linux-kernel - Re: [PATCH] bridge: missing null bridge device check causing null pointer dereference (bugfix)

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Message-ID: <545B3148.8000704@lab.ntt.co.jp>
Date:	Thu, 06 Nov 2014 17:28:56 +0900
From:	Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:	박수현 <suhyun.park@...lab.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	"David S. Miller" <davem@...emloft.net>
CC:	"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 2014/11/06 16:58, 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.
> 
> 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; 
> }

Seems to have been fixed for a year.
716ec052d228 ("bridge: fix NULL pointer deref of br_port_get_rcu")

Thanks,
Toshiaki Makita

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