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

[Wen Congyang]

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 <address@hidden>
>>> ---
>>>   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.

Thanks
Wen Congyang

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