linux-kernel - Re: [PATCH net] virtio_net: fix return value check in receive

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Date:   Tue, 5 Dec 2017 10:59:18 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     wangyunjian <wangyunjian@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "mst@...hat.com" <mst@...hat.com>, caihe <caihe@...wei.com>
Subject: Re: [PATCH net] virtio_net: fix return value check in
 receive_mergeable()



On 2017年12月04日 19:25, wangyunjian wrote:
>
>> -----Original Message-----
>> From: Jason Wang [mailto:jasowang@...hat.com]
>> Sent: Monday, December 04, 2017 3:10 PM
>> To: wangyunjian <wangyunjian@...wei.com>; linux-
>> kernel@...r.kernel.org
>> Cc: mst@...hat.com; caihe <caihe@...wei.com>
>> Subject: Re: [PATCH net] virtio_net: fix return value check in
>> receive_mergeable()
>>
>>
>>
>> On 2017年12月04日 14:02, wangyunjian wrote:
>>> From: Yunjian Wang <wangyunjian@...wei.com>
>>>
>>> The function virtqueue_get_buf_ctx() could return NULL, the return
>>> value 'buf' need to be checked with NULL, not value 'ctx'.
>>>
>>> Signed-off-by: Yunjian Wang <wangyunjian@...wei.com>
>>> ---
>>>    drivers/net/virtio_net.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>> index 19a985e..559b215 100644
>>> --- a/drivers/net/virtio_net.c
>>> +++ b/drivers/net/virtio_net.c
>>> @@ -756,7 +756,7 @@ static struct sk_buff *receive_mergeable(struct
>> net_device *dev,
>>>    		int num_skb_frags;
>>>
>>>    		buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
>>> -		if (unlikely(!ctx)) {
>>> +		if (unlikely(!buf)) {
>>>    			pr_debug("%s: rx error: %d buffers out of %d
>> missing\n",
>>>    				 dev->name, num_buf,
>>>    				 virtio16_to_cpu(vi->vdev,
>> Hi:
>>
>> The path looks good but I'm not sure this is a real fix since we add
>> data and ctx simultaneously in virtqueue_add_inbuf_ctx().
>>
>> Any bad result you see without this patch?
>>
> Now no problem has been found yet, and I found it when reviewing the code.
>
> Thanks

Then I think it's better to go net-next. Michael, any idea on this?

Thanks

>
>> Thanks