? 2021/5/31 ??3:19, Yongji Xie ??:> On Mon, May 31, 2021 at 2:49 PM Jason Wang <jasowang at redhat.com>
wrote:
>>
>> ? 2021/5/28 ??8:11, Xie Yongji ??:
>>> This adds validation for used length (might come
>>> from an untrusted device) to avoid data corruption
>>> or loss.
>>>
>>> Signed-off-by: Xie Yongji <xieyongji at bytedance.com>
>>> ---
>>> drivers/net/virtio_net.c | 28 +++++++++++++++++++++-------
>>> 1 file changed, 21 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>> index 073fec4c0df1..01f15b65824c 100644
>>> --- a/drivers/net/virtio_net.c
>>> +++ b/drivers/net/virtio_net.c
>>> @@ -732,6 +732,17 @@ static struct sk_buff *receive_small(struct
net_device *dev,
>>>
>>> rcu_read_lock();
>>> xdp_prog = rcu_dereference(rq->xdp_prog);
>>> + if (unlikely(len > GOOD_PACKET_LEN)) {
>>> + pr_debug("%s: rx error: len %u exceeds max size
%d\n",
>>> + dev->name, len, GOOD_PACKET_LEN);
>>> + dev->stats.rx_length_errors++;
>>> + if (xdp_prog)
>>> + goto err_xdp;
>>> +
>>> + rcu_read_unlock();
>>> + put_page(page);
>>> + return NULL;
>>> + }
>>> if (xdp_prog) {
>>> struct virtio_net_hdr_mrg_rxbuf *hdr = buf +
header_offset;
>>> struct xdp_frame *xdpf;
>>> @@ -888,6 +899,16 @@ static struct sk_buff
*receive_mergeable(struct net_device *dev,
>>>
>>> rcu_read_lock();
>>> xdp_prog = rcu_dereference(rq->xdp_prog);
>>> + 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++;
>>> + if (xdp_prog)
>>> + goto err_xdp;
>>> +
>>> + rcu_read_unlock();
>>> + goto err_skb;
>>> + }
>>
>> Patch looks correct but I'd rather not bother XDP here. It would be
>> better if we just do the check before rcu_read_lock() and use err_skb
>> directly() to avoid RCU/XDP stuffs.
>>
> If so, we will miss the statistics of xdp_drops. Is it OK?
It should be ok, we still had drops and it was dropped before dealing
with XDP.
The motivation is to have simple codes.
Thanks
>
> Thanks,
> Yongji
>