[Bridge] Fwd: [PATCH] net bridge: add null pointer check, fix panic

xiaoming gao gxm.linux.kernel at gmail.com
Thu Jun 20 06:53:44 UTC 2013


HI Eric
the problem is as follow:
br_del_if()-->del_nbp():

list_del_rcu(&p->list);
dev->priv_flags &= ~IFF_BRIDGE_PORT;

------>at this point, the nic be deleting still have rx_handler , so , may
in br_handle_frame()
------>br_port_exists() will return false,so br_get_port_rcu() will return
NULL
------>so in br_handle_frame , there will be a null panic.

netdev_rx_handler_unregister(dev);
synchronize_net();


i have checked commit 00cfec37484761a44, i think it didn't fix this bug..

thanks.




On Thu, Jun 20, 2013 at 12:55 PM, Eric Dumazet <eric.dumazet at gmail.com>wrote:

> On Thu, 2013-06-20 at 11:08 +0800, xiaoming gao wrote:
> > From: newtongao <newtongao at tencent.com>
> > Date: Wed, 19 Jun 2013 14:58:33 +0800
> > Subject: [PATCH] net bridge: add null pointer check,fix panic
> >
> > in kernel 3.0, br_port_get_rcu() may return NULL when network interface
> be deleting from bridge,
> > but in function br_handle_frame and br_handle_local_finish, the pointer
> didn't be checked before using,
> > so all br_port_get_rcu callers must do null check,or there occurs the
> null pointer panic.
> >
> > kernel 3.4 also has this bug,i have verified.
> > mainline kernel still did not  check br_port_get_rcu()'s NULL pointer,
> but i have not tested it yet.
>
> Please check current version before sending a patch.
>
> This was most probably fixed in commit 00cfec37484761a44
> ("net: add a synchronize_net() in netdev_rx_handler_unregister()")
>
> Thanks
>
>
>
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