8 +814,13 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
>                                        int page_off,
>                                        unsigned int *len)
>  {
> -       struct page *page = alloc_page(GFP_ATOMIC);
> +       int tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> +       struct page *page;
> +
> +       if (page_off + *len + tailroom > PAGE_SIZE)
> +               return NULL;
>
> +       page = alloc_page(GFP_ATOMIC);
>         if (!page)
>                 return NULL;
>
> @@ -823,7 +828,6 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
>         page_off += *len;
>
>         while (--*num_buf) {
> -               int tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
>                 unsigned int buflen;
>                 void *buf;
>                 int off;
> --
> 2.32.0.3.g01195cf9f
>