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 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2059,12 +2059,12 @@ static inline void skb_bond_set_mac_by_master(struct sk_buff *skb,
  * 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 (file)
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -11,7 +11,7 @@ int __vlan_hwaccel_rx(struct sk_buff *skb, struct vlan_group *grp,
        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 @@ vlan_gro_common(struct napi_struct *napi, struct vlan_group *grp,
 {
        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 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2483,6 +2483,7 @@ int netif_receive_skb(struct sk_buff *skb)
 {
        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 @@ int netif_receive_skb(struct sk_buff *skb)
 
        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++;