Racy addr->valid in sctp_inet6addr_event() and sctp_copy_laddrs()

[Sishuai Gong <sishuai.system@xxxxxxxxx>]

Hello,

We observed a data race over addr->valid between sctp_inet6addr_event() and 
sctp_copy_laddrs(). Under the following execution order, sctp_copy_laddrs()
might copy the addr that is no longer valid.

sctp_copy_laddrs()              sctp_inet6addr_event()
if (!addr->valid)
        continue;
                                		addr->valid = 0;
memcpy(&temp, &addr->a, sizeof(temp));

Thanks