netdev - Re: [patch net/stable v2] br: fix use of ->rx_handler_data in code executed on non-rx

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Message-Id: <20131206.154321.1673089712073824539.davem@davemloft.net>
Date:	Fri, 06 Dec 2013 15:43:21 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	jiri@...nulli.us
Cc:	netdev@...r.kernel.org, jtluka@...hat.com, zhiguohong@...cent.com,
	bridge@...ts.linux-foundation.org, stephen@...workplumber.org,
	edumazet@...gle.com, laine@...hat.com, mst@...hat.com
Subject: Re: [patch net/stable v2] br: fix use of ->rx_handler_data in code
 executed on non-rx_handler path

From: Jiri Pirko <jiri@...nulli.us>
Date: Thu,  5 Dec 2013 16:27:37 +0100

> br_stp_rcv() is reached by non-rx_handler path. That means there is no
> guarantee that dev is bridge port and therefore simple NULL check of
> ->rx_handler_data is not enough. There is need to check if dev is really
> bridge port and since only rcu read lock is held here, do it by checking
> ->rx_handler pointer.
> 
> Note that synchronize_net() in netdev_rx_handler_unregister() ensures
> this approach as valid.
> 
> Introduced originally by:
> commit f350a0a87374418635689471606454abc7beaa3a
>   "bridge: use rx_handler_data pointer to store net_bridge_port pointer"
> 
> Fixed but not in the best way by:
> commit b5ed54e94d324f17c97852296d61a143f01b227a
>   "bridge: fix RCU races with bridge port"
> 
> Reintroduced by:
> commit 716ec052d2280d511e10e90ad54a86f5b5d4dcc2
>   "bridge: fix NULL pointer deref of br_port_get_rcu"
> 
> Please apply to stable trees as well. Thanks.
> 
> RH bugzilla reference: https://bugzilla.redhat.com/show_bug.cgi?id=1025770
> 
> Reported-by: Laine Stump <laine@...hat.com>
> Debugged-by: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
> ---
> v1->v2: moved br_port_get_check_rcu definition below br_handle_frame definition

Applied and queued up for -stable, thanks Jiri.
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