Hi,

I found a problem to unix domain socket.

The unix_gc function removes socket buffers of the socket
which is connectted but not acceptted yet.

After one process executes "Mark phase" of unix_gc function,
another process registers socket buffer by using sendmsg with SCM_RIGHTS.
At the next moment, the socket buffer is removed.

I attached the test program.
When I execute one server and two clients on SMP machine
(kernel 2.4.16 and PentiumIII x 2), I can reporduce this problem.

Following is a patch to avoid this problem.

--- kernel-2.4.16/net/unix/garbage.c.sv       Mon Jan  7 15:46:22 2002
+++ kernel-2.4.16/net/unix/garbage.c  Mon Jan  7 15:51:22 2002
@@ -279,7 +279,7 @@
                                /*
                                 *      Do we have file descriptors ?
                                 */
-                               if(UNIXCB(skb).fp)
+                               if(s->dead && UNIXCB(skb).fp)
                                {
                                        __skb_unlink(skb, skb->list);
                                        __skb_queue_tail(&hitlist,skb);


Regards,

 Yasuma Takeda