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Commit 0641e4fb authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 54d259d4

include/linux/netdevice.h

+4 −4
Original line number Diff line number Diff line
@@ -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)

{

	if (master) {

		struct net_device *dev = skb->dev;

	struct net_device *master = dev->master;



	if (master) {

		if (master->priv_flags & IFF_MASTER_ARPMON)

			dev->last_rx = jiffies;

net/8021q/vlan_core.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

net/core/dev.c

+5 −3
Original line number Diff line number Diff line
@@ -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++;