net: Potential null skb->dev dereference
When doing "ifenslave -d bond0 eth0", there is chance to get NULL
dereference in netif_receive_skb(), because dev->master suddenly becomes
NULL after we tested it.
We should use ACCESS_ONCE() to avoid this (or rcu_dereference())
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c79a88b..fa8b476 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2059,12 +2059,12 @@
* duplicates except for 802.3ad ETH_P_SLOW, alb non-mcast/bcast, and
* ARP on active-backup slaves with arp_validate enabled.
*/
-static inline int skb_bond_should_drop(struct sk_buff *skb)
+static inline int skb_bond_should_drop(struct sk_buff *skb,
+ struct net_device *master)
{
- struct net_device *dev = skb->dev;
- struct net_device *master = dev->master;
-
if (master) {
+ struct net_device *dev = skb->dev;
+
if (master->priv_flags & IFF_MASTER_ARPMON)
dev->last_rx = jiffies;
diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index c0316e0..c584a0a 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -11,7 +11,7 @@
if (netpoll_rx(skb))
return NET_RX_DROP;
- if (skb_bond_should_drop(skb))
+ if (skb_bond_should_drop(skb, ACCESS_ONCE(skb->dev->master)))
goto drop;
skb->skb_iif = skb->dev->ifindex;
@@ -83,7 +83,7 @@
{
struct sk_buff *p;
- if (skb_bond_should_drop(skb))
+ if (skb_bond_should_drop(skb, ACCESS_ONCE(skb->dev->master)))
goto drop;
skb->skb_iif = skb->dev->ifindex;
diff --git a/net/core/dev.c b/net/core/dev.c
index bcc490c..59d4394 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2483,6 +2483,7 @@
{
struct packet_type *ptype, *pt_prev;
struct net_device *orig_dev;
+ struct net_device *master;
struct net_device *null_or_orig;
struct net_device *null_or_bond;
int ret = NET_RX_DROP;
@@ -2503,11 +2504,12 @@
null_or_orig = NULL;
orig_dev = skb->dev;
- if (orig_dev->master) {
- if (skb_bond_should_drop(skb))
+ master = ACCESS_ONCE(orig_dev->master);
+ if (master) {
+ if (skb_bond_should_drop(skb, master))
null_or_orig = orig_dev; /* deliver only exact match */
else
- skb->dev = orig_dev->master;
+ skb->dev = master;
}
__get_cpu_var(netdev_rx_stat).total++;