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veth: avoid a NULL deref in veth_stats_one

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commit 2681128f0c (veth: extend device features) added a NULL deref
in veth_stats_one(), as veth_get_stats64() was not testing if the peer
device was setup or not.

At init time, we call dev_get_stats() before veth pair is fully setup.

[  178.854758]  [<ffffffffa00f5677>] veth_get_stats64+0x47/0x70 [veth]
[  178.861013]  [<ffffffff814f0a2d>] dev_get_stats+0x6d/0x130
[  178.866486]  [<ffffffff81504efc>] rtnl_fill_ifinfo+0x47c/0x930
[  178.872299]  [<ffffffff81505b93>] rtmsg_ifinfo+0x83/0x100
[  178.877678]  [<ffffffff81505cc6>] rtnl_configure_link+0x76/0xa0
[  178.883580]  [<ffffffffa00f52fa>] veth_newlink+0x16a/0x350 [veth]
[  178.889654]  [<ffffffff815061cc>] rtnl_newlink+0x4dc/0x5e0
[  178.895128]  [<ffffffff81505e1e>] ? rtnl_newlink+0x12e/0x5e0
[  178.900769]  [<ffffffff8150587d>] rtnetlink_rcv_msg+0x11d/0x310
[  178.906669]  [<ffffffff81505760>] ? __rtnl_unlock+0x20/0x20
[  178.912225]  [<ffffffff81521f89>] netlink_rcv_skb+0xa9/0xd0
[  178.917779]  [<ffffffff81502d55>] rtnetlink_rcv+0x25/0x40
[  178.923159]  [<ffffffff815218d1>] netlink_unicast+0x1b1/0x230
[  178.928887]  [<ffffffff81521c4e>] netlink_sendmsg+0x2fe/0x3b0
[  178.934615]  [<ffffffff814dbe22>] sock_sendmsg+0xd2/0xf0

So we must check if peer was setup in veth_get_stats64()

As pointed out by Ben Hutchings, priv->peer is missing proper
synchronization. Adding RCU protection is a safe and well documented
way to make sure we don't access about to be freed or already
freed data.

Reported-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
CC: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-01-04 15:42:40 +00:00 committed by David S. Miller
parent 428ac43f77
commit d0e2c55e7c
1 changed files with 40 additions and 18 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

58
drivers/net/veth.c
View file

@ -32,7 +32,7 @@ struct pcpu_vstats {
}; };
struct veth_priv { struct veth_priv {
struct net_device *peer; struct net_device __rcu *peer;
atomic64_t dropped; atomic64_t dropped;
}; };
@ -89,10 +89,10 @@ static int veth_get_sset_count(struct net_device *dev, int sset)
static void veth_get_ethtool_stats(struct net_device *dev, static void veth_get_ethtool_stats(struct net_device *dev,
struct ethtool_stats *stats, u64 *data) struct ethtool_stats *stats, u64 *data)
{ {
struct veth_priv *priv; struct veth_priv *priv = netdev_priv(dev);
struct net_device *peer = rtnl_dereference(priv->peer);
priv = netdev_priv(dev); data[0] = peer ? peer->ifindex : 0;
data[0] = priv->peer->ifindex;
} }
static const struct ethtool_ops veth_ethtool_ops = { static const struct ethtool_ops veth_ethtool_ops = {
@ -107,9 +107,15 @@ static const struct ethtool_ops veth_ethtool_ops = {
static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev) static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
{ {
struct veth_priv *priv = netdev_priv(dev); struct veth_priv *priv = netdev_priv(dev);
struct net_device *rcv = priv->peer; struct net_device *rcv;
int length = skb->len; int length = skb->len;
rcu_read_lock();
rcv = rcu_dereference(priv->peer);
if (unlikely(!rcv)) {
kfree_skb(skb);
goto drop;
}
/* don't change ip_summed == CHECKSUM_PARTIAL, as that /* don't change ip_summed == CHECKSUM_PARTIAL, as that
* will cause bad checksum on forwarded packets * will cause bad checksum on forwarded packets
*/ */
@ -125,9 +131,10 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
stats->packets++; stats->packets++;
u64_stats_update_end(&stats->syncp); u64_stats_update_end(&stats->syncp);
} else { } else {
drop:
atomic64_inc(&priv->dropped); atomic64_inc(&priv->dropped);
} }
rcu_read_unlock();
return NETDEV_TX_OK; return NETDEV_TX_OK;
} }
@ -162,30 +169,36 @@ static struct rtnl_link_stats64 *veth_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *tot) struct rtnl_link_stats64 *tot)
{ {
struct veth_priv *priv = netdev_priv(dev); struct veth_priv *priv = netdev_priv(dev);
struct net_device *peer;
struct pcpu_vstats one; struct pcpu_vstats one;
tot->tx_dropped = veth_stats_one(&one, dev); tot->tx_dropped = veth_stats_one(&one, dev);
tot->tx_bytes = one.bytes; tot->tx_bytes = one.bytes;
tot->tx_packets = one.packets; tot->tx_packets = one.packets;
tot->rx_dropped = veth_stats_one(&one, priv->peer); rcu_read_lock();
tot->rx_bytes = one.bytes; peer = rcu_dereference(priv->peer);
tot->rx_packets = one.packets; if (peer) {
tot->rx_dropped = veth_stats_one(&one, peer);
tot->rx_bytes = one.bytes;
tot->rx_packets = one.packets;
}
rcu_read_unlock();
return tot; return tot;
} }
static int veth_open(struct net_device *dev) static int veth_open(struct net_device *dev)
{ {
struct veth_priv *priv; struct veth_priv *priv = netdev_priv(dev);
struct net_device *peer = rtnl_dereference(priv->peer);
priv = netdev_priv(dev); if (!peer)
if (priv->peer == NULL)
return -ENOTCONN; return -ENOTCONN;
if (priv->peer->flags & IFF_UP) { if (peer->flags & IFF_UP) {
netif_carrier_on(dev); netif_carrier_on(dev);
netif_carrier_on(priv->peer); netif_carrier_on(peer);
} }
return 0; return 0;
} }
@ -195,7 +208,7 @@ static int veth_close(struct net_device *dev)
struct veth_priv *priv = netdev_priv(dev); struct veth_priv *priv = netdev_priv(dev);
netif_carrier_off(dev); netif_carrier_off(dev);
netif_carrier_off(priv->peer); netif_carrier_off(rtnl_dereference(priv->peer));
return 0; return 0;
} }
@ -380,10 +393,10 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
*/ */
priv = netdev_priv(dev); priv = netdev_priv(dev);
priv->peer = peer; rcu_assign_pointer(priv->peer, peer);
priv = netdev_priv(peer); priv = netdev_priv(peer);
priv->peer = dev; rcu_assign_pointer(priv->peer, dev);
return 0; return 0;
err_register_dev: err_register_dev:
@ -404,7 +417,16 @@ static void veth_dellink(struct net_device *dev, struct list_head *head)
struct net_device *peer; struct net_device *peer;
priv = netdev_priv(dev); priv = netdev_priv(dev);
peer = priv->peer; peer = rtnl_dereference(priv->peer);
/* Note : dellink() is called from default_device_exit_batch(),
* before a rcu_synchronize() point. The devices are guaranteed
* not being freed before one RCU grace period.
*/
RCU_INIT_POINTER(priv->peer, NULL);
priv = netdev_priv(peer);
RCU_INIT_POINTER(priv->peer, NULL);
unregister_netdevice_queue(dev, head); unregister_netdevice_queue(dev, head);
unregister_netdevice_queue(peer, head); unregister_netdevice_queue(peer, head);