[TIPC]: Fix infinite loop in netlink handler

The tipc netlink config handler uses the nlmsg_pid from the
request header as destination for its reply. If the application
initialized nlmsg_pid to 0, the reply is looped back to the kernel,
causing hangup. Fix: use nlmsg_pid of the skb that triggered the
request.

Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/tipc/netlink.c

···
 		rep_nlh = nlmsg_hdr(rep_buf);
 		memcpy(rep_nlh, req_nlh, hdr_space);
 		rep_nlh->nlmsg_len = rep_buf->len;
-		genlmsg_unicast(rep_buf, req_nlh->nlmsg_pid);
+		genlmsg_unicast(rep_buf, NETLINK_CB(skb).pid);
 	}
 
 	return 0;