ipv6/route: Add a missing check on proc_dointvec

mainline inclusion
from mainline-v5.0-rc1
commit f0fb9b28
category: bugfix
bugzilla: 51403
CVE: NA

-------------------------------------------------

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: NAditya Pakki <pakki001@umn.edu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NXu Jia <xujia39@huawei.com>
Reviewed-by: NYue Haibing <yuehaibing@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/ipv6/route.c

@@ -5145,12 +5145,16 @@ int ipv6_sysctl_rtcache_flush(struct ctl_table *ctl, int write,
 {
 	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;
 }