diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 11c4ca1..5c5db66 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -257,6 +257,9 @@
 	int try_loading_module = 0;
 	int err;
 
+	if (protocol < 0 || protocol >= IPPROTO_MAX)
+		return -EINVAL;
+
 	sock->state = SS_UNCONNECTED;
 
 	/* Look for the requested type/protocol pair. */