net/ipv6: Fix misuse of proc_dointvec "flowlabel_reflect"

/proc/sys/net/ipv6/flowlabel_reflect assumes written value to be in the
range of 0 to 3. Use proc_dointvec_minmax instead of proc_dointvec.

Fixes: 323a53c4 ("ipv6: tcp: enable flowlabel reflection in some RST packets")
Signed-off-by: NEiichi Tsukata <devel@etsukata.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/sysctl_net_ipv6.c

@@ -114,7 +114,7 @@ static struct ctl_table ipv6_table_template[] = {
 		.data		= &init_net.ipv6.sysctl.flowlabel_reflect,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= &zero,
 		.extra2		= &flowlabel_reflect_max,
 	},