ipv6/route: Add a missing check on proc_dointvec

While flushing the cache via ipv6_sysctl_rtcache_flush(), the call
to proc_dointvec() may fail. The fix adds a check that returns the
error, on failure.

Signed-off-by: Aditya Pakki <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv6/route.c

···
 {
 	struct net *net;
 	int delay;
+	int ret;
 	if (!write)
 		return -EINVAL;
 
 	net = (struct net *)ctl->extra1;
 	delay = net->ipv6.sysctl.flush_delay;
-	proc_dointvec(ctl, write, buffer, lenp, ppos);
+	ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
+	if (ret)
+		return ret;
+
 	fib6_run_gc(delay <= 0 ? 0 : (unsigned long)delay, net, delay > 0);
 	return 0;
 }