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Date: Thu, 12 Sep 2013 20:16:35 +0800 From: Hong Zhiguo <honkiko@...il.com> To: netdev@...r.kernel.org Cc: davem@...emloft.net, zhiguohong@...cent.com Subject: [PATCH net-next] fix NULL pointer dereference in br_handle_frame From: Hong Zhiguo <zhiguohong@...cent.com> In function netdev_rx_handler_unregister it's said that: /* a reader seeing a non NULL rx_handler in a rcu_read_lock() * section has a guarantee to see a non NULL rx_handler_data * as well. */ This is true. But br_port_get_rcu(dev) returns NULL if: !(dev->priv_flags & IFF_BRIDGE_PORT) And this happended on my box 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_upper_dev_unlink(dev, br->dev); I got below Oops(some lines omitted): BUG: unable to handle kernel NULL pointer dereference at 0000000000000021 IP: [<ffffffff8150901d>] br_handle_frame+0xed/0x230 Oops: 0000 [#1] PREEMPT SMP RIP: 0010:[<ffffffff8150901d>] [<ffffffff8150901d>] br_handle_frame+0xed/0x230 RSP: 0018:ffff880030403c10 EFLAGS: 00010286 Stack: ffff88002c945700 ffffffff81508f30 0000000000000000 ffff88002d41e000 ffff880030403c98 ffffffff81477acb ffffffff81477821 ffff880030403c68 ffffffff81090e10 00ff88002d545c80 ffff88002c945700 ffffffff81aa50c0 Call Trace: <IRQ> [<ffffffff81508f30>] ? br_handle_frame_finish+0x300/0x300 [<ffffffff81477acb>] __netif_receive_skb_core+0x39b/0x880 Signed-off-by: Hong Zhiguo <zhiguohong@...cent.com> --- net/bridge/br_if.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c index c41d5fb..bd21159 100644 --- a/net/bridge/br_if.c +++ b/net/bridge/br_if.c @@ -133,6 +133,8 @@ static void del_nbp(struct net_bridge_port *p) sysfs_remove_link(br->ifobj, p->dev->name); + netdev_rx_handler_unregister(dev); + dev_set_promiscuity(dev, -1); spin_lock_bh(&br->lock); @@ -148,8 +150,6 @@ static void del_nbp(struct net_bridge_port *p) dev->priv_flags &= ~IFF_BRIDGE_PORT; - netdev_rx_handler_unregister(dev); - netdev_upper_dev_unlink(dev, br->dev); br_multicast_del_port(p); -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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