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Message-ID: <1415273711.13896.67.camel@edumazet-glaptop2.roam.corp.google.com> Date: Thu, 06 Nov 2014 03:35:11 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: 박수현 <suhyun.park@...lab.com> Cc: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>, Stephen Hemminger <stephen@...workplumber.org>, "David S. Miller" <davem@...emloft.net>, "bridge@...ts.linux-foundation.org" <bridge@...ts.linux-foundation.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> 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@....ntt.co.jp] > >Sent: Thursday, November 06, 2014 4:07 PM > >To: 박수현; Stephen Hemminger; David S. Miller > >Cc: bridge@...ts.linux-foundation.org; netdev@...r.kernel.org; linux- > >kernel@...r.kernel.org > >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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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