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    Subject[PATCH 3.13.y-ckt 052/156] team: fix possible null pointer dereference in team_handle_frame
    Date
    3.13.11-ckt19 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jiri Pirko <jiri@resnulli.us>

    commit 57e595631904c827cfa1a0f7bbd7cc9a49da5745 upstream.

    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: 3d249d4ca7d0 ("net: introduce ethernet teaming device")
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    drivers/net/team/team.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
    index b4a69a7..6d357b4 100644
    --- a/drivers/net/team/team.c
    +++ b/drivers/net/team/team.c
    @@ -42,9 +42,7 @@

    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)
    --
    1.9.1


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