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

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Date:   Wed, 19 May 2021 22:18:46 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     jasowang@...hat.com, davem@...emloft.net, kuba@...nel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_net: Remove BUG() to aviod machine dead

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().
>>
>> Signed-off-by: Xianting Tian <xianting.tian@...ux.alibaba.com>
>> ---
>>   drivers/net/virtio_net.c | 5 ++---
>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index c921ebf3ae82..a66174d13e81 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1647,9 +1647,8 @@ static int xmit_skb(struct send_queue *sq, struct
>> sk_buff *skb)
>>   		hdr = skb_vnet_hdr(skb);
>>
>>   	if (virtio_net_hdr_from_skb(skb, &hdr->hdr,
>> -				    virtio_is_little_endian(vi->vdev), false,
>> -				    0))
>> -		BUG();
>> +				virtio_is_little_endian(vi->vdev), false, 0))
>> +		return -EPROTO;
>>
> 
> why EPROTO? can you add some comments to explain what is going on pls?
> 
> is this related to a malicious hypervisor thing?
> 
> don't we want at least a WARN_ON? Or _ONCE?
> 
>>   	if (vi->mergeable_rx_bufs)
>>   		hdr->num_buffers = 0;
>> -- 
>> 2.17.1