net: sctp: only warn in proc_sctp_do_alpha_beta if write

Only warn if the value is written to alpha or beta. We don't care
emitting a one-time warning when only reading it.
Reported-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Reviewed-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sysctl.c

@@ -424,6 +424,7 @@ static int proc_sctp_do_alpha_beta(struct ctl_table *ctl, int write,
 				   void __user *buffer, size_t *lenp,
 				   loff_t *ppos)
 {
+	if (write)
 		pr_warn_once("Changing rto_alpha or rto_beta may lead to "
 			     "suboptimal rtt/srtt estimations!\n");