[NET]: Fix kfifo_alloc() error check.

The return value of kfifo_alloc() should be checked by IS_ERR().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_probe.c b/net/ipv4/tcp_probe.c
index 4be336f..f230eee 100644
--- a/net/ipv4/tcp_probe.c
+++ b/net/ipv4/tcp_probe.c
@@ -156,6 +156,8 @@
 	init_waitqueue_head(&tcpw.wait);
 	spin_lock_init(&tcpw.lock);
 	tcpw.fifo = kfifo_alloc(bufsize, GFP_KERNEL, &tcpw.lock);
+	if (IS_ERR(tcpw.fifo))
+		return PTR_ERR(tcpw.fifo);
 
 	if (!proc_net_fops_create(procname, S_IRUSR, &tcpprobe_fops))
 		goto err0;