Re: [PATCH] virtio_net: Remove BUG() to aviod machine dead

Jason Wang
2021-06-02T07:15:06Z

在 2021/6/2 下午1:59, Leon Romanovsky 写道:
> On Tue, May 25, 2021 at 02:19:03PM +0800, Jason Wang wrote:
>> 在 2021/5/19 下午10:18, Xianting Tian 写道:
>>> thanks, I submit the patch as commented by Andrew
>>> https://lkml.org/lkml/2021/5/18/256
>>>
>>> Actually, if xmit_skb() returns error, below code will give a warning
>>> with error code.
>>>
>>>     /* Try to transmit */
>>>     err = xmit_skb(sq, skb);
>>>
>>>     /* This should not happen! */
>>>     if (unlikely(err)) {
>>>         dev->stats.tx_fifo_errors++;
>>>         if (net_ratelimit())
>>>             dev_warn(&dev->dev,
>>>                  "Unexpected TXQ (%d) queue failure: %d\n",
>>>                  qnum, err);
>>>         dev->stats.tx_dropped++;
>>>         dev_kfree_skb_any(skb);
>>>         return NETDEV_TX_OK;
>>>     }
>>>
>>>
>>>
>>>
>>>
>>> 在 2021/5/18 下午5:54, Michael S. Tsirkin 写道:
>>>> typo in subject
>>>>
>>>> On Tue, May 18, 2021 at 05:46:56PM +0800, Xianting Tian wrote:
>>>>> When met error, we output a print to avoid a BUG().
>>
>> So you don't explain why you need to remove BUG(). I think it deserve a
>> BUG().
> BUG() will crash the machine and virtio_net is not kernel core
> functionality that must stop the machine to prevent anything truly
> harmful and basic.

Note that the BUG() here is not for virtio-net itself. It tells us that
a bug was found by virtio-net.

That is, the one that produces the skb has a bug, usually it's the
network core.

There could also be the issue of the packet from untrusted source
(userspace like TAP or packet socket) but they should be validated there.

Thanks

>
> I would argue that code in drivers/* shouldn't call BUG() macros at all.
>
> If it is impossible, don't check for that or add WARN_ON() and recover,
> but don't crash whole system.
>
> Thanks
>