netdev - Re: [PATCH net-next 2/2] bridge: fix NULL pointer deref of br_port_get

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Date:	Sat, 14 Sep 2013 11:47:59 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hong Zhiguo <honkiko@...il.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, vyasevic@...hat.com,
	Hong Zhiguo <zhiguohong@...cent.com>
Subject: Re: [PATCH net-next 2/2] bridge: fix NULL pointer deref of
 br_port_get_rcu

On Sat, 2013-09-14 at 22:42 +0800, Hong Zhiguo wrote:
> From: Hong Zhiguo <zhiguohong@...cent.com>
> 
> The NULL deref happens when br_handle_frame is called between these
> 2 lines of del_nbp:
> 	dev->priv_flags &= ~IFF_BRIDGE_PORT;
> 	/* --> br_handle_frame is called at this time */
> 	netdev_rx_handler_unregister(dev);
> 
> In br_handle_frame the return of br_port_get_rcu(dev) is dereferenced
> without check but br_port_get_rcu(dev) returns NULL if:
> 	!(dev->priv_flags & IFF_BRIDGE_PORT)
> 
> Eric Dumazet pointed out the testing of IFF_BRIDGE_PORT is not necessary
> here since we're in rcu_read_lock and we have synchronize_net() in
> netdev_rx_handler_unregister. So remove the testing of IFF_BRIDGE_PORT
> and by the previous patch, make sure br_port_get_rcu is called in
> bridging code.
> 
> Signed-off-by: Hong Zhiguo <zhiguohong@...cent.com>
> ---
>  net/bridge/br_private.h | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)

Acked-by: Eric Dumazet <edumazet@...gle.com>

Again this is suitable for net tree.

Thanks !


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