Thu, Dec 05, 2013 at 03:58:42PM CET, mst@xxxxxxxxxx wrote: >On Thu, Dec 05, 2013 at 03:50:25PM +0100, Jiri Pirko wrote: >> 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. >> >> Reported-by: Laine Stump <laine@xxxxxxxxxx> >> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxxx> > >I would also add: >https://bugzilla.redhat.com/show_bug.cgi?id=1025770 > >> --- >> net/bridge/br_private.h | 12 ++++++++++++ >> net/bridge/br_stp_bpdu.c | 2 +- >> 2 files changed, 13 insertions(+), 1 deletion(-) >> >> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h >> index 229d820..67a2d4b 100644 >> --- a/net/bridge/br_private.h >> +++ b/net/bridge/br_private.h >> @@ -204,6 +204,13 @@ static inline struct net_bridge_port *br_port_get_rcu(const struct net_device *d >> return rcu_dereference(dev->rx_handler_data); >> } >> >> +static inline bool br_rx_handler_check_rcu(const struct net_device *dev); > >Can't we reorder functions? >Forward-declaring it like this is ugly. I know. But makes more sense to have these getters here, near the struct. I originally moved the definitions near br_handle_frame_finish definition but I think that it is nicer to do it this way... > >> + >> +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; >> +} >> + >> static inline struct net_bridge_port *br_port_get_rtnl(const struct net_device *dev) >> { >> return br_port_exists(dev) ? >> @@ -426,6 +433,11 @@ 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; >> +} >> + >> /* 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, >> diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c >> index 8660ea3..bdb459d 100644 >> --- 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 *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; >> >> -- >> 1.8.3.1
