From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] l2tp: cast l2tp traffic counter to unsigned Date: Fri, 9 Jun 2017 15:16:21 -0700 Message-ID: <20170609151621.11e610a2@xeon-e3> References: <20170609142947.16969-1-dheidler@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Tom Parkin To: Dominik Heidler Return-path: In-Reply-To: <20170609142947.16969-1-dheidler@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, 9 Jun 2017 16:29:47 +0200 Dominik Heidler wrote: > This fixes a counter problem on 32bit systems: > When the rx_bytes counter reached 2 GiB, it jumpd to (2^64 Bytes - 2GiB) Bytes. > > rtnl_link_stats64 has __u64 type and atomic_long_read returns > atomic_long_t which is signed. Due to the conversation > we get an incorrect value on 32bit systems if the MSB of > the atomic_long_t value is set. > > CC: Tom Parkin > Fixes: 7b7c0719cd7a ("l2tp: avoid deadlock in l2tp stats update") > Signed-off-by: Dominik Heidler > --- > net/l2tp/l2tp_eth.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c > index 8b21af7321b9..668a75e002e9 100644 > --- a/net/l2tp/l2tp_eth.c > +++ b/net/l2tp/l2tp_eth.c > @@ -114,12 +114,13 @@ static void l2tp_eth_get_stats64(struct net_device *dev, > { > struct l2tp_eth *priv = netdev_priv(dev); > > - stats->tx_bytes = atomic_long_read(&priv->tx_bytes); > - stats->tx_packets = atomic_long_read(&priv->tx_packets); > - stats->tx_dropped = atomic_long_read(&priv->tx_dropped); > - stats->rx_bytes = atomic_long_read(&priv->rx_bytes); > - stats->rx_packets = atomic_long_read(&priv->rx_packets); > - stats->rx_errors = atomic_long_read(&priv->rx_errors); > + stats->tx_bytes = (unsigned long) atomic_long_read(&priv->tx_bytes); > + stats->tx_packets = (unsigned long) atomic_long_read(&priv->tx_packets); > + stats->tx_dropped = (unsigned long) atomic_long_read(&priv->tx_dropped); > + stats->rx_bytes = (unsigned long) atomic_long_read(&priv->rx_bytes); > + stats->rx_packets = (unsigned long) atomic_long_read(&priv->rx_packets); > + stats->rx_errors = (unsigned long) atomic_long_read(&priv->rx_errors); > + > } > > static const struct net_device_ops l2tp_eth_netdev_ops = { This is not the right way to fix this. 1. shouldn't be using atomic's for network counters, look at other network devices. 2. should be using u64_stats_fetch api to handle 64 bit counters.