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: NJiri Pirko <jpirko@redhat.com>
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Reviewed-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/sysctl.c

@@ -424,8 +424,9 @@ static int proc_sctp_do_alpha_beta(struct ctl_table *ctl, int write,
 				   void __user *buffer, size_t *lenp,
 				   loff_t *ppos)
 {
-	pr_warn_once("Changing rto_alpha or rto_beta may lead to "
-		     "suboptimal rtt/srtt estimations!\n");
+	if (write)
+		pr_warn_once("Changing rto_alpha or rto_beta may lead to "
+			     "suboptimal rtt/srtt estimations!\n");
 
 	return proc_dointvec_minmax(ctl, write, buffer, lenp, ppos);
 }