vlan: disable SIOCSHWTSTAMP in container

With NET_ADMIN enabled in container, a normal user could be mapped to
root and is able to change the real device's rx filter via ioctl on
vlan, which would affect the other ptp process on host. Fix it by
disabling SIOCSHWTSTAMP in container.

Fixes: a6111d3c ("vlan: Pass SIOC[SG]HWTSTAMP ioctls to real device")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/8021q/vlan_dev.c

@@ -370,10 +370,12 @@ static int vlan_dev_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 	ifrr.ifr_ifru = ifr->ifr_ifru;
 
 	switch (cmd) {
+	case SIOCSHWTSTAMP:
+		if (!net_eq(dev_net(dev), &init_net))
+			break;
 	case SIOCGMIIPHY:
 	case SIOCGMIIREG:
 	case SIOCSMIIREG:
-	case SIOCSHWTSTAMP:
 	case SIOCGHWTSTAMP:
 		if (netif_device_present(real_dev) && ops->ndo_do_ioctl)
 			err = ops->ndo_do_ioctl(real_dev, &ifrr, cmd);