netdev - Re: [PATCH] virtio-net: Add validation for used length

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Date:   Wed, 26 May 2021 15:52:03 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yongji Xie <xieyongji@...edance.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev@...r.kernel.org, linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virtio-net: Add validation for used length


在 2021/5/25 下午4:45, Yongji Xie 写道:
> On Tue, May 25, 2021 at 2:30 PM Jason Wang <jasowang@...hat.com> wrote:
>>
>> 在 2021/5/25 下午12:58, Xie Yongji 写道:
>>> This adds validation for used length (might come
>>> from an untrusted device) to avoid data corruption
>>> or loss.
>>>
>>> Signed-off-by: Xie Yongji <xieyongji@...edance.com>
>>> ---
>>>    drivers/net/virtio_net.c | 22 ++++++++++++++++++++++
>>>    1 file changed, 22 insertions(+)
>>>
>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>> index c4711e23af88..2dcdc1a3c7e8 100644
>>> --- a/drivers/net/virtio_net.c
>>> +++ b/drivers/net/virtio_net.c
>>> @@ -668,6 +668,13 @@ static struct sk_buff *receive_small(struct net_device *dev,
>>>                void *orig_data;
>>>                u32 act;
>>>
>>> +             if (unlikely(len > GOOD_PACKET_LEN)) {
>>> +                     pr_debug("%s: rx error: len %u exceeds max size %lu\n",
>>> +                              dev->name, len, GOOD_PACKET_LEN);
>>> +                     dev->stats.rx_length_errors++;
>>> +                     goto err_xdp;
>>> +             }
>>
>> Need to count vi->hdr_len here?
>>
> We did len -= vi->hdr_len before.


Right.


>
>>> +
>>>                if (unlikely(hdr->hdr.gso_type))
>>>                        goto err_xdp;
>>>
>>> @@ -739,6 +746,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
>>>        }
>>>        rcu_read_unlock();
>>>
>>> +     if (unlikely(len > GOOD_PACKET_LEN)) {
>>> +             pr_debug("%s: rx error: len %u exceeds max size %lu\n",
>>> +                      dev->name, len, GOOD_PACKET_LEN);
>>> +             dev->stats.rx_length_errors++;
>>> +             put_page(page);
>>> +             return NULL;
>>> +     }
>>> +
>>>        skb = build_skb(buf, buflen);
>>>        if (!skb) {
>>>                put_page(page);
>>> @@ -822,6 +837,13 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>>>                void *data;
>>>                u32 act;
>>>
>>> +             if (unlikely(len > truesize)) {
>>> +                     pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
>>> +                              dev->name, len, (unsigned long)ctx);
>>> +                     dev->stats.rx_length_errors++;
>>> +                     goto err_xdp;
>>> +             }
>>
>> There's a similar check after the XDP, let's simply move it here?
> Do we still need that in non-XDP cases?


I meant we check once for both XDP and non-XDP if we do it before if 
(xdp_prog)


>
>> And do we need similar check in receive_big()?
>>
> It seems that the check in page_to_skb() can do similar things.


Right.

Thanks


>
> Thanks,
> Yongji
>