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Re: [Qemu-devel] [PATCH] filter-buffer: fix segfault while start qemu wi

From: Hailiang Zhang
Subject: Re: [Qemu-devel] [PATCH] filter-buffer: fix segfault while start qemu with status=off property
Date: Fri, 1 Apr 2016 16:24:05 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1

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

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 ...


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