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 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 ...

> .
>