net: fix 64 bit counters on 32 bit arches

There is a small possibility that a reader gets incorrect values on 32
bit arches. SNMP applications could catch incorrect counters when a
32bit high part is changed by another stats consumer/provider.

One way to solve this is to add a rtnl_link_stats64 param to all
ndo_get_stats64() methods, and also add such a parameter to
dev_get_stats().

Rule is that we are not allowed to use dev->stats64 as a temporary
storage for 64bit stats, but a caller provided area (usually on stack)

Old drivers (only providing get_stats() method) need no changes.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 5 deletions

diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index c6456cb842fa..7865a4ce5250 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -803,11 +803,9 @@ static u32 vlan_ethtool_get_flags(struct net_device *dev)
         return dev_ethtool_get_flags(vlan->real_dev);
 }
 
-static struct rtnl_link_stats64 *vlan_dev_get_stats64(struct net_device *dev)
+static struct rtnl_link_stats64 *vlan_dev_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 {
-        struct rtnl_link_stats64 *stats = &dev->stats64;
-
-        dev_txq_stats_fold(dev, &dev->stats);
+        dev_txq_stats_fold(dev, (struct net_device_stats *)stats);
 
         if (vlan_dev_info(dev)->vlan_rx_stats) {
                 struct vlan_rx_stats *p, accum = {0};
diff --git a/net/8021q/vlanproc.c b/net/8021q/vlanproc.c
index df56f5ce887c..80e280f56686 100644
--- a/net/8021q/vlanproc.c
+++ b/net/8021q/vlanproc.c
@@ -278,6 +278,7 @@ static int vlandev_seq_show(struct seq_file *seq, void *offset)
 {
         struct net_device *vlandev = (struct net_device *) seq->private;
         const struct vlan_dev_info *dev_info = vlan_dev_info(vlandev);
+        struct rtnl_link_stats64 temp;
         const struct rtnl_link_stats64 *stats;
         static const char fmt[] = "%30s %12lu\n";
         static const char fmt64[] = "%30s %12llu\n";
@@ -286,7 +287,7 @@ static int vlandev_seq_show(struct seq_file *seq, void *offset)
         if (!is_vlan_dev(vlandev))
                 return 0;
 
-        stats = dev_get_stats(vlandev);
+        stats = dev_get_stats(vlandev, &temp);
         seq_printf(seq,
                    "%s  VID: %d  REORDER_HDR: %i  dev->priv_flags: %hx\n",
                    vlandev->name, dev_info->vlan_id,