Fri, Dec 06, 2013 at 10:10:28PM CET, stephen@xxxxxxxxxxxxxxxxxx wrote: >On Fri, 06 Dec 2013 15:43:21 -0500 (EST) >David Miller <davem@xxxxxxxxxxxxx> wrote: > >> From: Jiri Pirko <jiri@xxxxxxxxxxx> >> Date: Thu, 5 Dec 2013 16:27:37 +0100 >> >> > 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> >> > --- >> > v1->v2: moved br_port_get_check_rcu definition below br_handle_frame definition >> >> Applied and queued up for -stable, thanks Jiri. > >How come you ignored my simpler fix, that used the existing logic. >I don't like introducing this especially into the stable; much prefer >to go back to testing the flag as was being done before. Although your patch is technically sane, it depends on rtnl indirectly. My patch depends on rcu locking and synchronize_rcu which is direct. Therefore I think it is more appropriate. Jiri
