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team: fix possible null pointer dereference in team_handle_frame 

Currently following race is possible in team:

CPU0                                        CPU1
                                            team_port_del
                                              team_upper_dev_unlink
                                                priv_flags &= ~IFF_TEAM_PORT
team_handle_frame
  team_port_get_rcu
    team_port_exists
      priv_flags & IFF_TEAM_PORT == 0
    return NULL (instead of port got
                 from rx_handler_data)
                                              netdev_rx_handler_unregister

The thing is that the flag is removed before rx_handler is unregistered.
If team_handle_frame is called in between, team_port_exists returns 0
and team_port_get_rcu will return NULL.
So do not check the flag here. It is guaranteed by netdev_rx_handler_unregister
that team_handle_frame will always see valid rx_handler_data pointer.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Fixes: 3d249d4ca7 ("net: introduce ethernet teaming device")
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jiri Pirko 2015-02-23 14:02:54 +01:00 committed by David S. Miller
parent 46b9e4bb76
commit 57e5956319
1 changed files with 1 additions and 3 deletions
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4
drivers/net/team/team.c
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@ -43,9 +43,7 @@
static struct team_port *team_port_get_rcu(const struct net_device *dev)
{
struct team_port *port = rcu_dereference(dev->rx_handler_data);
return team_port_exists(dev) ? port : NULL;
return rcu_dereference(dev->rx_handler_data);
}
static struct team_port *team_port_get_rtnl(const struct net_device *dev)