My appologies, I was working on kernel 3.2.30 when I hit the crash. I only looked at the up-to-date kernel for br_handle_frame function where I still found "p->state" reference. Please disregard my patch. Thanks, Su-Hyun Park -----Original Message----- From: Eric Dumazet [mailto:eric.dumazet@xxxxxxxxx] Sent: Thursday, November 06, 2014 8:35 PM To: 박수현 Cc: Toshiaki Makita; Stephen Hemminger; David S. Miller; bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx Subject: Re: [PATCH] bridge: missing null bridge device check causing null pointer dereference (bugfix) On Thu, 2014-11-06 at 07:58 +0000, 박수현 wrote: > >-----Original Message----- > >From: Toshiaki Makita [mailto:makita.toshiaki@xxxxxxxxxxxxx] > >Sent: Thursday, November 06, 2014 4:07 PM > >To: 박수현; Stephen Hemminger; David S. Miller > >Cc: bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux- > >kernel@xxxxxxxxxxxxxxx > >Subject: Re: [PATCH] bridge: missing null bridge device check causing > >null pointer dereference (bugfix) > > > >On 2014/11/06 15:26, Su-Hyun Park wrote: > >> the bridge device can be null if the bridge is being deleted while > >> processing the packet, which causes the null pointer dereference in > >switch statement. > > > >How can this happen?? > >It is guarded by rcu. > >netdev_rx_handler_unregister() ensures rx_handler_data is non NULL. > > > > The RCU protect rx_handler_data, not the bridge member port. It can be NULL according to below code. > Where do you find this 'below code' ? Are you sending a patch for an old linux kernel ? > static inline struct net_bridge_port *br_port_get_rcu(const struct net_device *dev) { > struct net_bridge_port *port = rcu_dereference(dev->rx_handler_data); > return br_port_exists(dev) ? port : NULL; } Actual code is : static inline struct net_bridge_port *br_port_get_rcu(const struct net_device *dev) { return rcu_dereference(dev->rx_handler_data); } > > The crash happens at the below switch statement in br_handle_frame, where p is NULL. > > switch (p->state) Is your tree really including the fix we already did to fix this issue ? (commit 716ec052d2280d511e10e90ad54a86f5b5d4dcc2 ) bridge: fix NULL pointer deref of br_port_get_rcu
