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

[Jason Wang]

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