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br: fix use of ->rx_handler_data in code executed on non-rx_handler path

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br_stp_rcv() is reached by non-rx_handler path. That means there is no
guarantee that dev is bridge port and therefore simple NULL check of
->rx_handler_data is not enough. There is need to check if dev is really
bridge port and since only rcu read lock is held here, do it by checking
->rx_handler pointer.

Note that synchronize_net() in netdev_rx_handler_unregister() ensures
this approach as valid.

Introduced originally by:
commit f350a0a873
  "bridge: use rx_handler_data pointer to store net_bridge_port pointer"

Fixed but not in the best way by:
commit b5ed54e94d
  "bridge: fix RCU races with bridge port"

Reintroduced by:
commit 716ec052d2
  "bridge: fix NULL pointer deref of br_port_get_rcu"

Please apply to stable trees as well. Thanks.

RH bugzilla reference: https://bugzilla.redhat.com/show_bug.cgi?id=1025770

Reported-by: Laine Stump <laine@redhat.com>
Debugged-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jiri Pirko 2013-12-05 16:27:37 +01:00 committed by David S. Miller
parent d4fb84eefe
commit 859828c0ea
2 changed files with 11 additions and 1 deletions
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10
net/bridge/br_private.h
View file

@ -426,6 +426,16 @@ netdev_features_t br_features_recompute(struct net_bridge *br,
int br_handle_frame_finish(struct sk_buff *skb);
rx_handler_result_t br_handle_frame(struct sk_buff **pskb);
static inline bool br_rx_handler_check_rcu(const struct net_device *dev)
{
return rcu_dereference(dev->rx_handler) == br_handle_frame;
}
static inline struct net_bridge_port *br_port_get_check_rcu(const struct net_device *dev)
{
return br_rx_handler_check_rcu(dev) ? br_port_get_rcu(dev) : NULL;
}
/* br_ioctl.c */
int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
int br_ioctl_deviceless_stub(struct net *net, unsigned int cmd,

2
net/bridge/br_stp_bpdu.c
View file

@ -153,7 +153,7 @@ void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
goto err;
p = br_port_get_rcu(dev);
p = br_port_get_check_rcu(dev);
if (!p)
goto err;