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

Eric Dumazet said, at 2013-6-20 12:55:

On Thu, 2013-06-20 at 11:08 +0800, xiaoming gao wrote:

quoted

From: newtongao <redacted>
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

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.