3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Pirko <jiri@xxxxxxxxxxx> commit 859828c0ea476b42f3a93d69d117aaba90994b6f upstream. 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 f350a0a87374418635689471606454abc7beaa3a "bridge: use rx_handler_data pointer to store net_bridge_port pointer" Fixed but not in the best way by: commit b5ed54e94d324f17c97852296d61a143f01b227a "bridge: fix RCU races with bridge port" Reintroduced by: commit 716ec052d2280d511e10e90ad54a86f5b5d4dcc2 "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@xxxxxxxxxx> Debugged-by: Michael S. Tsirkin <mst@xxxxxxxxxx> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxxx> Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx> Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Cc: Andrew Collins <bsderandrew@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/bridge/br_private.h | 10 ++++++++++ net/bridge/br_stp_bpdu.c | 2 +- 2 files changed, 11 insertions(+), 1 deletion(-) --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -429,6 +429,16 @@ extern netdev_features_t br_features_rec extern int br_handle_frame_finish(struct sk_buff *skb); extern 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 */ extern int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd); extern int br_ioctl_deviceless_stub(struct net *net, unsigned int cmd, void __user *arg); --- a/net/bridge/br_stp_bpdu.c +++ b/net/bridge/br_stp_bpdu.c @@ -153,7 +153,7 @@ void br_stp_rcv(const struct stp_proto * 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; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html