[PATCH 3.19 020/177] team: fix possible null pointer dereference in team_handle_frame

Greg Kroah-Hartman
2015-03-16T14:11:44Z

From: Jiri Pirko <jiri@resnulli.us>

[ Upstream commit 57e595631904c827cfa1a0f7bbd7cc9a49da5745 ]

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/team/team.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

--- 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)