net: Potential null skb->dev dereference

[ Upstream commit 0641e4fbf2f824faee00ea74c459a088d94905fd ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 99914e6fa3fdf0a60e518e035e590410c702ec16..03e8d81a839109ef149217533a7b157160fe56d9 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2023,12 +2023,12 @@ 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 e75a2f3b10af7721610af6adf0c42e5c7fec2192..152760a487e66ad8bbd0f47d539ce9fdc5f7ba1e 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;
 
        __vlan_hwaccel_put_tag(skb, vlan_tci);
@@ -82,7 +82,7 @@ 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;
 
        __vlan_hwaccel_put_tag(skb, vlan_tci);

diff --git a/net/core/dev.c b/net/core/dev.c
index ec874218b20638887a54140ee3612f50659743b1..f51f940a077c1e345ca4ccc6c18693758d7b699e 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2421,6 +2421,7 @@ 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;
        int ret = NET_RX_DROP;
        __be16 type;
@@ -2440,11 +2441,12 @@ 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++;