Re: [Qemu-devel] [PATCH] filter-buffer: fix segfault while start qemu with status=off property

[Hailiang Zhang <zhang.zhanghailiang@huawei.com>]

On 2016/4/1 17:10, Wen Congyang wrote:
> On 04/01/2016 04:24 PM, Hailiang Zhang wrote:
>> On 2016/4/1 15:39, Jason Wang wrote:
>>>
>>>
>>> On 04/01/2016 03:08 PM, zhanghailiang wrote:
>>>> After commit 338d3f, we support 'status' property for filter object.
>>>> The segfault can be triggered by starting qemu with 'status=off' property
>>>> for filter, when the s->incoming_queue is NULL, we reference it directly
>>>> in qemu_net_queue_flush().
>>>>
>>>> Let's check the value of 's->incoming_queue' before calling
>>>> qemu_net_queue_flush().
>>>>
>>>> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
>>>> ---
>>>>    net/filter-buffer.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/net/filter-buffer.c b/net/filter-buffer.c
>>>> index cc6bd94..79e2ce3 100644
>>>> --- a/net/filter-buffer.c
>>>> +++ b/net/filter-buffer.c
>>>> @@ -34,7 +34,7 @@ static void filter_buffer_flush(NetFilterState *nf)
>>>>    {
>>>>        FilterBufferState *s = FILTER_BUFFER(nf);
>>>>
>>>> -    if (!qemu_net_queue_flush(s->incoming_queue)) {
>>>> +    if (s->incoming_queue && !qemu_net_queue_flush(s->incoming_queue)) {
>>>>            /* Unable to empty the queue, purge remaining packets */
>>>>            qemu_net_queue_purge(s->incoming_queue, nf->netdev);
>>>>        }
>>>
>>> We'd better handle this at generic layer and don't let a specific net
>>> filter need to worry about this.
>>>
>>> Looks like the issue is we may trigger status_changed() too early (even
>>> before the the filter was initialized).
>>>
>>
>> Yes ~
>>
>>> How about not call status_changed() if the initialization is not done?
>>>
>>
>> But seems that it is difficult to confirm if the filter is initialized
>> or not ...
>
> If nfc->setup() is not called, nf->netdev is NULL.
>

Yes, you right, Jason, what's opinion ?

Thanks,
hailiang

> Thanks
> Wen Congyang
>
>>
>>> .
>>>
>>
>>
>>
>>
>>
>
>
>
>
> .
>